U.S. patent application number 14/038885 was filed with the patent office on 2014-05-08 for open architecture imaging apparatus and coil system for magnetic resonance imaging.
This patent application is currently assigned to HOLOGIC, INC.. The applicant listed for this patent is HOLOGIC, INC.. Invention is credited to Christopher Luginbuhl, Cameron Anthony Piron, Donald B. Plewes.
Application Number | 20140128883 14/038885 |
Document ID | / |
Family ID | 34421553 |
Filed Date | 2014-05-08 |
United States Patent
Application |
20140128883 |
Kind Code |
A1 |
Piron; Cameron Anthony ; et
al. |
May 8, 2014 |
OPEN ARCHITECTURE IMAGING APPARATUS AND COIL SYSTEM FOR MAGNETIC
RESONANCE IMAGING
Abstract
This invention discloses a method and apparatus to deliver
medical devices to targeted locations within human tissues using
imaging data. The method enables the target location to be obtained
from one imaging system, followed by the use of a second imaging
system to verify the final position of the device. In particular,
the invention discloses a method based on the initial
identification of tissue targets using MR imaging, followed by the
use of ultrasound imaging to verify and monitor accurate needle
positioning. The invention can be used for acquiring biopsy samples
to determine the grade and stage of cancer in various tissues
including the brain, breast, abdomen, spine, liver, and kidney. The
method is also useful for delivery of markers to a specific site to
facilitate surgical removal of diseased tissue, or for the targeted
delivery of applicators that destroy diseased tissues in-situ.
Inventors: |
Piron; Cameron Anthony;
(Toronto, CA) ; Luginbuhl; Christopher; (Toronto,
CA) ; Plewes; Donald B.; (Toronto, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HOLOGIC, INC. |
Marlborough |
MA |
US |
|
|
Assignee: |
HOLOGIC, INC.
Marlborough
MA
|
Family ID: |
34421553 |
Appl. No.: |
14/038885 |
Filed: |
September 27, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12139123 |
Jun 13, 2008 |
8571632 |
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14038885 |
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|
11442944 |
Aug 28, 2006 |
7970452 |
|
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12139123 |
|
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|
10916738 |
Aug 12, 2004 |
7379769 |
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11442944 |
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60506784 |
Sep 30, 2003 |
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Current U.S.
Class: |
606/130 |
Current CPC
Class: |
A61B 2090/3908 20160201;
A61B 8/0841 20130101; A61B 2090/378 20160201; A61B 2017/3413
20130101; A61B 10/0233 20130101; A61B 90/17 20160201; A61B 8/0833
20130101; A61B 8/4245 20130101; A61B 2017/3411 20130101; A61B
5/0555 20130101; A61B 2090/374 20160201; A61B 90/11 20160201; A61B
8/4416 20130101; A61B 8/0825 20130101; A61B 8/5238 20130101; A61B
90/14 20160201; A61B 90/10 20160201; G01S 7/52049 20130101; A61B
8/406 20130101 |
Class at
Publication: |
606/130 |
International
Class: |
A61B 19/00 20060101
A61B019/00 |
Claims
1. A variable angle guide plug holder system for use in
interventional procedures, comprising: a guide plug holder for
receiving an angular determination fixture; the guide plug holder
movable relative to the angular determination fixture between a
plurality of positions, each position providing a different angle
of insertion relative to a point of origin on the angular
determination fixture; a plate plug portion removeably engaged with
the angular determination fixture; a guide plate having a plurality
of guide plate apertures, wherein the guide plug holder is
insertable into a respective guide plate aperture; and a medical
instrument for use in an interventional procedure, configured to be
inserted into the respective guide plate aperture at a respective
angle of insertion.
2. The variable angle guide plug holder system of claim 1, wherein
a user may specify any angle of insertion between a first angle of
insertion and a second angle of insertion.
3. The variable angle guide plug holder system of claim 1, wherein
the angular determination fixture comprises an arch reflecting an
angular position for the respective angle of insertion.
4. The variable angle guide plug holder system of claim 3, wherein
the angular determination fixture comprises a goniometer.
5. The variable angle guide plug holder system of claim 1, further
comprising a rotation plane for defining a rotation angle of
insertion for the medical device.
6. The variable angle guide plug holder system of claim 1, wherein
the guide plug holder includes a locking configuration configured
to fix the angle of insertion.
7. The variable angle guide plug holder system of claim 6, wherein
the locking configuration is configured to fix an angle of
rotation.
8. The variable angle guide plug holder system of claim 6, wherein
the guide plate further comprises fiducial holder receptacles for
receiving a fiducial holder.
9. The variable angle guide plug holder system of claim 6, further
comprising a second guide plug holder configured at a second angle
of insertion.
10. The variable angle guide plug holder system of claim 6, wherein
the guide plug holder is configured to be replaced by the second
guide plug holder.
11. The variable angle guide plug holder system of claim 1, wherein
the guide plate further comprises a sterile membrane.
12. The variable angle guide plug holder system of claim 1, wherein
the guide plate further comprises a compression portion and an
aperture portion.
13. The variable angle guide plug holder system of claim 12,
wherein the aperture portion is adjustable relative to the
compression portion.
14. The variable angle guide plug holder system of claim 12,
wherein the aperture portion is configured to position the
plurality of guide plate apertures over different regions of
patient tissue.
15. The variable angle guide plug holder system of claim 1, wherein
the medical device is inserted through a gimbal.
16. The variable angle guide plug holder system of claim 1, wherein
the guide plug holder engages a gimbal.
17. The variable angle guide plug holder system of claim 16,
wherein the gimbal is constructed an arranged with a flat portion
proximate to a patient surface to provide a plurality of
trajectories for accessing a common entry point on the patient
surface.
18. A method of configuring a variable angle guide plug holder for
the purpose of conducting an interventional procedure, comprising
the steps of: determining an angle for insertion of a medical
instrument for relative to a point of origin; setting the variable
angle guide plug holder having a guide plug holder to the
determined angle; inserting the variable angle guide plug holder
into a respective guide plate aperture of a plurality of guide
plate apertures of a guide plate; and inserting a medical
instrument through the guide plug holder and the respective guide
plate aperture of the plurality of guide plate apertures to a
tissue of interest.
19. The method of claim 18, further comprising limiting the
orientation of a plate plug portion of the guide plug holder, such
that inserting the variable angle guide plug holder into the
respective guide plate aperture of the plurality of guide plate
apertures of a guide plate is limited to one orientation of the
variable angle guide plug holder.
20. The method of claim 18, further comprising swapping the
variable angle guide plug holder with a second variable angle guide
plug holder configured with a second angle of insertion.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of and claims priority to
U.S. patent application Ser. No. 12/139,123, filed on Jun. 13,
2008, entitled "OPEN ARCHITECTURE IMAGING APPARATUS AND COIL SYSTEM
FOR MAGENTIC RESONANCE IMAGING," which is a continuation of and
claims priority to U.S. patent application Ser. No. 11/442,944,
filed Aug. 28, 2006, which is a continuation-in-part of and claims
priority to U.S. patent application Ser. No. 10/916,738, filed Aug.
12, 2004, titled HYBRID IMAGING METHOD TO MONITOR MEDICAL DEVICE
DELIVERY AND PATIENT SUPPORT FOR USE IN THE METHOD, which in turn
claims priority from U.S. Provisional Application No. 60/506,784,
filed Sep. 30, 2003, each of which applications are incorporated
herein by reference in their entirety.
FIELD OF THE INVENTION
[0002] This invention relates to the field of medical imaging and
particularly to a hybrid imaging method and apparatus used to
monitor and optimize the placement of interventional medical
devices in human tissues.
BACKGROUND OF THE INVENTION
[0003] A number of techniques, methodologies, apparatus and systems
have been proposed to improve the accuracy of instrumentality
placement such as needle or catheter placement into tissue based on
measurements from 3D imaging formats. These imaging formats (such
as Magnetic Resonance Imaging, sonographs (ultrasound),
fluoroscopy, X-ray, and the like) locate the needle entry device in
relation to treatment- or therapy-targeted tissue, such as
MR-detected target tissue. These imaging formats generate imaging
data that are used to determine the appropriate positioning of the
needle during treatment, which needle typically is placed in a
guide device and moved into the tissue. In many cases, the needle
is delivered solely on the basis of this imaging data information
and confirmation of the final needle position relative to the
target requires a second set of images to be acquired. In cases
where tissue stiffness variations are extreme, the needle may
deviate from the desired path and deflect on-route to the target
tissue. Similarly, the needle may distort the tissue itself and
thereby move the target tissue to a new location, such that the
original targeting coordinates are no longer correct. Further
limitations of current systems include the fact that needle
position is often determined by reference to its artifact generated
in the MR images. From this artifact, the operator infers the
actual needle position relative to the target position. In many
situations this is appropriate; however, when targeting small
lesions (i.e. <7 mm), the needle artifact (often 5-9 mm) may
obscure the target, limiting the ability to use even real-time
imaging data, as from MRI, to validate needle/target position.
[0004] Numerous articles have been published in the medical
literature describing imaging methods which can be used to monitor
and optimize the placement of interventional medical devices in
human tissues (e.g., Greenman et al, Magnetic Resonance in
Medicine, vol. 39:108-115, 1998; Orel et al., Radiology, vol. 193,
pp. 97-102, 1994; Kuhl et al., Radiology, vol. 204, pp. 667-675,
1997; Fischer et al., Radiology, vol. 192, pp. 272-272, 1994; Doler
et al., Radiology, vol. 200, pp. 863-864, 1996; Fischer et al.,
Radiology, vol. 195, pp. 533-538, 1995; Daniel et al., Radiology,
vol. 207, pp. 455-46, 1998; Heywang-Kobrunner et al., European
Radiology, vol. 9, pp. 1656-1665, 1999; Liney et al., Journal of
Magnetic Resonance Imaging, vol. 12, pp. 984-990, 2000; Schneider
et al., Journal of Magnetic Resonance Imaging, vol. 14, pp.
243-253, 2001; Sittek et al., Der Radiology, vol. 37, no. 9, pp
685-691, 1999; Jolesz, Journal of Magnetic Resonance Imaging, vol.
8, pp. 3-6, 1998; Lufkin et al., Radiology, vol. 197, pp. 16-18,
1995; Silverman et al., Radiology, vol. 197, pp. 175-181, 1995;
Kaiser et al., Investigative Radiology, Vol. 35, no. 8, pp.
513-519, 2000; Tsekos et al., Proceedings of the IEEE 2nd
International Symposium on Bioinformatics and Bioengineering
Conference, 2001, pp. 201-208).
[0005] To address limitations described in the published prior art,
a means to verify the actual trajectory of the needle is needed. A
satisfactory method must be capable of observing the target tissue
to ensure either that needle deflection or target tissue movements
can be incorporated into the needle delivery path, thereby ensuring
accurate needle delivery. Modified bore design MR magnet systems
have been developed to provide more open access to the patient. As
such, imaging and needle manipulation can take place concurrently
with the physician having some access to the patient while the
patient is positioned in the bore. However, these "open" systems
are not always available and are often of suboptimal field
strength, which can result in reduced image quality. Other proposed
solutions in the art involve in-bore robotic devices that enable
manipulation of the needle within the bore of the imaging magnet.
While this approach usefully addresses the issues of tissue/needle
deflection, it also removes the normally close interaction between
the radiologist and patient, which may lead to high levels of
patient anxiety.
SUMMARY OF THE INVENTION
[0006] The present technology provides a medical imaging system
capable of various imaging and interventional tasks based on
non-invasive detection, such as MR-detection, of diseased tissue,
with many of these applications utilizing a hybrid imaging approach
in combination with ultrasound imaging techniques. The apparatus
and techniques disclosed are combined in a system capable of
various imaging and interventional strategies that can be utilized
for comprehensive treatment protocols, for example, complete breast
cancer management. Typically, the devices are delivered through
thin needles (ranging from 20 to 9 gauge sizes (0.81 mm-2.91 mm))
which may either place devices into the tissue or retrieve tissue
from a specific anatomical region.
[0007] The present technology uses 3D imaging data obtained by
conventional non-invasive imaging techniques, particularly MRI
(magnetic resonance imaging), US (ultrasound), positron emission
tomography (PET), computerized tomography (CT), or other
three-dimensional imaging system. The technology discloses a number
of imaging and interventional functions required for complete
breast-MRI patient management, including screening for breast
cancer, determination of tumor extent and multi-focality of
previously diagnosed cancer, and diagnosis of suspicious lesions.
Further applications of the technology include MR-guided
positioning of wires and marking devices in the breast to
facilitate any treatment or diagnostic procedure, such as those
including but not limited to surgical excision/biopsy, MR-guided
core biopsy for lesion diagnosis without surgery, and MR-guided and
monitored minimally invasive therapy to destroy diseased tissue.
Multi-modality MR/US breast imaging disclosed in the descriptions
of the present technology enables a more effective means of
interventional device positioning (more accurate, faster, less
invasive to the patient), a means of tissue diagnosis without
biopsy (through ultrasound (referred to herein as "US
examination"), and a means of monitoring tissue ablation boundaries
when performing minimally invasive therapies.
[0008] While the method of the present technology was specifically
optimized for breast cancer management, it will be understood by
those of ordinary skill in the art that the techniques and
apparatus of this technology can be easily adapted to various other
body parts and pathologies. One aspect of the present technology is
to provide a patient physical support system, including patient
support and transport stretcher that is designed in such a manner
to enable maximum access to one or both breasts by the
operator.
[0009] A second aspect of this technology is to provide a
compression system with four or more independently movable plates
designed to avoid interference with US examination transducer and
biopsy needle delivery.
[0010] A third aspect of the present technology is to provide a
transport stretcher or gurney to aid patient access to the
interventional area, the apparatus to include a bridged
interventional gap, IV (intravenous) poles which accompany the
patient during the entire procedure, a headrest which accommodates
the patient's arms and permits a view out of the magnet, and minors
and lighting to help better position the patient.
[0011] A fourth aspect of this technology is to provide breast
compression plates with various apertures and fixtures to
accommodate various MR imaging coils or other radio frequency
devices, US examination-transparent imaging plates, device guide
plugs with straight or/and angled orientations, a goniometer system
for needle positioning, US examination transducer positioning
system, and freehand transducer calibration system.
[0012] A fifth aspect of the present technology is to provide
software to calculate needle trajectory based on fixed fiducial
positions, to enable multiple targeting, and to determine a
shortest distance to lesion.
[0013] A sixth aspect of this technology is to provide additional
software to calculate angled needle trajectory based on fixed
fiducial positions, to enable multiple targeting through multiple
incisions, to enable multiple targeting though a single incision,
to determine a shortest distance to lesion, and to determine any
potential interference of needle handle with surrounding
apparatus.
[0014] A seventh aspect of the present technology is to provide
software for US examination transducer delivery based on fixed
fiducial positions, to enable multiple targeting, to determine
shortest imaging distances to lesion, to recalculate with
transducer in two orientations, to recalculate with transducer at
various angulated orientations, and to convert tracked transducer
coordinates to corresponding stereotactic frame coordinates.
[0015] An eighth aspect of the present technology is to provide
still additional software to convert MR-data, set scan plane and
distance to target.
[0016] A ninth aspect of this technology is to provide additional
software for various MR/US image co-registration, visualization,
and image processing tasks
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1A shows the stretcher and patient support attached to
the MR imaging system according to the invention; FIG. 1B is a
side-view of the stretcher with patient in the `arms back`
position.
[0018] FIG. 2A shows the patient support structure without sternum
or contralateral breast support. FIG. 2B shows the support
structure with attached breast constraint and sternum support,
which is angled so as to provide good medial access to the breast.
FIG. 2C and FIG. 2D show the ability to access various positions in
the breast with various interventional probe orientations with
respect to the patient support structure and compression
plates.
[0019] FIG. 3 shows the extra interventional volume provided by an
opening in the stretcher according to the invention. FIG. 3A shows
one aspect in which the member bridging the opening may fold down
into the volume. FIG. 3B shows another aspect in which the member
may roll under the patient support in the stretcher. FIG. 3C shows
that the member may also break into multiple sections that may
swing laterally and out of the way. FIG. 3D shows another aspect in
which a portion of the patient support member may lower to provide
an accessible volume. FIG. 3E shows another aspect in which the
front and rear sections of the patient support raise in order to
provide an accessible volume. FIG. 3F shows another aspect in which
a slim support with a gap smaller than the support wheelbase
distance ensures one wheel on the head end of the apparatus is
always in contact. FIG. 3G Shows another aspect in which a bridge
support that may move either to the right or left side allowing
medial access to the breast while ensuring the wheels are in
contact with the stretcher support surface FIG. 3H Alternatively,
sections of the stretcher may be removed to permit increased access
to the breast.
[0020] FIG. 4A shows how the patient support structure may be
cantilevered over the interventional volume according to the method
of the invention. This design provides for the maximum access to
the breast. FIGS. 4B-4C show the shape of the arches relative to
the MR bore. In order to prevent the structure from tipping over
with a patient in place and separation of the patient support from
the stretcher, sliding or rolling constraints can be incorporated
into the system. FIGS. 4D-4F show various embodiments of these
constraints. FIG. 4G shows the extension of the arch support
structures so that they form a complete cylinder around the
patient.
[0021] FIGS. 5A-5D show the plate locking/positioning system of the
patient support and the related apparatus according to the
invention. The compression plates can be moved anterior/posterior
within the plate locking support. FIG. 5A illustrates how the
compression plates/locking supports can be introduced from the side
of the apparatus. Each plate can be moved independently and to any
position in the left/right direction. FIG. 5B shows that additional
compression plates in the superior/inferior direction can be
accommodated so as to "box" the breast. FIG. 5C shows another
aspect of the invention whereby various embodiments of rail
positions are possible as well as flexible sling designs to
compress the breast against the chest wall.
[0022] FIGS. 6A-6E illustrate how various compression plate designs
may be accommodated according to the invention. FIG. 6A Attached to
the compression plate are fiducial markers and fixed positions to
attach coils and positioning stages. FIG. 6B Attached to these
compression plates (or embedded within) are sets of coils. FIG. 6C
The compression plate may be a fenestrated plate for needle access.
FIG. 6D The plate may provide an acoustical opening for US imaging
and intervention. FIG. 6E A transducer positioning stage may be
attached at a fixed position on any compression plates.
[0023] FIGS. 7A-E show various coil configurations that may be used
according to the invention. FIG. 7A Bilateral imaging application
with 4 coil array. FIG. 7B Unilateral imaging configuration with 4
coil array. FIG. 7C Bilateral imaging with 4 coil array. In order
to minimize the interaction between the medial coils, their size
has been reduced and one or more RF devices which operate to
decouple the medial coils is introduced. These can be attached to
sternum support or positioned by attaching to the plate
locking/positioning system as shown in FIGS. 7D and 7E Additional
coils may be incorporated at other positions such as within an
anterior/posterior compression plate, or within the patient support
structure.
[0024] FIG. 8 shows various interventional compression plates that
may be used according to the invention. Different fenestration
shapes can be implemented as illustrated. A unique feature is the
addition of a notch to one side of the opening or indexing
component to make it asymmetric. This ensures plugs may be
positioned into the opening in only one orientation. A compression
plate consisting of a sterile membrane pulled taut across the frame
as illustrated can be used to compress the breast as well can
enable needle entry after making a small incision in the
surface.
[0025] FIGS. 9A-9C illustrate systems for breast biopsy disclosed
in the prior art which are based on a pair of parallel compression
plates to immobilize the breast and provide means to direct a
needle to a lesion based on fiducial marker measurements made in
the MR image.
[0026] FIG. 10A shows how a needle holder may be used according to
the invention to allow arbitrary orientations of a needle for
biopsy. After the correct orientation is achieved, the gimbal is
locked in position by tightening the threaded clamp. By reducing
the dimension of the gimbal as illustrated in FIG. 10B the point of
rotation is positioned near the skin surface.
[0027] FIG. 11 illustrates some useful aspects of needle
orientation geometry according to the invention.
[0028] FIG. 12 shows a goniometer that may be used according to the
invention to define needle guide orientation.
[0029] FIGS. 13A-C illustrate the angulated biopsy procedure
according to the invention.
[0030] FIGS. 14A-E show a combination fenestrated plate and
compression membrane. According to the invention, by compressing
the breast using a compression membrane with a fenestrated plate
that can move relative to the breast, more of the breast is
accessible for needle guidance.
[0031] FIG. 15 illustrates the MR-Guided delivery of tumor boundary
marking clips according to the invention.
[0032] FIG. 16 illustrates the MR/US co-registration procedure
which can be used according to the invention. The lesion and
fiducial markers are identified using MRI. Based on the MRI
information, an US transducer is delivered to the appropriate
position so that the lesion is centered in the US image using a
stereotactic frame.
[0033] FIG. 17 illustrates the MR/US co-registration procedure
where a free-hand US transducer positioning system may be used. A
touch point is used to register the coordinate system of the
tracking device to the fiducial marker defined, and therefore to
the MR image's coordinate system.
[0034] FIG. 18 shows different US probe delivery techniques which
can be used according to the invention. Using a mechanical stage
with 5 degrees of freedom, capable of fixing an US probe
horizontally or on edge, allows accurate transducer positioning.
Important features enable imaging near the chest wall (i.e.
apparatus and structure do not encumber access to this region).
FIG. 18A shows a frame with open central aperture and embedded
fiducial markers that may be inserted into the compression frame to
provide touch point reference to co-register the tracking system to
the images.
[0035] FIGS. 19A-D illustrate some useful features of the US
transparent compression frame according to the present invention.
The thin, angled top support member helps support the patient and
the U-shaped support frame enables full US imaging access to the
breast. FIGS. 19B-D show alternative embodiments of the US
permeable membrane with many cut away openings.
[0036] FIGS. 20A-D show various MR/US Hybrid biopsy configurations
according to the invention. FIG. 20A shows the breast compressed
between two sterile, US transparent plates. Imaging and
intervention occur from the same side. FIG. 20B shows a
configuration with one fenestrated plate one US permeable plate.
The needle approaches from the opposite side from US imaging. FIG.
20C shows a plate with larger fenestrations that can be used to
introduce a transducer and needle for same-sided imaging and
intervention. FIG. 20D shows transducer and needle delivery through
the same side using a positioning stage.
[0037] FIGS. 21A-D Illustrate various MR/US Hybrid biopsy
configurations according to the invention. a shows the breast
compressed between two sterile, US permeable plates. Imaging and
intervention occur from the same side with a medial approach FIG.
21B illustrates a configuration with one fenestrated plate and one
US permeable plate. Needle approach selected opposite side from US
imaging. FIG. 21C shows a plate with larger fenestrations that can
be used to incorporate a transducer and needle for same-side
imaging and intervention. FIG. 21D shows an embodiment with 2 point
needle positioning system on opposite side to US imaging.
[0038] FIG. 22 Shows hybrid device guidance for delivering multiple
markers in the breast to demarcate tumor boundaries using various
compression plate configurations. According to the invention, this
can be performed in an analogous manner to MR-guided marker
placement.
[0039] FIG. 23: Hybrid needle guidance for positioning of multiple
markers in the breast to define tumor boundaries demonstrated from
the physicians point-of-view.
[0040] FIG. 24A According to the invention, hybrid needle guidance
can be used to position tissue ablation probes and monitor therapy
progression. In this example, a cryoablation probe can be
positioned to the center of the lesion using hybrid guidance. FIG.
24B shows how reformatted MR images may be used to define the tumor
extent, while US may be used to monitor ice the development of the
resultant ice ball.
[0041] FIG. 25. Flowchart illustrating the MRI-guided needle
localization procedure according to the invention.
[0042] FIG. 26. Flowchart illustrating the MRI-guided core biopsy
procedure according to the invention.
[0043] FIG. 27. Flowchart illustrating another embodiment of the
MRI-guided core biopsy procedure according to the invention.
[0044] FIG. 28. Flowchart illustrating the hybrid MR/US imaging
procedure according to the invention.
[0045] FIG. 29. Flowchart illustrating the hybrid-guided core.
[0046] FIG. 30. Flowchart illustrating the hybrid-guided marker
placement procedure according to the invention.
[0047] FIG. 31. Flowchart illustrating the hybrid-guided delivery
of tissue ablation probes and monitoring of therapy according to
the invention.
[0048] The foregoing features, objects and advantages of the
present invention will be apparent to one generally skilled in the
art upon consideration of the following detailed description of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0049] The following described technology encompasses a hybrid
imaging method to monitor the placement of interventional medical
devices and apparatus that can be used in such an imaging method
and other medical or therapeutic procedures. The preferred
embodiments are described by reference to both the general and
specific attributes and features of the components of the
technology. However, this specification discloses only some
specific embodiments as examples of the present technology, which
as not intended to be limiting in the interpretation of the scope
of the claimed invention of this patent. It will be readily
apparent that variations and modifications may be effected without
departing from the true spirit and scope of the novel concepts of
the invention.
Patient Support Structure and Transport Stretcher
[0050] One of the areas of disclosure of this technology is a
patient support and transport apparatus including a structure,
gurney or transport stretcher 1 as indicated in FIGS. 1A-B,
supporting a patient support structure 2. This patient transport
stretcher 1 and table top patient support structure 2 act to
support the patient 26 and to immobilize the breasts 36, while
providing a transportation system for carrying the patient 26 to an
MR imaging system 4, as well as providing a stretcher 1 and support
structure 2 for the patient during imaging which can be attached
and detached from the MR imaging system 4 and moved to other
locations. The patient 26 lies on the patient support structure 2
in the prone position (face downward) and may be advanced feet
first into the bore 21 of the MR imaging system 4. The patient's
breasts 36 fall into an opening 19 at the chest level of the
patient support structure 2 and then can be immobilized by
compression plates (not shown in this FIG.) in a medial-lateral
direction. According to the technology described herein, the
patient support structure 2 has been designed to: 1) provide room
for large breasts to extend into the access volume without touching
the bottom of the magnet bore 21, 2) optimize room available for
the patient in the magnet bore 21, 3) allow the patient's arms to
be positioned forward above their head or at their sides, 4)
provide access both medially and laterally to either breast,
particularly towards the chest wall, 5) ensure devices with a wide
ranges of oblique orientations have maximal access to all points
within the breast, all with optimization for patient comfort. The
design of the present apparatus thus serves a multitude of imaging
and intervention functions, with very little adjustment of the
components. Medial and lateral interventions and hybrid imaging
interventions can be accomplished without prior knowledge of the
approach required. The apparatus disclosed by the present invention
is substantially different from systems currently available
commercially, such as, for example, the equipment made by MRI
Devices, and USA Instruments. Systems presented by Su (U.S. Pat.
No. 6,163,717), Liney et al, "Bilateral Open Breast Coil and
Compatible Intervention Device," Journal of Magnetic Resonance
Imaging, 2000 are dual function breast imaging and intervention
systems. These systems lay on the MRI bed with no modification to
the normal stretcher's table top. As space is limited in an MRI
magnet bore, the unmodified tabletop limits to space available for
access to the breast and for the patient in the magnet. None of
these systems are used for functions other than MR imaging or
MRI-only interventions and require significant setup time in the MR
imaging magnet to convert from an MR imaging to MR interventional
system.
[0051] The concept of a specially designed patient support system
and stretcher is not believed to have been presented in the prior
art. Schneider et al, 2001, presented a modified MR stretcher for
the purpose of MRI breast biopsy. This invention was also presented
in U.S. Pat. No. 5,855,554. The top support surface was modified to
enable more access to the breast, whereas the bottom part of the
stretcher was not modified. Breast biopsy systems presented by S.
H. Heywang-Kobrunner, 1999, Kuhl 1999, Fischer (U.S. Pat. No.
5,913,863), Cardwell (U.S. Pat. No. 6,423,076) all present
modifications to the top surface as well, with no modification made
to the stretcher component. These systems compromise MR imaging
capability for improved access to the breast. No integrated system
has been developed in an attempt to maximize access to the breast
by modification of the tabletop and stretcher, and providing
provisions to use the system for imaging, intervention and multiple
modality functions. These concepts can be easily transferred to
embodiments wherein the stretcher is a non-wheeled structure, or a
stationary structure.
[0052] As shown further in FIGS. 1A, 1B and FIGS. 2A and 2B, in an
exemplary embodiment of the technology described herein, the
patient support structure 2 consists of a winged structure with no
medial or central structural members. There is a cervical
(shoulders, neck and head) support area 6. The two arches 28
connect the head support 18 and arm support 25 (cervical section)
to the lower patient support 50 (lumbar or thoracic section). The
horizontal aspects of these arches 28 are positioned posterior to
the patient's breasts so as to maximize access to the patient's
breasts in a lateral approach. These arches 28 further provide a
restraint for the patient's arms when they prefer to have their
arms at their sides. Another feature of these arches 28 is to
ensure a strong structural joint between the superior and inferior
portions of the patient support structure 2. The arches can be made
as large as needed to ensure the required strength and introducing
a curved geometry to the arches ensures that the arches can be
introduced into the MR imaging bore. In the extreme, these arches
28 could form a complete cylinder in which the patient would be
placed to maximize the strength of the patient support. Double arch
supports have not been presented as a means to provide the
fundamental support or connectively between the cervical and
thoracic sections of the apparatus.
[0053] The patient support structure 2 may ramp upward (inferior
ramp 27) towards the opening 19, and may slope downward away from
the opening 19 towards the head support 18 (superior ramp 29). The
inferior ramp 27 positions the patient 26 so that her pendulant
breasts will not touch the floor of the magnet bore 21, providing a
large volume for interventional access. The superior ramp 29 (if
present) provides a region for the patient's arms to rest when in
the arms-forward position (arms above the head). The use of arching
members as the primary structural component to the system, with or
without a removable sternum support is unique. The geometry
presented in FIGS. 4A-4G, has been designed to provide structural
support and patient support so as not to interfere with access to
the breast.
[0054] The volume available for interventional access is maximized
by the transport stretcher and the design of the table top patient
support structure 2 to provide an angulated entry geometry to the
lateral aspect of the breast volume but creating wide or tapered
entry of the table structure toward the patient volume from the
lateral aspects. The access provided by this arch design is
illustrated in FIGS. 2A-2D. A bridge section 8 of the transport
stretcher 1 provides support when the patient support structure 2
is being rolled into the magnet bore 21, but is designed to retract
out of the way when the patient support structure 2 is fully
removed from the magnet bore 21 for intervention. In one embodiment
of this technology, a headrest 18 is situated at the superior end
of the patient support structure 2, whose height and angle may be
adjusted. Minors 40 may be provided below the headrest 18 to allow
the patient 26 a right-side-up view out the front of the magnet.
This feature of the technology is intended to reduce patient
anxiety. The embodiment shown has a single telescoping headrest 18
which incorporates tilting adjustment to maximize the room
available at the superior end of the structure, and to permit
adjustment and clamping of the headrest orientation with one hand.
A simplistic headrest design has been presented by Schneider et al,
1999, however this design does not embody any additional features
described above.
[0055] In further embodiments of the technology described herein,
bridge members may be used to support the patient over the breast
access volume, as shown in FIGS. 2A-D. For applications involving
both breasts (i.e., bilateral applications) a sternum support
member (44 as shown in FIG. 2B) may be used. For unilateral
applications, a bridge member breast support 34 that supports the
contralateral breast and compresses it against the chest wall is
attached. Unlike the device described by Heywang-Kobrunner et al.,
"MR-Guided percutaneous excisional and incisional biopsy," European
Radiology, vol. 9, pp. 1656-1665, 1999, in the present technology,
the angle of this support optimizes medial access to the breast
while supporting the patient in a comfortable position. Angulation
of the breast support 34 (10-30 degrees) further provides improved
access to the breast for medial access with an angulated device
approach. The embodiment of a removable sternum support member 44
and contralateral breast support 34 maximizes access to the breast
from medial and lateral aspects and is unique with respect to the
prior art. Removal of the breast and sternum supports are indicated
in FIGS. 2A-B. This resulting improved angulation with a breast
support 34 is demonstrated in FIG. 2C with the needle approaching
the breast beneath the contralateral breast support 34. Maintaining
the sternum support member 44 in place would result in a limited
angular access to the breast. Schneider et al, 2001 (E. Schneider,
K. W. Rohling, M. D. Schnall, R. O. Giaquito, E. A. Morris, and D.
Ballon, "An Apparatus for MR-Guided Breast Lesion Localization and
Core Biopsy: Design and Preliminary Results," Journal of Magnetic
Resonance Imaging, vol. 14, pp. 243-253, 2001) shows the top
portion of the tabletop could be rotated to accommodate either left
breast or right breast access. No attempt was made to improve
access to the breast for imaging or interventional procedures as is
provided by the system presented in this document by way of a
unique patient support structure 2 and optionally removable sternum
support member 44 and contralateral breast supports 34.
[0056] Another feature demonstrated in FIG. 2B and FIG. 2D is the
addition of a disposable blood barrier 42 that is attached to the
patient support structure. Features at the base of the thorax
(thoracic) support 33 and the shoulder and neck (cervical) support
31 allow attachment of various blood catchments (plastic diapers).
These can be easily attached and removed during the procedures. A
further preferred embodiment shown in FIGS. 2A and 2B consists of
IV poles 22 at the inferior and superior ends of the apparatus.
These poles act to hold the saline drip during the breast
procedures. No attempts have been made to implement any of these
embodiments in the prior art.
[0057] FIGS. 2C and 2D show a patient support structure with
respect to interventional and imaging probe access. FIG. 2C (Front
View) shows Interventional or imaging probes 30 may be introduced
at various orientations to the breast from either medial or lateral
directions. (Note: only a portion of the patient support structure
2 and compression plates 32 are shown in this view). Arrows
indicate range of probe 30 positioning without interfering with
apparatus infrastructure. FIG. 2D (Lateral view): Varied access of
probes 30 is shown in a side view. Tapered geometry of patient bed
(not shown) and positioning of compression plate 32 locking
mechanisms and rail guides (not shown) far from a breast enables
large angular and positional access. This tapered geometry extends
to the medial aspect through a gradually sloped contra-lateral
breast support 34.
Transport Stretcher
[0058] The transport stretcher 1 is used to transport the patient
to and from the MR imager 4, to dock to the MR imager 4 such that
the patient support structure 2 may be moved to advance the patient
26 into the magnet bore 21, and as a table for the patient support
structure 2 during interventional procedures and ultrasound (US)
exams, which are performed away from the MR magnet's field (FIGS.
1A-B). The patient support structure 2 (e.g., FIG. 2A) rolls on the
guides of the transport stretcher 1 when advancing into the guides
23 in the bore 21. On the underside of the patient support
structure 2 are a set of wheels (not shown). The cross-section of
the patient support structure 2 corresponds to the internal
geometry of the bore of the magnet. The transport stretcher 1
attaches (docks) to the connection mechanisms of the imaging system
4. The interlocks and safety mechanisms depend on the specific
design of the MR imaging system 4. In order to have complete access
to the breast when the patient 26 and the patient support structure
2, are removed from the magnet bore 21, a large section of the
transport stretcher 1 can be retracted (FIGS. 3A-D), leaving a
large gap. In the method of this technology, this can be
accomplished in a variety of ways as illustrated in FIGS. 3A-D).
The patient support structure 2 will be supported across this gap
and not be in a full cantilever position at any time (i.e., wheels
on patient support structure 2 will always be in contact with a
surface on the transport stretcher 1 or MRI bore 21 when the
patient support structure 2 is moving in or out of the bore 21). In
order for this to be accomplished, there are a variety of
embodiments. 1) A member (e.g., 56) that folds up from either the
torso, or the head end of the stretcher. 2) A member (e.g., 72)
that pulls out from under the torso end of the stretcher. 3) Two
members (e.g., 68) that split apart and hinge out laterally. The
gap 57 in the structure provides additional interventional volume.
Additional embodiments may also include side walls 58 that match
the geometry of the magnet. This provides the operator with a means
of verification that needles extending from the breast will not hit
the side of the magnet as the patient is returned into the magnet
for any additional MRI scanning. As the large interventional access
area is unique to this invention, mechanical provisions to enable
use of this additional space without compromising patient safety,
or complexity for the operator as presented in this document are
unique with respect to the prior art.
[0059] Additional features of the stretcher may include a set of
drawers in the side to organize all the secondary apparatus
associated with the system. Further embodiments of this technology
may include a set of lights 60 on the medial/lateral faces of the
right and left sides of the breast and at the bottom of the gap in
the stretcher. The orientations and intensities of these lights may
be adjusted by the technician or radiologist. Another embodiment
may be an adjustable minor 62, or a mirror positioned on the lower
part of the apparatus that allows the radiologist to more easily
see the position of the nipple when the breast is compressed. This
is a desirable feature in the method of the technology described
herein, because the nipple is often used as an imaging landmark in
the breast, and uneven compression may cause it to deviate either
medially or laterally, thereby providing an unreliable landmark.
These features of the present invention are shown in FIGS.
3A-D.
[0060] In FIG. 3D, the stretcher is shown with the telescoping
bridge 64 being elevated into support position.
[0061] FIG. 3E shows that the entire stretcher, with the exception
of the bridging 65 can be raised or lowered to provide a flat
surface when advancing the patient support into the bore or to
provide a gap facilitating device delivery and intervention.
[0062] FIG. 3F shows that the stretcher may have a slim support 66
with a gap smaller than the support wheelbase distance, which
ensures one wheel on the head end of the patient support is always
supported
[0063] FIG. 3G shows a stretcher with a bridge 69 that moves left
or right allow medial access to one or the other breast.
[0064] FIG. 3H shows a patient stretcher with a removable section
70 and the area from which it has been removed 71. This allows
medial access to the breasts while assuring that the patient
support structure 2 is in contact with the stretcher support
surface 1.
[0065] FIGS. 4A-4G show another embodiment of a transport stretcher
78 and a cantilevered patient support structure 77 which provides
patient support in a full cantilever position based on stronger
arched members, adjusting the mass distribution of the apparatus to
move the center of mass towards the inferior end of the bed and the
addition of sliding or rolling constraints in the transport
stretcher and magnet bore as needed to ensure the patient support
cannot tip from the transport stretcher during patient
manipulation. An example of appropriate tabletop constraints are
illustrated in FIGS. 4A-4D. In the context of a cantilevered
design, the shape of the cantilevered patient support structure 77
and the arches 28 ensure rigidity of the support and its stability
on the transport stretcher 78 while carrying a patient load. As
illustrated in FIG. 4D, the arches 28 may be extended around the
posterior of the patient to form a continuous or near continuous
cylinder 91. This extension of the arches provides a continuous
geometry that is extremely rigid and appropriate for a cantilevered
patient support strategy.
[0066] In FIGS. 4A and 4B, the cantilevered patient support
structure 77 may be cantilevered over the interventional volume 76
as indicated. This design maximizes access to the breast (not
shown). In order to prevent separation of the cantilevered patient
support structure 77 from the transport stretcher 78, sliding
constraints 79 are incorporated to prevent tipping. Also indicated
in FIG. 4A, is the addition of positional tracking devices 80 into
the body of the stretcher. Removable handles 81 ensure full access
to breasts (not shown).
[0067] In FIGS. 4B and 4C, the matched fit of the curved arch 83
into the curve of the MRI bore 85 is shown.
[0068] This cantilevered approach of FIGS. 4A-4G provides the
maximum real-estate and access in the vicinity of the breast for
ancillary instrumentation such as US (ultrasound) imaging probes,
therapeutic devices and positioning systems and to maximize access
to the breasts from medial, lateral, superior-inferior or oblique
directions for breast manipulation or interventional procedures.
Also present may be an embedded positional tracking system. By
integrating a positional tracking device into the stretcher (not
restricted to, but including optical and magnetic tracking devices)
at a position that provides line-of-sight, or reasonable proximity
to the interventional volume t enables or significantly simplifies
the procedures discussed further in this document.
[0069] FIGS. 4D-4F show alternative linear guides for the patient
support guides. In FIG. 4D, a tongue 90 in the transport stretcher
78 fits into a groove 92 in the patient support structure 77 to
prevent rotational movement. In order for the cantilevered patient
support structure 77 not to overturn during patient transport, it
is necessary to constrain the motion of the patient support
structure 77 to move in and out of the bore of the magnet 85 (S/I
patient orientation). Some possible alternative embodiments of
motion constraints are illustrated as FIG. 4E and FIG. 4F.
[0070] FIG. 4G shows a modification of the arch structure 91 of the
cantilevered design. The arches 91 in this illustration have been
extended to form a complete cylinder around the patient. The
opening provided in the arch structure 91 still enables access to
the breast in the manner illustrated in FIGS. 2C and 2D. The degree
to which the arches are extended around the patient is dependent on
the structural strength deemed appropriate. Furthermore, the
opening of the arch 91 may be widened in the Superior/Inferior
direction resulting in more access to the breast at the expense of
a relatively weaker structure.
[0071] FIGS. 5A-D show only the plate locking system 104 of the
patient support 100 and the related apparatus. The compression
plates 102 can be moved anterior/posterior within the plate locking
support 104. The compression plates/locking supports 104 can be
introduced from the side of the apparatus. FIG. 5A is a side view
and FIG. 5B is a bottom view. Each plate can be moved independently
and to any position in the left/right direction. Additional
compression plates in the superior/inferior direction can be
accommodated so as to "box" the breast. In FIG. 5C, are shown
height adjustable plates 112 and a guide 116 for the
anterior-posterior compression plate that slides left and right.
Various embodiments of rail positions that are possible are shown
in FIG. 5D, as well as flexible sling 124 designs to compress the
breast against the chest wall. Alternative locations for plate
locking guide rails 120 are also shown.
Compression System
[0072] Each breast is compressed in the medial-lateral direction by
a pair of compression plates 102 that are in turn held in place by
a pair of plate locking supports 104 (FIGS. 5A-5D). "Compression
plates" may have a number of different designs as described in the
practice of this technology. Two or four compression plates may be
used at a time depending whether unilateral or bilateral
applications are being performed. The plate locking supports 104
may be constrained to move along linear guides in a medial/lateral
direction. They may be free to be removed completely or added from
the left or right sides of the patient support structure 100 while
the patient is lying on it. The height of the compression plates
102 in the anterior-posterior direction can be adjusted along a
linear guide fixed to each plate locking support 104. The
compression plates 102 likewise can be added or removed from the
plate locking supports 104 from the top or bottom, though only from
the bottom when the patient is above them. Both plate locking
supports 104 and compression plates 102 are continuously adjustable
across the entire range of their support, do not interfere with one
another and can be locked in place. The system illustrated in FIGS.
5A-D shows two guide rails 120 to support the compression plate
102. With two guided rails on one side, this provides a completely
open geometry toward the opposite end of the compression plate 102
to maintain greatest access. However, with such a geometry, the
compression plate 102 may not demonstrate adequate rigidity that
can be overcome by placing one guide rail at the opposite end of
the compression plate 102. Similarly, using multiple guide rails
placed at each end of the compression would further stiffen the
system. In these figures we have illustrated the guide rails to be
rods and the compression plates 102 are fitted on the guide rails
with linear bearings. Multiple configurations are possible,
including the use of T slots and dovetails as dictated by the space
available for these mounting structures. The locking mechanism for
the compression plate 102 could be formed by a simple cam mechanism
or ratchet and pawl structure which allow the use of one hand to
both secure (lock) and position the compression plates 102. The
positioning of plate-locking guide rails 120 can be variously
positioned as shown in FIG. 5D.
[0073] Rail systems and tongue-and-groove compression plate support
systems have been presented in the prior art. The design presented
by Kuhl, 1997, demonstrates a dual rod system. This design differs
significantly from the presented embodiments in that the medial and
lateral plates can not be independently positioned, there is only
provision for access to one breast at a time, and both plates can
not be removed with the patient on the apparatus. Other designs
presented in the prior art including U.S. Pat. No. 5,913,863, U.S.
Pat. No. 5,855,554, U.S. Pat. No. 6,423,076 do not detail the
compression apparatus, or demonstrate limited ability to position
the plates as described by Kuhl 1997 (C. K. Kuhl, A. Elevelt, C. C.
Leutner, J. Gieseke, E. Pakos, and H. H. Schild, "Interventional
breast MR imaging: clinical use of a stereotactic localization and
biopsy device," Radiology, vol. 204, pp. 667-675, 1997) and
Heywang-Kobrunner 1999. (S. H. Heywang-Kobrunner, A. Heinig, and R.
P. Spielmann, "MR-Guided percutaneous excisional and incisional
biopsy," European Radiology, vol. 9, pp. 1656-1665, 1999.)
[0074] Another aspect of the present technology enables compression
of the breast in the anterior/posterior direction. This is a
particularly beneficial feature because US imaging and
interventional procedures are optimized by increased breast contact
with the compression plates. According to this technology, this can
be accomplished by compressing the breast into a box-like shape as
illustrated in FIG. 5D. U.S. Pat. No. 5,706,812 to Strenk et al.
discloses an inflated bladder which improves access to the breast
during US imaging. However, unlike the present technology, the
invention disclosed by Strenk et al. does not provide for
equivalent access to the lateral and medial sides of the breast
during imaging and interventional procedures. This concept may be
further extended to include rods, pointers, convex or concave
surfaces, or the like that are attached to the compression plates
and/or the patient support structure that perform the function of
improving breast contact with the compression plates.
[0075] Another feature of the present technology is the ability to
move and lock the medial and lateral plates independently through
the plate locking supports using just one hand. This enables the
operator to compress the breast with one hand, while locking it in
place with the other. The ability to adjust the positions of the
plates along the entire width of the bed is a useful feature which
accommodates the various sizes of patients and various clinical
applications (e.g. medial/lateral interventions, bilateral
imaging). Another further aspect of the invention enables movement
of the plates in the vertical direction during compression. This
allows the operator to position the plate as close to the chest
wall as possible. In the method of the invention, compression
plates inserted into the plate locking supports may take different
forms as described in the following section of this specification.
The present technology provides a method to quickly interchange
plates for various functions by vertically loading the plates into
the plate locking supports. Furthermore, compression plates may be
introduced or removed with the patient still on the apparatus by
way of removal or addition of the plate locking supports (FIGS. 5A
and 5B).
Compression Plates
[0076] According to the present technology, numerous functions are
accomplished using various types of compression plates. These
functions include:
[0077] MR imaging coils: various coil arrays--single or multiple
per compression plate.
[0078] Interventional plates: multiple hole plates, fenestrated
plate as shown in FIGS. 6C, 8 (with various aperture shapes)
[0079] US-transparent membrane and membrane support frame which
is
[0080] Reusable for imaging
[0081] Can be sterilized
[0082] Can be cut to allow incisions in the breast
[0083] Tension adjustable to adjust flexibility and
conformation
[0084] The compression plates also holds a breast immobile while a
fenestrated plate in contact with it is moved.
[0085] The plates disclosed by this invention can be sterilized and
can hold several fiducial markings 140 (e.g., FIG. 6A) visible on
MRI which act as reference points between the MR images and the
physical space. The plates can also have attachment points for MR
imaging coils (FIG. 6B), needle positioning apparatus (FIGS. 10A
and 10B) and US transducer positioning systems (FIG. 6E). The
design and function of these plates will be discussed in detail in
a subsequent section of the specification in the context of their
clinical use. A plurality of compression plates that may be used
according to the technology are identified on FIGS. 6A, 6B, and 6C.
The compression plates may be positioned at any of the 4
compression points (left medial, left lateral, right medial, right
lateral) on the breast in any combination required. FIG. 6C shows
compression plates with fenestrated plates 146. FIG. 6E shows a
transducer 148 and a positioning stage 150. These coils can be
interchanged in a modular fashion to maximize and optimize the
number and types of coils used, whether for unilateral or
bi-lateral imaging or intervention. Modular coils may also provide
either large or small coils of various designs, RF shields, and
coils for different field strength and field shapes.
[0086] FIGS. 7A-7E show various coil configurations from an axial
view of a patient on the apparatus. FIG. 7A shows a Bilateral
imaging application with 4 coil array. FIG. 7B shows a Unilateral
imaging configuration with 4 coil array. FIG. 7C shows a Bilateral
imaging with 4 coil array 160. In order to reduce coupling between
the medial coils, their size has been reduced and an RF-shield has
been inserted (attached to sternum support) to limit coil
interactions. This shield may take a variety of forms all with the
same purpose--passive medial coil decoupling. FIG. 7D shows
RF-shields have been attached to the medial compression frames.
FIG. 7E shows that Coils may also be attached to the A/P
(anterior/posterior) compression plate and used with any of the
aforementioned coil geometries. In all cases the maximum number of
allowable coils, for the maximum number of data collection channels
should be used. A sternum support 162 is also shown, as well as a
sternum support with RF shield 164, and RF-shields attached to the
medial compression plates 166.
Imaging Coils
[0087] MR imaging coils are considered in this technology. In one
embodiment, the coils may be incorporated into the system by being
embedded into the compression plates as by way of non-limiting
examples, using fixtures 122 for coil attachment in FIG. 6A. In
another embodiment, the coils 138 may be attached to the outside of
the interventional or US transparent plates 142 as shown in FIG.
6D. In another embodiment additional coils may be embedded into the
patient support structure. In another embodiment, the coils may be
positioned as close as possible to the breast in order to produce
higher-quality images. The MR coils may consist of a single pair of
coils per breast (1 medial, 1 lateral), or an array (more than two
coils, multiple pairs of coils) per compression plate. Further
enablement for coil configurations per se may be found in Schneider
et al., "An Apparatus for MR-Guided Breast Lesion Localization and
Core Biopsy: Design and Preliminary Results," Journal of Magnetic
Resonance Imaging, vol. 14, pp. 243-253, 2001, which is
incorporated herein by reference. However in that description, no
attempt was made to maximize the number of coils used for imaging
unilateral or bilateral anatomy. As a comparison, in the
description provided by Greenman, et al., MRM 1998, no attempt was
made to ensure the medial and lateral plates could both be
positioned as close as possible to the breast through an
appropriate compression system to maximize image quality. In the
present technology, moving the medial coils further from one
another would provide reduced coil decoupling and limit the issue
of coil interactions and the complexity of coil switching
circuitry. Furthermore, no attempt to substitute coil arrays so as
to maximize the number potentially used for unilateral or bilateral
imaging without has been made.
[0088] The present technology can also provide for coils specific
to different sized patients. A different set of coils could be used
for needle positioning sequences than those used for simple
imaging. These coils for needle positioning would have a large
central opening through which needles could be placed and would be
mounted over top of other compression plates (e.g. a fenestrated
plate and/or US transparent membrane). According to the invention,
these coils would be removable and their positions on the
underlying compression plate would be adjustable to ensure
clearance from a device being inserted into the breast.
Fiducial Marker System
[0089] In the methods of the present technologies, device delivery
may be based on the use of MR-visible fiducial markers as a
reference between MR images and physical space. "MR Imaging-guided
Localization and Biopsy of Breast Lesions: Initial Experience,"
Radiology, vol. 193, pp. 97-102, 1994, and Kuhl et al.,
"Interventional breast MR imaging: clinical use of a stereotactic
localization and biopsy device," Radiology, vol. 204, pp. 667-675,
1997 describe the use of fiducial markers placed at a known
position on the embedded or attached apparatus. The more reference
points that are used, the more accurate is the registration of the
two spaces (physical/imaging). Various embodiments of the fiducial
markers may be used. The fiducial markers may be embedded into some
compression plates in the apparatus for simplicity. In other
structures, such as fenestrated plates which may be moved relative
to the breast during a procedure, the markers may be removable.
They may also need to be removable if they may not be sterilized.
Device targeting and trajectory calculations can be automated if
the fiducials are at a known position on the apparatus. Another
embodiment of fiducial marker arrangements includes a detachable
plate which may be positioned at a fixed position in the
compression frame relative to the fenestrated plate positions (e.g.
FIG. 18A).
MR Breast Imaging
[0090] The prior art references indicate that the majority of
breast imaging procedures involve simple contrast-enhanced breast
imaging without intervention. It is important to have a system that
is capable of single or bilateral breast imaging for screening,
diagnostic or surgical planning purposes.
[0091] According to the present technology described herein, both
unilateral and bilateral breast imaging procedures can be performed
with the simple removal and replacement of compression plates
containing coils and coil arrays and the removal and replacement of
the central support member (used in bilateral imaging) with various
support members. The addition of coil decoupling mechanisms such as
coil windings, specially designed conductive layers, and
electronically active blocking circuits into the space between the
two coil pairs is enabled by the open architecture of the apparatus
of the present technology. One embodiment includes attachment of
the mechanism (illustrated in FIGS. 7A-7E as an RF shield), to the
bottom of the central support member. Quick attachment of this
member enables easy preparation of the system for various imaging
purposes. Alternatively, more than one RF shield could be
introduced and mounted on the guide rails to be positioned in a
patient-specific manner to optimize imaging performance. The open
architecture disclosed in this invention further enables improved
access to the breast for the operator for breast positioning before
imaging. The addition of lighting and a minor system enables
visualization of the breast. The ability to see the nipple and the
ability to move the medial and lateral plates independently
facilitates having the nipple pointed downward and in the middle of
the imaging field. This is important as the nipple is used as a
reference point for the radiologist. Furthermore, the ability to
move the plates up towards the chest wall ensures optimal
compression of the breast ensuring there is minimal motion during
the procedure.
[0092] According to this invention, the ability to use different
coil configurations for different purposes (bilateral, unilateral)
and to accommodate various patient breast sizes (e.g. one set for
large, one set for small breasts) is critical to acquire optimal
images. Depending on the number of data acquisition channels in the
MR imaging system, multiple coil arrays can be used. Various coil
geometries which may be used in the method of the invention are
presented in FIGS. 7A-7E. This concept of removable coils has not
been presented in the prior art with respect to 1) providing the
maximum number of coils for the imaging application (bi-lateral,
unilateral, interventional imaging) so as to maximize the number of
active data collection channels. 2) Adjusting coil arrays for
smaller or larger breasts, 3) Upgrading coils and coil cabling as
the associated MRI system is upgraded for increased number of data
channels, 4) Providing coils operating at different frequencies for
higher magnetic field applications. The ability to easily remove
coils and exchange them for other coils without modification of the
main imaging structure is a critical feature enabling optimized
imaging and interventional functions with a single apparatus.
MR-Guided Breast Interventions
[0093] Various breast interventional procedures are enabled by the
apparatus and method of the present invention. The ability to
perform core biopsy, wire localization, lesion marker placement,
guide tissue ablation devices and placement of tissue therapy
devices (chemotherapy, radiotherapy, cryotherapy, heat therapy,
gene therapy) are some of the clinical applications enabled by the
invention. Apparatus and techniques common to these procedures are
presented in the following section.
MR-Guided Device Delivery
[0094] The ability to accurately deliver a plurality of needles to
a lesion or to multiple sites within the breast using MRI guidance
is a fundamental aspect of the present invention. According to the
method of the invention, fiducial markers can be used as reference
points, so that the operator can position various MRI-compatible
needles (e.g. titanium and composite needles) ranging from fine
aspiration needles (approx 24 gauge (0.51 mm)), to wire delivery
needles (20 gauge, (0.81 mm)), to conventional core biopsy needles
(16 to 14 gauge (1.29 mm-1.63 mm)), coaxial introducer needles (14
to 11 gauge (1.63 mm-2.30 mm) to accommodate the core biopsy
needles), and large vacuum assisted biopsy needles and their
introducer needles (14 to 9 gauge (1.63 mm-2.91 mm), or larger).
The ability to infer needle position using signal void produced by
needle susceptibility artifacts is well established in the prior
art, for example, U.S. Pat. Nos. 4,989,608 and 5,154,179 to Ratner,
U.S. Pat. Nos. 5,744,958 and 5,782,764 to Werne, and U.S. Pat. No.
5,944,023 to Johnson et al.
[0095] Delivery of hollow needles for purposes such as acquiring
tissue samples by biopsy, or implanting wires or other markers as
guides for surgical excision is founded on the same general
procedure. Initially the breast of interest is compressed between
two plates designed to allow needle access to the breast. These
plates may take many different forms as indicated in FIG. 8. One
embodiment consists of a plate with a large number of apertures to
guide needles of interest. Other plates contain a series of
apertures of specific shapes and size which provide access to the
breast to prepare for intervention by injecting local anesthesia
and making a skin incision. These are known as fenestrated plates.
An array of square apertures have been disclosed in prior art
references, for example, U.S. Pat. No. 5,855,554 to Schneider et al
and U.S. Pat. No. 6,423,076 to Cardwell et al. Various other
implementations may include circular, triangular, hexagonal, or
other aperture shapes, with various positioning, or packing
orientations on the compression plate 180 as indicated in FIG. 8.
Each plate 180 may have features 181 for positional adjustment
(e.g., anterior-posterior). Each fenestration preferably has an
asymmetrical shape to assure proper orientation within the support
assembly 182 that has a membrane 142, fixture for fenestrated plate
attachment 183, and fixture for orienting coil attachment 185.
There may be keyed fenestrations 186 and ultrasound transparent
membranes 187 in the assemblies of the compression plates 180.
Needle guidance is accomplished by installing a guide plug with
appropriate cross section in one of the apertures. These guide
plugs have bore-holes sized to guide interventional devices (such
as needles) of various gauge sizes and lengths. The simplest
implementation involves an array of holes in a plug sized to fit
into one of the fenestrated plate's array of apertures. These
smaller holes act to guide the needle into the breast in a straight
manner, minimizing the tendency for the needle to deviate from a
medial-lateral trajectory. Other types of needle guide plugs can be
used with the system. For a particular fenestrated plate, a number
of guide plugs can be provided to accommodate various needle gauge
sizes.
[0096] The procedure of MRI needle guidance according to the
invention is demonstrated in FIGS. 9A-9C. A typical example of such
a fixation frame 200 is shown in FIG. 9A, which serves to hold the
breast 220 in a fixed geometry during the biopsy procedure and also
support MRI-visible fiducial markers 204, which are used for
subsequent registration. The frame 200 holds the breast while the
patient is in a prone position in the MR system. The frame holds
the breast in a medial-lateral direction. The biopsy needle 202 and
MR coils 203 are shown. A cancer lump 212 is shown within the
breast 220 and guide holes 208 are shown in the guide plate 206.
Plug inserts 214 are shown for the window assembly 216. Other
orientations such as cranial-caudal or oblique are possible,
however have not been presented in the prior art to our knowledge.
A means of MRI-guided needle delivery as indicated in FIGS. 9A-C
has been presented in various forms in the Prior Art (Orel et al.,
Radiology, vol. 193, pp. 97-102, 1994; Kuhl et al., Radiology, vol.
204, pp. 667-675, 1997; Fischer et al., Radiology, vol. 192, pp.
272-272, 1994; Doler et al., Radiology, vol. 200, pp. 863-864,
1996; Fischer et al., Radiology, vol. 195, pp. 533-538, 1995;
Heywang-Kobrunner et al., European Radiology, vol. 9, pp.
1656-1665, 1999; Liney et al, Journal of Magnetic Resonance
Imaging, 2000, Su (U.S. Pat. No. 6,163,717), Fischer (U.S. Pat. No.
5,913,863), Cardwell (U.S. Pat. No. 6,423,076)) and embodied in
commercial breast imaging devices by MRI Devices Inc, USA
Instruments, MachTech Inc. The basic premise of this approach is
not novel for use as an MRI-guided needle positioning method. This
prior art forms the basis of many of the inventions described
further in this document where guidance of needles based on
fiducial markers at known relative positions to fenestrated guides
and plates is required. Differing features are highlighted where
appropriate with respect to MRI-guided needle insertion and the
associated apparatus.
[0097] Fundamental to MR-guided needle guidance in the manner
described above is a compression frame constructed of a fenestrated
plate 206, which serves to accept a guide plug 214. As shown in
FIGS. 9A-C, this holder has an array of small apertures, on close
centers. Fiducial markers 204 are placed on the grid array of the
window assembly 216 and imaged along with the breast 220 during the
MRI aspect of a procedure. These markers 204 are visible in the MRI
data set along with the suspicious mass 212. By measuring the
location of this mass relative to the fiducial markers in the
image, the exact location of the lesion can be determined relative
to the grid array frame in physical space.
[0098] According to the invention, it may be desirable to deliver
devices to multiple locations within the breast (e.g. core biopsy
requiring multiple core samples) or to bring the device along an
oblique trajectory. In these applications, limiting the needle
orientation to a straight (medial to lateral) trajectory is
undesirable. Positioning the needle in a straight manner limits the
accuracy, which the needle may be positioned, and multiple samples
would require multiple skin incisions. Since device delivery can
only be achieved through a finite number of holes, the specificity
of device positioning is limited. So for some applications a
different guide plug capable of defining an angled needle
trajectory is required. An embodiment of such a guide plug 230 is
shown in FIGS. 10A and 10B. It is composed of a gimbal 240 which
allows rotational freedom in two directions. The needle guide 232
is a hollow tube passing through the centre of the gimbal 240 which
allows free rotation of the gimbal 240 about a centre of rotation
in the insert form 238. By turning the clamp 234, it is possible to
lock the needle guide orientation. We later propose a goniometer to
set this orientation (FIGS. 11, 12). Such a design for a gimballed
guide plug has been demonstrated in previous U.S. Patent documents
(U.S. Pat. No. 6,195,577 Truwit et al, U.S. Pat. No. 6,267,769
Truwit, and U.S. Pat. No. 6,368,329 Truwit) and is embodied in the
Navigus brain biopsy system developed by Image Guided Neurologics,
Inc. However, the design of the system of the present invention is
substantially different in that the base of the guide plug can only
be positioned in the slots of the fenestrated plate in one
orientation. Furthermore, the present invention can be further
distinguished from the prior art because the plug is constructed so
as to minimize the variations in the needle entry point for varying
angles of the gimbal as discussed above This is desired to provide
a common entry point to the skin for gathering multiple tissue
samples. As such, it is desired to have the design optimized such
that the centre of rotation of the needle 233 is close to the
surface of the skin in order to facilitate multiple needle entries
at different needle trajectories without the need to increase the
size of the incision as discussed above. This can be achieved by
removing a portion of the gimbal is shown in FIGS. 10A and 10B to
create a flat zone which is applied to the skin surface while still
providing a spherical surface for rotation and locking of the
gimbal. In FIG. 10B, the insert form 250 is shown with an
alternatively designed gimbal 252.
[0099] Once the gimbal is set, its orientation relative to the
fenestrated plate must be fixed. This is accomplished by the use of
a key or some other unique shape which aligns with a feature in the
fenestrations of the compression plate. Based on the MRI
coordinates, the lesion 260 location is defined by two angles shown
as .alpha. and .beta., and an insertion depth z as shown in FIG.
11. The angle .beta. determines the offset angle of the needle
trajectory 262 from a perpendicular delivery into the tissue and
describes a cone with its apex at the center of the needle gimbal
264. The surface of the cone passes through the lesion at azimuthal
angle .alpha. on this cone surface. To prescribe these two angles
to the guide plug, a goniometer 270 may be used as shown in FIG.
12. This device is a simple mechanical structure, provides
specified orientation of the needle (not shown) in the gimballed
guide plug 272 prior to insertion. The guide plug 272 is placed in
the keyed guide plug disc or needle holder disk 274 and a sterile
needle guide extender 276 is placed over the needle guide plug disk
274. This extender is used to deliver the desired angles in the
goniometer system. First the guide plug disc 274 is rotated to
angle .alpha. and the guide plug slider clamp 278 is secured to
preserve this angle on the slider ring 280. Then the slider clamp
is rotated to define the angle .beta. as shown, after which this is
also clamped to prevent further motion. To preserve the orientation
of the guide plug, a clamp on the guide plug 234 is activated to
lock the gimbal and needle holder in position. The guide plug can
be removed and inserted into the fenestrated array. Once in
position, the needle is advanced the necessary distance as
determined from the MRI data to intersect the lesion as
desired.
[0100] In order to ensure sterility throughout the procedure, the
guide plug disc, guide plug and needle guide extender can be
sterilized for each patient, or may be disposable items. If
multiple biopsies or entries into the tissue are needed, multiple
guide plugs can be used, each of which are positioned to the
desired location by the goniometer prior to or during the biopsy
procedure. With each guide plug pre-set, or set elsewhere by an
assistant, the biopsy procedure can be efficient and rapid.
[0101] According to the present invention, it is possible to
introduce a device at an arbitrary orientation while preparing
another device orientation in a separate guide plug using a
goniometer. The design and use of a goniometer to define and set
the position of a guide plug for interventional procedures is
unique with respect to the prior art. Attempts to precisely define
angulations through mechanical apparatus at the site of interest
have resulted in bulky and inappropriate devices as demonstrated in
U.S. Pat. No. 6,048,321 by McPherson et al, and a neurological
application U.S. Pat. No. 5,984,930, by Maciunas. Specific
implementations for breast biopsy include U.S. Pat. No. 6,423,076,
Cardwell et al, and Heywang-Kobrunner 1999. These designs differ in
that the angular position of the needle is defined by an apparatus
attached to the compression frame immobilizing the breast. In this
manner, large bulky apparatus are required and limited angulation
is available.
[0102] Various embodiments of the fenestrated plates, gimballed
plug and goniometer are possible according to the invention. The
apertures of the fenestrated plates, the base of the guide plug and
the corresponding aperture in the goniometer are of the same
cross-section (e.g., circular, square, triangular, hexagonal, etc).
Furthermore the goniometer would serve the same purpose if either
the arch or the disc (but not both) subtended only one-half of the
range shown (i.e. either 90 degrees or 180 degrees respectively).
In the method of the invention, the needle can be introduced from
either the medial or lateral sides of the breast by placing a grid
plate on the corresponding side of the breast. The needle
trajectory is preferentially determined such that the minimal
amount of breast tissue is traversed, however in cases where many
needle passes may be required, a constraint to minimize the number
of skin incisions and make all passes through one aperture may take
precedence. This system enables a flexibility to allow for many
different needle trajectories to approach the lesion. Similarly, it
allows the needle to be introduced at arbitrary angles to ensure
safe and appropriate insertion of a needle into a tumour. For
example, for lesions near the chest wall, it is imperative that the
needle follows a path parallel to the chest wall and not inclined
to it, so that the possibility of chest wall penetration is
eliminated.
[0103] A weakness with a fixed fenestrated plate is that various
regions of breast tissue are inaccessible to the needle (areas at
the edges of the fenestrated plate and those occluded by the
material of the plate itself). Due to limitations on the angulation
of the gimballed guide plug, large areas of tissue may be
inaccessible. A solution to this is provided by the present
invention as shown in FIGS. 13A-13C. By decoupling the two
functions of compression/immobilization of the breast and
stereotactic frame, accessibility of the breast tissue can be
optimized to minimize the effects of "blind-spots" in the breast.
This fenestrated compression plate consists of a frame 292 with a
sterile plastic membrane 294 pulled taut across its surface that
can be cut and punctured with a scalpel or a needle (e.g.,
Opsite.TM. surgical material, or other membrane transparent to
ultrasound). This plate is used to compress and immobilize the
breast. Attached to this frame/membrane combination on the side
opposite the breast is a fenestrated plate 290 as identified in
FIGS. 13A-13C. This effectively decouples the function of the
previous embodiment of the stereotactic frame: the film compresses
the breast, while the frame provides a plug and needle guidance
reference frame). Fiducial markers 296 may either be attached to
the compression plate 292 or the fenestrated plate 290. The
fenestrated plate 290 must be designed such that it can be attached
to the frame in various orientations, adjustable for position such
that the fenestrations can be centered over different regions of
breast tissue. Removing the fenestrated plate and repositioning it
into the frame at a different orientation, or adjusting its
position (in superior-inferior or anterior-posterior directions)
without removing it would provide access to tissue which would
otherwise be occluded. When the fenestrated plate is moved or
removed, the breast would not move relative to the compression
plate, as the function of breast compression and immobilization is
provided by its membrane. Different embodiments of this concept are
illustrated in FIGS. 13A-13C. Furthermore, it is important to
distinguish that required repositioning of the fenestrated plate to
access previously inaccessible regions depends on whether
fenestrations are organized in a hexagonally package structure or a
rectangular grid and indicated in FIGS. 14A-14E. For example, in
this figure, consider a desired point for biopsy 300. In the
various fenestrated plate orientations, the openings have been
shifted (by shifting the fenestrated plate within the frame) to
assure that the desired target point 300 is accessible through a
hole 302. The plates may be shifted up, down, left and right to
align the hole 302 with the target point 300. If we had a
rectangular grid of holes moving the plate up does not put the
point at the centre of a hole. A second repositioning of the plate
is required in the S/I direction. As such hexagonal arrangements
are more efficient. As mentioned previously, many fenestrated plate
systems are available, and have been presented in the Prior Art.
However none have demonstrated the ability to decouple the function
of compression and providing a stereotactic frame. This invention
provides a significant advantage to access the "blind-spots"
associated with fenestrated plate stereotactic systems.
[0104] According to the invention, both straight and angled needle
trajectories can be determined with a calculation based on various
criteria:
[0105] Adopt shortest needle path to target (medial or lateral
approach as appropriate, minimal angulation of needle).
[0106] Limit multiple samples through a single fenestration.
[0107] Select arbitrary fenestration--determine appropriate needle
trajectory.
[0108] Avoid patient support apparatus and other equipment.
[0109] Avoid anatomical features such as chest wall.
Needle Position Verification:
[0110] According to the invention, for all MR-guided needle
guidance strategies, MRI verification is required to ensure the
needle is positioned appropriately. However a strategy that
includes software verification of the needle trajectory before
needle insertion can be embodied in the needle trajectory guidance
software. Visualization of the planned needle trajectory on the MR
image set used to identify the lesion can be accomplished by
superimposing an indicator on the MR images. This is particularly
important to identify the expected position of biopsy needles after
insertion.
[0111] Identification of the lesion after needle insertion may be
difficult in situations where the lesion is smaller than the
artifact generated in the MR image. According to the invention,
software may be implemented to determine whether the lesion has
moved after needle positioning. Imaging along the length of the
needle (axial image acquisition corresponding to a needle
trajectory in the medial/lateral direction), enables visualization
of the needle depth. Identification of anatomical features of the
breast before and after needle insertion provides a comparison to
identify whether there has been gross motion of the lesion
(inferring lesion motion from the surrounding interfaces when the
lesion cannot be identified). MR images acquired before or after
contrast agent injection prior to needle insertion can be compared
to images acquired after needle insertion. Scaling and registration
of these images, detection of tissue interfaces in the images and
determination of the differences in these edge positions enables
measurement of the tissue motion after needle insertion. In cases
where there is large tissue deflection and/or deformation, the
needle position may be corrected.
EXAMPLES OF CLINICAL APPLICATIONS OF THE INVENTION
Example 1
MR-Guided Wire Localization
[0112] The use of device guidance techniques to deliver a
localization wire or marker to guide surgical intervention is
illustrated in the flowchart shown in FIG. 25. The patient is first
positioned on the patient support apparatus. The breast of interest
is then compressed between two fenestrated compression plates with
attached fiducial markers, which are attached in turn to the
compression plate locking supports. These fenestrated plates are
sterile and can be introduced while the patient is in the prone
position. These plates can be moved in the anterior-posterior
direction to positions near the chest wall to enable full
interventional access to the breast. MR imaging coils are attached
to these compression plates. MR imaging is then used to identify
the lesion and the fiducial markers. Using this information, the
appropriate fenestrated plate aperture and needle guide plug hole
are determined in order to position the needle as closely as
possible to the desired target position. Medial or lateral needle
trajectories will be selected to minimize the depth of tissue being
traversed, depending on the position of the target within the
breast.
[0113] The patient is then removed from the imaging magnet and the
marker guide needle (which is hollow in order to permit delivery of
markers through it) is inserted according to the trajectory
calculations. If more access room is required, the interventional
volume below the breast may be accessed by retracting the bridge in
the transport stretcher. The MRI coils may be removed as required
to provide more access to the breast, and can be repositioned on
the compression plates in order to reduce any interference with the
marker guide needle or wire/marker. The transport stretcher's
bridge is replaced. Walls on the side of the stretcher's bridge may
be used to ensure clearance of all devices from the magnet bore.
The patient and patient support are next advanced back into the
magnet bore and MRI is used to validate the needle position.
Strategies to determine if surrounding tissue has deflected in
cases where the lesion may not be well visualized may be
implemented based on the images acquired. The needle position may
be repositioned and again verified for position. The final step
entails insertion of the wire or marker into the tissue through the
hollow guide needle and removal of the needle leaving the wire or
marker in place in the breast. The guide plug, fenestrated plate
and compression plates may then be removed from the breast and the
interventional procedure completed.
Example 2
MR-Guided Angulated Breast Biopsy
[0114] According to the invention, a core biopsy needle may be
delivered to the breast on an oblique trajectory as illustrated in
the flowchart shown in FIG. 26. A needle guide plug having straight
(medial-lateral) holes of a larger diameter than the biopsy needle,
or angulating guide plugs may be used in cases. Patient positioning
with fenestrated plates and MR imaging is performed in an identical
manner as described under MR-guided wire localization, with the
option of implementing the various compression plates indicated in
the diagram. Calculation of the needle trajectory is done using
compound angles to define the needle trajectory and a goniometer is
used to set the orientation of the guide plug. In cases where
access to some targets is limited by the fenestration access, the
fenestrated plate's position may be altered without moving the
breast.
[0115] Introducer needle insertion is preceded by producing an
incision in the skin at the center of the fenestration to
facilitate needle entry into the breast. MR validation of needle
position is performed before the biopsy sample is taken. In cases
where small corrections in needle orientation are required, the
guide plug gimbal can be unlocked and the needle orientation
corrected by hand. In cases where a large correction is required, a
new needle trajectory can be calculated based on the MRI validation
images and a new guide plug orientation defined. In cases where
multiple samples are required, multiple guide plug orientations may
be defined in parallel with biopsy sample acquisition. Various
systems in clinical use (Koebrunner 1999, Kuhl 1997) use angulated
needle trajectories to acquire multiple samples, however this
technique is unique in that the definition of the guide plug
orientation is done away from the patient with the use of a
goniometer. This enables multiple trajectories to be prescribed
rapidly and accurately (currently in with an included angle of 60
degrees).
Example 3
MR-Guided Marker Placement
[0116] The concept of MR-guided biopsy presented in EXAMPLE 2 can
easily be extended to placement of small position markers in the
breast, according to the invention. This may or may not be done in
conjunction with MR-guided biopsy, or done in conjunction with
MR-guided needle localization. This application would take
advantage of the fact that a large tissue segment can be accessed
through a single incision point (repositioning of the fenestrated
plate to provide better access may be required). As shown in FIG.
15, a linear tumor 320 can be delineated by way of a set of markers
326 These markers 326 may be identified after the procedure
defining the maximal extent of the tumor. Markers such as
endovascualar occlusion coils, surgical clips, or any of the
devices as disclosed by Foester et al. in U.S. Patent Application
Ser. 2002/0193815 A1 may be used. Furthermore, radiotherapy
implantable seeds, or local chemotherapy delivery devices may also
be distributed around the periphery of the tumor. Clips can be
delivered through the center of a hollow needle 324, and when fully
extended and uncoiled, they remain fixed in the tissue at the end
of the needle 324. These clips would have to be made of the
appropriate MR-compatible material (e.g., titanium, platinum,
stainless steel, etc.) to ensure they can be identified and do not
compromise subsequent MR images, and to ensure they can be safely
used within the MR magnet room. The use of this procedure according
to the invention is illustrated in the flow chart shown in FIG.
27.
Example 4
MR-Guided Interstitial Therapy Delivery and Monitoring
[0117] In the method of the present invention, the techniques
described above may be easily extended to deliver a variety of
tissue investigation or ablation devices such as invasive
ultrasound tissue ablation devices, RF-heating devices, cryotherapy
systems, local delivery of chemotherapeutic agents, local delivery
of radioactive material for therapy, optical ablation (lasers),
optical photodynamic systems or any other tissue destruction
technique. Monitoring of these devices may be done using MR imaging
to measure temperature distributions, chemical concentrations or
other parameters during therapy. In the case of the optical
systems, the treatment region may be defined using other techniques
(i.e. T2-weighted contrast sequences).
MR/US Hybrid Imaging and Intervention
[0118] With the system outlined above, an apparatus for delivering
a device to a lesion is described with an arbitrary trajectory.
However, the needle path may deviate from the planned trajectory
due to either tissue heterogeneity which can cause needle
deflection. A hard lesion and surrounding tissue may move during
device entry. Further, the ability to biopsy small lesions can be
limited due to the size needle-generated artifact on the MR images
as previously mentioned. This is particularly problematic when
preformed on a high field imaging system (i.e., greater than 1.5 T
magnetic field strength). Ideally, a means to observe the needle
path in real-time is optimal to ensure correct lesion penetration.
According to the present invention, an ultrasound imaging
capability can be added in the same biopsy apparatus in order to
deliver a US transducer using the same stereotactic delivery
strategy as outlined in the previous section. A device can then be
delivered into the breast under the guidance of this real-time US
imaging in several ways.
[0119] Through a simple modification to the biopsy system, removal
of the compression plates and substitution with an acoustically
transparent window held in a frame containing fiducial reference
points, the invention can be used to perform hybrid (MR/US)
imaging. This aspect of the invention involves detecting the lesion
using MRI, than removing the patient from the MR magnet's intense
field to perform US imaging. Using the system in this manner
constitutes an automated strategy to identify MR-detected lesions
in US images as well as a means of fusing MR and US images. The
real-time US data can be used to position a device accurately into
the lesion and to verify its position. This may be done using US
exclusively when the lesion can be identified on the US image, or
using a combination of the MRI and US data if the lesion is not
easily identified using US, or if the patient may have moved.
[0120] The approach to breast imaging disclosed by the present
invention has many useful clinical applications as generally
demonstrated in the following examples. These applications can also
be extended to existing MR and US imaging modalities (e.g.
contrast-enhanced MRI/US, compound US imaging, US Doppler imaging,
etc), or to those available in the future, without departing from
the scope of the invention.
Example 5
Hybrid MR/US Imaging
[0121] This application involves accurate location and assessment
of extent of an MRI-detected lesion using US in the same procedure
while the patient remains in the same apparatus that was used for
MR imaging. This offers an alternative to retrospective US
detection of MRI-detected lesions in two different procedures. This
retrospective technique can be inaccurate and time consuming as the
patient is in two very different configurations for both imaging
procedures. This relies on the skill of the radiologist to mentally
transform data from the two modalities. Hybrid MR/US imaging
enables the radiologist to confidently identify MR-detected lesions
using US which may allow them to improve diagnostic ability based
on features visible under US. It also allows them to identify
anatomical landmarks which can be used for subsequent US-guided
biopsy with the patient removed from the biopsy apparatus.
Knowledge of the US characteristics of the lesion could lead to
easy identification of the lesion in a follow-up US examination. In
cases where the lesion is difficult to identify on the US image,
the option to view the lesion as an image where MR and US-visible
features are combined.
Example 6
Hybrid Biopsy
[0122] This application of hybrid imaging involves biopsy
acquisition under US-guidance while the patient remains on the
biopsy table with their breast immobilized. The region of interest
for US examination is identified using previously acquired MR
images. This procedure involves stereotactic delivery of the US
transducer in conjunction with free-hand, or stereotactic delivery
of the biopsy needle. This may be augmented by the use of combined
MR/US data set, and with or without the use of a US transducer
whose position and orientation are measured in real-time, and/or
tracked biopsy needle. This image can be superimposed onto the
MR/US fused dataset in such a way that the needle is easily
identified on the MR/US fused image set, and in a way that the
presented MR/US image(s) updates with the changing position of the
US transducer.
Example 7
Hybrid-Guided Marker Placement
[0123] In a similar manner as hybrid-guided biopsy, and in the same
way as MR-guided marker placement differed from MR-guided biopsy,
this system can be utilized to place numerous implantable devices
to denote breast tumor extent. In this case the applicator needle
placement will be performed using US-guidance and may be done
either using free-hand applicator guidance or stereotactic needle
delivery with the ability to correct for applicator and tissue
deflection. In this case the fused MRI/US data may provide better
determination of lesion boundaries than US guidance would give
alone.
Example 8
Interstitial Therapy Device Delivery and Monitoring
[0124] The hybrid device delivery technique may also be used to
deliver devices other than biopsy needles, or marker placement
devices. This system can also be used to position a variety of
tissue investigation or ablation devices, such as invasive
ultrasound tissue ablation devices, RF-heating devices,
cryoablative systems and, optical photodynamic systems as described
previously. In many cases it is advantageous to monitor the therapy
using the US images, particularly using cryotherapy. This technique
may offer the ability to improve the accuracy of the delivery, was
well as reducing the amount of MR imaging required. Again this can
be done using the combined MR/US data set, or using only the US
data if the lesion can be confidently identified on the US image.
However, the use of the combined MR/US data may be beneficial as
MRI may provide much better definition of tumor boundaries.
[0125] In all applications described above, US imaging modes (e.g.
Doppler, 3D imaging, US contrast agents) may improve lesion
detection. According to the invention, various means of image
fusion can be used to assist in image correction in both the MR and
US images. For all MR/US hybrid imaging procedures set forth in
Examples 5-8, standard apparatus may be used as outlined in the
following section. The methods are useful for accurate location of
the US transducer to all regions of breast tissue, transformation
of coordinates between the MR and US imaging data, MR/US image
fusion/integration techniques, MR/US image correction and
reformatting. According to the invention, this equipment can be
integrated with the biopsy system presented in the previous
sections, (i.e. the patient support, biopsy table, compression
system, MR imaging coils).
US Transducer Delivery
[0126] Another aspect of the invention provides the ability to
deliver an US imaging transducer to a particular MR-detected
position in space using MR-detectable fiducial references. A US
transducer holder and positioning apparatus is affixed at a known
position relative to these markers. If the position of a target on
an MR image is known relative to these MR detected markers, then
the position of a US transducer relative to these same markers can
be calculated such that the device and the corresponding US imaging
plane can intercept that target. If the US imaging plane and field
of view is known relative to the US transducer, then a
transformation from MR to US image coordinates can be obtained. The
devices involved include a constraint plate incorporating an
acoustically permeable membrane to immobilize the breast, a
stereotactic frame with embedded/attached fiducial markings 340 and
attachment points 344 for a transducer positioning/tracking system
342. FIG. 16, FIG. 17, FIG. 18, and FIG. 18A show these components.
FIG. 16 is the positioning stage where a mechanical stage with five
degrees of freedom and capable of two different transducer
orientations allows accurate transducer positioning. FIG. 17 is the
tracking system with a free-hand position tracking device 350 and
registration apparatus for free-hand tracking 352. FIG. 18 shows
how a nest 360 may be positioned in two or more orientations. FIG.
18A shows touch points 370 at known positions relative to MRI
visible fiducial markers to provide an alternative means of
free-hand registration.
[0127] In the method of the invention, the function of the membrane
is to provide a means to compress the breast as well as provide a
window for US imaging. A polymeric membrane that is acoustically
matched and is thin enough to not attenuate the US beam in a manner
that affects US image quality is suitable (e.g., polyethylene,
polystyrene, polyester, polycarbonate, etc.). It is important that
the breast is well compressed and that the breast is coupled to the
membrane (US coupling gel is applied between the breast and the
membrane before the procedure begins). Designing the membrane such
that it bends a small amount to conform to the curvature of the
breast ensures that there is maximum coupling between the breast
and the membrane. This allows maximum imaging access to the breast
(FIGS. 19A-19D). Strategies to constrain the breast in other
directions enable full access to all of the breast, including
regions behind the nipple. In an initial presentation of this
concept devoid of technical details, the anticipated implementation
involved US imaging and intervention occurring on opposite sides of
the breast (Plewes et al, 2001 IEEE Ultrasonics Symposium). This
was the only presentation of this concept as Prior Art. However
this simplistic embodiment without redesigned patient support for
probe and needle angulation capacity and without a compression
membrane and breast constraints in other orientations proved to be
ineffective for clinical usage. The compression membrane
configuration presented in FIGS. 19A-19D is key to providing
complete access to the breast, and at first glance is not obvious.
FIGS. 19A and 19C show that lesion 402 is difficult to access with
ultrasound (US) imaging with a taut frame holding the membrane 400
stiff. FIG. 19B and FIG. 19D shows compression with a larger,
deformable membrane 404 that places more membrane in contact with
the breast. In FIG. 19A and FIG. 19C, the two rigid frames 406 also
make the breast difficult to access for US imaging, while in FIGS.
19B and 19D the curvature 408 (as seen from below the breast)
allowed with a less rigid or taut system allows the lesions 410
more accessibility in US imaging.
[0128] According to the invention, the US transducer holding and
positioning system can take two general forms; 1) a mechanical
stage, 2) a free-hand tracking device. Both techniques involve
holding an US transducer in a conformal nest which is then attached
to either a mechanical stage, or to a tracking device at a known
position and orientation. A mechanical positioning system enables
accurate positioning of the transducer with various degrees of
freedom. This positioning system is then attached to the
compression plate at a known position with the axes of USH motion
corresponding to the MR imaging axes (L/R, A/P, S/I), and therefore
to the physical frame of reference. This facilitates
transformations between the MR frame of reference and the
transducer frame of reference as well as eliminating the need to
register the positioning apparatus to the stereotactic frame during
the procedure. In the embodiment shown in FIG. 18 the transducer
can be moved through 5 or more degrees of freedom. This design,
with positioning tracks on the periphery of the breast imaging
volume, enables access to areas near the chest wall, which is
critical for complete access to the breast. The rotational axes of
the positioning system further enable the transducer to be angled
to image regions of breast tissue that would be inaccessible with a
simple horizontal or vertical imaging approach. The design of this
stage allows for large angulations of the transducer without
interference. This device ensures that the transducer can be moved
in the vertical (A/P) and horizontal directions (S/I) with the
transducer face always in contact with the membrane surface. This
allows for effective scanning through the breast volume,
facilitating 3D US imaging applications and also enables a lesion
to be inspected using multiple transducer orientations. This design
further enables accommodation of various transducers during the
procedure by interchanging the transducer nest. The position of the
US imaging plane is known because the position of the transducer
relative to the USH is known. The ability to easily remove US
transducers from the USH allows the radiologist position the US
transducer by hand. Once a lesion is identified in the US image,
the US transducer can be removed from the nest and be manipulated
free-hand. This allows visualization of the lesion through multiple
imaging planes which is known to be a critical element of US
imaging, however once removed from the nest, the position of the
transducer is no longer known. There are no inventions presented in
the Prior Art that pertain to a mechanical positioning stage for an
US transducer accounting for the presented constraints.
[0129] The invention also provides another tracking option that
more closely resembles the traditional manner of imaging with the
US transducer; namely, a 6 degree of freedom tracking device (or
other lower order degree of freedom systems) such as an optical
(fiber optic), electromagnetic tracking, ultrasonic tracking, or
other non-contact position tracking system in which the transducer
is free to move in space without fixtures. This aspect of the
invention accommodates a technique which is more familiar to the
radiologist; however, the accuracy with which the transducer can be
free-hand positioned to a particular position may be limited. To
use such a non-contact tracking system to determine transducer
position relative to the fiducial markers, the orientation of the
tracking system must be calibrated to the orientation of the
stereotactic frame, and thereby to the MR image coordinates. This
can be accomplished by positioning the transducer/receiver at
points on the stereotactic frame at known positions relative to the
fiducial markers, measuring these positions and determining a
correlation to convert the tracking system coordinates to the
corresponding MR coordinates and vice versa.
[0130] In another embodiment of the invention, an algorithm is
applied which translates a given MR-detected coordinate to a
corresponding USH position for a given US transducer in a given
orientation (vertical or horizontal for the USH system presented in
FIGS. 16, 17, 18 and 18A), such that the target of interest will
appear in the center of the transducer imaging field at a
calculated depth. A US imaging plane can be identified such that
the shortest imaging distance to the lesion is selected, or to
intersect the lesion using a specific transducer orientation. This
algorithm enables conversion of a single MR-detected position to a
set of USH axis-positions and a unique position on the US image.
Techniques to register and fuse MR and US images (i.e. more than
one corresponding point at one time) are explained in the following
section.
Image Integration:
[0131] The present invention provides a method for registering MRI
and US breast images (2D and 3D images) to various levels of
sophistication based on accurate stereotactic transducer
positioning and/or subsequent transducer position tracking. By
knowing the orientation of the US transducer, a 3D MR data set can
be reformatted to generate an MR image that corresponds to what is
visualized on the US image (i.e. generate a 2D image from the 3D MR
image set that is the same scale and size and corresponds to the
same plane as the acquired US image). The actual transducer
position can be determined by either the mechanical systems, or the
non-contact transducer position measurement systems presented
previously. Presenting the two images side-by-side allows the
radiologist to validate that the lesion and surrounding structures
in the US image correspond with the MRI data. Segmentation (image
processing) and integration of the MRI data in ways to depict
anatomical landmarks and functional information such as contrast
agent uptake parameters would facilitate identification of the
lesion and surrounding landmarks in the breast. This system can
further be enhanced by non-contact position tracking of devices
such as biopsy needles, or tissue ablation devices. Tracking the
position of devices permits indication of the device position on
this reformatted MR data and permits free-hand device delivery
without guidance plugs or fenestrated plates. In addition, the
real-time position-tracked US image of a device can be superimposed
onto this image.
[0132] There are many tracking systems in the Prior Art related to
the tracking of devices for the purpose of display and manipulation
of medical images. In Comeau et al, (Med Phys, 27(4), 2000) a
presentation of such an integrated system for the purpose of
tracking an US probe relative to a patient's skull for the purpose
of co-registration with respect to a set of pre-acquired MR images
was presented. Here a method of optically tracking the US probe,
and using US information to help correct for tissue shift errors
associated with MR brain surgery was presented. The use of such a
system to assist brain surgery is facilitated by the constraining
nature of the boney skull. Such a concept has not been translated
to deformable structures such as the breast as there has been no
way to appropriately constrain the breast while providing adequate
access required for intervention. Furthermore, the procedural
difficulties associated with previous attempts have precluded its
further development. An integrated system as presented in the
invention enables application of image co-registration techniques
in a way that is clinically practical.
[0133] Similarly, according to the invention, MR data can be
displayed with a superimposed marker indicating the position of the
scan plane of the US transducer. Visualization strategies such as
maximum intensity projection could be used to effectively depict
the 3-D MR data in a way the radiologist can clearly interpret.
Furthermore, four-dimensional, or time series data could be
combined and presented as a 3 dimensional color-coded
representation. This technique would be most useful when a
free-hand tracking system is used for the transducer. In the method
of the invention, the same concept of image registration and image
integration could be extended to modify the real-time US images.
Segmenting the critical structures from the 3D MR data (i.e.
anatomical landmarks, contrast-enhanced lesion), and knowing the
position of the transducer relative to the MR data by way of a
tracking system, the two image modalities could be integrated into
one image. This technique does not require the lesion to appear in
the US image. Rather the MR image of the lesion is identified as
the target and is superimposed on the US image. The radiologist
could simply adjust the transducer until the superimposed lesion
appears in the US image, and guide a needle to that point at a
trajectory determined using knowledge of the transducer position.
Similarly, the image may include a superimposed marker representing
a position-tracked device to assist in its visualization. Image
fusion in this manner will also permit a quantitative measure of
the accuracy with which the images have been combined. A measure of
how well the MR and US modalities are registered can be obtained by
performing a cross correlation calculation at any time. The
radiologist can ensure that the registration is accurate before
proceeding with the intervention. In the method of the invention,
the integration of 3-D MRI and 2-D US information and the overlay
of segmented data (data which has been processed to highlight
anatomical features), needle position and US image plane
orientation enables real-time tracking of the needle position and
US beam path to facilitate real-time guidance of a device towards a
target by ensuring they are co-aligned throughout the
imaging/intervention procedure.
[0134] There is no known Prior Art presenting a system that
incorporates these technologies so as to provide an MRI/US combined
approach to perform intervention, or imaging procedures on MRI
detected targets in non-rigid regions of the body that are required
to be constrained to reduce errors associated with motion and
deformations. The physical and mechanical restrictions associated
with such an invention have been presented as aspects of the
invention thus far.
Image Error Correction:
[0135] The present invention also provides for integration of MR
and US data, whereby information from one modality can be used to
correct errors associated with the other modality.
Correction for US positional Errors
[0136] Another aspect of the invention provides image integration
techniques, whereby MRI data can be used to correct for errors in
the US data set. It is well known that the location of features in
a US image is determined using known values for the average speed
of sound in tissue. However, fat and fibrous tissues are known to
exhibit speeds of sound that differ by 5-10%. In routine US images,
a fixed speed of sound is assumed to determine location. This is an
approximation and will result in positional errors in the
co-registration of the MR and US data sets. For example, if the
space between the skin surface and the lesion is composed of purely
fat and represents a thickness of .sup..about.3 cm, then the
location of the lesion in the US image would be in error by
approximately 1.5-3 mm and as such the MRI and US images would not
be accurately co-registered. In most applications of US imaging,
this is not a limitation, as relative position is often all that is
required. In the method of this invention, absolute position in
terms of an MRI coordinate frame is what is required. In practical
terms, the main effect of the assumption of constant US
speed-of-sound will be to distort the image in the direction
parallel to the sound propagation, causing the image to be either
compressed or expanded depending on the assumed speed of sound.
However, refraction together with the fact that each point in the
image is formed by multiple RF measurements from each element in a
typical US transducer can lead to lateral distortions as well. This
will be evident on the US image as spatial errors or regions of
misalignment as one attempts to overlay the US and MRI image. In
order to overcome these distortions corrections for the actual
speed-of-sound for each transducer element must be made reflecting
the actual tissues through which the US field propagates. Two
possible approaches can be taken to overcome this limitation.
[0137] An approach is to attempt to correct for speed of sound
variations by combining the MRI and US data. This can be achieved
in an interactive fashion by repeatedly correcting the US data on
the basis of knowledge of the tissue composition from the MRI data.
In its most simple form, the MRI data can be used to make a first
order correction of US position by estimating the amount of fat and
fibroglandular tissue through which each US measurement is made. We
note that standard T1-weighted MRI images render fat and
fibroglandular tissues with very different signal intensities.
Typically, fat appears with a high signal level (bright) as a
result of a short spin-lattice (T1) time constant while
fibroglandular tissues with longer T1 times, exhibit a lower signal
and are seen as a dark region on the image. One this basis of this
contrast between these two tissues, it is straightforward to
segment the varying regions of the MRI data from which to calculate
the distant of US propagation (and speed) for both fat and
fibroglandular tissue. As the location of the US transducer has
been positioned over the tissue on the basis of measurements from
the MRI image, we know the position of the US transducer in the MRI
imaging field to first order. From this the corresponding paths of
the US field for each US transducer element can then be determined
for each point within the US image. By referring to the same point
on the MRI data the path length of the fat and fibroglandular
tissue can then be estimated and the corresponding speed of sound
variations for that location and US transducer element can be
determined. This can then be used to scale the all the US RF data
to the varying speed of sound within the tissue. The corrected RF
data can then be combined to form the US image and create a
corrected US image. This corrected image will represent a first
order correction to align the US and MRI data. When attempting to
overlay the US and MRI images, the boundaries of well-defined
anatomical structures, such as interfaces between fat and
fibroglandular tissue, should be better coregistered.
[0138] As a result of this operation, each point in the corrected
US image will now be closer to its true location within the US
image. This same process could be repeated in an interactive or
interative manner with each successive iteration moving the points
in the US image to gradually migrate to their true corresponding
location on the MRI data.
[0139] The discussion above, presumes that the geometry of MRI data
is geometrically accurate; however, it is known that various
factors will make the MRI image also exhibit spatial distortions.
The most significant of these are positional errors arising from
magnetic field gradient non-linearities. Most manufacturers of MRI
equipment attempt to provide some form of correction for these
gradient non-linearities on the basis of pre-determined
measurements of the gradient spatial performance over the 3D
imaging volume. In order for the segmentation scheme outlined above
to be most effective, correction of MRI data is needed.
[0140] An alternative approach to this problem is to use image
co-registration methods to map the US data to the MRI data. A
number of co-registration methods exist which transform the
location of point with one image to best match its location in
another by satisfy varying metrics of image similarity such as
mutual information (Hill D L, Batchelor P G, Holden M, Hawkes D J
Medical image registration Phys Med Biol. 2001 March;
46(3):R1-45.). With these techniques it would be possible to
correct for subtle changes arising from variations in the speed of
sound in the US images and match them to MRI images. As such,
lesions which are expected to appear on the US images can be
determined uniquely from MR image. In addition, we could use the
calculated deformation field to calculate the speed of sound
variations that would be needed to generate this deformation in an
iterative manner similar to that described above. As such, the MRI
data will be used to constantly update the US data in real-time to
provide accurate co-registration of the two data sets.
Defining the MR Image Plane to Track US Transducer Motions
[0141] A further aspect of this invention uses motions detected
with US data during an intervention to modify the MR image,
reflecting the new tissue geometry. The MRI image would appear to
be updated in a real-time manner, without necessitating acquisition
of new images in the MR magnet. In the method of the invention, the
entire post-MRI imaging operation could be done outside of the
magnet room by detaching the transport stretcher from the magnet
and rolling the patient out of the magnet's field. This would
reduce the amount of time needed for MR magnet access but ensure
that meaningful use of the MR images would be made during an
intervention. Further embodiments include gathering 3D US data
(rather than the normal 2D images) during intervention to monitor
tissue and device motions. Another embodiment involves measuring
the orientation of the needle from an external tracking system to
overlay this estimate of device orientation on the image data. This
would serve to corroborate the device orientation with that visible
on the US image, helpful when the device position is unclear in the
US image. Furthermore, US imaging serves to reduce the need for
further MRI.
[0142] As mentioned previously, Cormeau et al, 2000, presented a
system that integrates US and MRI data registered using fiducial
points and with probes positioned and tracked using an optical
tracking system. This embodiment has been specifically developed
for brain applications and does not translate to breast
applications for reasons previously mentioned. Tissue shift
correction techniques presented by Cormeau using information from
both modalities can be translated to the breast application. The
current invention differs in that a well-immobilized breast with US
imaging access provided through multiple access points (medial and
lateral) enables high quality US imaging (shortest distance imaging
to the target) to be performed without gross tissue motion
associated with craniotomy associated with neurological procedures.
The current invention also considers the nature of imaging errors
associated with mis-registration errors not considered by
Cormeau.
Additional Examples of Clinical Applications of the Invention
Example 9
Hybrid MR/US Imaging
[0143] The simplest implementation of hybrid imaging involves the
detection of a lesion using MRI, followed by positioning of an US
transducer, such that the lesion appears in the center of the US
field of view at a calculated position, as illustrated in the
flowchart shown in FIG. 28. The breast of interest would be
compressed between two acoustically transparent compression plates.
Attached to these compression plates would be an array of coils for
MR imaging. The lesion would be detected using MR imaging
techniques and other MR imaging techniques may be used to identify
features of the breast that would be visible using US. This would
serve to provide features common to both imaging modalities (e.g.
T2-weighted MR imaging is appropriate for imaging cysts,
T1-weighted for fat-fibroglandular interfaces). The position of the
target lesion and the fiducial markers as seen on the MR image
would be entered into a computer program which determines the
appropriate USH co-ordinates such that the lesion will appear in
the US image. The ability to image from medial or lateral sides of
the breast without prior knowledge of the lesion position ensures
optimal images may be obtained from the side closest to the lesion.
After finding the lesion under MRI, the patient is transported from
the MR imaging system while still immobilized on the patient
stretcher, away from the magnet's field. At this point the MR
imager is free to be used for another patient. The MR imaging coils
are then removed from the compression plates and the mechanical, or
freehand US position tracking system may be attached. The
transducer can then aligned with the lesion as indicated by the MR
image. The lesion of interest should appear at the center of the US
image, at a calculated depth from the surface of the imaging face.
Lesions can then be freely examined using a variety of US
techniques.
[0144] In some cases, the lesion may be difficult to visualize in
the US image, or the position prescribed for the US transducer may
be in error for various reasons. In these cases, additional
techniques can be applied with some increase of complexity. The
techniques of MR/US image fusion/integration and image correction
may provide the radiologist with tools to aid in identifying the
lesion and provide more accurate registration between the images.
Freehand transducer positioning provides a means of visualizing the
lesion in three dimensions by imaging it through different planes.
One important technique involves the identification of common
features found in MR and US images in order to confidently identify
the lesion. In FIGS. 20A-20D and 21A-20D, various MR/US Hybrid
biopsy configurations are shown. In a lateral biopsy approach in
FIGS. 20A-20D, a breast 458 (for example) is compressed between two
sterile, US permeable plates 451. Imaging and intervention occur
from the same side. FIGS. 21A-21D re essentially the same
configuration as FIGS. 20A-20D, with a medial biopsy approach
selected. FIG. 20B is a configuration with one fenestrated plate
and one US permeable plate. Needle approach is from the opposite
side from US imaging. FIG. 21B is the same configuration as FIG.
20B with a needle guide plug used to deliver needle. FIG. 20C uses
a plate with larger fenestrations which can be used to incorporate
a transducer and needle for same side imaging and intervention.
FIG. 21C is the same configuration as FIG. 20C showing a view from
a lateral side. FIG. 20D shows an alternative transducer and needle
delivery through the same side using a positioning stage. FIG. 21D
is another embodiment with 2-point needle positioning system on
opposite side to US imaging.
[0145] A radiologist may use the information in the registered
MR/US images to determine the pathological status of the tissue in
question. For example, a breast lesion may be defined as malignant
or benign based on well-understood features visible in the US image
such as lesion morphology, or blood flow characteristics. The
radiologist may also identify unique features of the lesion such as
its appearance, size or location relative to anatomical landmarks
in order that it may be identified on a subsequent retrospective
US-guided biopsy.
Example 10
Hybrid Biopsy
[0146] A preferred embodiment of the hybrid imaging technique
disclosed by the present invention is its application in acquiring
biopsy samples of lesions that are detected using MRI and cannot be
biopsied retrospectively through any other traditional means (e.g.
if the lesion is not identifiable on the basis of US alone). Biopsy
would then be performed making use of hybrid imaging.
[0147] According to this invention, the procedure for hybrid biopsy
is similar to that for hybrid imaging, but in addition a biopsy
needle would be introduced into the breast with US verification
imaging. The general procedure is illustrated in the flowchart
shown in FIG. 29. This procedure requires the same apparatus as the
hybrid imaging procedure, except the compression plates used would
differ and a needle guidance strategy and apparatus may be
incorporated into the procedure as required. Various setups for the
procedure are shown in FIGS. 21A-21D and FIG. 22. In all cases
shown, the contralateral breast is compressed against the chest
wall. However both breasts can be constrained between plates and
biopsied if both breasts extend into the interventional volume
below the patient support. This would limit the biopsy approach to
a lateral approach on either breast.
[0148] In each of the configurations shown in FIGS. 20A-20D and
21A-21D, the compression plates have electrical connections for MR
imaging coils (connections not shown). MR imaging is performed to
detect the tumor and breast's features along with fiducial markers.
The relative positions fiducial marker and target lesion are used
to determine appropriate USH axis positions, bringing the US
imaging plane through the lesion. After this point the biopsy
techniques employed differ according to the particular strategy
used.
[0149] According to one aspect of the invention, the breast of
interest would be compressed between two US-transparent compression
plates, as shown in FIGS. 20A-20D and 21A-21D. These plates would
be prepared with a sterilized membrane, as well as requiring that
the coupling gel between the membrane and the sterilized breast
would be sterile. Such a compression system presented as a sterile
surface and an acoustically transparent member has not been
presented in any Prior Art and is fundamental to the success of
such a technique. After lesion detection, an appropriate US
transducer position would be determined such that the following
criteria are satisfied: i) the shortest imaging distance is
selected (either medial or lateral approach) ii) transducer
position provides clearance for biopsy needle entry and avoidance
of biopsy system components, iii) the transducer orientation is
optimized for lesion visualization. The transducer may be delivered
to the appropriate orientation using the USH device and/or a
free-hand tracking technique. The transducer positioning technique
that provides the greatest access to the breast for needle
positioning is preferred. The access provided by the system to the
breast further enables the option of freehand US imaging with one
hand from one side of the breast, and needle positioning from the
other side of the breast. This configuration may not be optimal
from the standpoint of the radiologist's dexterity, however this
approach option is provided in one embodiment of the invention. The
approach shown in FIGS. 20A-20D and 21A-21D with needle delivery
and US imaging from the lateral approach would be used when the
lesion is positioned in the lateral region of the breast. The
approach shown with needle delivery and US imaging from the medial
side of the breast would be used when the lesion is located in the
medial region. In all cases the lesion would first be identified on
the US images using the techniques previously presented. When
identified, the transducer would be positioned so as to provide
room for needle entry, or positioned so as to monitor the needle as
it is introduced into the breast. In cases where the lesion is not
obvious, addition of MR/US fusion strategies could be applied.
Further application of needle tracking and presentation on the
fused image set would also be of great benefit in this application
as well as all other hybrid imaging strategies to assist in needle
identification.
[0150] In another embodiment of the invention, the breast would be
compressed between one US-transparent compression plate and one
fenestrated plate on the opposite side, as illustrated in FIGS.
20A-20D and 21A-21D. It is customary to select the shortest biopsy
trajectory in order to minimize breast trauma. In this
configuration the hybrid biopsy concept can be performed in a
variety of ways, each using the basic concept of US transducer
positioning and either free-hand needle delivery or stereotactic
needle delivery. These techniques are described below, in
accordance with the invention.
[0151] 1.) Stereotactic Us Transducer Delivery, Freehand Needle
Delivery
[0152] The lesion and fiducial are located using MRI. The
patient/biopsy apparatus are removed from the MR imager and
apparatus prepared for US imaging and needle intervention. The US
transducer would be delivered according to MR image coordinates,
and the lesion is identified on the US images. The US transducer
may be repositioned to aid in identifying the lesion. On the
opposite side of the breast, the appropriate aperture of the
fenestrated plate is selected for needle entry using knowledge of
the lesion's position. The needle would be introduced into the
breast and its trajectory modified based on the US images. A biopsy
sample would then be acquired the guide needle is in the
appropriate position. Multiple samples may be acquired using,
offsetting the biopsy needle's position for each. Multiple lesions
may also be examined in the same breast, in the same procedure
using this strategy.
[0153] 2.) Stereotactic Us Transducer Delivery, Stereotactic Needle
Delivery (No MR Verification)
[0154] This embodiment of the invention is similar to the one
proposed above, differing only in the extent to which the MRI data
is used to help position the needle and transducer. The lesion and
fiducial markers would be identified using MRI. These positions
would then be entered into a program that would determine the
appropriate needle delivery trajectory based on the shortest
distance to the lesion, or restricted to a fenestration selected by
the radiologist. Based on the needle orientation, the transducer
orientation would be calculated such that the needle would appear
in the plane of the US transducer as it is introduced into the
breast. The patient would then be removed from the magnet bore, and
prepared for US imaging. The US transducer would be positioned
according to the above calculation and the lesion identified on the
US image. The needle would be introduced into the opposite side of
the breast through the needle guide plug and its trajectory
modified based on the MR or US verification images. The guide plug
may be loosened and the needle trajectory modified as required.
Multiple samples may be acquired.
[0155] 3.) Stereotactic US Transducer Positioning, Stereotactic
Needle Delivery (MR Verification)
[0156] In a third embodiment of the invention used with this plate
configuration, MRI is used to detect and to validate the needle
position before the US imaging procedure is performed. The lesion
and fiducial markers would be located using MRI. The appropriate
needle delivery orientation to the lesion would be calculated based
on the MR data such that the shortest distance to the lesion would
be selected (also considering the positioning of the US transducer
and limitations of the apparatus in the immediate area). An MRI
compatible needle would then be delivered to the lesion at the
desired orientation using the angled needle guide plug presented
previously. MR imaging would then be used to validate needle
position. The needle position may be modified as required with
additional MR imaging. The patient would be removed from the MR
magnet room and the apparatus setup for US imaging. The US
transducer would be positioned to an appropriate orientation to
allow the needle and lesion to be imaged. The needle trajectory may
be modified as required by unlocking the needle guide plug before
the biopsy sample is acquired.
[0157] The examples presented above are all embodiments of the
invention. Each embodiment has certain advantages. For instance,
one embodiment requires the operator to deliver the needle by
free-hand guidance. This strategy is a fast technique requiring no
needle guidance apparatus, however it relies on the radiologist's
dexterity. A second embodiment (employing stereotactic needle
delivery outside the MR magnet) requires more apparatus; however it
provides a fast means of needle delivery and has fewer demands for
accuracy on the radiologist. The third embodiment, which requires
MR-verification of the needle before US imaging/needle verification
is a longer procedure, however it does provide an additional MR
image as verification. The last embodiment is limited in that the
patient must remain in the prone position with the biopsy needle in
the breast for a longer period of time.
[0158] In another aspect of the invention, fenestrated plates that
have openings large enough to accept either the front end of an US
transducer, or a biopsy needle, or a needle guide plug, are
positioned as medial and lateral compression plates. This
configuration enables imaging and intervention from either medial
or lateral approaches. This configuration further enables free-hand
biopsy, or stereotactic needle delivery techniques. The design of
the plates should be such that the openings are large enough to
allow the transducer access to the breast, however not large enough
that a large volume of breast tissue bulges through the openings.
According to the invention, an acoustically permeable membrane is
pulled taut and positioned between the breast and the fenestrated
plate can be used to constrain the breast in this implementation.
This has the benefit of good breast immobilization, good access for
US imaging, and provides a frame to which needle positioning plugs
may be attached.
[0159] In yet another aspect of the invention, two different needle
positioning strategies are applied. The implementation of the
two-point needle positioning device corresponding to the US
transparent membrane is shown in FIGS. 20D and 21D. This can be
used on either the same side of the breast as the US transducer or,
as shown here, on the opposite side. In FIG. 21D we see an
additional needle guide attached to the US transducer positioning
device. In all of the above hybrid biopsy strategies, the lesion
may not be visible to US. In some cases the lesion may not be
identifiable due to poor US image contrast. In these cases, the
operator may choose to biopsy the tissue identified by the MR
images. A biopsy may be acquired more confidently if image fusion
techniques are employed. According to the invention, other imaging
techniques, including US Doppler, Harmonic and US micro-bubble
contrast, may be used to enhance the quality of the images
acquired. In the method of the invention, all biopsy strategies can
be extended to multiple lesions in a single procedure. None of
these techniques have been described in detail in previous Prior
Art. An article by Plewes 2001, IEEE, presents a simplistic form of
the technique where US and needle delivery is performed from
opposing sides with the shortest distance taken to be from the
needle insertion to lesion center, however none of the enabling
aspects of the invention were presented.
Example 11
Hybrid Marker Placement
[0160] According to the invention, using a technique similar to
MR-guided biopsy of the breast, a small position-marking device may
be implanted in the breast in conjunction with a biopsy or wire
localization procedure. Any of the previously presented hybrid
biopsy techniques could be applied as needed. Marker placement
using MR-guidance alone would require multiple image acquisitions
to verify position prior to each marker placement. Lesions only
visible under contrast enhancement cannot be imaged repeatedly with
MRI during the same procedure. Guidance of marker placement devices
using US is not restricted by time-limited lesion contrast
enhancement, and does not require long periods of expensive MR
magnet time. US cannot always be relied upon to visualize a
lesion's exact location or extent, but can be used to track tissue
motions during the intervention. In this technique, MR images are
reformatted to reflect the changing image plane of a US transducer,
and modified in real-time to indicate tissue distortion detected
with US. This confers the ability to image in real-time with
ultrasound, but to still visualize lesions to the extent possible
with MRI.
[0161] The marker placement device's position would be known from
both the US data and from a separate position tracking system. A
representation of the device's location would be overlaid on the
reformatted MR image described above. Markers may then be
positioned relative to a lesion as it appears on MRI, but whose
morphology is being updated based on US monitoring. According to
the invention, these markers do not have to be made of MR
compatible materials. In one embodiment, they are constructed of
materials and geometries that are easily identified on US images
(highly US reflective scattering). In another embodiment, these
markers are made of MR compatible materials so that their positions
may be verified relative to the lesion enhancement pattern on
subsequent MR imaging procedures (e.g. supine MR imaging may be
preferable, in order to locate markers with the patient in the
position used for surgery). This procedure is demonstrated in FIG.
22 and FIG. 23 and in the flowchart shown in FIG. 30. Marker
placement under mammography, ultrasound and MRI have been presented
in recent years, however multiple marker placement, and MR/US
combined marker placement have not been presented in the prior art.
FIG. 22 shows the positioning of multiple clips 500 at a lesion 502
in a breast 458 by devices 452 guided by transducer 450 from a
medial perspective. FIG. 23 shows an image of the devices inserting
the markers from the physician's point of view.
[0162] FIG. 24A shows that hybrid needle 542 (e.g., tissue ablation
probe such as a cryotherapy probe) may be delivered to a lesion 502
in a breast 458, with delivery made in multiple positions based on
MRI imaging. In FIG. 24B, it is indicated that therapy can be
monitored with US and/or corresponding MR data as a US image 545 or
reformatted MRI image 544. A lesion 502 may be segmented from the
MRI data through various means, with probe position 542 and tissue
architecture demonstrated in the reformatted MR image 544. The
corresponding features may be present in the corresponding US image
as an US visible lesion 545 with or without fused MRI data to
assist in validation of lesion position and/or probe position.
Example 12
Hybrid Monitoring of Therapy Delivery
[0163] According to the invention, this system can be used to
accommodate a variety of tissue investigation or ablation devices,
such as invasive ultrasound tissue ablation devices, RF heating
devices, cryotherapy systems, local delivery of chemotherapeutic
agents, optical ablation (lasers), optical photodynamic systems, or
any other tissue destruction technique. Monitoring of these
therapies may be performed using the position-tracked US transducer
with imaging techniques such as standard grayscale imaging, Doppler
imaging to characterize in blood flow, or measurement of
temperature as a function of changes in the speed of sound and
attenuation properties. Grayscale US imaging has been shown to be a
reliable technique to monitor delivery of cryoablative therapy, as
the ice formed in the tissue is readily detected as a highly
US-reflective surface. The utility of US as the monitoring and
device guidance technique is to provide more accurate device
placement, as well as limit the amount of expensive MR imaging time
required to monitor long treatments (thermal ablation of tumors may
be up to ninety minutes in duration). This procedure is
demonstrated in FIGS. 24A and B and in the flowchart shown in FIG.
31.
[0164] Minimally invasive tissue ablation techniques have been
presented in recent years for breast, brain prostate and liver
therapy. Limited use for breast cancer ablation has been presented.
No prior art has been presented involving a combined MRI detection
and US guidance strategy for these therapies. MRI detection and MRI
monitoring has been used for cryoablation and laser ablation of
breast tumors, without US guidance and monitoring. Differing from
the presented invention is a system developed by TxSonics Inc using
MRI guidance to detect tumors and monitor therapy, and high-power
US to ablate tumors. Only through a modification of the approaches
taken in inventions thus far can an appropriate embodiment be
realized. Only the use of US-guidance to monitor ablation therapies
can decrease the expensive MRI time required to perform these
procedures making them more economically appropriate. The preceding
specific embodiments are illustrative of the practice of the
present invention. It is to be understood that other embodiments
known to those skilled in the art or disclosed herein may be
employed without departing from the invention or the scope of the
claims.
[0165] The practice of the invention as described above provides
the following systems functions:
[0166] Technique for medial/lateral MR-guided delivery of needle to
the breast using straight or angled needle trajectories.
[0167] Techniques for MR/US hybrid biopsy
[0168] Technique to co-register MR and US images
[0169] Reformatting of MR image to correspond to US image
[0170] Correction of US image for speed of sound variations
[0171] Correction of image co-registration errors
[0172] Registration of common anatomical features used to calculate
co-registration accuracy
[0173] Delivery of a variety of needle gauge sizes as well as
various minimally invasive treatment devices.
[0174] Positioning of multiple marking coils into the breast to
define boundaries of lesions through a single incision.
[0175] According to the invention, the following functions are
provided with minimal reconfiguration of the apparatus:
[0176] High quality breast images in bilateral screening and
unilateral follow-up examinations using various MR coil
configurations can be used for both procedures, and comprising an
optimal breast compression strategy as well as optimizing access to
the breast by the MR technician;
[0177] MR-guided localization, including medial or lateral biopsy,
without prior knowledge of lesion location;
[0178] MR-guided multiple biopsy, including medial or lateral
biopsy, with or without angulated needle approach;
[0179] MR-guided marker placement for improved surgical excision,
under MR guidance, wherein a marker is positioned at the edges of
the lesion as defined by MRI. The procedure would be similar to the
MRI-guided biopsy procedure, however, a marker would be placed into
the breast rather removing a sample of tissue. This may be
conducted in conjunction with MR-guided biopsy, in conjunction with
MR-guided needle localization.
[0180] MR-guided positioning of devices other than biopsy needles,
including tissue investigation or ablation devices, such as
invasive ultrasound tissue ablation devices, RF-heating
applicators, cryoablative systems, miniature imaging coils, or
optical photodynamic systems. According to the invention,
monitoring of these devices may be done using the MR system to
measure heating or cooling patterns during therapy. In the case of
the optical systems, treatment region may be determined using other
techniques (i.e. T2-weighted contrast sequences). MR-US fusion
imaging, wherein real-time US data can be used to position a device
accurately into the lesion. This may be done using US exclusively
when the lesion is visible on the US image, or using a combination
of the MRI and US data fused using a variety of techniques. This
strategy involves detecting the lesion using MRI, then removing the
patient from the MR magnet room to perform US imaging. According to
the invention, US imaging could involve a number of procedures
[0181] US imaging--simple use of the US so as to identify the
lesion and determine its malignancy status. Identification of the
lesion in this manner could also act to provide lesion location and
US properties with which the lesion may be identified for
subsequent US-guided biopsy with the patient removed from the
biopsy apparatus. Knowledge of the US features of the lesion could
lead to easy identification of the lesion in a follow-up US
examination. In cases where the lesion is difficult to identify in
the US image, the option to view the lesion as a fusion image may
assist in visualization.
[0182] Hybrid biopsy--this technique involves the use of the
interventional US imaging membrane. This procedure requires
stereotactic positioning of the US transducer in conjunction with
free-hand delivery of the biopsy needle. This may be augmented by
the use of a fused MR/US data set, and with or without the use of
position-tracked US transducer and biopsy needle. Markers can be
superimposed onto the MR/US fused dataset in such a way that the
needle is easily identified on the MR/US fused image set, and in a
way that the presented MR/US image updates to reflect the position
of the US transducer.
[0183] Hybrid marker placement. Based on the procedure above,
except that a MR and US-visible marker is implanted in the breast.
This results in more accurate marker placement and reduces the
amount of time spend in the MR-magnet room.
[0184] Hybrid treatment. The hybrid device delivery technique may
also be used to deliver devices other than biopsy needles and
marker placement devices such as tissue investigation or ablation
devices. In this case it is advantageous to monitor the therapy
using US. This offers the ability to improve the accuracy of the
delivery and reduces the amount of time required for MR imaging.
Again, this can be used with either the combined MR/US images, or
using only the US images if the lesion can be confidently
identified on the US image. The use of the fused MR/US data is
beneficial when MRI provides better definition of tumor
boundaries.
[0185] According to the invention, numerous techniques and methods
can be used to enable the practice of the various embodiments of
the invention, as illustrated by the following specific
examples:
[0186] Stereotactic positioning of needle/US transducer based on MR
coordinates:
[0187] Specification to deliver needle in straight (e.g.
medial-lateral) orientation.
[0188] Specification of angulated needle delivery:
[0189] ability to select shortest needle paths, or desired needle
angle.
[0190] ability to eliminate occluded areas behind fenestrated
constraint plates
[0191] ability to identify guide needle position on MR images to
ensure that the chest wall will not be punctured during biopsy
acquisition
[0192] Specification of exact US transducer orientation and
position, with transducer mounted horizontally or vertically, under
various constraints (minimal distance, selected orientation,
etc.)
US transducer position tracking co-registered with breast frame of
reference:
[0193] Ability to determine transducer frame of reference relative
to breast frame of reference.
[0194] This enables the device plane to correspond with the MRI
coordinates.
[0195] Uses of tracking position of US imaging plane:
[0196] Calculating corresponding plane from 3D MR data set
(creating virtual US image composed of reformatted MR data) will
correspond to US image position and orientation.
[0197] distance to lesion through-plane will be determined and
shown relative to virtual US image.
[0198] position of lesion center on US image will be
identified.
[0199] MR data can be combined with the virtual US image to form a
fused MR/US image.
[0200] Segmentation of MR lesion from contrast-enhanced data will
be superimposed on the virtual US image to form a composite
image.
[0201] Other auditory, tactile and visual cues may be used to guide
free-hand US transducer movement, enabling the user to operate the
system with or without a view of the US image.
[0202] Means of displaying position information about an
interventional device:
[0203] a device's position may be tracked and an indication of its
position superimposed over an acquired image (i.e. tracking a
biopsy needle and superimposing an image of the device on the
co-registered MR, US, or fused MR/US images.
[0204] Integration of images and position tracking data to validate
US and MR image co-registration:
[0205] use of landmarks identified on US and MR images to confirm
that the MR image is aligned with the US image
[0206] use of image processing techniques and image acquisition
techniques to better identify common landmarks on both imaging
modalities. (i.e. breast parachymal patterns, vessels, cysts).
[0207] Method to quantify the similarity of two modalities. Means
of presenting the result to the operator.
[0208] Means of correcting the registration between the two
modalities:
[0209] Speed of sound correction.
[0210] Use the MRI data to determine composition of the breast, use
known speed of sound values for the appropriate tissues and correct
the US image.
[0211] Gradient warp shifts.
[0212] Correct for large errors due to gradient warp in the MR
imaging system.
[0213] Position or registration error due to patient motion.
[0214] Relies on operator identification of similar features on
both modalities. Once selected, the user may displace one image set
to match the other, or may use automated image processing
algorithms for this purpose.
[0215] As discussed herein, the benefits of the invention include,
but are not limited to: System that can be used for breast imaging
and multiple intervention functions.
[0216] Improved access to the entire breast volume for imaging and
intervention. Improved breast immobilization through full
compression of breast (including volume near chest wall).
[0217] Improved breast compression technique for operator ease of
use.
[0218] Improved probe delivery using MRI guidance:
[0219] More accurate probe delivery--angled delivery provided
greater access.
[0220] Multiple target sampling through a single incision
point.
[0221] Flexibility in the selection of biopsy approach (medial or
lateral) to minimize trauma to the breast
[0222] Real-time US guided probe delivery through hybrid
technique.
[0223] US guided sampling in the fringe field or even in another
procedure room.
[0224] Flexibility in the selection of biopsy approach (medial or
lateral) to minimize trauma to the breast and distance of breast
tissue traversed for US imaging.
[0225] Ability to obtain many tissue samples through one small skin
incision.
[0226] Ability to use standard interventional devices under US
guidance, not limited to equipment that is MR compatible, thus
reducing disposable equipment costs and permitting use of superior,
non-MR-compatible devices.
[0227] Separation of MR imaging and biopsy procedure into two
stages that can be performed in different locations using one
dedicated transport stretcher, thus freeing the MR facility and its
own dedicated patient transport stretcher for the next patient.
[0228] The foregoing description of the invention is not intended
to describe every object, feature, advantage, and implementation of
the present invention. While the description of the embodiments of
the invention is focused on applications for breast imaging, it
will be understood by those skilled in the art that the present
invention has utility to applications elsewhere in the body. The
primary differences would relate essentially to the geometry of the
frames, which would hold the needle entry plate and the US
plate.
[0229] All patents and printed publications referenced herein are
hereby incorporated by reference into the specification hereof,
each in its respective entirety.
* * * * *