U.S. patent application number 12/197939 was filed with the patent office on 2009-03-26 for computed tomography breast imaging and biopsy system.
This patent application is currently assigned to FISCHER MEDICAL TECHNOLOGIES, INC.. Invention is credited to David E. Gustafson, Morgan Nields, Ronald B. Shores, Michael Tesic.
Application Number | 20090080604 12/197939 |
Document ID | / |
Family ID | 40378719 |
Filed Date | 2009-03-26 |
United States Patent
Application |
20090080604 |
Kind Code |
A1 |
Shores; Ronald B. ; et
al. |
March 26, 2009 |
COMPUTED TOMOGRAPHY BREAST IMAGING AND BIOPSY SYSTEM
Abstract
A prone CT breast x-ray imaging system is described that can
image a full breast to create a conventional 2D digital image in
very high resolution (e.g. <=25 micron pixels). The system is
capable of imaging the entire breast in 3D based on multiple
projection views from a 1D or 2D detector. Data can be acquired and
reconstructed with a limited number of views from limited angles or
with conventional cone beam CT algorithms. The resulting 3D image
enables the detection and diagnosis of fine micro calcifications
and small masses as may be distributed throughout the breast, thus
allowing radiologists to make an improved determination of
malignancy as opposed to conventional 2D digital mammography. In
addition, the injection of intravenous contrast in conjunction with
or without pre and post contrast subtraction imaging provides a
radiologist with morphologic information on the existing tumor
burden in the breast. This capability may obviate the need for an
independent contrast MRI exam of the breast which is increasingly
performed for local staging and determination of tumor extent in a
patient with a known cancer. Integrated biopsy capability permits
convenient and rapid biopsy of any area suspicious for
malignancy.
Inventors: |
Shores; Ronald B.;
(Greenwood Village, CO) ; Nields; Morgan;
(Englewood, CO) ; Gustafson; David E.;
(Westminster, CO) ; Tesic; Michael; (Superior,
CO) |
Correspondence
Address: |
MARSH, FISCHMANN & BREYFOGLE LLP
8055 East Tufts Avenue, Suite 450
Denver
CO
80237
US
|
Assignee: |
FISCHER MEDICAL TECHNOLOGIES,
INC.
Broomfield
CO
|
Family ID: |
40378719 |
Appl. No.: |
12/197939 |
Filed: |
August 25, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60957620 |
Aug 23, 2007 |
|
|
|
61034336 |
Mar 6, 2008 |
|
|
|
Current U.S.
Class: |
378/37 |
Current CPC
Class: |
A61B 10/0233 20130101;
A61B 6/032 20130101; A61B 6/4452 20130101; A61B 6/482 20130101;
A61B 6/4021 20130101; A61B 6/4085 20130101; A61B 6/4078 20130101;
A61B 6/0435 20130101; A61B 6/466 20130101; A61B 6/502 20130101;
A61B 6/487 20130101; A61B 2090/364 20160201 |
Class at
Publication: |
378/37 |
International
Class: |
A61B 6/04 20060101
A61B006/04 |
Claims
1. A breast imaging apparatus, comprising: a locator for
positioning a patient's breast within a predetermined frame of
reference having a predetermined axis extending away from a
boundary plane of the predetermined frame of reference, wherein an
axis of a patient's breast that extends from a patient chest wall
through a patient's breast nipple is alignable with said
predetermined axis for imaging; an imaging beam source for
transmitting an imaging beam though said predetermined frame of
reference; an imaging signal detector for receiving said imaging
beam and providing an output signal in response thereto, wherein at
least one of said imaging beam source and said imaging signal
detector is movable relative to said predetermined frame of
reference, and wherein said apparatus is operable so that said
output signal comprises projection image data corresponding with a
predetermined angular range of projection views of a patient's
breast; and, a processor for computed tomography processing said
projection image data to provide a reconstructed image.
2. An apparatus as recited in claim 1, wherein said locator
comprises: a table for supporting a patient in a prone position,
wherein said table includes at least one aperture for receiving a
pendulant patient breast therethrough.
3. An apparatus as recited in claim 2, wherein said table is
selectively, vertically positionable.
4. An apparatus as recited in claim 1, wherein said locator
comprises: a holder for holding a patient's breast in a fixed
position within said predetermined frame of reference.
5. An apparatus as recited in claim 4, wherein said holder consists
of one of a cup-shaped member for receiving a patient's breast
therewithin or a pair of opposing plate members for compressively
engaging a patient's breast therebetween.
6. An apparatus as recited in claim 5, further comprising: a
display for utilizing said image signal to display one or more
images of a patient's breast located within said predetermined
frame of reference.
7. An apparatus as recited in claim 6, further comprising: one of a
biopsy device, a surgical device and a treatment device supportable
in known relation to said predetermined frame of reference, wherein
said display is located to be viewable by a user when operating
said one device.
8. An apparatus as recited in claim 1, further comprising: a
movable, first member for supporting said imaging beam source,
wherein said imaging beam source is selectively positionable across
a first predetermined angular range relative to said predetermined
axis of said predetermined frame of reference.
9. An apparatus as recited in claim 8, wherein said first support
member is pivotable about said predetermined axis of said
predetermined frame of reference, wherein said imaging beam source
is selectively, radially positionable across a first predetermined
angular range relative to said predetermined axis of said
predetermined frame of reference.
10. An apparatus as recited in claim 1, wherein said imaging beam
source and said imaging signal detector are each movable relative
to said predetermined frame of reference.
11. An apparatus as recited in claim 10, wherein said imaging beam
source and said imaging signal detector are each independently
movable relative to said predetermined frame of reference.
12. An apparatus as recited in claim 10, further comprising: a
movable, first support member for supporting said imaging beam
source, wherein said imaging beam source is selectively
positionable across a first predetermined angular range relative to
said predetermined axis of said predetermined frame of
reference.
13. An apparatus as recited in claim 12, further comprising: a
movable, second support member for supporting said imaging signal
detector.
14. An apparatus as recited in claim 13, wherein said first support
member and second support member are each independently pivotable
about said predetermined axis of said predetermined frame of
reference.
15. An apparatus as recited in claim 14, wherein said first support
member is pivotable about said predetermined axis of said
predetermined frame of reference, wherein said imaging beam source
is selectively, radially positionable across a first predetermined
angular range relative to said predetermined axis of said
predetermined frame of reference, and wherein said imaging signal
detector is selectively positionable across a second predetermined
angular range relative to said predetermined axis of said
predetermined frame of reference.
16. An apparatus as recited in claim 15, wherein said first
predetermined angular range and said second predetermined angular
range are each .ltoreq.270.degree..
17. An apparatus as recited in claim 13, wherein said imaging beam
source is moveable relative to said first support member.
18. An apparatus as recited in claim 17, wherein said imaging beam
source is rotatably positionable across a predetermined rotation
range relative to said first support member.
19. An apparatus as recited in claim 18, wherein said predetermined
rotation range is .ltoreq.180.degree..
20. An apparatus as recited in claim 18, wherein said first support
member is pivotable about said predetermined axis of said
predetermined frame of reference, and wherein said second support
member is pivotably interconnected to said first support member at
an adjoinment location offset from said predetermined axis of said
predetermined frame of reference.
21. An apparatus as recited in claim 20, wherein said second
support member is pivotable about and said imaging beam source is
rotatable about a first axis that extends through said adjoinment
location and that is parallel to said predetermined axis of said
predetermined frame of reference.
22. An apparatus as recited in claim 17, wherein said imaging beam
source and said imaging signal detector are disposed for
co-rotation about said first axis.
23. An apparatus as recited in claim 14, further comprising: at
least one automated drive, operatively interconnected to said
processor, for automated positioning of said first support member
and said second support member to provide a predetermined plurality
of projection views within said predetermined angular range.
24. An apparatus as recited in claim 1, wherein said imaging signal
detector comprises: an array of detector elements, wherein during
operation an active array of detector elements is scanned across a
region of interest within said predetermined frame of reference,
said active array having a length defined by at least one column of
aligned detector elements extending parallel to said predetermined
axis of said predetermined frame of reference and having a width
defined by at least one detector element extending in a direction
orthogonal to said length, wherein said width of the active array
is less than a width of a patient's breast located within said
predetermined frame of reference.
25. An apparatus as recited in claim 24, wherein said array of
detector elements is disposed for physical movement relative to
said predetermined frame of reference.
26. An apparatus as recited in claim 24, wherein said array of
detector elements comprises a plurality of columns of aligned
detector elements, and wherein different ones of said columns are
activated during operation to define said active array of detector
elements.
27. An apparatus as recited in claim 1, wherein said processing
includes iteratively generating an estimated image using said
projection image data and constraining variation of the estimated
image.
28. An apparatus as recited in claim 1, wherein said imaging beam
source is located so that a center ray of said imaging beam is one
of parallel and divergent relative to said boundary plane.
29. An apparatus as recited claim 28, wherein said imaging beam is
a divergent beam.
30. An apparatus as recited in claim 29, wherein said divergent
beam is one of a fan shape beam and a cone beam.
31. An apparatus as recited in claim 30, wherein said imaging beam
is transmittable through said predetermined frame of reference
substantially free from passage through said boundary plane.
32-44. (canceled)
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application Ser. No. 60/957,620, filed Aug. 23, 2007, entitled
"PRONE BREAST IMAGING AND BIOPSY SYSTEM", and U.S. Provisional
Application Ser. No. 61/034,336, filed Mar. 6, 2008, entitled
"TOMOGRAPHY BREAST IMAGING AND BIOPSY SYSTEM, the entirety of each
of which is hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to medical imaging and biopsy
systems and methods, and in particular, to improved systems and
methods that may be particularly apt for prone breast imaging and
biopsy, including imaging with divergent beams (e.g. fan beams and
cone beams), computed tomography (CT) processing and/or slot scan
image signal detectors.
BACKGROUND
[0003] Existing prone breast biopsy systems such as described in
U.S. Pat. No. 5,078,142 to Siczek et al. and U.S. Pat. No.
5,289,520 to Pellegrino et al. allow stereotactic needle biopsy of
a breast, but with a limited field of view, e.g. typically a field
of view of only 5 cm.times.5 cm. In cases where poorly visualized
microcalcifications are detected on a screening mammogram, or as a
result of diagnostic mammography, it is difficult to position that
portion of the breast in the small field of view provided by the
prone biopsy system, given the subtle nature of the
microcalcifications and the lack of well defined landmarks in the
breast. In addition, microcalcifications frequently involve one or
more quadrants of the breast and sampling tissue from several areas
is challenging for the radiologist and extends procedure time as
the breast needs to be constantly repositioned and recompressed for
additional imaging and biopsy.
[0004] Mammography and ultrasound are commonly employed to
determine the extent of cancer present in a patient's breast once a
known tumor has been diagnosed by ultrasound or stereotactic x-ray
needle biopsy. However the sensitivity of mammography and
ultrasound together falls short of the sensitivity provided by
magnetic resonance imaging (MRI) with contrast.
[0005] Contrast MRI is extremely sensitive to the presence of
breast cancer (>95% sensitivity), although MRI specificity is
reported significantly lower at 30% to 60%. MRI imaging exams of
one or both breasts are increasingly requested by radiologists and
surgeons for patients with a known breast cancer, in order to
determine the extent of disease. Should multifocality be detected
(i.e. cancer present in more than one area of the breast) or if
cancer is detected in the contralateral breast, surgical treatment
may be more extensive, up to and including bilateral mastectomy. On
the other hand, should no additional disease be detected by the MRI
exam, a minimal surgical procedure such as a lumpectomy may be the
preferred form of treatment. In addition to determining local
extent of breast cancer ("local staging") MRI breast imaging can
also be employed to search for small cancers in asymptomatic women
where cancer may be expected to develop.
[0006] In relation to the foregoing, several multi-institutional
studies have now shown that MRI is an effective method of screening
women who are at risk for breast cancer. See, e.g. Lehman CD et
al., "Cancer Yield of Mammography, MR and U.S. in High-Risk Women:
Prospective Multi-Institution Breast Cancer Screening Study",
Radiology, (August 2007); Kreige M. et al., "Efficacy of MRI and
Mammography for Breast-Cancer Screening in Women with a Familiar or
Genetic Predisposition". New England Journal of Medicine, (Jul. 29,
2004); and Leach M et al., "MRI Surveillance for Hereditary Breast
Cancer Risk", The Lancet, Volume 365 at 1769-1778 (2005). The
American Cancer Society has recently adopted guidelines for annual
MRI breast screening for women who have a lifetime risk of 20-25%.
See, e.g. Saslow D. et al., "American Cancer Society Guidelines for
Breast Screening with MRI as an Adjunction to Mammography", CAA
Cancer Journal for Clinicians, Volume 57 at 75-89 (2007). As many
as 1.2 million women could be considered at high risk for breast
cancer based on the guidelines, suggesting a need for significant
MRI capacity for annual breast cancer screening.
[0007] In addition to screening for breast cancer with MRI, and as
noted above, a role has emerged for MRI imaging of the
contralateral breast when a breast cancer is diagnosed. Several
studies have shown an incidence ranging from 3 to 18%. See, e.g.
Lehman, "MRI Evaluation of the Contralateral Breast in Women with
Recently Diagnosed Breast Cancer", New England Journal of Medicine,
Volume 356 at 1295-1303 (2007); Pediconi F., "Contrast-Enhanced MR
Mammography for Evaluation of the Contralateral Breast in Patients
with Diagnosed Unilateral Breast Cancer or High-Risk Lesions",
Radiology, Volume 243: Number 3 (June 2007). About 250,000 breast
cancers are found annually in the US (invasive and DCIS) suggesting
that a cost effective procedure to rule out cancer in the
contralateral breast will likely become a standard of care.
[0008] A significant limitation with MRI imaging of the breast is
the difficulty of acquiring tissue using needle biopsy techniques.
In this regard, an MRI guided breast biopsy is more difficult and
time consuming than an ultrasound or stereotactic x-ray guided
needle biopsy due to instrument requirements, and limited breast
access.
[0009] That is, in MRI procedures the patient is normally
positioned in the bore of a magnetic resonance MR scanner in a
strong magnetic field that requires special non-metallic biopsy
instruments capable of functioning within a strong magnetic field.
In addition, since MRI patients are imaged in a prone position with
the breast hanging pendulant within a breast coil, access to the
medial portion of the breast is difficult as is access to tissue
near the chest wall since most needle biopsy solutions for MRI
systems provide only a lateral approach with a Cartesian grid
location system, which by design necessarily inhibits needle access
to tissue adjacent to the chest wall.
[0010] In addition to the foregoing, since the specificity of MRI
in breast imaging is not as high as the sensitivity, it is
difficult for many radiologists to confidently interpret an
enhancing lesion of the breast with MRI without the performance of
a difficult and time consuming needle biopsy procedure. As such,
some physicians prefer not to order an MRI exam unless biopsy of
all enhancing areas can be undertaken in order to provide the
patient assurance that these areas of enhancement were indeed
benign. In turn, MRI enhancement in a patient known to have breast
cancer can create more uncertainty than if the exam had not been
performed.
[0011] Finally, MRI imaging is also expensive compared to
ultrasound or mammography and the procedure is not normally
available in a breast center for near immediate scheduling such as
other breast imaging procedures. For the noted reasons,
alternatives to MRI breast imaging are of high interest.
[0012] Some imaging centers have experimented with contrast
injection in conjunction with conventional multi detector CT (MDCT)
imaging. The published results appear to be very similar to MRI
imaging of the breast with contrast. See, e.g. Inoue et al.,
"Dynamic Multidetector CT of Breast Tumors: Diagnostic Features and
Comparison with Conventional Techniques", American Journal of
Roentgenology, (September 2003); Tozaki et al., "Diagnosis of
Tis/T1 Breast Cancer Extent by Multislice Helical CT: A Novel
Classification of Tumor Distribution", Radiation Medicine, Volume
21: No. 5, at 187-192, (2003). However, conventional CT breast
imaging techniques subject patients to radiation levels that are
higher than desired due to the classical design of the axial CT
scanner which necessarily images the entire thorax (i.e. lungs and
heart) in order to include the breasts in the imaging field. In
addition, state of the art conventional multidetector CT scanners
(MDCT) are limited to providing spatial resolution of about 1
lp/mm. Further, this resolution may be achieved only with high
resolution kernels (e.g., bone kernel) at the expense of increased
image noise.
[0013] The ability to diagnose breast cancer based on morphologic
imaging depends both on the uptake of contrast material into the
cancerous tissue as well as the spatial frequency of the image,
since breast cancer is frequently indicated by thin straight lines
(i.e. spiculation) emanating from a lesion. Benign masses such as
fibroadenomas are normally characterized by smooth oval shapes
which may also take up contrast. MRI imaging of the breast allows a
3D review of the entire breast with capabilities such as MIP
(maximum intensity projection) and with MR pulse sequences which
suppress signals from fat (fat suppression imaging) to improve the
conspicuity of the contrast in the tumor and parenchymal
tissue.
[0014] Prototype prone breast x-ray imaging systems that use cone
beam CT in conjunction with commercially available flat panel
digital detectors have been described. See, e.g. U.S. Pat. No.
6,987,831 B2 to Ning; and John Boone et al., "Computed Tomography
for Imaging the Breast", Journal Mammary Gland Biol Neoplasia,
11(2) at 103-111, (April, 2006). These systems acquire a series of
cone beam views as the flat panel and x-ray source rotate around
the breast and the images are reconstructed into 3D images using
cone beam CT algorithms. The flat panels provide an intrinsic pixed
size of about 100-200 microns or spatial resolution of 2.5-5 lp/mm.
X-ray scatter provides design challenges as each view is
essentially a digital mammogram of the entire uncompressed breast
and using conventional static or moving grids to reduce scatter
increases image processing complexities. In addition, the
kilovoltage as described for these systems ranges up to 80 kVp
which will produce images of lower contrast than conventional
digital mammography systems which typically use kilovoltage in the
range of 30-40 kVp.
SUMMARY
[0015] In one aspect of the present invention, a breast imaging
apparatus is provided that includes a locator for positioning a
patient's breast within a predetermined frame of reference having a
predetermined axis extending away from a boundary plane of the
predetermined frame of reference, wherein an axis of a patient's
breast that extends from a patient's chest wall through a patient's
breast nipple may be aligned with the predetermined axis for
imaging. In this regard, the apparatus may further include an
imaging source beam (e.g. an x-ray beam source) for transmitting an
imaging beam through the predetermined frame of reference, and an
imaging beam detector for receiving the imaging beam and providing
an output signal in response thereto.
[0016] One or both of the imaging beam source and imaging detector
may be moveable relative to the predetermined frame of reference,
wherein the apparatus is operable to provide an output signal that
comprises projection image data corresponding with a predetermined
angular range of different projection views of a patient's breast.
In turn, the apparatus may include a processor for processing the
projection image data to provide a reconstructed image. For
example, in one approach computed tomography processing may be
employed to yield one or more reconstructed three-dimensional
image(s). In this regard, computed tomography may preferably refer
to image reconstruction approaches (e.g. software algorithms) that
process image data corresponding with a predetermined number of
projection views (e.g. at least 10 projections) obtained across a
predetermined angular range (e.g. more than 50.degree.) relative to
a patient breast axis. The reconstructed image(s) may be
advantageously displayed on a user display.
[0017] In another aspect, image data corresponding with a given
view of a patient's breast may be utilized (e.g. by a processor) to
generate quasi real-time images, e.g. fluoroscopic images, wherein
the quasi real-time images may be displayed on a quasi real-time
basis, thereby facilitating biopsy, surgical and/or treatment
procedures. In this regard, stereotactic imaging or computed
tomography imaging may be employed in a first mode of operation
that yields one or more images for review by medical personnel.
Then, in a second mode of operation fluoroscopic imaging may be
employed to generate quasi real-time images that may be displayed
and reviewed by medical personnel in conjunction with the
positioning of biopsy, surgical and/or treatment devices.
[0018] By way of primary example, the locator for positioning the
patient's breast may include a table for supporting the patient in
a prone position, wherein the table includes at least one aperture
for receiving a patient's pendulant breast therethrough, wherein
the breast extends into a predetermined frame of reference for
imaging that is defined below the table. Relatedly, the table may
be provided for selective, vertical positioning, thereby providing
enhanced access to and positioning of a patient's breast within the
imaging predetermined frame of reference.
[0019] In some applications, a breast positioning device may be
provided. For example, in one approach, a cup-shaped member may be
supportably interconnected to the apparatus and selectively
positionable to maintain a patient's breast in a given position,
(e.g. in a position in which the breast axis is aligned with the
predetermined axis of the predetermined frame of reference) below a
patient support table. In this regard, the cup-shaped member may be
sized to maintain the position of a breast, while avoiding the
application of compressive forces thereto. In certain embodiments
the cup-shaped member may comprise one or more aperture(s) or
cut-out portion(s) to facilitate the passage of biopsy, surgical
and/or treatment devices therethrough. In other embodiments,
opposing compression plates may be provided for breast
positioning.
[0020] A unique feature of embodiments of the present invention is
to allow the imaging and biopsy of very small, difficult to
visualize microcalcifications. In one approach, a slot scan imaging
detector with imaging capability of 25 microns or smaller may be
positioned behind the area of interest (e.g. a region of a
patient's breast located within a predetermined frame of reference)
and may scan in order to produce a high resolution image of the
calcifications. High spatial resolution of microcalcifications may
provide further diagnostic information to the radiologist regarding
the potential for malignancy.
[0021] Should the radiologist determine that tissue biopsy,
surgical removal and/or treatment is required the slot scan
detector may scan in a reciprocating fashion to provide a quasi
real time (<30 fps) fluoroscopic image of the calcifications
enabling tissue biopsy under image guidance. For example, as a
biopsy needle is positioned into an area to be biopsied the
fluoroscopic image may provide an ability to dynamically direct the
needle into the area of interest and to confirm the position of the
needle relative to the calcifications to be biopsied. Images
acquired at a higher dose, e.g. similar to a "snapshot" image can
be taken and archived so that there is a medical record of exactly
where the biopsy needle was positioned. In addition, the slot scan
detector provides increased primary to scatter x-ray ratio yielding
improved contrast resolution to allow better delineation of the
extent of disease for mass lesions.
[0022] In certain embodiments, the imaging beam source and imaging
detector may be positioned and the processor may be configured to
create a stereotactic pair of images or a CT image of the breast,
wherein one or more two-dimensional and/or three-dimensional breast
image(s) may be reconstructed or generated from multiple projection
views. Stereo imaging can be performed with or without compression.
In turn, the imaging beam source and imaging detector may be
positioned and the processor may be further configured for
fluoroscopic imaging, thereby facilitating the real-time display of
images that show the progressive positioning of biopsy, surgical
and/or treatment devices. Further, a needle biopsy assembly may be
employed that has software that is able to calculate the
appropriate trajectory for a needle to be positioned in the area of
interest in order to carry out a needle biopsy procedure as is
currently practiced in needle biopsy of the breast. By way of
example, biopsy-related technology may be employed as described in
U.S. Pat. No. 5,735,264 issued to Siczek et al., and U.S. Pat. No.
6,022,325 issued to Siczek et al., the entirety of each of which is
hereby incorporated by reference.
[0023] The utilization of a slot scan detector in various
embodiments may reduce x-ray scatter, improve the operative signal
to noise ratio, reduce x-ray dosage, and in an embodiment, may
produce a line of image data approximately every 200-300
microseconds using time delay and integration, as described in U.S.
Pat. No. 5,526,394 to Siczek et al., the entirety of which is
hereby incorporated by reference.
[0024] As employed herein a "slot scan imaging detector" refers to
a detector having an array of detector elements, wherein during
imaging operations an active array of the elements (e.g. elements
from which accumulated charge is shifted to yield an output signal
comprising image data) may be scanned across a region of interest
of a patient's breast in a direction substantially parallel to the
patient's chest wall. In this regard, a length of the active array
may be oriented substantially orthogonal to a patient's chest wall
(e.g. parallel to a center axis of a predetermined frame of
reference for imaging the patient's breast), and a width of the
active array may be less than a width of the imaged region of
interest (e.g. a width of a patient's breast).
[0025] In one implementation, a slot scan imaging detector may be
provided to define an active array comprising a plurality of
detector elements aligned in a single column. In another
implementation, an imaging detector may be provided to define an
active array comprising a plurality of detector elements arranged
in a plurality of parallel columns and corresponding rows, wherein
accumulated charge resulting from the receipt of an imaging beam
may be shifted along a row of detector elements (e.g. from column
to column) to operate in a time delay and integration mode.
[0026] In one approach, an active array of detector elements may be
mechanically scanned (e.g. physically moved) in relation to a
patient's breast within a predetermined frame of reference during
slot scanning operations. In another approach, a detector array may
be utilized that is of a size sufficient to remain stationary (e.g.
the array may be of a length and width that is greater then the
length and width of a patient's breast to imaged), wherein a
dynamically changing, active array of such detector elements may be
electrically scanned during slot scan operations by successively
shifting out charge from a different element column or different
adjacent sets of detector element columns across the detector array
during each successive time interval. In each of the noted
approaches, an imaging signal may be scanned across a patient's
breast in timed relation to detector scanning operations. For
example, in one embodiment a narrow beam, e.g. a fan beam, may be
scanned across a patient's breast in synchronous relation to active
detector array scanning, wherein the beam and active array are
maintained in aligned relation during imaging.
[0027] In various embodiments of the present invention, the imaging
beam source or multiple imaging beam sources and/or the imaging
signal detector may be separately positionable relative to the
predetermined framed of reference. In this regard, in certain
implementations, an imaging beam source and/or imaging signal
detector may be independently positionable to yield a plurality of
different projection views.
[0028] More particularly, in some embodiments a moveable first
member may be provided to support the imaging beam source, wherein
an imaging beam source is selectively positionable across a first
predetermined angular range relative to the predetermined axis of
the predetermined frame of reference. For example, the first
support member may be pivotable about the predetermined axis of the
predetermined frame of reference, wherein the imaging beam source
may be selectively, radially positioned across the first
predetermined angular range.
[0029] Similarly, a moveable, second support member may be provided
for supporting the imaging signal detector. In one approach, the
second support member may be pivotable about the predetermined axis
of the predetermined frame of reference, wherein the imaging signal
detector may be selectively, radially positioned across a second
predetermined angular range relative to the predetermined axis.
[0030] As may be appreciated, the separate moveability of the
imaging beam source and imaging signal detector yields an
arrangement in which multiple projection views may be readily
obtained in a wide variety of approaches. Further, such an
arrangement facilitates access to a patient's breast by medical
personnel. For example, in certain implementations, 360.degree.
access to a patient's breast may be realized. Such access may be of
particular advantage in relation to breast biopsy, surgical and/or
treatment procedures carried out during and with the visual
assistance of CT image generation.
[0031] Additional image reconstruction capability may be enhanced
by the use of new algorithms where a limited number of views, and
limited angles, can be utilized to reconstruct image data thus
delivering a reduced dose of x-ray to the patient. By way of
example, image reconstruction may employ approaches disclosed in
PCT Publication No. WO2007/095312, published Aug. 23, 2007,
corresponding with PCT Application No. PCT/US2007/003956 entitled
"IMAGE RECONSTRUCTION FROM LIMITED OR INCOMPLETE DATA", the
entirety of which is hereby incorporated by reference.
[0032] Embodiments of dedicated prone breast CT imaging systems may
image a complete breast with an absorbed radiation level similar to
that of bi-lateral mammography. In an embodiment, a dedicated cone
beam, slot scanning imaging system with a high-resolution detector
may provide a spatial resolution of about 10-15 lp/mm. Embodiments
of systems described herein may include the use of contrast media,
wherein a 3D reconstruction using cone beam CT as described herein
may allow similar review capabilities, as compared to MRI, when the
precontrast image (may be) registered and subtracted from the post
contrast image. Additionally, as described in Seo et al., Journal
of Clinical Imaging 29: at 172-178 (2005), the increase in
Hounsfield Unit (HU) density of the area of contrast uptake may
allow visualization of tumor enhancement without subtraction even
at low dose. Such a reconstruction may have significantly higher
spatial resolution than an MRI image or conventional Multi-Detector
Computed Tomography (MDCT) image. Voxel linear dimensions on the
order of 0.8 mm to 1.00 mm are available with MRI or MDCT systems
while a dedicated cone beam CT system as described herein will
permit voxel sizes on the order of 100 microns or smaller for small
areas of interest where higher resolution may be required. For
example, a detector pixel size of 25 microns may allow a 3-D image
to be reconstructed at a voxel linear dimension smaller than 25
microns depending on the geometry of the imaging system.
[0033] Embodiments of systems described herein may be similar in
layout to the stereotactic biopsy tables of prior art products.
Embodiments of systems described herein may provide an imaging
detector that may extend from the anterior portion of the breast to
the chest wall and an x-ray field that may be collimated to the
length and width of a 1D or 2D detector. This system may be capable
of creating a 3D cross sectional x-ray image of the breast while
avoiding ionizing radiation to the lungs and heart. This type of
dedicated breast CT imaging system may be able to demonstrate the
extent of cancer in the breast following the intravenous injection
of non-ionic contrast similar to the MRI breast imaging exam. The
lower cost of this type of imaging system compared to the cost of
an MRI imaging system and per procedure cost may provide improved
access to patients for an important exam that could help the
patient and surgeon determine an optimal course of surgical
treatment. The lower cost may also allow screening of women at high
risk for breast cancer in place of the more expensive MRI exam. The
breast CT imaging system described herein is capable of producing a
CT image of the breast at a radiation dose level equal to or less
than two-view mammography while the non-ionic contrast used in the
CT imaging procedure has an improved safety profile over gadolinium
agents used with MRI exams. In addition, a cone beam CT imaging
system described herein may be compatible with known biopsy or
ablation systems that may be used for biopsy or treatment of
identified tissue targets. In contrast, it has been difficult to
develop biopsy or ablation technologies (RF, microwave, High
Intensity Focused Ultrasound (HIFU), etc.) that are compatible with
MRI systems due to the presence of strong magnetic fields and RF
and gradient coil subsystems.
[0034] An added benefit of a cone beam CT imaging system as
provided herein results from recent advances in deformable
registration techniques which allow the fusion of two 3-D medical
images from different modalities, such as Position Emission
Tomography (PET)/CT. It is apparent this system offers the ability
to fuse 3-D data sets from contrast MRI exams with a cone beam CT
breast imaging system that provides anatomic landmarks as well as
integrated biopsy capability. In this way, an accurate method of
biopsy may be carried out in a breast center while the MRI
examination may have been conducted at a different location.
Following registration of the 3-D data sets which may be executed
by the processors of the cone beam CT imaging system, a biopsy
device may target the MRI enhancement that has been registered and
fused with the 3-D CT data set. This task is made easier as both
imaging systems image the patient in the prone position without
compression and accurate registration of the images may be carried
out potentially without the use of fiducial markers either on the
skin or in the breast tissue.
[0035] Following breast conserving surgical treatment (e.g.
lumpectomy) of a diagnosed breast cancer, adjuvant radiation is
generally used to lower the risk of local cancer recurrence.
Accelerated Partial Breast Irradiation (APBI) has recently been
gaining favor as it can be delivered in fractions in a week or less
compared to conventional radiation therapy which requires 6 weeks
of fractionated radiation. In these types of procedures,
brachytherapy or electronic brachytherapy is delivered through a
balloon catheter that is generally placed in the lumpectomy cavity
by the breast surgeon. A cone beam CT imaging system as described
herein may provide an accurate 3-D image of the pendulant breast to
be treated. This allows for precise measurements of the cavity and
the location of the cavity in relation to the skin, areola complex
and chest wall of the patient as well as the conformance of the
balloon to the lumpectomy cavity.
[0036] Radiation treatment planning is currently performed
following imaging by conventional MDCT which again subjects the
patient to radiation of the heart and lungs. A breast cone beam CT
system as described herein may offer the capability of actually
using the breast CT system to perform the brachytherapy treatments
and on-board imaging may be used to verify the precise location of
the balloon in the breast since the formation of a seroma in the
lumpectomy cavity may alter the radiation actually delivered to the
wall of the lumpectomy cavity.
[0037] There has also been interest in delivering an accelerated
intensity modulated dose of radiation to the breast using a
conventional linear accelerator with the patient in the prone
position. See, e.g., Fromenti SG, "Phase I-II Trial of Prone
Accelerated Intensity Modulated Radiation Therapy to the Breast to
Optimally Spare Normal Tissue", Journal of Clinical Oncology,
Volume 25(16) at 2236-42, (Jun. 1, 2007). In this type of treatment
the patient is treated in a prone position with the breast
pendulant. Within the limits of the current design of linear
accelerator systems, this type of patient positioning will reduce
the amount of radiation to the heart and lung thus providing a
potential to reduce cardiac toxicity and fibrosis in the lungs. It
is expected that prone breast radiation treatment systems will be
developed to totally avoid treating non-target areas such as the
thorax. In these types of systems a 3-D conformal treatment plan
will provide an opportunity to accurately simulate the breast in
the prone treatment position and will be enabled by the breast CT
system described herein.
[0038] A prone breast imaging system as described herein may also
provide for image guided surgery of breast cancer. Image guided
surgery is routinely used in brain and spinal surgery. These
systems provide a 3-D pre-operative CT or MRI data set that is used
to guide surgery where the surgical instruments are encoded with
various types of sensors which enable the surgeon to visualize the
location of the instrument within the framework of the virtual 3-D
data set, even though the instrument is not visible under the
surgical microscope. There would be substantial benefits to use
such an approach to breast surgery but to date all breast surgery
is performed with the patient in the supine position, while breast
MRI is performed in the prone position. Given soft tissue
deformation and the lack of a method to confine the breast in a
stable position, image guided surgery of the breast has been
limited to the use of ultrasound in the operating room as part of
the lumpectomy procedure to aid the surgeon in insuring the
cancerous mass is removed. The surgeon does not have correlated or
registered image data showing the extent of disease as determined
by pre-operative contrast MRI or CT exams.
[0039] The prone breast imaging system described herein offers the
opportunity to change the paradigm of breast lumpectomy procedures
by enabling a method where the surgeon may operate on the patient's
breast in the prone position while using the imaging system in
surgery as the operating platform. In this type of configuration
the 3-D cone beam CT data provides a 3-D operative field for the
surgeon to appreciate the extent of the cancer. Any one of several
surgical or ablative methods may be used to remove the cancerous
tissue while the ability to conduct intraoperative CT examinations
offer the surgeon a new method of determining surgical margins.
These types of surgical instruments may be operated within the
framework of the guidance device for accurate targeting within the
breast so that specific lumpectomy instruments may be used to
remove the tissue. Alternatively, surgical instruments may be
located in 3-D space as is commonly the case in neurosurgical
procedures, or current resection devices or electrocautery surgical
instruments as used for lumpectomy may be used as they are normally
used for the removal and cauterization of breast tissue. The major
benefit of such a system is the potential to improve the surgical
margins that currently create a major drawback to lumpectomy
techniques. Poor surgical margins result in a reoperation range
currently from about 10-40%. Improving margin control while
achieving good cosmesis is the objective of the surgeon. Gross
disease is frequently left in the breast and many times not known
since the pathologist only samples the tissue and does not review
margins at all contiguous points on the resected tumor.
[0040] The system described herein may also allow for the insertion
of a brachytherapy balloon at the end of the lumpectomy with
immediate delivery of one fraction of radiation to the lumpectomy
cavity, particularly in the case of electronic brachytherapy.
Research has suggested that one dose of brachytherapy radiation
could deliver sufficient dose intraoperatively to the lumpectomy
site so that the patient does not need to return for further
adjunctive radiation treatment.
[0041] In another aspect, a method for computed tomography breast
imaging is provided and includes locating a patient's breast within
a predetermined frame of reference having a predetermined axis
extending away from a boundary plane of the predetermined frame of
axis, wherein an axis of the patient's breast extending from the
chest wall of the patient to a nipple of the patient's breast is
aligned with the predetermined axis (e.g. positioned parallel to or
coaxial with the predetermined axis) for imaging. In turn, the
method provides for the transmission of an imaging beam from an
imaging beam source through the patient's breast, and reception of
at least a portion of the imaging beam transmitted through the
patient's breast at an imaging signal detector to yield an output
signal.
[0042] In conjunction with such method, one or both of the imaging
beam source an imaging signal detector may be moved relative to the
predetermined frame of reference, wherein the output signal
comprises projection image data corresponding with a predetermined
angular range of projection views of the patient's breast. In turn,
computed tomography (CT) processing of the projection image data
may provide at least one reconstructed image.
[0043] In some embodiments the imaging signal detector may comprise
a slot scan detector that includes an array of detector elements,
wherein the receiving step may include scanning an active array of
the array of detector elements across the patient's breast. In this
regard, the active array may have a length defined by at least one
column of line detector elements extending parallel to the
predetermined axis of the predetermined frame of reference, and
having a width defined by at least one detector element extending
in a direction orthogonal to the length, wherein the width of the
active array is less than a width of a patient breast located
within the predetermined frame of reference.
[0044] In one approach, an array of detector elements may be
moveable relative to the predetermined frame of reference. In turn,
the scanning step may comprise moving the array of detector
elements relative to the predetermined frame of reference. For
example, such scanning may be carried out in timed relation to
movement of the imaging beam across a patient's breast.
[0045] Alternatively and/or additionally, the array of detector
elements may comprise a plurality of columns of aligned detector
elements. In turn, the scanning step may comprise activating
different ones of the columns to dynamically define the active
array of detector elements.
[0046] In a further aspect, the locating step may comprise
supporting a patient in a prone position on a table, wherein a
patient breast is pendulantly received through an aperture of the
table to extend into the predetermined frame of reference. In such
arrangement, the imaging predetermined frame of reference is
located below the patient support table.
[0047] In an additional aspect, the transmitting step of the
described method may be completed free from passage of the imaging
beam through the boundary plane of a predetermined frame of
reference, thereby limiting patient exposure to the imaging beam.
In this regard, the imaging beam may be transmitted so as to extend
parallel to or otherwise diverge away from the boundary plane.
Alternatively and or additionally, a radio opaque barrier may be
positioned to preclude the passage of the imaging beam across the
boundary plane. By way of example, where a patent support table is
employed, a radio opaque material may comprise the table.
[0048] In a further aspect, the imaging beam employed in the noted
method may comprise a divergent beam, wherein the transmitting step
comprises moving the divergent beam across the patient's breast in
a direction substantially parallel to a chest wall from the
patient. By way of example, the divergent beam may comprise a cone
beam or a fan-shaped beam. In the later regard, the fan-shaped beam
may be provided by blocking portions of a cone-beam generated by an
x-ray source.
[0049] In certain embodiments, the imaging beam source may be
supported by a first support member and the imaging signal detector
may be supported by a second support member. In turn, the moving
step may comprise pivoting one and/or both of the first support
member and the second support member about the predetermined axis
of the predetermined frame of reference.
[0050] In an additional aspect, the noted method may further
comprise introducing an image contrast media into the patient (e.g.
iodixanal). For example, the contrast media may be introduced via a
vascular catheter.
[0051] Relatedly, the processing step may include processing a
first portion of the projection image data obtained prior to the
introducing step, and processing a second portion of the projection
image data obtained after the introducing step, wherein
corresponding first and second reconstructed images may be
obtained. In turn, the first and second reconstructed images may be
utilized (e.g. in an image subtraction sub-step) to generate a
contrast-enhanced image. The method may further provide for the
display of one or more reconstructed images, or a contrast-enhanced
image, on a display.
[0052] In yet another aspect, an inventive method may comprise the
locating, transmitting, receiving and moving steps noted above,
wherein the output signal comprises image data corresponding with
at least two views of the patient's breast. In turn, either or both
computed tomography processing or stereotactic image generation can
be utilized to provide an image (e.g. a two-dimensional image or
three-dimensional image). In turn, the method may further include
utilizing image data corresponding with a given projection view of
the patient's breast to generate fluoroscopic images in quasi
real-time. In one approach, the method may further include
displaying the quasi real-time fluoroscopic images on a display
located adjacent to the predetermined imaging frame of reference.
In this regard, such display may be viewed by medical personnel in
conjunction with procedures carried out on a patient's breast on a
quasi real-time viewing basis. By way of primary example, the
display may be viewed by medical personnel carrying out a biopsy
procedure (e.g. utilizing a biopsy needle instrument), a surgical
procedure (e.g. lumpectomy), and/or a treatment procedure (e.g.
brachytherapy).
[0053] Additional aspects and advantages of the present invention
will become apparent to one skilled in the art upon consideration
of the further description that follows. It should be understood
that the detailed description and specific examples are intended
for purposes of illustration only and are not intended to limit the
scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] For a more complete understanding of the present invention
and further advantages thereof, reference is now made to the
following Detailed Description of the Invention taken in
conjunction with the accompanying drawings, wherein:
[0055] FIG. 1 is a side view illustration of an embodiment of a
prone breast imaging and biopsy system and a patient.
[0056] FIG. 2 is a top view schematic diagram of the prone breast
imaging and biopsy system of FIG. 1.
[0057] FIG. 3 is a side view illustration of another embodiment of
a prone breast imaging system.
[0058] FIG. 4 is a top view illustration of the embodiment of FIG.
3.
[0059] FIG. 5 is a top view illustration of yet another embodiment
of a prone breast imaging and biopsy system.
[0060] FIG. 6 is a top view illustration of yet another embodiment
of a prone breast imaging and biopsy system.
[0061] FIG. 7A is a side view illustration of another embodiment of
a prone breast imaging system.
[0062] FIG. 7B is an end view of the embodiment of FIG. 7A, with
the imaging source and imaging detector of FIG. 7A each rotated
90.degree. from the positions shown in FIG. 7A.
[0063] FIG. 7C is another side view illustration of the embodiment
of FIG. 7A, with opposing compression plates and a biopsy device
interconnected for use.
[0064] FIG. 8 is a schematic diagram of an exemplary imaging
system.
[0065] FIG. 9 is a flow diagram of one embodiment of an image
reconstruction methodology employable in conjunction with the
systems described in FIGS. 1-6.
DETAILED DESCRIPTION OF THE INVENTION
[0066] In the following description, the invention is set forth in
the context of prone breast imaging and biopsy systems and methods.
Certain aspects of the invention may also be employed in upright
breast imaging and biopsy systems and methods.
[0067] FIG. 1 is an illustration of an embodiment of a prone breast
imaging and biopsy system 100 and a patient 101. The prone breast
imaging and biopsy system 100 includes a detector assembly 102
(e.g., a slot scan detector assembly). The detector assembly 102
may, for example, have an imaging capability of 25 microns. The
detector assembly 102 may be positioned behind the area of interest
103 within a breast 108 and may scan rapidly (e.g., from left to
right) in order to provide a quasi real time fluoroscopic image of
the breast or a region of interest of the breast. The prone CT
breast imaging and biopsy system 100 may also include a needle
biopsy assembly 104. As a needle 105 is positioned into the area to
be biopsied, a fluoroscopic image may provide the ability to direct
the needle 105 into the area of interest 103 (e.g. along a path
and/or to a desired depth or position), and to confirm the position
of the needle 105 relative to the suspicious lesion to be
biopsied.
[0068] The imaging detector 102 may be positioned to create a
stereotactic pair of images of the breast 108 or a CT image of the
breast 108 reconstructed from a series of projection views. The
needle biopsy assembly 104 may have software that is able to
calculate the appropriate trajectory for the needle 105 to be
positioned in the area of interest 103 in order to carry out a
needle biopsy procedure.
[0069] The present invention allows a woman (e.g., patient 101) in
a prone position to undergo a high-resolution digital x-ray imaging
exam (e.g., 25 micron pixels allows spatial resolution as high as
20 lp/mm) of the entire breast 108. In addition, any part of the
breast 108 that may require needle biopsy due to the detected
presence of a suspicious lesion may be accessed by an orbital
biopsy system, wherein the lesion to be biopsied is positioned at
the isocenter of the system such that any entry point on the
surface of the breast 108 is available and will ensure that the
lesion is sampled when the device tip is advanced into the
isocenter of the system which supports the biopsy instrument (e.g.,
needle 105).
[0070] The prone breast imaging and biopsy system 100 may comprise
a table 109 with one or two holes for both breasts or one breast
and a patient's arm. The breast 108 is pendulant and may be
restrained by a compression device (not shown) that facilitates
needle biopsy and/or digital mammography. Alternatively, if a 3D
image of the breast 108 is desired, the breast 108 may be fixed in
a radiolucent holder (not shown) in order to prevent motion during
image acquisition as well as to enable biopsy of the breast in a
constrained position.
[0071] FIG. 2 is schematic diagram of the prone breast imaging and
biopsy system 100 as seen from above. The table 109 is shown in the
phantom dashed lines in FIG. 2. An embodiment may include the table
109 with two concentric support arms 112, 113 that are independent
of each other and supported by the pedestal 110 from below the
table 109. Means are provided to attach an x-ray source 111 or
multiple x-ray sources on the outer ring arm 112. The x-ray
source(s) on the outer ring arm 112 may be moved along an encoded
arc 115 such that precise location of the corresponding x-ray focal
spot(s) is known at all times. The inner ring arm 113 supports a
high-resolution detector (1D or 2D) assembly 102 capable of
receiving x-ray signals during a scanning procedure. The x-ray
detector 102 is also position encoded so that its precise location
along arc 114 is known at all times. Both the inner ring arm 113
and outer ring arm 102 provide means for a motor control of the
x-ray source 111 or sources as well as the detector 114. Means is
provided for the table 109 to move up and down by a motor and in
the x and y planes by bearings supporting the table 109. The two
concentric arms 112, 113 provide for clearance for the needle
biopsy assembly 104. In this regard, the needle biopsy assembly 104
may be operable to position and advance the needle 105 into the
breast 108 at any appropriate angle.
[0072] In one preferred method, the outer ring arm 112 provides
means for vertical travel to move the focal spot or focal spots in
a range at least as long as the maximum length of the detector. The
x-ray source(s) 111 may be moved under control of a computer which
also activates x-ray energy in a continuous or pulsed mode while a
collimator with variable filters may shape the x-ray beam during
x-ray exposure. The inner ring arm 113 may also provide means to
change the vertical position of the detector assembly 102 at any
time during the procedure. The x-ray source 111 and/or the detector
assembly 102 may be operable to be swiveled relative to their
respective frames 112, 113 and/or tilted. The design provides for
totally independent paths of the x-ray focal spot(s) and the x-ray
detector assembly 102, unlike currently known cone beam CT breast
imaging systems.
[0073] Although shown as inner ring arm 113 and outer ring arm 102,
other configurations to position the x-ray source 111 or sources
and detector 102 or detectors may be utilized. For example, the
x-ray source 111 may be interconnected to a C-arm and may be
supported and controlled similarly to a conventional C-arm system,
albeit placed on its side instead of supported substantially
vertically. For another example, the x-ray source 111 may be
interconnected to a continuous ring and be supported and controlled
similarly to a conventional closed CT x-ray imaging system, albeit
placed on its side instead of supported substantially vertically.
The detector 102 or detectors may be similarly supported as the
x-ray source(s) 111, or may be supported in any of the
above-described manners.
[0074] In an embodiment, the x-ray source(s) 111 may be independent
from the x-ray detector assembly 102. With independent motion
control of both the x-ray source 111 and detector assembly 102,
which are not configured in a classical rigid frame, it is possible
to acquire views that allow the use of both 3rd and 4th generation
CT geometries.
[0075] The x-ray source 111 may consist of multiple selected x-ray
sources or a field emission x-ray source such as described in U.S.
Pat. No. 7,227,924 B2 to Zhou et al. These multiple x-ray sources
are capable of each pulsing at various temporal frequencies and at
varying kVps as well as focal spot sizes and amperage depending on
the photon flux requirements as described in U.S. Pat. No.
7,245,692 to Lu et al. This type of configuration allows a unique
means of overall system control. Through the recent availability of
flexible reconstruction algorithms embodying limited angle and
limited view imaging, the x-ray imaging parameters can be modulated
during the actual imaging process to optimize image quality,
acquisition time, and radiation dose consistent with the area of
interest of concern in the breast and the overall purpose of the
exam.
[0076] The prone CT breast imaging and biopsy system 100 may employ
dual energy or polychromatic x-ray imaging. Dual energy x-ray
imaging has shown a benefit in imaging tissue by the ability to
emphasize characteristics that are visualized easier with higher or
lower kV energies. For example, in the case of imaging the breast
with non-ionic contrast medium, it is of benefit to image at
energies below and above the k-edge of iodine. Acquiring images of
the breast at below 30 kVP and above 40 kVP following intravenous
injection of contrast media which has its k-edge at 33.16 KeV
provides the opportunity to subtract the two images and display the
result which will show the contrast distribution with fewer
artifacts and allow a more precise diagnosis of the extent of
cancer in the breast.
[0077] The prone CT breast imaging and biopsy system 100 may
include a novel method of determining the x-ray source 111 and/or
detector assembly 102 imaging path prior to and during an imaging
exam (e.g., CT imaging) of the breast 108. Most CT x-ray imaging
systems operate based on a predetermined x-ray imaging protocol and
image reconstruction follows after projection images are acquired.
The prone breast imaging and biopsy system 100 may allow the area
of the breast 108 to be indicated prior to initiation of data
acquisition. Based on the requirements of the exam, the number of
x-ray exposures required from specific angles or views may be
determined such that x-ray exposure is minimized while
high-resolution images are reconstructed following the completion
of the acquisition sequence. In addition, while data acquisition is
underway, information that has been reconstructed may be used to
alter the balance of the imaging acquisition protocol in order to
insure an optimum result.
[0078] Additional image reconstruction capability of the prone CT
breast imaging and biopsy system 100 may be enhanced by the use of
new algorithms where a limited number of views, and limited angles,
can be utilized to reconstruct image data thus delivering a reduced
dose of x-ray to the patient. An example of these new algorithms
can be found in Emil Y. Sidky et al.; Accurate image reconstruction
from few-views and limited-angle data in divergent-beam CT; The
Journal of X-Ray Science and Technology; 14:119-139, 2006. As
noted, other employable algorithms are disclosed in PCT Publication
No. WO2007/095312.
[0079] Another benefit of the prone breast imaging and biopsy
system 100 incorporating multiple x-ray sources 111 may be that a
large number of x-ray views of an object can be acquired with very
high temporal resolution since it may not be necessary to
physically move the x-ray sources 111. Significant leverage in
rapidly acquiring a large number of x-ray views with this type of
x-ray source 111 arrangement is provided by embodiments described
herein where the x-ray detector 102 is able to move independently
of the x-ray source 111 position.
[0080] The detector assembly 102 may use a wireless means of
transmitting data to a receiver and power may be supplied to the
detector 102 by means of an on board battery, or conventional slip
ring or radio frequency air coupling technology for providing the
electrical power required to activate the detector 102 during a
scan. The x-ray source 111 or sources may receive power from
conventional high voltage cables or from slip ring technology used
routinely in conventional CT scanners.
[0081] Reference is now made to FIGS. 3 and 4 which illustrate
another embodiment of a prone CT breast imaging system 200 and a
patient breast 208 positioned relative thereto. The prone CT breast
imaging system 200 includes an imaging beam source 211 and an
imaging detector 202 which are disposed in known relation to define
a predetermined imaging frame of reference therebetween. In this
regard, the imaging beam source 211 and/or imaging detector 202 may
be selectively positioned across a predetermined range of
positions, wherein at least a portion of an imaging beam 240
transmitted through the predetermined frame of reference by the
imaging beam source 211 may be received by the imaging detector 202
to yield an output signal comprising one-dimensional or
two-dimensional image data that corresponds with a plurality of
different projection views of a patient breast 208 located in the
predetermined frame of reference.
[0082] More particularly, the prone breast imaging system 200 may
include a patient support table 209 having an aperture 220 for
receiving a pendulant patient breast 208 therethrough, wherein the
pendulant breast extends into the predetermined frame of reference
230 located bellow the patient support table 209. In turn, the
imaging beam source 211 and imaging detector 202 may be disposed
for relative movement below the table 209.
[0083] In this regard, and as shown in FIG. 3, the imaging beam 240
may be provided so that the rays of the corresponding beam extend
parallel to or diverge away from an imaging boundary plane BP.
Alternatively, or additionally, a boundary plane BP may be defined
by a radio opaque, bottom surface of the patient support table 209
or a similar structure. In either approach, it is desirable to
provide an arrangement in which an imaging beam 240 only passes
through a patient's breast(s) on a first side of a bounding plane
BP and is blocked or otherwise shaped/located to avoid passage
through other bodily portions of a patient located on an opposing,
second side of a bounding plane BP (e.g. a patient's chest wall or
other torso regions).
[0084] In the illustrated embodiment, relative movement of the
imaging beam source 211 and imaging detector 202 may be realized by
supportably mounting the imaging beam source 211 to a first support
member 212 that is pivotable about an axis AA extending though the
predetermined frame of reference 230. As such, imaging beam source
211 may be moved along an arcuate path, e.g. radially about axis
AA, at a first radial distance D1. Further, the imaging beam source
211 may be rotatably mounted to the first support member 212,
wherein the imaging beam source 211 is rotatable about an axis BB
that may be disposed substantially parallel to axis AA.
[0085] Additionally or alternatively in other embodiments, the
imaging detector 202 may be supportably mounted to a movable second
support member 213. For example, the second support member 213 may
be disposed for pivotable movement about axis AA. As such, imaging
detector 208 may be moved along an arcuate path, e.g. radially
about axis AA, at a second radial distance D2. In the illustrated
embodiment, the first support arm 212 and second support arm 213
may be disposed to extend laterally (e.g. horizontally) from and be
supported by an upright (e.g. vertical) pedestal member 210. As
further illustrated, radial distance D1 may be greater than radial
distance D2 (i.e. D1>D2).
[0086] As shown in FIGS. 3 and 4, the aperture 220 may be located
so that a pendulant breast 208 positioned therethrough may define a
breast axis extending from a patient's chest wall (e.g.
orthogonally) through a nipple of the breast 208 alignable with the
axis AA noted above. For example, the aperture 220 may be located
so that the breast axis is coaxial or otherwise parallel with the
axis AA. In the embodiment shown in FIG. 4, the breast axis is
coaxial with axis AA.
[0087] As illustrated by FIG. 3, the imaging beam 240 may comprise
a divergent beam. For example, in the illustrated embodiment, the
imaging signal 240 is a fan-shaped beam. The fan-shaped imaging
beam 240 may be provided in the illustrated embodiment by an x-ray
source 211 that transmits a cone-beam into an interconnected beam
shaping member 242 having a slot 244 that defines the fan
configuration of the imaging beam 240 by blocking portions of the
cone-beam that do not pass through the slot 244. The x-ray imaging
source 211 may be provided so that a focal spot 246 of the imaging
beam 240 is located on an anode track 248a that is co-rotational
with an x-ray tube 248b of the source 211. In another arrangement,
an imaging beam source 211 may be fixedly mounted to a first
support member 212, and a beam shaping member 242 having a slot 244
may be rotatably mounted to the first support member 212 or imaging
beam source 211 to rotate about a focal spot of the imaging beam
source 211, wherein an imaging beam may be scanned across a
patient's breast in timed relation to slot scanning operation of a
slot-scan type imaging-detector (e.g. wherein the imaging beam and
active array of the detector are maintained in alignment).
[0088] As noted, first support member 212 and second support member
213 may be pivotable about axis AA, and imaging beam source 211 may
be rotatable about axis BB. Such relative component moveability
allows for the selective obtainment of a range of projection views
of a patient breast, while also facilitating the establishment of
corresponding limited ranges of componentry movement, e.g. less
than 180.degree. relative to pivot axis AA or rotational axis BB,
so as to simplify apparatus and operation complexity.
[0089] For example, and with particular reference to FIG. 4, the
first support member 212 is shown by solid lines in a first
position and by phantom lines in a second position, wherein the
first support member 212 and imaging beam source 211 may be
selectively positioned across an angular range I relative to the
axis AA. Similarly, the second support member 213 is shown by solid
lines in a first position and by phantom lines in a second
position, wherein the second support member 213 and imaging
detector may be selectively positioned across an angular range II
relative to the axis AA. Further, imaging beam source 211 is shown
in solid lines in a first position and in phantom lines in a second
position, wherein the imaging beam source 211 and slotted beam
shaping member 242 may be selectively positioned across a
rotational range III relative to axis BB.
[0090] In one implementation angular range I may be established at
equal to or less than 270.degree., angular range II may be
established at equal to or less than 270.degree. and angular range
III may be established at equal to or less than 180.degree.. In
another implementation, angular range I may be established at equal
to or less than 180.degree., angular range II may be established at
equal to or less than 180.degree. and angular range III may be
established at equal to or less than 90.degree.. In yet another
implementation angular range I may be established at equal to or
less than 90.degree., angular range II may be established at equal
to or less than 90.degree. and angular range III may be established
at equal to or less than 45.degree.. In each of the noted
implementations it may be preferred to establish angular range I
and angular range II at equal or greater than 30.degree..
[0091] As may be appreciated, the pivotable movement of the first
support member 212 and second support member 213, and the
rotational movement of the imaging beam source 211, may be
automated via a single or multiple drivers. For example, a servo
motor(s) may be provided at the pedestal 210 for selective pivotal
movement of first support member 212 and second support member 213.
Further, a servo motor may be provided at the interface between the
imaging beam source 211 and the first support member 212 for
selective rotational movement of the imaging beam source 211.
[0092] The automated movement of the noted componentry may be
timed-coordinated in accordance with one or more predetermined
control protocols to obtain the desired projection views of a
patient breast. For example, control logic may provide for
synchronized relative movement and/or sequential movement of the
noted components.
[0093] By way of example, in one approach one or more automated
drive(s) may be processor controlled so that the first support
member 212 moves across a predetermined angular range I over a time
period R1 which is greater than a time period R2 over which a
second support member 213 moves through a corresponding angular
range II. In one implementation R2 may be at least two times
greater than R1. As may be appreciated, the processor controlled,
automated drive(s) may also be provided to yield different velocity
profiles (e.g. non-linear profiles) for the imaging beam source 211
located on the first support member 212 and the imaging detector
202 located on the second support member 213. In conjunction with
the noted approach, a computer-controlled drive may also be
provided so as to rotate an imaging beam source 211 through a
rotational range III over a time period R3 that is substantially
the same as the R2 time period for the second support member 213
and image detector 202 mounted thereupon.
[0094] In one example, the first support member 212 and supported
imaging beam source 211 may be positioned at a plurality of
different angular positions relative to axis AA for breast imaging,
wherein two or more stereotactic images or a CT image may be
generated (e.g. by successively moving the imaging beam 240 (e.g.
via rotational movement about axis BB) in timed-relation to radial
movement of the second support member 213 and a slot scan detector
202 supported thereby). In turn, a three-dimensional image may be
displayed and reviewed by medical personnel. Then, the first
support member 212 and imaging beam source 211 may be positioned at
a set location for fluoroscopic breast imaging (e.g. by
successively moving the imaging beam 240 (e.g. via rotational
movement about axis BB) in timed-relation to radial movement of the
second support member 213 and a slot scan detector 202 supported
thereby). A biopsy, surgical or treatment procedure may be
completed during fluoroscopic breast imaging, wherein progressive
device positioning may be viewed by medical personnel.
[0095] Reference is now made to FIG. 5 which illustrates another
embodiment of a prone breast imaging system 300 and a patient
breast 301 positioned relative thereto. In this embodiment, an
imaging beam source 311 may be supportably mounted to a first
support member 312 that is pivotable about an axis AA. Unlike the
embodiment shown in FIGS. 3 and 4, the imaging beam 311 may be
fixedly mounted to the first support member 312. Further, an
imaging detector 202, may be supportably mounted to a second
support member 313 that is pivotably mounted to the first support
member 312. Relatedly, a beam shaping member 342 having a slot 346
may be fixedly interconnected to the second support member 313 for
co-movement therewith.
[0096] In this regard, the imaging beam source 311 may be provided
to transmit an imaging beam 340 that comprises a cone-beam, wherein
the slot 346 of the beam shaping member 344 defines a fan beam
configuration for a portion of the imaging beam 340 that is
transmitted through the slot 346. It may be appreciated that, by
fixedly interconnecting the slotted beam shaping member 344 to the
second support member 313, different portions of the cone beam
imaging beam 340 transmitted by the imaging source 311 may be
utilized to define the fan-shaped beam as the second support member
313 and the imaging detector 312 interconnected thereto are pivoted
across a predetermined angular range relative to the first support
member 312.
[0097] Reference is now made to FIG. 6 which illustrates another
embodiment of a prone breast imaging system 600 and a patient
breast 601 positioned relative thereto. The prone breast imaging
system 600 comprises selected features of the embodiment
corresponding with FIGS. 3 and 4, and the embodiment corresponding
with FIG. 5. In the former regard, an imaging beam source 611 may
be supportably mounted to a first support member 612 that is
pivotable about an axis AA. As such, the imaging beam source 611
may be moved along an arcuate path, e.g. radially about axis AA.
Further, the imaging beam source 611 may be rotatably mounted to
the first support member 612, wherein the imaging beam source 611
is rotatable about an axis BB that may be disposed substantially
parallel to axis AA. In turn, a fan-shaped imaging beam 640 may be
scanned across a patient breast 601 in a side-to-side direction. In
this regard, the imaging beam source 611 may transmit a cone-beam
into an interconnected beam shaping member 642 having a slot 644
that defines the fan configuration of the imaging beam 640 by
blocking portions of the cone-beam that do not pass through the
slot 644. As illustrated, an imaging detector 602 may be
supportably mounted to a second support member 613 that is
pivotably mounted along the length of first support member 612 for
pivotable movement about a pivot axis CC.
[0098] Reference is now made to FIGS. 7A, 7B and 7C, which
illustrate yet a further embodiment of a prone breast imaging
system 700 and a patient breast 701 positioned relative thereto.
The prone breast imaging system 700 comprises features similar to
the features shown in relation to the embodiment corresponding with
FIGS. 1 and 2, and the embodiment corresponding with FIGS. 3 and 4.
In this regard, the prone imaging system 700 may include a patient
support table 709 having an aperture 720 for (shown in phantom
lines) receiving a pendulant patient breast 708 therethrough,
wherein the pendulant breast 708 extends into a predetermined frame
of reference 730 located below the patient support table 709.
[0099] As best shown by FIG. 7B, a portion of a top surface of the
patient support table 709 may be contoured to define a concave or
recessed region through which aperture 720 is provided. Relatedly,
and as best shown by FIG. 7A, a bottom surface of the support table
709 may be contoured define a concave or recessed region sized and
located to receive a portion of an imaging beam source 711 and/or
imaging detector 702 during imaging operation of the prone breast
imaging system 700.
[0100] In this regard, the imaging beam source 711 and an imaging
detector 702 may be disposed in opposing known relation to define a
predetermined imaging frame of reference 730 therebetween, and
patient breast 708 may be pendulantly extended into the
predetermined frame of reference 730. In turn, the imaging beam
source 711 and/or imaging detector 702 may be selectively
positioned across a range of imaging positions, wherein a plurality
of different projection views of a patient breast 708 may be
obtained.
[0101] In this regard, an imaging beam signal 740 may be provided
by imaging beam source 711 so that the rays of the corresponding
beam may extend parallel to an imaging boundary plane BP. Again, as
noted above, the boundary plane BP may alternatively be defined by
a radio opaque bottom surface of the patient support table 709 or a
similar structure. In either approach, imaging beam 740 may be
provided that only passes though a patient's breast 708 thereby
reducing the source imaging signal dosage.
[0102] In this embodiment, relative movement of the imaging beam
source 711 and imaging detector 702 may be realized by supportably
mounting the imaging beam source 711 to an arcuate support member
712 that is pivotable about an axis AA extending through the
predetermined frame of reference 730. In the later regard, the
aperture 720 may be disposed so that a pendulant patient breast 708
positioned therethrough may define a breast axis extending from a
patient's chest wall (e.g. orthogonally) through a nipple of the
breast 708 that is alignable with the axis AA. For example, the
aperture 720 may be located so that the breast axis is coaxial or
otherwise parallel with axis AA. In the embodiment shown in FIGS.
7A, 7B and 7C, the breast axis is coaxial with axis AA.
[0103] Since the support member 712 is pivotable about axis AA, the
imaging beam source 711 may be moved along an arcuate path, e.g.
radially about axis AA. Further, the imaging source may be
rotatably mounted to the first support member 712, wherein the
imaging beam source 711 is rotatable about an axis BB that may be
disposed substantially parallel to axis AA.
[0104] As shown, the imaging detector 702 may be supportably
mounted to a moveable second support member 713. More particularly,
the second support member 713 may be disposed for pivotable
movement about axis AA. As such, imaging detector 702 may be moved
along an arcuate path, e.g. radially about axis AA. In the
illustrated embodiment, the first support arm 712 and second
support arm set 713 may be disposed to extend laterally (e.g.
horizontally) from and be supported by an upright (vertical)
pedestal member 710.
[0105] As best illustrated by FIG. 7A imaging beam 740 may comprise
a divergent beam. For example, the imaging beam 740 may be
fan-shaped. The fan-shaped imaging beam 740 may be provided by an
x-ray imaging beam source 711 that transmit(s) a cone-beam into an
interconnected beam shaping member 742 having a slot that defines
the fan configuration by blocking portions of the cone-beam that do
not pass through the slot. The x-ray imaging beam source 711 may be
provided so that a focal point 746 of the imaging beam 740 is
located on an annular track that is a-rotational with an x-ray tube
comprising the source 711.
[0106] As shown in FIG. 7C, the prone breast imaging system 700 may
be configured to further comprise a biopsy, surgical or treatment
instrument 705, and opposing compression plates 755. In this
regard, the compression plates 755 may be selectively positioned to
immobilize a patient breast 708 for imaging and/or a biopsy,
surgical and/or treatment procedure. In biopsy/surgical/treatment
procedures, the instrument 705 may be manually and/or automatically
positioned so as to selectively remove a tissue sample or to
selectively remove or treat a tissue mass from a targeted region.
As noted above, quasi real-time imaging utilizing the source 711
and detector 702 may yield images displayable on a user interface
(not shown) positioned adjacent to the predetermined frame of
reference 730. In turn, the displayed images may be dynamically
viewed by medical personnel during a procedure to position and
reposition the instrument 705 as desired. In the later regard,
instrument 705 may be disposed for pivotal movement about and along
axis AA, as well as angular positioning and displacement relative
axis AA.
[0107] With reference to FIG. 8, an exemplary imaging system 400
for implementing the invention includes a general purpose computing
device in the form of a computing environment 402, including a
processing unit 404, a system memory 406, and display 408, A system
bus 410, may couple various system components of the computing
environment 402, including the processing unit 404, the system
memory 406, and the display 408. The processing unit 404 may
perform arithmetic, logic and/or control operations by accessing
system memory 406. For example, the processing unit 404 may control
the various system components to acquire data for imaging and may
process the acquired data to generate an image. Alternatively,
different system processors, or different devices including, for
example, graphical processing units (GPUS) may control the various
system components to acquire date for imaging and may process the
acquired data to generate an image.
[0108] The system memory 406 may store information and/or
instructions for use in combination with processing unit 404. For
example, the system memory 406 may store computer readable
instructions, data structures, program modules or the like for
operation of the imaging system 400, including, for example,
control of movement of any of an imaging source 412, and imaging
detector 420 and control of the functionality of the source and the
detector, as discussed below. Further, the system memory 406 may
store data obtained from detector 420 and the processor 404 or
auxiliary processor such as GPUs may process the data for display
on the display 408, as discussed in more detail below. The system
memory 406 may include volatile and non-volatile memory, such as
random access memory (RAM) and read only memory (ROM). It should be
appreciated by those skilled in the art that other types of
computer readable media which can store data that is accessible by
a computer, such as magnetic cassettes, flash memory cards, random
access memories, read only memories, and the like, may also be used
in the exemplary computer environment. A user may enter commands
and/or information, as discussed below, into the computing
environment 402 through input devices such as a mouse and keyboard,
not shown. The commands and/or information may be used to control
operation of the imaging system, including acquisition of data and
processing of data, FIG. 8 further shows imaging source 412
communicating with computing environment 402 via line 414. Source
412 may be stationary or may move relative to and imaging detector
420. Line 414 may also control movement of source 412, such as by
sending commands to a motor (not shown) to move all or a part of
source 412. For example, in relation to the embodiment of FIGS. 3
and 4 above, the motor may move the imaging source 211 by pivoting
a first support member 212 or by rotating the imaging source 211
relative to the first support member 212.
[0109] FIG. 8 further shows detector 420 communicating with
computing environment 402 via lines 424 and 426. Line 424 may
comprise a control line whereby the processing unit may control at
least one characteristic of detector 420. Line 426 may comprise a
data line whereby a detector output signal comprising image data
sensed from the detector may be sent to computing environment 402
for processing by processing unit 404 (e.g. digital image
processing). Detector 420 may be stationary or may move relative to
source 412. Line 424 may control movement of detector 420, such as
by sending commands to a motor (not shown) to move all or a part of
detector 420. For example, in relation to the embodiment of FIGS. 3
and 4 above, the motor may move an imaging detector 202 by pivoting
a second support member 213.
[0110] As noted above, imaging systems comprising the present
invention may include an imaging detector that provides an output
signal comprising projection image data corresponding with a
predetermined angular range of projection views of a patient's
breast, and a processor for processing such projection image data
to provide an image signal (e.g. via computed tomography processing
or utilizing fluoroscopic image generation). In turn, such imaging
signal may be utilized to display two dimensional and/or a three
dimensional images of a patient's breast to medical personnel. In
turn, such images may be utilized for diagnostic purposes, and
additionally for use in planning and completing a tissue biopsy
procedure. In the later regard, two dimensional and/or three
dimensional images may be utilized in connection with the
positioning and advancement of a biopsy device relative to a
patient's breast.
[0111] In conjunction with imaging systems of the present
invention, the image data output by an imaging detector may
correspond with a 360.degree. angular range of projection views
relative to a patient's breast, wherein the data may be processed
utilizing conventional computer tomography fan beam or cone beam
reconstruction algorithms. Alternatively, and as noted above,
relatively new algorithms may be employed to facilitate the use of
a limited angular range of projection views, and corresponding
image data, in reconstructing image data.
[0112] In this regard, and by way of particular example, image
reconstruction methodology and algorithms may be utilized as
disclosed in the above-referenced PCT Publication No.
WO2007/095312. The basic methodology described in the referenced
publication is to iteratively constrain the variation of an
estimated image in order to reconstruct an image. In this regard,
and with reference to FIG. 9, a flow chart 500 of one example of
the methodology is illustrated. As shown at block 502, an initial
estimate of the image to be recovered may be selected or generated.
The initial estimate may be part of an initialization
procedure.
[0113] As shown at block 504, using the initial estimate, estimated
measurements may be determined. One example of determining the
estimated measurements may include using a linear transform
operator to determine a linear transform of the initial estimate
image.
[0114] An intermediate image may be determined based on the
estimated measurements. For example, the intermediate image may be
determined based on a comparison of the estimated data with the
actual data. As shown at blocks 506 and 508, the intermediate image
is determined. As shown at block 506, the estimated data is
compared with the actual data. One example of comparing the
estimated data with the actual data comprises determining the
difference. As shown at block 508, the intermediate estimate may be
generated based on the comparison of the estimated data with the
actual data. For example, the intermediate estimate may be
generated using the adjoint, the approximate adjoint, the exact
inverse, and/or the approximate inverse of the linear transform
operator. Further, the intermediate estimate may be derived from
the image or by reducing (in one step or iteratively) the
differences between the estimated and actual measurements.
[0115] A new estimated image may be determined by analyzing at
least one aspect (such as variation) of the intermediate estimate
image. Specifically, the variation in the intermediate estimate
image may be constrained to generate the new estimated image, as
shown at block 510. For example, generalized total variations (TVs)
from Sidky et al. of the intermediate estimated image may be
minimized to generate the new estimated image. The new estimated
image may be used as the initial estimate for block 504 and blocks
504 through 512 may be repeated until the intermediate estimated
image and new estimated image converge (such as be less than a
predetermined amount, as shown at block 512) or until the estimated
data is less than a predetermined amount than the actual data. One
may use either intermediate estimated image or the new estimated
image as the final estimate of the image. The intermediate image
may generally be less smooth than the new estimated image.
[0116] Various aspects of the present invention may also be
implemented in arrangements where a patient is positioned upright.
In such arrangements, a patient's breast may be immobilized between
opposing compression plates for imaging and/or biopsy procedures.
Relatedly, the features of the embodiment shown in FIGS. 3 and 4
may be translated, or rotated 90.degree.. In relation to all
embodiments described herein, a patient's breast may be located in
a cup-shaped, radiolucent holder to facilitate biopsy
procedures.
[0117] While various embodiments of the present invention have been
described in detail, it is apparent that further modifications and
adaptations of the invention will occur to those skilled in the
art. However, it is to be expressly understood that such
modifications and adaptations are within the spirit and scope of
the present invention.
* * * * *