U.S. patent application number 11/059336 was filed with the patent office on 2005-08-18 for method and apparatus for registration, verification, and referencing of internal organs.
Invention is credited to Glossop, Neil David.
Application Number | 20050182319 11/059336 |
Document ID | / |
Family ID | 34891327 |
Filed Date | 2005-08-18 |
United States Patent
Application |
20050182319 |
Kind Code |
A1 |
Glossop, Neil David |
August 18, 2005 |
Method and apparatus for registration, verification, and
referencing of internal organs
Abstract
Systems and methods for registering, verifying, dynamically
referencing, and navigating an anatomical region of interest of a
patient are provided. In one embodiment, the anatomical region of
interest is imaged using an imaging device such as, for example, an
x-ray device. A tracked registration device may then be removably
inserted in a conduit within the anatomical region and the position
of the registration device may be sampled by a tracking device as
the registration device is moved within the anatomical region
through the catheter. The sampled position data is registered to
the image data to register the path of the conduit to the
anatomical region of interest. The same or a similar device may be
used to dynamically reference the movements affecting the
anatomical region and modify the registration in real time. The
registration may also be verified.
Inventors: |
Glossop, Neil David;
(Toronto, CA) |
Correspondence
Address: |
PILLSBURY WINTHROP SHAW PITTMAN, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Family ID: |
34891327 |
Appl. No.: |
11/059336 |
Filed: |
February 17, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60544344 |
Feb 17, 2004 |
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60605139 |
Aug 30, 2004 |
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60626422 |
Nov 10, 2004 |
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60626488 |
Nov 10, 2004 |
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Current U.S.
Class: |
600/424 |
Current CPC
Class: |
A61B 5/418 20130101;
A61B 2090/3966 20160201; A61B 6/037 20130101; A61B 8/4245 20130101;
A61B 2034/2051 20160201; A61B 8/0841 20130101; A61B 2090/3925
20160201; A61B 5/031 20130101; A61B 5/061 20130101; A61B 2090/374
20160201; A61B 34/20 20160201; A61B 5/283 20210101; A61B 2090/376
20160201; A61B 8/481 20130101; A61M 25/0105 20130101; A61B 5/7221
20130101; A61B 6/541 20130101; A61B 5/20 20130101; A61B 5/066
20130101; A61B 5/42 20130101; A61B 2562/222 20130101; A61B 8/5238
20130101; A61B 5/12 20130101; A61B 8/12 20130101; A61M 25/0108
20130101; A61B 6/12 20130101; A61B 6/5247 20130101; A61B 8/0833
20130101; A61B 2034/2055 20160201; A61B 2034/2061 20160201; A61B
8/4263 20130101; A61B 2090/364 20160201; A61M 25/0127 20130101;
A61B 5/062 20130101; A61B 8/5261 20130101; A61B 5/02 20130101; A61B
5/7285 20130101; A61B 5/08 20130101; A61B 2090/3954 20160201; A61B
5/43 20130101; A61B 6/032 20130101; A61B 2034/107 20160201; A61B
5/03 20130101 |
Class at
Publication: |
600/424 |
International
Class: |
A61B 005/05 |
Claims
We claim:
1. A system for registering an anatomical region of a patient,
comprising: an imaging device adapted to produce image data of the
anatomical region of the patient in a first frame of reference; a
registration device including at least one position indicating
element, wherein the registration device is adapted to be inserted
into a conduit within the anatomical region of the patient; a
tracking device adapted to produce position data regarding the path
of the conduit within the anatomical region in a second frame of
reference, wherein the position data is obtained by the tracking
device sampling coordinates of the at least one position indicating
element as the position indicating element is moved within the
conduit; and a computer element having a processor, wherein the
processor is adapted to receive the image data from the imaging
device, receive the position data from the tracking device, and map
the image data and the position data together.
2. The system of claim 1, wherein the imaging device includes one
of an x-ray device, an ultrasound device, a fluoroscopic device, a
computerized tomography device, a positron emission tomography
device, an isocentric fluoroscope, a rotational fluoroscopic
reconstruction system, a multislice computerized tomography device,
an intravascular ultrasound imager, a single photon emission
computer tomographer, or a magnetic resonance imaging device.
3. The system of claim 1, wherein the conduit within the anatomical
region of the patient includes a naturally existing conduit.
4. The system of claim 1, wherein the conduit within the anatomical
region of the patient includes a naturally existing conduit, and
wherein the naturally existing conduit comprises one of a
circulatory vessel, a respiratory vessel, a lymphatic vessel, a
urinary tract vessel, a cerebrospinal fluid vessel, a reproductive
vessel, an auditory vessel, or a digestive vessel.
5. The system of claim 1, wherein the conduit within the anatomical
region of the patient includes a manufactured conduit that has been
inserted into the anatomical region of the patient.
6. The system of claim 1, wherein the conduit within the anatomical
region of the patient includes a manufactured conduit that has been
inserted into the anatomical region of the patient, and wherein the
manufactured conduit comprises one of a tube, a catheter, or a
lumen within a flexible endoscope.
7. The system of claim 1, wherein the conduit within the anatomical
region of the patient includes a manufactured conduit within a
naturally existing conduit.
8. The system of claim 1, wherein the conduit within the anatomical
region of the patient includes a first manufactured conduit within
a second manufactured within a naturally existing conduit.
9. The system of claim 1, wherein the conduit within the anatomical
region of the patient is an artificial conduit.
10. The system of claim 1, wherein the conduit is adapted to be
inserted into the anatomical region in a manner that causes the
conduit to at least partially fill a space within the anatomical
region.
11. The system of claim 1, wherein the registration device includes
at least one lumen, wherein the registration device has first and
second ends, and wherein at least one of the first or second ends
is closed.
12. The system of claim 1, wherein the tracking device comprises
one of an ultrasonic tracking device, a fiber-optic tracking
device, a global positioning system enabled tracking device, an
optical tracking device or a radar tracking device.
13. The system of claim 1, wherein the at least one position
indicating element comprises a wire coil that produces a magnetic
field, and wherein the tracking device comprises an electromagnetic
tracking device that detects the magnetic field.
14. The system of claim 1, wherein the at least one position
indicating element comprises a wire coil that detects a magnetic
field, and wherein the tracking device comprises an electromagnetic
tracking device that produces the magnetic field.
15. The system of claim 1, wherein the at least one position
indicating element is located at the tip of the registration
device, and wherein the at least one position indicating element is
moved within the conduit by removing the registration device from
the conduit.
16. A computer-implemented method for registering an anatomical
region of a patient, comprising: receiving image data of the
anatomical region of the patient in a first frame of reference from
an imaging device; receiving position data regarding the path of a
conduit within the anatomical region of the patient in a second
frame of reference from a tracking device, wherein the position
data is obtained by a tracking device sampling the position of at
least one position indicating element as the at least one position
indicating element moves within the conduit; and mapping the image
data and the position data together using a registration
transformation.
17. The method of claim 16, wherein the imaging device includes one
of an x-ray device, an ultrasound device, a fluoroscopic device, a
computerized tomography device, a positron emission tomography
device, an isocentric fluoroscope, a rotational fluoroscopic
reconstruction system, a multislice computerized tomography device,
an intravascular ultrasound imager, a single photon emission
computer tomographer, or a magnetic resonance imaging device.
18. The method of claim 16, wherein the conduit within the
anatomical region of the patient includes a naturally existing
conduit, and wherein the naturally existing conduit comprises one
of a circulatory vessel, a respiratory vessel, a lymphatic vessel,
a urinary tract vessel, a cerebrospinal fluid vessel, a
reproductive vessel, an auditory vessel, or a digestive vessel.
19. The method of claim 16, wherein the conduit within the
anatomical region of the patient includes a manufactured conduit
that has been inserted into the anatomical region of the patient,
and wherein the manufactured conduit comprises one of a tube, a
catheter, or a lumen within a flexible endoscope.
20. The method of claim 16, wherein the conduit within the
anatomical region of the patient includes a manufactured conduit
within a naturally existing conduit.
21. The method of claim 16, wherein the conduit within the
anatomical region of the patient includes a first manufactured
conduit within a second manufactured within a naturally existing
conduit.
22. The method of claim 16, wherein the tracking device comprises
one of an ultrasonic tracking device, a fiber-optic tracking
device, a global positioning system enabled tracking device, an
optical tracking device or a radar tracking device.
23. The method of claim 16, wherein the at least one position
indicating element comprises a wire coil that produces a magnetic
field, and wherein the tracking device comprises an electromagnetic
tracking device that detects the magnetic field.
24. The method of claim 16, wherein the at least one position
indicating elements comprises a wire coil that detects a magnetic
field, and wherein the tracking device comprises an electromagnetic
tracking device that emits the magnetic field.
25. The method of claim 16, wherein the at least one position
indicating element is located at the tip of the registration
device, and wherein the at least one position indicating element is
moved within the conduit by removing the registration device from
the conduit.
26. A method for registering an anatomical region of a patient, the
method comprising: imaging the anatomical region using an imaging
device to produce image data regarding the anatomical region in a
first frame of reference; inserting a registration device having
first and second ends into a conduit within the anatomical region,
wherein the first end of the registration device is inserted into
the conduit, and wherein the registration device includes at least
one position indicating element located at the first end of the
registration device; moving the registration device from the
conduit while sampling coordinates of the at least one position
element to produce position data regarding a path of the conduit
within the anatomical region in a second frame of reference,
wherein the coordinates of the one or more position indicating
elements are sampled by a tracking device; mapping together the
image data and the position data using a registration
transformation to produce a set of registration data regarding the
conduit relative to the anatomical region.
27. The method of claim 26, wherein the imaging device includes one
of an x-ray device, an ultrasound device, a fluoroscopic device, a
computerized tomography device, a positron emission tomography
device, an isocentric fluoroscope, a rotational fluoroscopic
reconstruction system, a multislice computerized tomography device,
an intravascular ultrasound imager, a single photon emission
computer tomographer, or a magnetic resonance imaging device.
28. The method of claim 26, wherein imaging the anatomical region
further comprises inserting the conduit into the anatomical region
so that the conduit at least partially fills a space within the
anatomical region.
29. The method of claim 26, wherein inserting a registration device
further comprises inserting the registration device through an
orifice within the patient.
30. The method of claim 26, wherein inserting a registration device
further comprises inserting the registration device through an
orifice within the patient, and wherein the orifice is a naturally
occurring orifice.
31. The method of claim 26, wherein inserting a registration device
further comprises inserting the registration device through an
orifice within the patient, and wherein the orifice is created
during a surgical procedure.
32. The method of claim 26, wherein the conduit within the
anatomical region of the patient includes a naturally existing
conduit, and wherein the naturally existing conduit comprises one
of a circulatory vessel, a respiratory vessel, a lymphatic vessel,
a urinary tract vessel, a cerebrospinal fluid vessel, a
reproductive vessel, an auditory vessel, or a digestive vessel.
33. The method of claim 26, wherein the conduit within the
anatomical region of the patient includes a manufactured conduit
that has been inserted into the anatomical region of the patient,
and wherein the manufactured conduit comprises one of a tube, a
catheter, or a lumen of a flexible endoscope.
34. The method of claim 26, wherein the conduit within the
anatomical region of the patient includes a manufactured conduit
within a naturally existing conduit.
35. The method of claim 26, wherein the conduit within the
anatomical region of the patient includes a first manufactured
conduit within a second manufactured within a naturally existing
conduit.
36. The method of claim 26, wherein the tracking device comprises
one of an ultrasonic tracking device, a fiber-optic tracking
device, a global positioning system enabled tracking device, an
optical tracking device or a radar tracking device.
37. The method of claim 26, wherein the at least one position
indicating element comprises a wire coil that produces a magnetic
field, and wherein the tracking device comprises an electromagnetic
tracking device that detects the magnetic field.
38. The method of claim 26, wherein the at least one position
indicating element comprises a wire coil that detects a magnetic
field, and wherein the tracking device comprises an electromagnetic
tracking device that emits the magnetic field.
39. The method of claim 26, further comprising: displaying a
location of the registration device within the conduit on an image
of the anatomical region; inserting a verification device having
one or more verification position indicating elements into the
conduit; calculating a location of the one or more verification
position indicating elements on the image of the anatomical region
using the registration transformation; and comparing the location
of the one or more verification position indicating elements to the
location of the registration device.
40. The method of claim 26, further comprising: inserting one or
more referencing position indicating elements into the conduit;
obtaining spatial relationship data regarding the one or more
referencing position indicating elements relative to one another;
creating a model of the anatomical region using the spatial
relationship data; sampling movement of the one or more referencing
position indicating elements; and applying the sampled movement to
the model of the anatomical region to create a dynamic model of the
anatomical region.
Description
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 60/544,344, filed Feb. 17, 2004; U.S.
Provisional Patent Application Ser. No. 60/605,139 filed Aug. 30,
2004; U.S. Provisional Patent Application Ser. No. 60/626,422,
filed Nov. 10, 2004; and to U.S. Provisional Patent Application
Ser. No 60/626,488, filed Nov. 10, 2004, each of which are
incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
[0002] This invention relates to methods and devices for
registering an anatomical region with images of the anatomical
region, verifying registration of an anatomical region, and
dynamically referencing the anatomical region.
BACKGROUND OF THE INVENTION
[0003] Image Guided Surgery (IGS), also known as "frameless
stereotaxy" has been used for many years to precisely locate and
position therapeutic or medical measurement devices in the human
body. Proper localization including position and orientation of
these devices is critical to obtain the best result and patient
outcome.
[0004] Some image guided surgery techniques use an externally
placed locating device, such as a camera system or magnetic field
generator together with an instrument containing a trackable
component or "position indicating element" that can be localized by
a locating device or tracking system (collectively referred to
hereinafter a "tracking device"). These position indicating
elements are associated with a coordinate system and are typically
attached to instruments such as surgical probes, drills,
microscopes, needles, X-ray machines, etc. and to the patient. The
spatial coordinates and often the orientation (depending on the
technology used) of the coordinate system associated with the
position indicating elements can be determined by the tracking
device in the fixed coordinate system (or fixed "frame of
reference") of the tracking device. Many tracking devices may be
able to track multiple position indicating elements simultaneously
in their fixed frame of reference. Through geometrical
transformations, it is possible to determine the position and
orientation of any position indicating element relative to a frame
of reference of any other position indicating element.
[0005] A variety of different tracking devices exist, having
different advantages and disadvantages over each other. For
example, optical tracking devices may be constructed to enable the
highly accurate position and orientation of a tool equipped with
position indicating elements to be calculated. However, these
optical tracking devices suffer from line-of-site constraints,
among other things. Electromagnetic (EM) tracking devices do not
require a line-of-sight between the tracking device and the
position indicating elements. Electromagnetic tracking devices may
therefore be used with flexible instruments where the position
indicating elements are placed at the tip of the instruments. One
disadvantage, however, is that electromagnetic tracking devices are
subject to interference from ferromagnetic materials and
conductors. This interference may degrade accuracy when such
ferromagnetic materials or conductors are placed in the proximity
of position indicating elements or EM tracking devices. Other known
tracking devices include, but are not limited to, fiber optic
devices, ultrasonic devices and global positioning ("time of
flight") devices.
[0006] By combining data obtained from a tracking device and a
position indicating element with preoperative or intraoperative
scans (such as for example, x-rays, ultrasounds, fluoroscopy,
computerized tomographic (CT) scans, multislice CT scans, magnetic
resonance imaging (MRI) scanning, positron emission tomographic
(PET) scans, isocentric fluoroscope images, rotational fluoroscopic
reconstructions, intravascular ultrasound (IVUS) images, single
photon emission computer tomographer (SPECT) systems, or other
images), it is possible to graphically superimpose the location of
the position indicating element (and thus any surgical instrument
having a position indicating element) over the images. This enables
the surgeon to perform an intervention/procedure more accurately
since the surgeon is better able to locate or orient the instrument
during the procedure. It also enables the surgeon to perform all or
part of the procedure without the need for additional x-rays or
other images, but instead to rely on previously acquired data. This
not only reduces the amount of ionizing radiation the surgeon and
patient are exposed to, but can speed the procedure and enable the
use of higher fidelity images than can not normally be acquired
intra-operatively. Surgical plans may also be annotated onto these
images (or indeed used without the images) to be used as templates
to guide medical procedures.
[0007] Image Guided Surgery can be most effectively performed only
if an accurate "registration" is available to mathematically map
the position data of position indicating elements expressed in
terms of the coordinate system of the tracking device, i.e.,
"patient space," to the coordinate system of the externally imaged
data, i.e., "image space" determined at the time the images were
taken. In rigid objects such as the skull or bones, one method of
registration is performed by using a probe equipped with position
indicating elements (therefore, the probe itself is tracked by a
tracking device) to touch fiducial markers (such as, for example,
small steel balls (x-spots) made by the Beekley Corporation,
Bristol, CT) placed on the patient to obtain the patient space
coordinates of the fiducials. These same fiducials are visible on
an image such as, for example, a CT scan and are identified in the
image space by indicating them, for example, on a computer display.
Once these same markers are identified in both spaces, a
registration transformation or equivalent mathematical construction
can be calculated. In one commonly used form, a registration
transformation may be a 4.times.4 matrix that embodies the
translations, magnification factors and rotations required to bring
the markers (and thus the coordinate systems) in one space in to
coincidence with the same markers in the another space.
[0008] Fiducial markers used for registration can be applied to
objects such as bone screws or stick-on markers that are visible to
the selected imaging device, or can be implicit, such as
unambiguous parts of the patient anatomy. These anatomical
fiducials might include unusually shaped bones, osteophytes or
other bony prominence, features on vessels or other natural lumens
(such as bifurcations), individual sulci of the brain, or other
markers that can be unambiguously identified in the image and
patient. A rigid affine transformation such as the 4.times.4 matrix
described above may require the identification of at least three
non-collinear points in the image space and the patient space.
Often, many more points are used and a best-fit may be used to
optimize the registration. It is normally desirable that fiducials
remain fixed relative to the anatomy from the time of imaging until
the time that registration is complete.
[0009] Registration for image-guided surgery may be done by
different methods. Paired-point registration is described above and
is accomplished by a user identifying points in image space and
then obtaining the coordinates of the corresponding points in
patient space. Another type of registration, surface registration,
can be done in combination with, or independent of, paired point
registration. In surface registration, a cloud of points is
digitized in the patient space and matched with a surface model of
the same region in image space. A best-fit transformation relating
one surface to the other may then be calculated. In another type of
registration, repeat-fixation devices may be used that involve a
user repeatedly removing and replacing a device in known relation
to the patient or image fiducials of the patient.
[0010] Automatic registration may also be done. Automatic
registration may, for example, make use of predefined fiducial
arrays or "fiducial shapes" that are readily identifiable in image
space by a computer. The patient space position and orientation of
these arrays may be inferred through the use of a position
indicating element fixed to the fiducial array. Other registration
methods also exist, including methods that attempt to register
non-rigid objects generally through image processing means.
[0011] Registrations may also be performed to calculate
transformations between separately acquired images. This may be
done by identifying "mutual information" (e.g., the same fiducial
markers existing in each space). In this way, information visible
in one image, but not the other, may be coalesced into a combined
image containing information from both. In the same manner, two
different tracking devices may be registered together to extend the
range of a tracking device or to increase its accuracy.
[0012] Following registration, the two spaces (patient and image)
are linked through the transformation calculations. Once
registered, the position and orientation of a tracked probe placed
anywhere in the registered region can be related to, for example, a
scan of the region. Typically the tracking device may be connected
to a computer system. Scans may also be loaded onto the computer
system. The computer system display may take the form of a
graphical representation of a probe or instrument's position
superimposed onto preoperative image data. Accordingly, it is
possible to obtain information about the object being probed as
well as the instrument's position and orientation relative to the
object that is not immediately visible to the surgeon. The
information displayed can also be accurately and quantitatively
measured enabling the surgeon to carry out a preoperative plan more
accurately.
[0013] An additional concept in image guided surgery is that of
"dynamic referencing." Dynamic referencing can account for any bulk
motion of the anatomy relative to the tracking device. This may
entail additional, position indicating elements, or other
techniques. For example, in cranial surgery, position indicating
elements that form the dynamic reference are often attached
directly to the head or more typically to a clamp meant to
immobilize the head. In spine surgery, for example, a dynamic
reference attached (via a temporary clamp or screw) to the
vertebral body undergoing therapy is used to account for
respiratory motion, iatrogentic (e.g., doctor-induced) motion
caused by the procedure itself, as well as motion of the tracking
device. In an analogous manner, the tracking device itself may be
attached directly to the anatomy, moving with the anatomy when it
moves. For example, a small camera may be attached to a head-clamp
so that movement of the head would produce movement of the camera,
thus preserving registration.
[0014] "Gating" may also be used to account for motion of the
anatomy. Instead of continually compensating for motion through
dynamic referencing, "gated measurements" are measurements that are
only accepted at particular instants in time. Gating has been used
in, for example, cardiac motion studies. Gating synchronizes a
measured movement (e.g., heartbeat, respiration, or other motion)
to the start of the measurement in order to eliminate the motion.
Measurements are only accepted at specific instants. For example,
gating during image guided surgery of the spine may mean that the
position of a tracked instrument may be sampled briefly only during
peak inspiration times of a respiratory cycle.
[0015] Both registration and use of an image guided surgery system
in the presence of anatomical motion (such as that which occurs
during normal respiration) is generally regarded as safer and more
accurate if a dynamic reference device is attached prior to
registration (and/or if gating is used). Instead of reporting the
position and orientation of a position indicating element of a
tracked instrument in the fixed coordinate system of the tracking
device, the position and orientation of the position indicating
element of the tracked instrument is reported relative to the
dynamic reference's internal coordinate system. Any motion
experienced mutually by both the dynamic reference and the tracked
instrument is "cancelled out."
[0016] There are many difficulties and problems in image guided
surgery and the prior techniques. These are not limited to, but
include: (a) obtaining adequate registration and (b) adequately
dynamically referencing the anatomy or a portion thereof, and (c)
verifying that registration is accurate enough to perform the
procedure using image guidance.
[0017] Paired-point registration in rigid or near-rigid anatomical
objects can be accomplished using direct probing. Paired-point
registration is less-attractive when the anatomical object is
either inaccessible, non-rigid, or both. When the anatomical object
is not accessible but rigid (such as pelvic bone), it may be
necessary to either palpate the surface of the object through
probing through an opening in the skin, or through the rigid
attachment of a palpatable registration object prior to imaging. In
rigid and non-rigid organs or anatomically connected regions,
methods such as ultrasound and laser surface scanning are used with
varying amounts of success.
[0018] Registration and referencing of non-rigid and/or moving
organs such as the liver, gall bladder, stomach, pancreas, kidney,
lung, colon, heart, prostate gland, etc. is a difficult task. Use
of devices such as probes generally deform the organ. Furthermore,
it is difficult to attach any kind of dynamic reference to a soft
moving object. Such organs tend to be generally inaccessible
directly through the skin without damaging intervening tissue or
the organ itself. Techniques using ultrasound are complicated by
different sound velocities and attenuation from different
tissues.
[0019] Current registration and dynamic referencing techniques
usually assume that the tracked organ is rigid. Newer techniques
are being proposed that are not limited to rigid organs. These can
benefit from placement of multiple dynamic references. However,
problems still exist since multiple dynamic references must be
temporarily fixed to a deformable anatomical object.
[0020] Another limitation of current dynamic referencing techniques
stems from the use of reference sensors. The most widely used
method of referencing known in the art is to place a single, rigid,
six degree-of-freedom (6 DOF), trackable device onto the organ of
interest. This is typically screwed, clamped or otherwise rigidly
attached to the organ of interest. Such rigid bodies are typically
of large footprint, and give information only at the location to
which they are attached. In the event that they are attached some
distance from the site of intervention/procedure, or attached to a
non-rigid object, the motion of the dynamic reference may not
accurately track the motion at the site of
intervention/procedure.
[0021] Another limitation of current image guided surgery
techniques may include the difficulty of verifying that a
registration has been performed correctly. Before proceeding to
navigate the anatomical region of the patient based on preoperative
images and registration, it may be important to ensure that the
registration is accurate. In image guided procedures in hard
tissue, a probe can be touched onto hard surfaces or features
(after registration) to ensure the registration is accurate. This
technique suffers from the same issues as registration itself in
soft tissue, e.g., deformation of soft tissue during verification,
access to the tissue, paucity of verification landmarks, and other
problems.
[0022] A further limitation of current approaches is the amount of
fluoroscopy that must be used to correctly position the therapy
device in the event that image guided surgery is not used. While it
does provide accurate and direct information of the progress of the
intervention, images are two-dimensional in nature and require
continuous exposure of the patient and surgical team to ionizing
radiation. Three-dimensional images may be more useful.
[0023] These land other problems exist.
SUMMARY OF THE INVENTION
[0024] The invention addresses these and other problems by
providing systems and methods for registration of an anatomical
region of a patient, verification of the registration of the
anatomical region, and dynamic referencing of the anatomical
region.
[0025] As used herein, an anatomical region of a patient may
include one or more organs, tissues, systems, cavities, and/or
other regions (including regions having soft tissue and/or
deformable bodies) of a human being or other animal. In one
embodiment, the invention may use a conduit within the anatomical
region to, inter alia, aid in providing image information and
position information from within the anatomical region. This
conduit may supply sufficient coordinate information regarding the
anatomical region to be used for registration of the anatomical
region. For example, a coronary artery surrounding the heart may
provide sufficient topographical coordinate information regarding
the heart to be used as a conduit for registration by a method of
the invention.
[0026] In one embodiment, a conduit as used herein may include a
naturally existing conduit within the anatomical region such as,
for example, an artery, vein, or other vessel of the circulatory
system or other naturally occurring conduit existing within the
anatomical region of interest. In some embodiments, an "artificial
conduit" may be created within the anatomical region such as, for
example, a percutaneous puncture of tissue within the anatomical
region by a cannula such as might be caused by a hypodermic needle.
The process of insertion of this cannula may, in turn, form an
artificial conduit within the anatomical region.
[0027] In other embodiments, a conduit may include a manufactured
conduit that may be placed within the anatomical region such as,
for example, a tube, a catheter, hollow endoscope, a tubular
vascular guidewire, or other manufactured conduit that may be
inserted into the anatomical region of interest. In some
embodiments, a manufactured conduit and a naturally existing or
artificial conduit may be used together. In some embodiments, a
manufactured conduit may be inserted within an anatomical region to
fill and/or conform to the dimensions of a space within that
anatomical region. For example, a catheter or other conduit may be
fed into a cavity within an anatomical region, such that the
catheter coils, bends, folds, or otherwise "balls up" (without
obstructing any lumens therein) inside the cavity, thus at least
partially filling the volume of, or conforming to the dimensions
of, the cavity. The methods described herein may then be performed
using the catheter as it exists within the cavity.
[0028] In some embodiments, artificial conduits may used in
conjunction with natural conduits and/or manufactured conduits. For
example, an artificial conduit may be created (e.g., with a needle)
in certain tissue (e.g., skin, connective tissue, or other tissue)
to reach a natural conduit within the anatomical region (e.g.,
vein) or to insert a manufactured conduit (e.g., catheter).
[0029] In one embodiment, the invention provides a registration
device for registration of an anatomical region of a patient. The
registration device may include a tube, catheter, vascular
guidewire, or other device that may be inserted into a conduit
within the anatomical region to be registered. In some embodiments,
the registration device may be constructed of a torqued bundle of
metal filars or a helical wound spring with a central, large empty
lumen that can accommodate one or more position indicating
elements, detectable elements, wires, and/or other elements.
[0030] In some embodiments, the registration device may be freely
slidable in within a conduit. In some embodiments, the registration
device may be temporarily fixed within a conduit using one or more
fixating elements such as, for example, balloons, deployable hooks,
cages, stiffening wires, vacuum ports, or other elements.
[0031] In one embodiment, the registration device may include at
least one position indicating element. The position indicating
element may include an element whose location, position,
orientation, and/or coordinates relative to a tracking device may
be determined and recorded. As such, the position of the position
indicating element within the conduit, and thus the position of at
least one point of the conduit within the anatomical region of the
patient, may be determined. The position indicating element may
include, for example, a coil that may produce a magnetic field that
is detectable by an electromagnetic tracking device. Other types of
position indicating elements and/or tracking devices may be
used.
[0032] In some embodiments, the registration device may include one
or more features typically found in guidewires used in medical
procedures such as, for example, a tapered tip, a hydrophilic
coating (or other type of coating), safety or torque transmission,
stiffening and/or support structures, metal filar tube windings
(such as, for example, a helical spring winding, braided or twisted
filars etc.), or other elements. In some embodiments, the distal
tip portion of the registration device may contain malleable
material, enabling the shape of the tip to be manually adjusted
during a medical procedure. In some embodiments, the distal tip of
the registration device may be closed or may contain a plug to
prevent material seeping into the device.
[0033] In one embodiment, the position indicating element may be
located at or near the tip of the registration device. In other
embodiments, multiple position indicating elements may be located
at various points along the length of registration device.
[0034] In one embodiment, the invention provides a method for
registration of an anatomical region of a patient. One or more
images of the anatomical region of the patient and/or the conduit
within the anatomical region may be obtained by an imaging device.
An imaging device may include, for example, an x-ray device or
other imaging device. Position information regarding the path of
the conduit within the anatomical region may then be obtained in
the frame of reference of the image(s) (i.e., the path of the
conduit in "image space").
[0035] In one embodiment the spatial pathway of the conduit in the
frame of reference of the patient (i.e., in the "patient space")
may be obtained. In one embodiment, this spatial pathway (or
position information) may be obtained via a registration device
that is inserted into the conduit, wherein the registration device
includes at least one position indicating element. In one
embodiment, the position indicating element may be located the
distal tip of the registration device. A tracking device may sample
the coordinates of the position indicating element included within
the registration device as the inserted registration device is
moved within the conduit, resulting in position information
regarding the path of the conduit within the anatomical region in
the frame of reference of the tracking device (this may also be
referred to as the frame of reference of the patient, i.e., the
"patient space"). In one embodiment, the movement of the
registration device may include withdrawing the inserted
registration device from the conduit.
[0036] In one embodiment, a registration transformation may then be
calculated and the image data (e.g., information from the image
space) of the anatomical region and the position data (information
from the patient space) of the path of the conduit within the
anatomical region may be mapped together (or "registered"), using
the registration transformation. In some embodiments a registration
transformation may include a registration transformation matrix or
other suitable representation of the registration transformation.
An exemplary registration transformation calculation method is
known as singular valued decomposition (SVD) in which the same
point locations are identified in each coordinate system (e.g., the
image space and the patient space). Other registration
transformations may be used.
[0037] In one embodiment, registration or mapping may be performed
by bringing the coordinates of the anatomical region derived from
the image data (the image space) into coincidence with the
coordinates of the conduit within the anatomical region derived
from the tracking device/position indicating element (the patient
space). In some embodiments, additional coordinate sets may also be
"co-registered" with the image and tracking device data. For
example, a magnetic resonance image dataset may be first
co-registered with a computerized tomography dataset (both image
space), which may in turn be registered to the path of the conduit
in the frame of reference of the patient (patient space).
[0038] The result of mapping the image space data and the patient
space data together may include or enable accurate graphical
representations (e.g., on the original image data) of an instrument
or other tool equipped with a position indicating element through
the anatomical region. In some embodiments, this navigation may
enable image guided surgery or other medical procedures to be
performed in/on the anatomical region.
[0039] In one embodiment, the invention provides a method for
verifying registration of an anatomical region. In one embodiment,
an image of an anatomical region of interest may be acquired using
an imaging device. This anatomical region may include or be
equipped with one or more conduits. A registration of the
anatomical region may then be performed. This registration may use
the methods described herein or may use other methods. In
performing this registration, a registration transformation such
as, for example, a registration transformation matrix, may be
calculated.
[0040] One or more position indicating elements may then be placed
into the anatomical region of interest. These position indicating
elements may be different from those used for registration. As
such, they may also be referred to as verification position
indicating elements. Placement of the one or more position
indicating elements may utilize a conduit within the anatomical
region. In one embodiment, the one or more position indicating
elements may be placed within the anatomical region of interest
using a verification device. The verification device may include a
tube, a catheter, vascular guidewire, or other device having one or
more position indicating elements attached to it.
[0041] The position of the one or more position indicating elements
may then be sampled by a tracking device. This position information
may be combined with the previously mentioned registration. This
combination may produce an "overlay image" or "composite image"
where the image space positions of the one or more position
indicating elements are calculated and displayed on the previously
acquired image (or other image) of the anatomical region. Graphical
icons representing the location and/or orientation of the one or
more position indicating elements within the anatomical region may
be displayed in the overlay or composite image. This location
and/or orientation may be determined by the combined registration
transformation and the coordinate of the one or more position
indicating elements as sampled by the tracking device.
[0042] In some embodiments, the one or more position indicating
elements may be moved within the anatomical region as their
positions are sampled by the tracking device. The transformed
location (as calculated using the registration transformation) of
the one or more position indicating elements as they are moved may
be displayed on the image. Errors in the registration may be
indicated by movement of the one or more position indicating
elements outside of the registered path within the anatomical
region (e.g., such as outside a conduit registered within the
anatomical region). The absence of errors may used to verify the
registration.
[0043] In one embodiment, another method of verification of
registration of an anatomical region may be performed and may be
used together or separately from the verification method described
above. In this method, one or more position indicating devices
(such as those included in a verification device described above)
may be placed into an anatomical region of a patient by way of, for
example, a conduit within the anatomical region. The location of
the one or more position indicating elements within the anatomical
region may then be imaged using an imaging device such as, for
example an x-ray device or other imaging device. The visualized
location of the position indicating elements within the anatomical
region may then be compared to points within the anatomical region
as obtained by a registration. Discrepancies between the images of
the position indicating elements and the points obtained by the
registration may be indicative of errors in the registration.
[0044] In another embodiment, if the verification device includes
one or more position indicating elements, at least one of which
resides at the distal tip of the verification device, an image of
the one or more position indicating elements as they are moved
within the conduit may be taken over a period of time, thus,
producing an image of the path if the conduit within the anatomical
region. This may be compared to points within the anatomical region
obtained by the registration for verification purposes.
[0045] In one embodiment, the invention provides a referencing
device for dynamic referencing of an anatomical region of a
patient. The referencing device may be or include a tube, a
catheter, a vascular guidewire, or similar object that may be
inserted into a conduit within the anatomical region to be
referenced.
[0046] In one embodiment, the referencing device may be freely
slidable in the conduit, and may be inserted into or removed from
the conduit. In some embodiments, the referencing device may be
fixed or held within the conduit by one or more restraining devices
such as, for example, a balloon, vacuum ports along its length,
deployable hooks, cages, stiffening wires, or other restraining
devices. During and following registration procedures with which
the referencing device is used, the referencing device may be held
fixed relative to the anatomical region.
[0047] The referencing device may include one or more position
indicating elements along its length. In some embodiments, these
position indicating elements may be different from the position
indicating elements used for other purposes, as such, they may also
be referred to as referencing position indicating elements. The
position indicating elements may enable the location, position,
orientation, and/or coordinates of one or more points of reference
of the referencing device to be detected by a tracking device as
they exist within the fixed frame of reference of the tracking
device. As such, the position indicating elements may enable
detection of the location, position, orientation, coordinates
and/or motion over time of one or more points of reference within
an anatomical region of a patient.
[0048] In some embodiments, the referencing device or other element
of the invention may contain a pressure sensor, an electromyograph
(EMG) sensor, an electrocardiograph (ECG) sensor, or other devices
or sensors, which may be used to gate the sampling of the reference
sensors, to measure blood pressure, air pressure, or other
quality.
[0049] In one embodiment, the invention provides a method for using
referencing device to dynamically reference an anatomical region of
a patient. In one embodiment, a referencing device having one or
more position indicating elements may be inserted into one or more
conduits within the anatomical region of interest. The spatial
relationships (e.g., position, orientation) of the one or more
position indicating elements relative to one another and/or
relative to the anatomical region may then be determined via the
tracking device or by other method. These spatial relationship
measurements may by used to form a tracking model, such as a rigid
body model (discussed above), piecewise rigid body representation,
or deformable model of the anatomical region.
[0050] Any movement affecting the conduit within the anatomical
region of interest may be detected via its effect on the one or
more position indicating elements. This motion may include any
motion that affects the contents of the anatomical region of
interest such as, for example, a heartbeat, breathing, voluntary or
involuntary movement by the patient, movement of the soft or
deformable organs or tissues within the anatomical region due to
intervention by a medical professional or instrument, gross
movement of the body of the patient, or other movement. This
movement may be monitored for by monitoring the position of the
position indicating elements using the tracking device.
[0051] In one embodiment, the information provided by the position
indicating elements may be used together with the model of the
anatomical region to determine the motion of the anatomical region.
This "model of motion" may be used to account for the motion of the
anatomical region. In one embodiment, the model of motion may be
used to adjust a registration of the anatomical region so as to
account for, in real time, any movement affecting the anatomical
region. In another embodiment, the model of motion may be used to
adjust coordinates reported by the position indicating elements
attached to an instrument in the anatomical region so as to account
for, in real time, any movement affecting the anatomical region. In
another embodiment, the model of motion may be used to form a local
coordinate system in the vicinity of an instrument containing
position indicating elements within the anatomical region. The
model of motion may also be used to adjust the position of this
local coordinate system. If the position indicating elements
attached to the instrument are expressed in terms of this local
coordinate system, it may be possible to account for, in real time,
any movement affecting the anatomical region. Thus, re-registration
need not be performed to account for movement affecting the
anatomical region.
[0052] In some embodiments, the invention may include a
computer-implemented integrated system ("integrated system") for
performing one or more of the methods described herein (as well as
other methods such as, for example, therapeutic, diagnostic, or
other methods) and utilizing the apparatus described herein (as
well as other apparatus). In one embodiment, an integrated system
according to the invention may include a computer element. The
computer element may include a processor, a memory device, a power
source, a control application, one or more software modules, one or
more inputs/outputs, a display device, a user input device, and/or
other elements. The computer element may receive, send, store,
and/or manipulate any data necessary to perform the processes
described herein (including performing any calculations) or
necessary for the function of the elements described herein.
[0053] According one embodiment, the computer element may host a
control application. The control application may comprise a
computer application which may enable one or more software
modules.
[0054] In some embodiments, the one or more software modules may
enable the processor to receive, send, and/or manipulate imaging
data regarding the location, position, and/or coordinates of one or
more instruments, devices, detectable elements, position indicating
elements, or other elements of the invention inside an anatomical
region of a patient. In some embodiments, the one or more software
modules may also enable the processor to receive, send, and/or
manipulate data regarding the location, position, and/or
coordinates of one or more position indicating elements or other
elements of the invention inside the anatomical region of the
patient.
[0055] In some embodiments, the one or more software modules may
also enable the processor to calculate one or more registration
transformations, perform registration of coordinates from two or
more coordinate systems according to the one or more transformation
calculations, and produce one or more images from registered data.
In some embodiments, images produced from image data, position
data, registration data, other data, or any combination thereof may
be displayed on the display device.
[0056] In some embodiments, the one or more software modules may
enable the processor to receive, send, and/or manipulate data
regarding the location, orientation, position, and/or coordinates
of one or more position indicating elements for use in constructing
a rigid-body description of an anatomical region of a patient. In
some embodiments, the one or more software modules may enable the
processor to create a dynamic, deformable model of the anatomical
region of the patient, and display real time images regarding the
anatomical region. In some embodiments, these images may be
displayed on display the device.
[0057] In some embodiments, the integrated system may include a
registration device. In one embodiment data may be sent and
received between the registration device and computer element. The
registration device may, inter alia, aid in providing image data,
location data, position data, and/or coordinate data regarding an
anatomical region of the patient or one or more elements of the
invention within the anatomical region of the patient. The
registration device may otherwise enable registration of the
anatomical region the patient, (including soft tissues and/or
deformable bodies).
[0058] In some embodiments, the integrated system may include a
referencing device. In some embodiments data may be sent and
received between the referencing device and computer element. The
referencing device may, inter alia, aid in providing image data,
location data, position data, coordinate data, and/or motion data
regarding an anatomical region of the patient. The referencing
device may otherwise enable dynamic referencing of an anatomical
region of a patient, (including soft tissues and/or deformable
bodies).
[0059] In one embodiment, the integrated system may include a
tracking device. The tracking device may include an electromagnetic
tracking device, global positioning system (GPS) enabled tracking
device, an ultrasonic tracking device, a fiber-optic tracking
device, an optical tracking device, a radar tracking device, or
other type of tracking device. The tracking device may be used to
obtain data regarding the three-dimensional location, position,
coordinates, and/or other information regarding one or more
position indicating elements within an anatomical region of the
patient. The tracking device may provide this data/information to
the computer element.
[0060] In one embodiment, the integrated system may include an
imaging device. The imaging device may send and receive data from
the integrated system. In one embodiment, the imaging device may be
used to obtain image data, position data, or other data necessary
for enabling the apparatus and processes described herein. The
imaging device may provide this data to the computer element. The
imaging device may include x-ray equipment, computerized tomography
(CT) equipment, positron emission tomography (PET) equipment,
magnetic resonance imaging (MRI) equipment, fluoroscopy equipment,
ultrasound equipment, an isocentric fluoroscopic device, a
rotational fluoroscopic reconstruction system, a multislice
computerized tomography device, an intravascular ultrasound imager,
a single photon emission computer tomographer, a magnetic resonance
imaging device, or other imaging/scanning equipment
[0061] Other devices and or elements such as, for example,
temperature sensors, pressure sensors, motion sensors, electrical
sensors, EMG equipment, ECG equipment, or other equipment or
sensors may be part of or send and receive data from the integrated
system.
[0062] Those having skill in the art will appreciate that the
invention described herein may work with various system
configurations. Accordingly, more or less of the aforementioned
system components may be used and/or combined in various
embodiments. It should also be understood that various software
modules and control application that are used to accomplish the
functionalities described herein may be maintained on one or more
of the components of system recited herein, as necessary, including
those within individual tools or devices. In other embodiments, as
would be appreciated, the functionalities described herein may be
implemented in various combinations of hardware and/or firmware, in
addition to, or instead of, software.
[0063] The various objects, features, and advantages of the
invention will be apparent through the detailed description of the
preferred embodiments and the drawings attached hereto. It is also
to be understood that the following detailed description is
exemplary and not restrictive of the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0064] FIG. 1A is an exemplary diagram of a registration device
according to an embodiment of the invention.
[0065] FIG. 1B is an exemplary diagram of a registration device
according to an embodiment of the invention.
[0066] FIG. 1C is an exemplary diagram of a registration device
according to an embodiment of the invention.
[0067] FIG. 2 is an exemplary process of registration of an
anatomical region according to an embodiment of the invention.
[0068] FIG. 3 is an exemplary process for verification of
registration of an anatomical region according to an embodiment of
the invention.
[0069] FIG. 4 is an exemplary diagram of a referencing device
according to an embodiment of the invention.
[0070] FIG. 5 is an exemplary process for dynamic referencing of an
anatomical region according to an embodiment of the invention.
[0071] FIG. 6A is an exemplary diagram of an apparatus according to
an embodiment of the invention.
[0072] FIG. 6B is an exemplary diagram of an apparatus according to
an embodiment of the invention.
[0073] FIG. 7A is an exemplary diagram of an apparatus within an
anatomical region of a patient according to an embodiment of the
invention.
[0074] FIG. 7B is an exemplary diagram of an apparatus within an
anatomical region of a patient according to an embodiment of the
invention.
[0075] FIG. 7C is an exemplary diagram of an apparatus within an
anatomical region of a patient according to an embodiment of the
invention.
[0076] FIG. 7D is an exemplary diagram of an apparatus within an
anatomical region of a patient according to an embodiment of the
invention.
[0077] FIG. 7E is an exemplary diagram of an apparatus within an
anatomical region of a patient according to an embodiment of the
invention.
[0078] FIG. 7F is an exemplary diagram of an apparatus within an
anatomical region of a patient according to an embodiment of the
invention.
[0079] FIG. 7G is an exemplary diagram of an apparatus within an
anatomical region of a patient according to an embodiment of the
invention.
[0080] FIG. 8 is an exemplary integrated system according to an
embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0081] The invention provides systems and methods for registration
of an anatomical region of a patient, verification of the
registration of the anatomical region, and dynamic referencing of
the anatomical region, wherein the anatomical region may include
soft tissue and/or deformable bodies.
[0082] In one embodiment, the invention may use a conduit within an
anatomical region of a patient to, inter alia, aid in providing
image information and position information from within the
anatomical region. This conduit may supply sufficient coordinate
information regarding the anatomical region to be used for
registration of the anatomical region. For example, a coronary
artery surrounding the heart may provide sufficient topographical
coordinate information regarding the heart to be used as a conduit
for registration by a method of the invention.
[0083] In one embodiment, a conduit as used herein may include a
naturally existing conduit within the anatomical region such as,
for example, an artery, vein, or other vessel of the circulatory
system; a bronchial tube or other vessel of the respiratory system;
a vessel of the lymphatic system; an intestine or other vessel of
the digestive system; a urinary tract vessel; a cerebrospinal fluid
vessel; a reproductive vessel; an auditory vessel; a cranial
ventricle; an otolaryngological vessel; or other naturally
occurring conduit existing within the anatomical region of
interest.
[0084] In some embodiments, an "artificial conduit" may be created
within the anatomical region such as, for example, a percutaneous
puncture of tissue within the anatomical region by a cannula such
as might be caused by a hypodermic needle. The process of insertion
of this cannula may, in turn, form an artificial conduit within the
anatomical region.
[0085] In other embodiments, a conduit may include a manufactured
conduit that may be placed within the anatomical region such as,
for example, a tube, a catheter, hollow endoscope, a tubular
vascular guidewire, or other manufactured conduit that may be
inserted into the anatomical region of interest. In some
embodiments, a manufactured conduit and a naturally existing or
artificial conduit may be used together. For example, a catheter,
cannula, or tube may be navigated inside a naturally existing
vessel of the anatomical region. In some embodiments, a first
manufactured conduit may be inserted within a second manufactured
conduit, which may in turn be inserted into the anatomical region,
an artificial conduit within the anatomical region, or within a
naturally existing conduit within the anatomical region.
[0086] In some embodiments, a manufactured conduit may be inserted
within an anatomical region to at least partially fill and/or
conform to the dimensions of a space within that anatomical region.
For example, a catheter or other conduit may be fed into a cavity
within an anatomical region, such that the catheter coils, bends,
folds, or otherwise "balls up" (without obstructing any lumens
therein) inside the cavity, thus at least partially filling the
volume of, or conforming to the dimensions of, the cavity. The
methods described herein may then be performed using the catheter
as it exists within the cavity.
[0087] In some embodiments, artificial conduits may used in
conjunction with natural conduits and/or manufactured conduits
(described below). For example, an artificial conduit may be
created (e.g., with a needle) in certain tissue (e.g., skin,
connective tissue, or other tissue) to reach a natural conduit
within the anatomical region (e.g., vein) or to insert a
manufactured conduit (e.g., catheter).
[0088] In one embodiment, the invention provides a registration
device for registration of an anatomical region of a patient. As
described below, the registration device may be part of, or be
operatively connected to, an integrated system for registration,
verification of registration, dynamic referencing, navigation,
and/or other functions (hereinafter "integrated system"), which is
described in detail below.
[0089] FIGS. 1A-1C illustrate a registration device 101 according
to an embodiment of the invention. Registration device 101 may
include a tube, catheter, vascular guidewire, or other device that
may be inserted into a conduit within the anatomical region to be
registered. In some embodiments, registration device 101 may be
constructed of a torqued bundle of metal filars or a helical wound
spring with a central, large empty lumen that can accommodate one
or more position indicating elements, detectable elements, wires,
and/or other elements. In one embodiment, registration device 101
may be similar to the design of the "act-one" from ASAHI INTECC
Co., LTD of Japan.
[0090] In some embodiments, registration device 101 may be freely
slidable in within a conduit. In some embodiments, registration
device 101 may be temporarily fixed within a conduit using one or
more fixating elements such as, for example, balloons, deployable
hooks, cages, stiffening wires, or other elements.
[0091] In one embodiment, registration device 101 may include at
least one position indicating element 103. Position indicating
element 103 may include an element whose location, position,
orientation, and/or coordinates relative to a tracking device may
be determined and recorded. As such, the position of position
indicating element 103 within the conduit, and thus the position of
at least one point of the conduit within the anatomical region of
the patient, may be determined. Position indicating element 103 may
include a device whose position may be detectable by a tracking
device in the frame of reference of the tracking device. For
example, position indicating element 103 may include a coil that
may produce a magnetic field that is detectable by an
electromagnetic tracking device. In one embodiment, position
indicating element 103 may include a coil that detects a magnetic
field emitted by the electromagnetic tracking device. In some
embodiments position indicating elements and their position in the
frame of reference of a tracking device may be enabled by "Hall
Effect" transducers or superconducting quantum interference devices
(SQUID). In other embodiments, position indicating element 103 may
include an element whose position is detectable by a global
positioning system (GPS) enabled tracking device, an ultrasonic
tracking device, a fiber-optic tracking device (e.g., Shape-Tape,
MEasurand, Inc., Fredricton, New Bruswick), an optical tracking
device, or a radar tracking device. Other types of position
indicating elements and/or tracking devices may be used. In one
embodiment, the tracking device used to detect the position of
position indicating element 103 may be part of, or operatively
connected to, an integrated system.
[0092] In one embodiment, registration device 101 may include lead
wires 109 extending from position indicating element 103 back
through the device to electrical connections 107. Electrical
connections 107 may include contacts that may be flush with, or
smaller than, the outer diameter of registration device 101.
Electrical connections 107 may also include, for example, a plug,
contact bands, or other connections. Electrical connections 107 may
facilitate measurement of the position of one or more position
indicating elements 103 and connection of registration device 101
to a tracking system, an integrated system, and/or other
computer-implemented system.
[0093] In one embodiment, lead wires 109 may be shielded to prevent
electromagnetic interference. Shielding of lead wires 109 may
involve electrical shielding 121. In one embodiment, lead wires 109
may be encased in an insulating tube placed inside of the
registration device 101 or otherwise insulated by electrical
insulation 119. In some embodiments, lead wires 109 may be embedded
in a tube such as that made by the Phelps Dodge company which
includes conductors embedded in the walls of the tube.
Alternatively, lead wires 109 may be conductors placed within a
filar bundle that makes up the wall of the tube itself (as is known
in the art).
[0094] Registration device 101 may contain one or more detectable
elements 105a-105n. In one embodiment, detectable elements
105a-105n may be placed on or adjacent to position indicating
element 103, such that the location of detectable elements
105a-105n may be correlated to the location and/or orientation of
position indicating element 103 as disclosed in U.S. Pat. No.
6,785,571, which is incorporated herein by reference in its
entirety. Detectable elements 105a-105n may include radio-opaque
elements or elements that are otherwise detectable to certain
imaging modalities such as, for example, x-ray, ultrasound,
fluoroscopy, computerized tomography (CT) scans, positron emission
tomography (PET) scans, magnetic resonance imaging (MRI), or other
imaging devices. Detectable elements 105a-105n may enable the
detection and/or visualization of certain points of reference of
registration device 101 within a conduit residing in an anatomical
region of a patient, which may aid in registration, verification of
registration, dynamic referencing, navigation, and/or other
uses.
[0095] In some embodiments, registration device 101 may include one
or more features typically found in guidewires used in medical
procedures such as, for example, a tapered tip 111, a hydrophilic
coating 113 (or other type of coating), safety or torque
transmission, stiffening and/or support structures 115, metal filar
tube windings 117 (such as, for example, a helical spring winding,
braided or twisted filars etc.), or other elements.
[0096] In some embodiments, the distal portion of registration
device 101 may comprise a floppy portion with bending stiffness
less than the rest of the device. A floppy, bendable tip may enable
registration device 101 to be navigated into hard-to-reach,
arborized paths, which may not otherwise be possible without a
floppy tip. This may be accomplished by grinding the exterior of
registration device 101 to reduce its bending stiffness, or
otherwise changing the material properties of the tip in another
manner. In some embodiments, the distal tip portion of registration
device 101 may contain a pre-bent section, which may be bent from
approximately 15 to 120 degrees to assist in navigating an
anatomical region. In some embodiments, the distal tip of
registration device 101 may take on complex shapes such as, for
example, a "J" shape, or other shapes. In some embodiments, the
distal tip portion of registration device 101 may contain malleable
material, enabling the shape of the tip to be manually adjusted
during a medical procedure. In some embodiments, the distal tip of
registration device 101 may be closed or may contain a plug to
prevent material seeping into the device.
[0097] In one embodiment, position indicating element 103 may be
located at or near the tip of registration device 101. In other
embodiments, multiple position indicating elements may be located
at various points along the length of registration device 101.
[0098] FIG. 1B illustrates a cross-section of registration device
101 according to an embodiment of the invention as viewed from line
segment B-B of FIG. 1A. FIG. 1C illustrates a cross section of
registration device 101 according to an embodiment of the invention
as viewed from line segment C-C of FIG. 1A. FIGS. 1A-1C are
exemplary only. One of skill in the art would appreciate that
registration device 101 may include alternate configurations, some
or all of the components discussed herein, and/or additional
components.
[0099] FIG. 2 illustrates an exemplary process 200 according to an
embodiment of the invention, wherein registration of an anatomical
region of a patient may be performed. In an operation 201, one or
more images of the anatomical region of the patient and/or the
conduit within the anatomical region may be obtained by an imaging
device. An imaging device may include, for example, an x-ray
device, an ultrasound device, a fluoroscopic device, a computerized
tomography (CT) device, a positron emission tomography (PET)
device, a magnetic resonance imaging (MRI) device, an isocentric
fluoroscope, a rotational fluoroscopic reconstruction system, a
multislice computerized tomography device, an intravascular
ultrasound imager, a single photon emission computer tomographer,
or other imaging device. In some embodiments, the imaging device
may be part of, connected to, and/or exchange data with an
integrated system.
[0100] In an operation 203, position information regarding the path
of the conduit within the anatomical region may be obtained in the
frame of reference of the image(s) taken in operation 201 (i.e.,
the path of the conduit in "image space"). In one embodiment, the
path of the conduit may be obtained through a segmentation process
in which the images are examined for the conduit and connected
regions within the images (that are identified as the conduit) may
be coalesced to determine the spatial pathway of the conduit in the
coordinate system of the images. Several such methods are known in
the art such as, for example, those outlined by L. M. Lorigo in
Lorigo et al., CURVES: Curve Evolution for Vessel Segmentation, 5
Medical Image Analysis 195-206 (2001).
[0101] In an operation 205, the spatial pathway of the conduit in
the frame of reference of the patient (i.e., in the "patient
space") may be obtained. In one embodiment, this spatial pathway
(or "position data") may be obtained via a registration device
(similar to, or the same as, registration device 101 of FIG. 1)
that is inserted into the conduit, wherein the registration device
includes at least one position indicating element.
[0102] In one embodiment, the registration device may contain a
position indicating element at its tip. In an operation 205a, the
registration device may be inserted into the conduit within in the
anatomical region of the patient. In an operation 205b, the
tracking device may then sample the coordinates of the position
indicating element included within the registration device as the
registration device is moved within the conduit, resulting in
position information regarding the path of the conduit within the
anatomical region in the frame of reference of the tracking device
(this may also be referred to as the frame of reference of the
patient, i.e., the "patient space").
[0103] In other embodiments, the registration device may contain
multiple position indicating elements along its length. In these
embodiments, the registration device may be inserted into the
conduit within the anatomical region of the patient. The
coordinates of the multiple position indicating elements may then
be detected by a tracking device while the position indicating
elements are either moved or kept stationary within the conduit,
resulting in position information regarding the path of the conduit
within the anatomical region in the frame of reference of the
tracking device (i.e., the patient space). In one embodiment, if
the registration device contains multiple position indicating
elements and their coordinates are sampled within the conduit as
the conduit is moving (e.g., movement affecting the anatomical
region that in turn affects the conduit), enhanced tempero-spatial
information regarding the movement of the patient space may be
obtained.
[0104] In an operation 207, a registration transformation may be
calculated. In some embodiments a registration transformation may
include a registration transformation matrix or other suitable
representation of the registration transformation.
[0105] A transformation is a mathematical tool that relates
coordinates from one coordinate system to coordinates from another
coordinate system. There may be multiple methods to calculate the
registration transformation. One exemplary registration
transformation calculation method may include "brute force"
approach. A brute force approach may involve treating the
pre-registration image data and the registration position data as
completely independent datasets and manually attempting to match
the two datasets by altering each translation, rotation, and
scaling parameter in turn to create the best match. This however,
may be inefficient.
[0106] Another exemplary method may include an Iterative Closest
Point (ICP) algorithm, one version of which is described in U.S.
Pat. No. 5,715,166, which is incorporated herein by reference in
its entirety.
[0107] Another exemplary registration transformation calculation
method is known as singular valued decomposition (SVD) in which the
same point locations are identified in each coordinate system
(e.g., the image space and the patient space).
[0108] In an operation 209, the image information of the anatomical
region (image space) and the position information of the path of
the conduit within the anatomical region (patient space) may be
registered or mapped together using the registration
transformation. The registration or mapping may be performed by
bringing the coordinates of the anatomical region derived from the
image data (the image space) into coincidence with the coordinates
of the conduit within the anatomical region derived from the
tracking device/position indicating element (the patient space). In
some embodiments, additional coordinate sets may also be
"co-registered" with the image and tracking device data. For
example, a magnetic resonance image dataset may be first
co-registered with a computerized tomography dataset (both image
space), which may in turn be registered to the path of the conduit
in the frame of reference of the patient (patient space).
[0109] The result of mapping the image space data and the patient
space data together may include or enable accurate graphical
representations (e.g., on the original image data, surgical plan or
other representation) of an instrument or other tool equipped with
a position indicating element through the anatomical region. In
some embodiments, this navigation may enable image guided surgery
or other medical procedures to be performed in/on the anatomical
region.
[0110] For example, following registration, instruments such as
needles, probes, flexible endoscopes, stents, coils, drills,
ultrasound transducers, pressure sensors, or indeed any flexible or
rigid instrument that is equipped with a position determining
element, may be navigated into the anatomical region where the
registration occurred (in particular, near the conduit or regions
immediately adjacent to it). In one embodiment, images of the
anatomical region embellished with icons representing the
instrument location and orientation as it is moved may be
enabled.
[0111] In one embodiment, the invention provides a method for
verifying registration of an anatomical region. FIG. 3 illustrates
an exemplary process 300 according to an embodiment of the
invention, wherein registration of an anatomical region may be
verified. In an operation 301, an image of an anatomical region of
interest may be acquired using an imaging device. This anatomical
region may include or be equipped with one or more conduits. In an
operation 303, a registration of the anatomical region may be
performed. This registration may use the methods described herein
or may use other methods. In performing this registration a
registration transformation such as, for example, a registration
transformation matrix, may be calculated.
[0112] In an operation 305, one or more position indicating
elements may be placed into the anatomical region of interest.
Placement of the one or more position indicating elements may
utilize a conduit within the anatomical region. In one embodiment,
one or more position indicating elements may be placed within the
anatomical region of interest using a verification device. The
verification device may include a tube, a catheter, vascular
guidewire, or other device having one or more position indicating
elements attached to it. In one embodiment, the verification device
may be the same as or similar to registration device 101 of FIG.
1.
[0113] In an operation 307, the position of the one or more
position indicating elements may be sampled by a tracking device.
This position information may be combined with the registration of
operation 303. This combination may produce an "overlay image" or
"composite image" where the image space positions of the one or
more position indicating elements are calculated and displayed on
the image acquired in operation 301. In an operation 309, graphical
icons representing the location and/or orientation of the one or
more position indicating elements in the anatomical region may be
displayed in the overlay or composite image. This location and/or
orientation may be determined by the combined registration
transformation and the coordinates of the one or more position
indicating elements as sampled by the tracking device in operation
307.
[0114] In an operation 311, the one or more position indicating
elements may be moved within the anatomical region as their
positions are sampled by the tracking device. The transformed
location (as calculated using the registration transformation of
operation 307) of the one or more position indicating elements as
they are moved may be displayed on the image. Errors in the
registration may be indicated by movement of the one or more
position indicating elements outside of the registered path within
the anatomical region (e.g., such as outside a conduit registered
within the anatomical region). The absence of errors may be used to
verify the registration.
[0115] In one embodiment, another method of verification of
registration of an anatomical region may be performed and may be
used together or separately from the verification method described
above. In this method, one or more position indicating devices
(such as those included in a verification device described above)
may be placed into an anatomical region of a patient by way of, for
example, a conduit within the anatomical region. The location of
the one or more position indicating elements within the anatomical
region may then be imaged using an imaging device such as, for
example an x-ray device, ultrasound device, fluoroscopy device,
computerized tomography (CT) device, positron emission tomography
(PET) device, magnetic resonance imaging (MRI), or other imaging
device. The visualized location of the position indicating elements
within the anatomical region may then be compared to points within
the anatomical region as obtained by a registration. Discrepancies
between the images of the position indicating elements and the
points obtained by the registration may be indicative of errors in
the registration. In one embodiment, this operation may be
performed entirely numerically and automatically, e.g., through the
use of a computer to compare the two paths.
[0116] In one embodiment, if the verification device includes
multiple position indicating elements along its length, an image of
the position indicating elements as they are positioned at a single
point in time may be obtained. This image, as indicated above, may
be compared to points within the anatomical region obtained by the
registration for verification of the registration.
[0117] In another embodiment, if the verification device includes
one or more position indicating elements, at least one of which
resides at the distal tip of the verification device, an image of
the one or more position indicating elements as they are moved
within the conduit may be taken over a period of time, thus,
producing an image of the path if the conduit within the anatomical
region. This image may be compared to points within the anatomical
region obtained by the registration for verification purposes.
[0118] In another embodiment, the verification device itself may
comprise or be injected with a detectable material, such that an
image of the verification device inserted into the conduit at a
single point in time may produce an image of the path of the
conduit within the anatomical region. This also may be compared to
points within the anatomical region obtained by the registration
for verification purposes.
[0119] In one embodiment, the invention provides a referencing
device for dynamic referencing of an anatomical region of a
patient. As described below, the referencing device may be part of,
or be operatively connected to, an integrated system. In some
embodiments, the components of a referencing device may be the same
as, or similar to, registration device 101 of FIG. 1. FIG. 4
illustrates a referencing device 401 according to an embodiment of
the invention. Referencing device 401 may be or include a tube, a
catheter, a vascular guidewire, or similar object (referred to
herein for convenience as tube 407) that may be inserted into a
conduit within the anatomical region to be referenced.
[0120] In one embodiment, referencing device 401 may be freely
slidable in the conduit, and may be inserted into or removed from
the conduit. In some embodiments, referencing device 401 may be
fixed or held within the conduit by one or more restraining devices
403 such as, for example, a balloon, vacuum ports along its length,
deployable hooks, cages, stiffening wires, or other restraining
devices. During and following registration procedures with which
referencing device 401 is used, referencing device 401 may be held
fixed relative to the anatomical region.
[0121] Referencing device 401 may include one or more position
indicating elements .sup.405a-405n along its length. Position
indicating elements 405a-405n may enable the location, position,
orientation, and/or coordinates of one or more points of reference
of referencing device 401 to be detected by a tracking device as
they exist within the fixed frame of reference of the tracking
device. As such, position indicating elements 405a-405n may enable
detection of the location, position, orientation, coordinates
and/or motion over time of one or more points of reference within
an anatomical region of a patient.
[0122] In one embodiment, a position indicating element 405 may
include a device whose position may be detectable by a tracking
device in the frame of reference of the tracking device. For
example, a position indicating element 405 may include a coil that
may produce a magnetic field that is detectable by an
electromagnetic tracking device. In one embodiment, position
indicating element 405 may include a coil that detects a magnetic
field emitted by an electromagnetic tracking device. In some
embodiments position indicating elements 405a-405n and their
position in the frame of reference of a tracking device may be
enabled by "Hall Effect" transducers or superconducting quantum
interference devices (SQUID). In other embodiments, position
indicating elements 405a-405n may include elements whose position
is detectable by a global positioning system (GPS) enabled tracking
device, an ultrasonic tracking device, a fiber-optic tracking
device, an optical tracking device or a radar tracking device.
Other types of position indicating elements and/or tracking devices
may be used. In one embodiment, the tracking system used to detect
the position of position indicating elements 405a-405n may be part
of, or operatively connected to, an integrated system.
[0123] Referencing device 401 may include electrical wiring,
electrical shielding, insulation, electrical connections, or other
electrical elements such as those described with regard to
registration device 101 of FIG. 1. These electrical components may
enable the operation of one or more position indicating elements
and/or the connection of the referencing device to an integrated
system according to the invention. In some embodiments, the
companion tracking device to position indicating elements 405a-405n
(or other element of the invention) may be part of, connected to,
and/or exchange data with an integrated system according to the
invention.
[0124] In some embodiments, one or more of position indicating
elements 405a-405n may be located along the length of referencing
device 401. In some embodiments, referencing device 401 may be
constructed so that the region surrounding one or more position
indicating elements 403 does not bend. In some embodiments, one or
more position indicating elements .sup.405a-405n may be encased in
an insulating tube placed inside of referencing device 401.
[0125] In one embodiment, the outside of referencing device 401 (or
other aspects of the invention) may include a lubricious and/or
hydrophilic coating. In some embodiments, the distal portion of
referencing device 401 may include a floppy portion with bending
stiffness less than the rest of the device. This floppiness may be
accomplished by grinding the exterior of the tube to reduce its
bending stiffness or otherwise. In some embodiments, the distal tip
of referencing device 401 may be closed or include a plug to
prevent material seeping into the device. In some embodiments,
referencing device 401 may include an intrinsic or shapeable
curve.
[0126] Referencing device 401 or other element of the invention may
contain a pressure sensor, an electromyograph (EMG) sensor, an
electrocardiograph (ECG) sensor or other devices or sensors, which
may be used to gate the sampling of the reference sensors, to
measure blood pressure, air pressure, or other quality.
[0127] FIG. 5 illustrates an exemplary method 500 according to an
embodiment of the invention wherein a referencing device may be
used to dynamically reference an anatomical region of a patient. In
an operation 501, a referencing device having one or more position
indicating elements may be inserted into one or more conduits
within the anatomical region of interest.
[0128] In some embodiments, it may be desirable to approximate or
model the anatomical region as a rigid body (a "rigid body model").
In these cases, it may be desirable to utilize a device capable of
resolving six degrees of freedom. In some embodiments, it may be
desirable to use a registration device having position indicating
elements that each measure less than six-degrees of freedom, as
they may be simpler to manufacture, can generally be made smaller,
and may have other advantages. To resolve six degrees of freedom
where fewer than six degrees of freedom are measured by a single
position indicating element, multiple position indicating elements
may be utilized in combination. This may be best facilitated if the
position indicating elements are in a known spatial relationship to
one another.
[0129] As a priori spatial relationships between the position
indicating elements may not be consistently known, it may be
difficult to formulate the six degrees of freedom representation
unless the spatial relationship between the position indicating
elements can be determined. In one embodiment, this relationship
may be determined by imaging the position indicating elements of
the referencing device within the anatomical region to determine
their relative location, position, and/or orientation and hence,
their spatial relationship to one another. In one embodiment, one
or more detectable elements detectable by an imaging device may
exist on or near the position indicating elements of the
referencing device to aid determination of this spatial
relationship. In other embodiments the position indicating elements
themselves may be detectable by an imaging device. In one
embodiment, a tracking device may be placed in multiple relative
locations to the position indicating elements, and the relative
location of the position indicating elements may be calculated,
enabling determination of a six degree of freedom representation of
the position indicating elements.
[0130] In some embodiments, a subset or weighted combination of the
position indicating elements may be used in the creation of a rigid
body model of the anatomical region. In general, the position
closest to an identified point of interest (e.g., where a medical
procedure is to be performed) may be weighted higher than those
distant in calculating the rigid body (some of which may be
weighted at 0).
[0131] For certain anatomical regions having consistent or nearly
consistent, repetitive predictable motion (e.g., heartbeat,
breathing, or other motion), the motion in one part of the
anatomical region may be inferred and modeled from a single point
measurement.
[0132] In one embodiment, multiple rigid body models of the same
region may be used. To construct these multiple rigid body models,
the positions of different combinations of position indicating
elements may detected be at different times. For example, in an
embodiment where three position indicating elements are placed
within an anatomical region, elements one and two may be detected
at a certain point in time to form a first rigid body, elements one
and three may be detected at a different point in time for form a
second rigid body, and elements two and three may be detected at a
third point in time to form a third rigid body. In some
embodiments, the different points in time may be selected to
correspond to movement affecting the anatomical region. In some
embodiments, the points in time wherein the different combinations
are detected may not be different. It will be understood to those
skilled in the art that the number of position indicating elements
may be more than three, as may be the number of points in time at
which the positions of one or more combinations of position
indicating elements are detected.
[0133] In one embodiment, the rigid body models used for dynamic
referencing of that region may be modeled from different
combinations of position indicating elements than an adjacent
anatomical region. The rigid body model that is formed may thus be
synchronized both spatially, and temporally with the anatomical
region. A sensor, such as a pressure transducer, electrocardiogram
monitor, or other sensor may be placed on the patient and used to
measure phases of these cycles to assist with selection of the
appropriate combination of position sensing elements.
[0134] In some embodiments, a rigid body model used to represent
the motion of the anatomical region may be obtained by using least
squares combination of data from all elements of the invention
(imaging, registration, referencing, and/or other data) to create a
rigid approximation of the anatomical region of interest (even if
the anatomical region is deformable). The resulting approximation
may be more accurate than, for example, selecting two position
indicating elements as they exist in the anatomical region, and
creating a rigid body based on them alone.
[0135] In other embodiments, a rigid body model may not by used to
model the motion of the anatomical region. In these embodiments,
the position indicating elements may be used to drive a finite
element model or other non-rigid (deformable) model of the
anatomical region by for example, acting as boundary
conditions.
[0136] In an operation 503, the spatial relationships (e.g.,
position, orientation) of the one or more position indicating
elements relative to one another and/or relative to the anatomical
region may then be determined via an imaging device, the tracking
device, and/or by other method. These spatial relationships may be
determined by the methods discussed above. In an operation 505,
these spatial relationship measurements may by used to form one or
more models, such as a rigid body model (discussed above),
piecewise rigid body representation, or deformable model of the
anatomical region.
[0137] Any movement affecting the conduit within the anatomical
region of interest may be detected via its effect on the one or
more position indicating elements. This motion may include any
motion that affects the contents of the anatomical region of
interest such as, for example, a heartbeat, breathing, voluntary or
involuntary movement by the patient, movement of the soft or
deformable organs or tissues within the anatomical region due to
intervention by a medical professional or instrument, gross
movement of the body of the patient, or other movement. In an
operation 507, this movement may be monitored for by monitoring the
position of the position indicating elements using the tracking
device.
[0138] In an operation 509, the information provided by the
position indicating elements may be used together with the model of
the anatomical region to determine the motion of the anatomical
region. Operation 509 may produce a dynamic model of the anatomical
region that models any motion affecting the anatomical region in
real time. This "model of motion" may be used to account for the
motion of the anatomical region. In one embodiment, the model of
motion may be used to adjust a registration of the anatomical
region so as to account for, in real time, any movement affecting
the anatomical region. In another embodiment, the model of motion
may be used to adjust coordinates reported by the position
indicating elements attached to an instrument in the anatomical
region so as to account for, in real time, any movement affecting
the anatomical region. In another embodiment, the model of motion
may be used to form a local coordinate system in the vicinity of an
instrument containing position indicating elements within the
anatomical region. The model of motion may also be used to adjust
the position of this local coordinate system. If the position
indicating elements attached to the instrument are expressed in
terms of this local coordinate system, it may also be possible to
account for, in real time, any movement affecting the anatomical
region. Thus, re-registration need not be performed to account for
movement affecting the anatomical region.
[0139] FIGS. 6A and 6B illustrate a device 600 that may be used, by
itself or in conjunction with a naturally existing conduit to
enable and/or aid the apparatus or processes described herein. In
one embodiment, device 600 may include a tube, a catheter, or other
conduit 601. For convenience, this embodiment will refer to a
catheter 601. The invention is not so limited. Catheter 601 may
have properties otherwise consistent with its use as described
herein as would be apparent to those having ordinary skill in the
art. In some embodiments, catheter 601 may comprise a material that
does not mask other features of the invention otherwise detectable
to imaging devices. In one embodiment, catheter 601 need not be
independent, and could itself be a lumen or in a lumen within an
endoscope such as a cystoscope, brochioscope, or other
instrument.
[0140] In some embodiments, catheter 601 may include a primary
lumen 603 that may accommodate one or more of a registration
device, a verification device, a referencing device, a therapeutic
instrument, an endoscope, a biopsy device, a brush, a guidewire, a
tube for inflation or activation of fixation methods or members, a
channel for injection of contrast agent, or other device. In some
embodiments, catheter 601 may include two or more lumens, internal
tubes, or channels. These lumens may each accommodate one or more
of a registration device, a verification device a referencing
device, a guidewire, a tube for inflation or activation of fixation
methods or members, a channel for injection of contrast agent, a
channel for deploying a therapeutic device (e.g., endoscope,
ultrasound probe, etc.), or other elements. Some of these lumens
may be shared by multiple devices/elements, if appropriate.
[0141] FIG. 6B illustrates a cross section of apparatus 600. In one
embodiment, apparatus 600 may include one or more of a registration
device lumen 605, a referencing device lumen 607, a contrast agent
lumen 609, a lumen for other devices such as medical tools for
performing an intervention and/or medical procedure (not otherwise
indicated), and/or other lumens or channels. In some embodiments
one or more of the aforementioned lumens may enable devices to be
removably inserted into catheter 601 and freely slidable
therein.
[0142] Contrast agent lumen 609 may enable the introduction of a
radio-opaque (or otherwise detectable) contrast agent such as, for
example, barium compounds or similar compounds. This contrast agent
may enable the visualization of catheter 601 and/or the anatomical
region near (or beyond) the distal end of catheter 601 by an
imaging device.
[0143] In some embodiments, catheter 601 may include one or more
restraining devices 602 for fixating itself within an anatomical
region of a patient such as, for example, a balloon, deployable
hooks, cages, stiffening wires, screws, hooks, vacuum devices,
helical catheter arrangement, or other restraining devices.
[0144] In some embodiments, catheter 601 may include a hub 611
containing ports that can accommodate various wires and tubes
described herein. Hub 611 may comprise various fittings depending
on the number of lumens/capabilities of the catheter. For example,
hubs used to insert a referencing device as described herein may
include constructions capable of locking the referencing device in
a particular position and sealing it from any fluid flow, if
appropriate. Other hubs may be adaptable to attach multi-port
valves for selecting a fluid source such as, for example, a
contrast agent that may be injectable into catheter 601. Other hubs
may be used, for example, those for handling wires, cables,
electrical connections, or for other uses.
[0145] In some embodiments, catheter 601 may include one or more
detectable elements and or position indicating elements along its
length (not otherwise illustrated in FIG. 6). In some embodiments,
detectable elements and/or position indicating elements included
in/on catheter 601 may be used for preliminary positioning of
catheter 601 in the anatomical region of the patient. In some
embodiments, the detectable elements and/or position indicating
elements may be used to enable catheter 601 itself to be used as a
registration device, a verification device, a referencing device,
and/or for other uses. In some embodiments, the detectable elements
and/or position indicating elements may enable catheter 601 to
serve as a secondary or backup device for registration,
verification, and or dynamic registration (primary methods being
performed by the devices described herein or by other devices).
[0146] While separate devices (e.g., catheter, referencing device,
registration device, etc.) are described herein for performing
various tasks (e.g., registration of an anatomical area of a
patient, verification of registration, dynamic referencing of an
anatomical region, contrast agent injection into an anatomical
region, navigation within an anatomical region, or other tasks), it
would be understood by one having skill in the art that a single
device (e.g., catheter 101), when equipped with the proper subset
of components (e.g., position indicating elements, detectable
elements, lumens, guidewires, etc.) may be used to perform any
subset or combination of the functions described herein. As such,
in one embodiment of the invention, some or all of the features of
the registration device, the verification device, and/or the
referencing device may be included in a manufactured conduit
(similar to or the same as catheter 601) to enable the apparatus or
processes described herein.
[0147] In some embodiments, one or more of the devices and/or
processes described herein may be used with each other in various
combinations. FIGS. 7A-7G are exemplary illustrations according to
an embodiment of the invention wherein a catheter 701, referencing
device 709, and a registration device 713 may be used to perform
registration and referencing of an anatomical region near a
patient's heart 702. Those having ordinary skill in the art will
realize that similar devices and techniques according to the
invention may be used in the lung to map out pulmonary pathways, in
the colon to map out parts of the digestive system, the urethra to
map out the urinary system, or in other areas of the human or
mammalian anatomy to map or image other areas.
[0148] FIG. 7A, illustrates a catheter 701 (similar to or the same
as catheter 601 of FIG. 6) or other hollow tube that may be
introduced into a patient through an orifice of the patient (not
otherwise illustrated) such as, for example, the mouth, the nose,
the urethra, the anus, an incision into the circulatory system, a
manufactured channel created during a surgical procedure, or other
orifice (whether naturally existing or created) in the patient.
FIG. 7B is an exemplary illustration according to an embodiment of
the invention wherein catheter 701 is inserted into a vessel 703 of
patient 704. Referring back to FIG. 7A, catheter 701 may be
introduced through a portal, over a guidewire or any other method
as known in the art. Catheter 701 may be introduced through an
orifice into vessel 703 or region of the patient such as, for
example the bronchial tree, the digestive tract, ventricles in the
brain, the esophagus, the circulatory system, or other vessels or
regions of the anatomy of the patient.
[0149] Catheter 701 may be placed using conventional techniques
(e.g., fluoroscopy) to a position in the body. Target 705 is
illustrated in FIG. 7A as a dark circle. Target 705 may include
something of interest such as, for example, a stenosis, an
aneurysm, a tumor, a polyp, a calcification, or other element or
condition of interest. Is should be noted that because FIG. 7A is
illustrative only, target 705 may not necessarily exist in the
circulatory system but may exist in another anatomical region of
the body. Additionally, target 705 need not exist in the precise
anatomical system in which catheter 701 and other elements of the
invention are placed, but may be nearby, such as a tumor present in
the same or adjacent tissue to that being monitored by catheter
701.
[0150] Catheter 701 may be fixed in place to prevent motion within
vessel 703. FIG. 7C illustrates catheter 701 fixed in place in
through the use of an inflatable member such as, for example, a
balloon 707. In some embodiments, catheter 701 may be fixed using
deployable cages, hooks, insertable stiffening wires, vacuum
devices, helical catheter arrangement designed to maintain catheter
location within an anatomical region or conduit therein, or other
methods known in the art. In some embodiments, catheter 701 may be
fixed at several locations or continuously along its length, not
just the tip, so that it does not move independently of the anatomy
or change its shape once placed.
[0151] FIG. 7C illustrates a referencing device 709 (similar to or
the same as referencing device 401 of FIG. 4) may be inserted into
a lumen of catheter 701 (if it is not already integrally present in
the construction of catheter 701). Referencing device 709 may
contain multiple position indicating elements 711a-71n, enabling
position information of position indicating elements 711a-711n and
ultimately, vessel 703 to be determined. In some embodiments,
referencing device 709 may be placed elsewhere (such as another
vessel) or omitted entirely and a different method of dynamic
referencing used, or dynamic referencing not employed.
[0152] Once in embodiment, referencing device 709 may be fixed in
place within catheter 701 so that it moves with the anatomy (which
may be advantageous for performing dynamic referencing). If, for
example, referencing device 709 is fixed or held stationary within
catheter 701, and catheter 701 is fixed to and moves with the
anatomy, then referencing device 709 may be able to move with the
anatomy. If referencing device 709 is initially independent of
catheter 701, deployable hooks, cages or balloons or other
restraining devices (not otherwise illustrated) may be used to fix
referencing device 709 in place.
[0153] FIG. 7D illustrates a registration device 713 (similar to or
the same as registration device 605 in FIG. 6 or registration
device 101 in FIG. 1) that may be used to register the anatomical
region. In some embodiments, registration device 713 may be
positioned almost entirely within catheter 701. Registration device
713 may include at least one position indicating element 715 which
may, in some embodiments, be located near the tip of registration
device 713.
[0154] As described above, registration of an anatomical region may
include imaging the anatomical region. In one embodiment, the
imaging may include simultaneous or "coordinated" biplanar x-rays,
or other methods of imaging. In some embodiments, in conjunction
with imaging, a bolus of contrast agent 717 may be injected into
catheter 701 so that catheter 701 is filled with contrast agent
717. In some embodiments, contrast agent 717 may include radio
opaque or other detectable (by an imaging device) contrast agent
such as, for example, a barium compound or other suitable agent. By
way of example, in vascular surgery, a contrast agent containing a
barium compound or a bolus of carbon dioxide gas is routinely
injected into a catheter to visualize the vasculature in the
vicinity of the tip of a catheter. In pulmonary surgery, a
propyliodone or Xenon-133 mixture may be administered to the
patient. FIG. 7D illustrates contrast agent 717 distal to the tip
of catheter 701.
[0155] In some embodiments, the injection of contrast agent 717
into catheter 701 may have at least two effects: (1) it may render
catheter 701 radio-opaque or otherwise detectable, so its path can
be determined through an imaging device; and (2) excess contrast
agent 717 may be directed out of the distal end of catheter 701 so
that contrast agent 717 occupies the vessels, cavities, tissue, or
other area surrounding catheter 701, enabling clear visualization
image of the paths in the vicinity and beyond the tip of catheter
701. Without this contrast agent, these areas are not usually
visible to an imaging modality. FIG. 7E is an exemplary
illustration of the visualization that may be provided by
introduction of contrast agent 717 into the distal vessels of the
anatomical region of interest.
[0156] The second effect of introduction of contrast agent 717 into
catheter 701 may also be achieved by injecting contrast agent 717
through a separate catheter, lumen, needle, or other method
appropriate for the intervention being performed. The first effect
may also be achieved by making registration device 713, catheter
701, or some component of catheter 701 from radio-opaque material
so as to show the pathway of registration device 713.
[0157] While a similar result to the first and second effects of
introducing a contrast agent into catheter 701 may be achieved by
enhancing the whole anatomical vessel with contrast agent, it is
generally desirable to inject as little contrast agent as possible
into the anatomy of the patient, as: (a) these compounds tend to be
nephrotoxic (toxic to the kidneys), so it is preferable to inject
as little contrast as possible; (b) visualizing the path of
catheter 701 alone would better reflect the precise path of a
device contained within the catheter, since flooding a whole vessel
or entire anatomical region with contrast agent, especially if a
large or complex region is involved, lends inaccuracy to the actual
path taken by an instrument (e.g., contrast agent may travel along
areas not traveled by the instrument); and (c) the injection of
contrast agent 717 may be easily facilitated in the local
anatomical region near the distal end of the catheter and is more
conducive to precise visualization beyond the catheter tip if
required.
[0158] In one embodiment, the 2D anatomical region may be
optionally co-registered with a preoperative image, where
applicable. For example, if a pre-operative scan (e.g., MRI,
arterial phase image, or other scan) were conducted and revealed a
tumor or other lesion, the preoperative scan may be co-registered
with an image taken for registration purposes prior to
registration.
[0159] In some embodiments, during registration, a three
dimensional path of the center of the registration device (the
"centerline") may be calculated in the coordinate system of the
previously obtained images of the anatomical region. In some
embodiments, a three-dimensional (3D) map of the anatomical area of
interest and/or the location of at least part of registration
device 713 may be constructed during this calculation. Simultaneous
biplane fluoroscopy (the rays of which are indicated as imaging
waves 719), multi-slice CT, or other fast 3D image acquisition of
the anatomical region may be used, in conjunction with images
(those mentioned above or other images) of the anatomical region to
construct the 3D map and/or the location of at least part of
registration device 713. A 3D mathematical map of the structure and
channels of the anatomical region to be navigated beyond the tip of
catheter 701 may also be constructed using the images (those
mentioned above or other images) or scan information of the
anatomical region (particularly if a contrast agent 717 has been
introduced therein). In some embodiments, the image data (e.g., the
3d model/map) regarding the anatomical region and the conduit
therein (e.g., vessel 705 and/or catheter 701) may be expressed as
a 3D spline, parametric equations, voxels, polygons, coordinate
lists, or other indicators of the walls or path of the component
structures, or simply a "skeleton" of the central axis (centerline)
of the component tubes and structures, existing in the coordinate
system of the image devices.
[0160] Other surrounding areas of interest may also be incorporated
into the map. In vascular surgery, for example, the 3D map may
include the vessels enhanced at the end of the catheter showing the
path to a stenosis or narrowing of one of the vessels.
[0161] The 3D map of registration device 713 within catheter 701
may be reconstructed from images of the contrast agent 717
constrained within catheter 701, from the image of catheter 701
itself, from images of registration device 713, and/or from other
images or source of information regarding the 3D path. This 3D path
may form the coordinates of the path of registration device 713 in
the "image space" or coordinate system of the imaging device.
[0162] During registration of an anatomical region, a tracking
device may be activated and the coordinates of registration device
713's path in a coordinate system of the tracking device (as
indicated by position indicating element 715) or, the coordinates
in the frame of reference of a coordinate system created by
referencing device 709 (if used) may be determined. In some
embodiments, this may be accomplished by sliding the registration
device 713 through catheter 701 while a tracking device
simultaneously samples the coordinates of position indicating
element 715. This essentially retraces the image space path that
had been visualized by the previous operations and provides a
corresponding set of position data in the "patient space" or
coordinate system of the tracking system. FIGS. 7F and 7G
illustrate registration device 713 and position indicating element
715 being moved within catheter 701. The position data obtained by
the tracking device may also be expressed as a 3D spline,
parametric equations along the registration tube, coordinate lists,
or other suitable formats.
[0163] A registration transformation may then be calculated. As
noted herein, there may be multiple methods to calculate the
registration transformation. In an exemplary registration
transformation calculation method, the (x,y,z) positions may be
parameterized as a function of distance along the path traveled by
registration device 713. In one embodiment, at the start of
position data collection, registration device 713 is located within
catheter 701 at the time of imaging (e.g., x-ray and/or other
imaging data) to determine its path (i.e., S(0)). As registration
device 713 is moved within catheter 701, position indicating
element 715 moves a distance, S(t), which can be estimated from the
(x,y,z) position of position indicating element 715 using the
incremental Euclidian distance, i.e.
sqrt((x.sub.k-x.sub.i).sup.2+(y.sub.k-y.sub.i).s-
up.2+(z.sub.k-z.sub.i).sup.2), where Pk=(x.sub.k, y.sub.k, z.sub.k)
are the position indicating element coordinates at the k.sup.th
sample and Pi=(x.sub.i, y.sub.i, z.sub.i) are the sensor
coordinates of the i.sup.th sample. In general, the criteria for
selecting i and k may be as follows:
1 set S = 0 set sample = 0 NEXT_i: set i = P (sample) NEXT_k: set
sample = sample +1 set k = P (sample) set time = sample +1 if
sqrt((x.sub.k - x.sub.i).sup.2 + (y.sub.k - y.sub.i).sup.2 +
(z.sub.k - z.sub.i).sup.2) > threshold distance { S = S +
sqrt((x.sub.k - x.sub.i).sup.2 + (y.sub.k - y.sub.i).sup.2 +
(z.sub.k - z.sub.i).sup.2) // distance from sample 0 to sample k.
// calculate corresponding point in image space, of distance S from
the start set sample = sample +1 if more samples: go to NEXT_i }
else { if more samples: go to NEXT_k }
[0164] Once position indicating element 715 moves more than a
predefined amount (the threshold distance), S can be calculated
from the image data showing the path of registration device 713.
Unless this is done, noise will be continually added to the
estimate of S, and the estimates of S will always be higher than
the correct measurements. At corresponding values of S, the data
from the image data (image space) is matched to the position
indicating element space data (patient space), producing a high
quality paired point matching at locations all along catheter
701.
[0165] Having determined an image space set of coordinates of the
path of catheter 701 and a patient space set of coordinates of the
same path, registration may be performed between the position data
of the patient space and the imaging data of the patient space. As
discussed, this registration may involve calculation of a
transformation matrix to bring the two sets of data from different
coordinate systems into coincidence with one another. In one
embodiment, additional coordinate sets may also be "co-registered"
with the image and tracking coordinates. In a non-rigid
registration, the registration matrix may be allowed to vary over
time and location in the registered region.
[0166] Once an anatomical region has been registered, a tube, a
navigation device, therapeutic tools, needles, probes, flexible
endoscopes, stents, coils, drills, ultrasound transducers, pressure
sensors, or indeed any flexible or rigid device that is equipped
with a position indicating element may be inserted into the
respective conduit and used for navigation purposes, for a
therapeutic or other medical procedure, or for other purposes. In
one embodiment, the registration may be used to generate or
highlight an image wherein the navigable conduit is visible. The
position indicating element of the device or tool may be tracked by
a tracking device, and the position of the device or tool may be
displayed in the generated or highlighted image, enabling
navigation. Additionally, verification of the registered area
according to the methods described herein (or other methods) may
also be performed.
[0167] In some embodiments (e.g., where contrast agent was injected
into regions distal to the tip of a catheter or tube used for
registration), regions distal to the tip of the catheter may be
displayed in an image and navigated as well.
[0168] By way of example, in a cardiac case, it may be possible to
navigate the 3D models of any structures or vessels that were
enhanced distal to catheter 701. Once registration, dynamic
referencing and verification have been performed (as deemed
necessary), these 3D models may be used as a map (a "roadmap") to
provide an indication of the current position of a position
indicating element in an instrument without the need for additional
fluoroscopy. Once the instrument or guidewire containing position
indicating elements has achieved its target position, its location
may be confirmed (if desired) using x-rays, ultrasound, or other
method. Tracking may be discontinued and catheter 701 (and other
elements used for navigation, registration, dynamic referencing,
and verification) may be removed by sliding it over the proximal
portion of the instrument or guidewire while leaving the instrument
or guidewire in position. A second catheter, which may be a
special-purpose catheter such as, for example, one designed for
stent employment or for other purposes, may then by slid over the
instrument or guidewire to perform some any number of specialized
tasks or therapies at this, the target location.
[0169] In complex situations, it may be necessary to repeat some or
all of the steps above to obtain revised registrations or navigable
paths.
[0170] In some embodiments, the devices described herein such as,
for example, a conduit (e.g., catheter), the registration device,
the verification device, and/or the referencing device may be
combined with one another and/or with one or more of a pressure
sensor capable of monitoring fluid or gas pressure, an
electrocardiograph (ECG) to monitor the phase of the heart beat, a
respiratory apparatus to measure the phase of respiration,
electrical sensors to measure the electrical activity in a region,
or other devices. The addition of one or more of the aforementioned
devices may enable position sampling to be gated to particular
phases in cardiac, respiratory, or other physiological cycle.
Gating involves sampling only at a particular instant during a
motion. By restricting measurements to only those times when it is
known that the system is in a stable or more predictable state, it
may be possible to increase the accuracy of position measurements
or render them more applicable to particular phases during these or
other physiological cycles. Additionally, the addition of one or
more of the aforementioned devices may enable measurement of the
ambient blood, fluid, or air pressure and/or measurement of
chemical, biological agent, or drug concentration at particular
locations and possibly correlated to the phase of a given
physiological cycle.
[0171] In some embodiments, the invention may include a
computer-implemented integrated system ("integrated system") for
performing one or more of the methods described herein, including
any of the features, function, or operations described in FIGS. 2,
3, or 5 (as well as other methods such as, for example,
therapeutic, diagnostic, or other methods). The integrated system
may also enable any of the devices, elements, or apparatus
described herein (as well as other apparatus). FIG. 8 is an
exemplary illustration of an integrated system 800 according to an
embodiment of the invention. In one embodiment, an integrated
system according to the invention may include a computer element
801. Computer element 801 may include a processor 803, a memory
device 805, a power source 807, a control application 809, one or
more software modules 811a-811n, one or more inputs/outputs
813a-813n, a display device 817, a user input device 819, and/or
other elements.
[0172] Computer element 801 may include one or more servers,
personal computers, laptop computers, or other computer devices.
Computer element 801 may receive, send, store, and/or manipulate
any data necessary to perform any of the processes, calculations,
or operations described herein (including any of the features,
functions, or operations described in FIGS. 2, 3, or 5. Computer
element 801 may also perform any processes, calculations, or
operations necessary for the function of the devices, elements, or
apparatus described herein.
[0173] According one embodiment, computer element 801 may host a
control application 809. Control application 809 may comprise a
computer application which may enable one or more software modules
811a-811n
[0174] In some embodiments, computer element 801 may contain one or
more software modules 811a-811n enabling processor 803 to receive,
send, and/or manipulate imaging data regarding the location,
position, and/or coordinates of one or more instruments, devices,
detectable elements, position indicating elements, or other
elements of the invention inside an anatomical region of a patient.
This imaging data may be stored in memory device 805 or other data
storage location.
[0175] In some embodiments, one or more software modules 811a-811n
may also enable processor 803 to receive, send and/or manipulate
data regarding the location, position, orientation, and/or
coordinates of one or more position indicating elements or other
elements of the invention inside the anatomical region of the
patient. This data may be stored in memory device 805 or other data
storage location.
[0176] In some embodiments, one or more software modules 811a-811n
may also enable processor 803 to calculate one or more registration
transformations, perform registration (or mapping) of coordinates
from two or more coordinate systems according to the one or more
transformation calculations, and produce one or more images from
registered data. In some embodiments, images produced from image
data, position data, registration data, other data, or any
combination thereof may be displayed on display device 817.
[0177] In some embodiments, one or more software modules 811a-811n
may also enable processor 803 to receive, send, and/or manipulate
data regarding the location, orientation, position, and/or
coordinates of one or more position indicating elements for use in
constructing a rigid-body description of an anatomical region of a
patient. In some embodiments, one or more software modules
811a-811n may enable processor 803 to create of dynamic,
deformable, and/or other models of an anatomical region of the
patient, and may enable the display of real time images regarding
the anatomical region. In some embodiments, these images may be
displayed on display device 817.
[0178] In one embodiment, integrated system 800 may include a
registration device 821 (the same as or similar to registration
device 101 of FIG. 1). In some embodiments, registration device 821
may be operatively connected to computer element 801 via an
input/output 813. In other embodiments, registration device 821
need not be operatively connected to computer element 801, but data
may be sent and received between registration device 821 and
computer element 813. Registration device 821 may, inter alia, aid
in providing image data, location data, position data, and/or
coordinate data regarding an anatomical region of the patient or
one or more elements of the invention within the anatomical region
of the patient. The registration device may otherwise enable
registration of the anatomical region the patient, (including soft
tissues and/or deformable bodies).
[0179] In one embodiment, integrated system 800 may include a
referencing device 823 (the same as or similar to referencing
device 401 of FIG. 4). In some embodiments, referencing device 823
may be operatively connected to computer element 801 via an
input/output 813. In other embodiments, referencing device 823 need
not be connected to computer element 801, but data may be sent and
received between referencing device 823 and computer element 813.
Referencing device 823 may, inter alia, aid in providing image
data, location data, position data, coordinate data, and/or motion
data regarding an anatomical region of the patient or one or more
elements of the invention within the anatomical region of the
patient. Referencing device 823 otherwise enable dynamic
referencing of an anatomical region of a patient, (including soft
tissues and/or deformable bodies).
[0180] In one embodiment, integrated system 800 may include a
tracking device 825. In one embodiment, tracking device 825 may be
operatively connected to computer element 825 via an input/output
813. In other embodiments, tracking device 825 need not be
operatively connected to computer element 825, but data may be sent
and received between tracking device 825 and computer element 813.
Tracking device 825 may include an electromagnetic tracking device,
global positioning system (GPS) enabled tracking device, an
ultrasonic tracking device, a fiber-optic tracking device, an
optical tracking device, a radar tracking device, or other type of
tracking device. Tracking device 825 may be used to obtain data
regarding the three-dimensional location, position, coordinates,
and/or other information regarding one or more position indicating
elements within an anatomical region of the patient. Tracking
device 825 may provide this data/information to computer element
801.
[0181] In one embodiment, integrated system 800 may include an
imaging device 827. In one embodiment, data may be sent and
received between imaging device 827 and computer element 813. This
data may be sent and received via an operative connection, a
network connection, a wireless connection, through one or more
floppy discs, or through other data transfer methods. Imaging
device 827 may be used to obtain image data, position data, or
other data necessary for enabling the apparatus and processes
described herein. Imaging device 827 may provide this data to
computer element 813. Imaging device 827 may include x-ray
equipment, computerized tomography (CT) equipment, positron
emission tomography (PET) equipment, magnetic resonance imaging
(MRI) equipment, fluoroscopy equipment, ultrasound equipment, an
isocentric fluoroscopic device, a rotational fluoroscopic
reconstruction system, a multislice computerized tomography device,
an intravascular ultrasound imager, a single photon emission
computer tomographer, a magnetic resonance imaging device, or other
imaging/scanning equipment
[0182] Other devices and or elements such as, for example,
temperature sensors, pressure sensors, motion sensors, electrical
sensors, EMG equipment, ECG equipment, or other equipment or
sensors may be included in and/or may send and receive data from
integrated system 800. Additionally, any therapeutic diagnostic, or
other medical tools or devices may also be included in and/or may
send and receive data from integrated system 800.
[0183] In one embodiment, the various instruments and/or devices
described herein may be interchangeably "plugged into" one or more
inputs/outputs 813a-813n. In some embodiments, the software,
hardware, and/or firmware included integrated system 800 may enable
various imaging, referencing, registration, navigation, diagnostic,
therapeutic, or other instruments to be used interchangeably with
integrated system 800.
[0184] Those having skill in the art will appreciate that the
invention described herein may work with various system
configurations. Accordingly, more or less of the aforementioned
system components may be used and/or combined in various
embodiments. It should also be understood that various software
modules 811a-811n and control application 809 that are used to
accomplish the functionalities described herein may be maintained
on one or more of the components of system recited herein, as
necessary, including those within individual medical tools or
devices. In other embodiments, as would be appreciated, the
functionalities described herein may be implemented in various
combinations of hardware and/or firmware, in addition to, or
instead of, software.
[0185] Other embodiments, uses and advantages of the invention will
be apparent to those skilled in the art from consideration of the
specification and practice of the invention disclosed herein. The
specification should be considered exemplary only, and the scope of
the invention is accordingly intended to be limited only by the
following claims.
* * * * *