U.S. patent application number 14/589506 was filed with the patent office on 2015-04-30 for methods and systems for guiding an emission to a target.
This patent application is currently assigned to Vantage Surgical Systems, Inc.. The applicant listed for this patent is Vantage Surgical Systems Inc.. Invention is credited to Hubschman P. Jean, Steven Schwartz, Tsu-Chin Tsao, Jason Wilson.
Application Number | 20150115178 14/589506 |
Document ID | / |
Family ID | 44368176 |
Filed Date | 2015-04-30 |
United States Patent
Application |
20150115178 |
Kind Code |
A1 |
Jean; Hubschman P. ; et
al. |
April 30, 2015 |
METHODS AND SYSTEMS FOR GUIDING AN EMISSION TO A TARGET
Abstract
Disclosed are methods and systems for guiding emissions to a
target. The methods and systems utilize, in part, Markerless
Tracking software to detect a beam of energy, such as a laser,
toward a target such as a tissue that is the subject of a medical
procedure.
Inventors: |
Jean; Hubschman P.; (Beverly
Hills, CA) ; Schwartz; Steven; (Los Angeles, CA)
; Wilson; Jason; (Los Angeles, CA) ; Tsao;
Tsu-Chin; (Manhattan Beach, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Vantage Surgical Systems Inc. |
Irvine |
CA |
US |
|
|
Assignee: |
Vantage Surgical Systems,
Inc.
Irvine
CA
|
Family ID: |
44368176 |
Appl. No.: |
14/589506 |
Filed: |
January 5, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12704947 |
Feb 12, 2010 |
8954132 |
|
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14589506 |
|
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Current U.S.
Class: |
250/491.1 |
Current CPC
Class: |
A61B 6/547 20130101;
A61B 2034/2072 20160201; A61B 2034/2063 20160201; G06T 7/75
20170101; A61B 2018/00577 20130101; A61B 2034/2055 20160201; A61B
5/055 20130101; G06T 7/136 20170101; A61B 18/18 20130101; G21K 5/10
20130101; A61B 6/466 20130101; G06T 2207/10016 20130101; A61B
2034/107 20160201; G06T 2207/10056 20130101; G06T 2207/10101
20130101; G06T 2207/30096 20130101; G06T 2207/30244 20130101; A61B
2034/2051 20160201; A61B 34/10 20160201; A61B 18/20 20130101; A61B
34/20 20160201; G06T 7/251 20170101; G06T 2207/10048 20130101 |
Class at
Publication: |
250/491.1 |
International
Class: |
G21K 5/10 20060101
G21K005/10 |
Claims
1. A method of directing an emission to a target on a tracking
object, the method comprising: generating a 3-dimensional model of
the tracking object including the target; generating real-time
imagery of the object using an imaging device; aligning the
3-dimensional and the real-time imagery to determine a position and
an orientation of the object with respect to the imaging device;
determining a position and an orientation of an emission device
with respect to the imaging device; and directing the emission from
the emission device to the target, wherein the emission is
configured to include at least two power levels including a
first-low power level for real-time feedback adjustment and a
second high power level used to direct the emission to the
target.
2. The method of claim 1, wherein the step of determining the
position and the orientation of the emission device with respect to
the imaging device further comprises: calibrating a relative pose
of the imaging device to the emission device by treating the
emission device as a pin-hole camera.
3. The method of claim 2 further comprising: calculating the
relative pose by identifying a pixel position of one or more
emission spots visible to the imaging device on the tracking object
and determining an angle of the emission device to the one or more
emission spots visible to the imaging device.
4. The method of claim 1, wherein the step of generating the
3-dimensional model further comprises: generating a rigid or a
compliant wireframe model.
5. The method of claim 1, wherein the step of determining the
position and the orientation of the object with respect to the
imaging device further comprises aligning the 3-dimensional model
to an image of the object to generate a keyframe.
6. The method of claim 1, additionally comprising: tracking the
target in real-time using the position and the orientation of the
3-dimensional model with respect to the imaging device.
7. The method of claim 1, wherein the step of observing the
emission on the target comprises: observing the location of the
emission as a pixel location.
8. The method of claim 1, wherein the step of directing the
emission comprises: directing a laser.
9. The method of claim 1, wherein the step of generating real-time
imagery of the object comprises: capturing at least one image using
a camera.
10. The method of claim 2, further comprising: using computer
vision algorithms to determine the relative pose.
11. A system for directing an emission to a target on an object,
comprising: an emission device; an imaging device positioned to
view the object; at least one processor in communication with said
emission device and said imaging device and configured to execute
software code for: generating a wireframe model of the object;
determining a position and an orientation of the object with
respect to the imaging device by aligning the wireframe model and a
real-time imagery; determining a position and an orientation of the
emission device with respect to the imaging device; aligning the
wireframe model to a real-time image to generate a keyframe; and
directing an emission from the emission device to the target,
wherein the emission includes at least two power levels, the first
of the at least two power levels being a low power level emission
configured for real-time feedback adjustment and the second of the
at least two power levels is a high power level configured for
directing the emission to the target.
12. The system of claim 11, wherein the emission device is a
laser.
13. The system of claim 11, wherein the imaging device is a
camera.
14. The system of claim 11, wherein the at least one processor is
further configured to execute software code for: calibrating a
relative pose of the imaging device to the laser.
15. The system of claim 11, wherein the at least one processor is
further configured to execute software code for: identifying a
pixel position of one or more laser spots visible to the camera on
an object; and determining a mirror angle corresponding to the
pixel position of said one or more laser spots.
16. The system of claim 11, wherein the at least one processor is
further configured to execute software code for: determining a
relative pose.
17. The system of claim 11, wherein the executable software code is
stored on one or more memory devices in communication with said at
least one processor.
Description
RELATED APPLICATIONS
[0001] This application is a continuation application of U.S.
patent application Ser. No. 12/704,947 filed Feb. 12, 2010.
FIELD OF THE INVENTION
[0002] The disclosure relates to the field of emission technology.
More particularly, the disclosure pertains to guiding an emission
to a target.
BACKGROUND
[0003] Emission devices, such as lasers, require mechanisms to
guide an emission to a target. There are several limitations to
prior art devices regarding how they direct an emission to a
target. For instance, typical prior art camera laser calibration
requires the position of the camera relative to the calibration
object to be known. In addition, when an object is used to
calibrate the laser, the geometry of the object must be known.
Moreover, many of these systems do not have real-time feedback to
correct errors in targeting the emission device to the target.
[0004] There is a need for systems having improved direction of
emissions to targets. In particular, there is a need for improved
targeting of emissions in medical applications. There is,
therefore, a need for new systems that allow for the use of
algorithms to calibrate the direction of an emission to a specific
location on a target and to provide feedback to correct any errors
relating to the direction of the emission.
SUMMARY
[0005] The present invention is based, in part, upon the discovery
that emission devices can be directed using "Markerless Tracking"
software and information relating to the relative pose of an
imaging device and an emission device. Markerless tracking
algorithms are known in the art and have been described previously
(see U.S. Pat. No. 7,428,318, incorporating herein by reference the
portion of said patent's disclosure entitled, "Markerless
Tracking;" U.S. Pub. No. 2005/I90972, incorporated herein by
reference; and Comport et al. IEEE Trans Visual. Comp. Graph.
12(4); 615-628 (2006), which is also incorporated herein by
reference). This discovery has been exploited to provide systems
and methods for directing emissions, such as lasers to a target. In
addition, methods and systems are disclosed herein comprising
feedback mechanisms to correct for any errors in the targeting of
the laser.
[0006] Aspects of the methods provide directing an emission to a
target on a three-dimensional object. The methods comprise
generating a model of the three dimensional object and using an
imaging device to generate real-time imagery of the three
dimensional object.
[0007] Other aspects of the methods described herein include a
method of directing an emission to a target on a tracking object.
The method comprises generating a model of the tracking object
including the target and using an imaging device to generate
real-time imagery of the object. The method also includes
determining a position and orientation of the object with respect
to the imaging device by aligning the model and the real-time
imagery, determining a position and orientation of an emission
device with respect to the imaging device, and directing an
emission from the emission device to the target.
[0008] In certain embodiments, the method also comprises
determining the position and orientation of the emission device
with respect to the imaging device. The method further comprises
calibrating the relative pose of the imaging device to the emission
device by treating the emission device as a pi n-hole camera. In
particular embodiments, the method further comprises calculating
the relative pose by identifying a pixel position of one or more
emission spots visible to the imagery device on the tracking object
and determining an emission direction of the emission device, each
emission direction corresponding to the pixel position of each
emission spot.
[0009] In more specific embodiments, the model is a wireframe
model. In particular embodiments, the wireframe model is rigid or
compliant. In more particular embodiments, the determining a
position and orientation of the tracking object relative to the
imaging device comprises aligning the wireframe model to an image
of the object to generate a keyframe. In still more particular
embodiments, the wireframe model is considered correctly aligned to
the real-time imagery when it matches the alignment shown in the
keyframe. In even more particular embodiments, the wireframe model
is aligned with real-time imagery of the object by identification
of surface features on the object. In still more particular
embodiments, the target is tracked in real-time using the position
and position and orientation of the wireframe model in the camera
coordinates.
[0010] In certain embodiments, the target is a location in the
object which is specified as a location in the wireframe model. In
other embodiments, the target is visible on the surface of the
object. In still other embodiments, the target is not visible on
the surface of the object.
[0011] In some embodiments, the method further comprises observing
the emission on the object with the imagery device and calculating
the error between a desired location of the emission on the object
and an observed location of the emission. In still other
embodiments, the location of the emission is observed as a pixel
location in the image. In more particular embodiments, the error is
defined as a vector distance between the desired location and the
observed location.
[0012] In even more particular embodiments, the method further
comprises calculating a feedback correction term whereby the
emission device is adjusted to correct for the error in location of
the emission. In some embodiments, at least two power levels of the
emission device are used with low power level of the emission
device for real-time feedback adjustment until the error is below a
predetermined threshold level and a high power level of the
emission device is used to direct the emission to the target when
the error is ascertained to be below the predetermined threshold
level.
[0013] In some embodiments, the emission device is a laser. In
other embodiments, the imaging device is a camera. In still other
embodiments, determining the position and orientation of the laser
with respect to the imaging device comprises calibrating the
relative pose of the imaging device to the laser by treating the
laser as a pin-hole camera.
[0014] In certain embodiments, the method further comprises
calculating the relative pose by identifying a pixel position of
one or more laser spots visible to the camera on an object and
determining a mirror angle used for directing the laser, each
mirror angle corresponding to the pixel position of each laser
spot. In particular embodiments, the method further comprises using
computer vision algorithms to determine the relative pose.
[0015] Aspects described herein relate to a system for directing an
emission to a specific location on an object. The system comprises
an emission device and an imaging device positioned to view the
object. The system also includes logic. For instance, the system
comprises logic for generating a model of the object and logic for
determining a position and orientation of the object with respect
to the imaging device by aligning the model and a real-time
imagery. The system also includes logic for determining a position
and orientation of the emission device with respect to the imaging
device and logic for directing an emission from the emission device
to the target.
[0016] In certain embodiments, the emission device is a laser. In
other embodiments, the imaging device is a camera.
[0017] In some embodiments, the system includes logic for
calibrating the relative pose of the imaging device to the laser by
treating the laser as a camera. In still other embodiments, the
system further comprises logic for identifying a pixel position of
one or more laser spots visible to the camera on an object and
determining a mirror angle used for directing the laser, each
mirror angle corresponding to the pixel position of each laser
spot. In particular embodiments, the system further comprises logic
to implement computer vision algorithms for determining the
relative pose.
[0018] In certain embodiments, logic for the determining a position
and orientation of the object relative to the imaging device
comprises aligning the wireframe model to an image of the object to
generate a keyframe.
[0019] In particular embodiments, all of the logics comprise
executable code, the executable code being stored on one or more
memory devices.
[0020] Aspects described herein also relate to a method of
targeting a tissue of a patient with an emission beam. The method
comprises using an imaging device to generate a real-time image of
tracking tissue of the patient and obtaining a diagnostic scan of
the tissue containing the tracking tissue and the targeted tissue.
The method also comprises aligning the diagnostic scan to the model
to identify the location of the targeted tissue in the model and
overlaying the model on a real-time imagery of the tracking tissue.
The method further comprises determining a position and orientation
of an emission device with respect to the imaging device and
directing an emission beam to the location of the targeted tissue
based on the model alignment with the imagery of the tracking
tissue.
[0021] In certain embodiments, tracking tissue refers to visible
tissue used for tracking. In particular embodiments, the tracking
tissue is the same as the targeted tissue.
[0022] In certain embodiments, the energy beam is a laser. In
particular embodiments, the imaging device is a camera. In more
particular embodiments, the tissue is a body part, an organ, or a
tissue of a subject.
[0023] In certain embodiments, the model is a wireframe model. In
more certain embodiments, the wireframe model is aligned with the
real-time imagery of the tracking tissue by identification of
surface features on the tissue. In still more certain embodiments,
a diagnosis of the targeted tissue is performed using information
obtained from the emission beam. In even more certain embodiments,
the tissue is a tissue requiring treatment. In some embodiments,
the tissue that is targeted is normal tissue. In other embodiments,
the tissue that is targeted is a lesion.
BRIEF DESCRIPTION OF THE FIGURES
[0024] The foregoing and other objects of the present invention,
the various features thereof, as well as the invention itself may
be more fully understood from the following description, when read
together with the accompanying drawings in which:
[0025] FIG. 1 is a diagrammatic representation showing the
organization of the hardware and logic for a representative system
used to direct an emission to a target tissue in the brain of a
patient;
[0026] FIG. 2 is a graphical representation showing a camera and
laser and their corresponding coordinate system of a camera and
laser while producing an alignment of a contour model on a
real-time image of a retina; and
[0027] FIG. 3 is a diagrammatic representation showing a point
correspondence in which a point in space is simultaneously affected
by an emission device which is observed by an imaging device.
DETAILED DESCRIPTION
[0028] The issued US patents, allowed applications, published
foreign applications, and references, that are cited herein are
hereby incorporated by reference in their entirety to the same
extent as if each was specifically and individually indicated to be
incorporated by reference. Patent and scientific literature
referred to herein establishes knowledge that is available to those
of skill in the art.
[0029] 1.1. General
[0030] Methods and systems are disclosed for directing an emission
to a target on a tracking object. As used herein, the term
"tracking object" means a 2- or 3-dimensional object that is
observed by an imaging device and whose position and orientation is
computed by means of markerless tracking. The methods comprise
generating a model of the tracking object including a target and
using an imaging device to generate real-time imagery of the
object. The method also includes determining a position and
orientation of the object with respect to the imaging device by
aligning the model and the real-time imagery. In addition, a
position and orientation of an emission device is determined with
respect to the imaging device. An emission is directed from the
emission device to the target. The model described above allows for
the relative position and orientation of an object to be tracked.
The tracking occurs because the model is positioned relative to the
object and utilizes the shape of the object. In such a system, the
texture can vary from object to object so long as the shape of the
object remains similar. This is useful for biological objects where
the shape of anatomy is the same but the texture varies (e.g.
retina).
[0031] In addition, the methods comprise determining a position and
orientation of the object with respect to the imaging device. The
methods comprise aligning the model and the real-time imagery. The
method also comprises determining a position and orientation of an
emission device with respect to the imaging device. The methods
also comprise directing an emission from the emission device to the
target.
[0032] Software available from companies such as Total Immersion is
used to implement the tracking algorithms described above. A
version of this tracking software is Markerless Tracking Markerless
Tracking ("MLT") software. MLT uses a representative wireframe
model and its alignment to the target in a key frame to track the
position and orientation of the object using natural feature
points. As used herein, a "keyframe" is an image of the tracking
object and the wireframe that shows proper alignment of the
wireframe model to the tracking model. The methods and systems
disclosed herein use Markerless Tracking to allow an emission to be
directed to a specific location on an object that is tracked. This
can be of significant importance for industrial and medical
applications.
[0033] The emission device can be a laser, an X-ray device, focused
ultrasound, electron gun (like in a CRT monitor), water jet, and
air jet. Accordingly, representative emissions useful in the
present methods include, but are not limited to, laser emissions,
X-rays, visible light, coherent light, liquid, ultrasound, sound,
thermal emission, and infrared light.
[0034] The methods described herein use one or more imaging
devices. In particular embodiments, the imaging device is a camera,
Optical Coherence Tomography, 8-Scan, scanning laser microscope,
scanning laser ophthalmoscope, directional microphone, and
directional infrared sensors, industrial welding robots, automatic
tattoo removal, surface etching, micromachining, weapons targeting,
and robot navigation
[0035] In certain nonlimiting examples, the methods comprise
computing the position and orientation of the imaging device
relative to the emission device by treating the emission device as
a pinhole (projective) camera. In treating the emission device as a
camera, the methods utilize algorithms originally developed for
2-view geometry to calibrate the emission device (See, e.g.,
Hartley and Zisserman, Multiple View Geometry in Computer Vision,
Cambridge University Press, March 2004). This is performed by
extending the pinhole camera model to emission steering hardware.
The pinhole camera concept is well known in the art. In these
embodiments, calibration up to scale has only recording pixel
locations of the emission (e.g., a spot in the view of the imaging
device) and the determining the corresponding emission device's
guidance equipment angles to steer the emission on a calibration
object of unknown geometry. In a laser example, the guidance
equipment is the laser's steering mirrors. The scale ambiguity can
be resolved by knowing the depth of one or more point
correspondence or the metric relationship between two or more point
correspondences. In certain cases, "scale ambiguity" refers to the
ambiguity of the scale of the position of the laser with regard to
the camera.
[0036] The methodology of directing an emission device is
accomplished with the use of information that is acquired in the
calibration of the device. The pixel location of the emission spot
is identified and visible to the imaging device on a calibration
object. In some embodiments, the emission device is a laser. In
such embodiments, the laser is directed with knowledge of the
mirror angle used for directing the laser to the particular
location. Each mirror angle corresponds to the pixel position
(e.g., point) of each laser spot generated with the particular
mirror angle. These point correspondences refer to pairs of pixels
and mirror angles. One point correspondence would be (Xe, Yc, UL,
pL), where Xe and Yc are a camera pixel, UL and PL are mirror
angles (i.e., UL is a mirror that steers the laser's emission in a
horizontal direction and PL is a mirror that steers the laser's
emission in a vertical direction). Again, the calibration process
up to scale involves the computer steering the laser to different
points on a target (of unknown geometry) and recording pixels and
mirror angles. In notable embodiments, the relative pose of the
imaging device and the laser (or any emission device) is determined
using a computer vision algorithm, such as the 8-point algorithm to
initialize a non-linear optimization. These computer vision
algorithms are known in the art (see, e.g., Ma, et al., An
Invitation to 3-D Vision: from Images to Geometric Models,
SpringerVerlag, 2003).
[0037] The methods and systems also comprise allowing for an object
to be tracked in real time. Such tracking is useful when an object
moves in a field or the view of the object is adjusted.
Furthermore, the methods and systems described herein allow for
calculating the error between a desired location of the emission on
an object and an observed location of the emission. If an improper
calibration occurs, the emission is "off-target" and does not hit
its desired location. As such, the emission does not produce its
desired effect and much time will be wasted. In the case of
surgical procedures, there could also be injury to tissues.
[0038] Accordingly, the methods and systems provide mechanisms to
correct calibration problems by, for instance, calculating a
feedback correction term whereby the emission device is adjusted to
correct for the error in location of the emission. Such correction
is accomplished using a known projection of the desired treatment
area in the camera, as well as the location of the laser spots that
are visible to the camera; it is possible to use feedback control
to drive the laser to the proper pixel location.
[0039] 1.2 Systems
[0040] Systems for directing an emission to a specific location on
a three-dimensional object are also described herein. Systems
typically include an emission device and an imaging device. The
imaging device is typically positioned to view a tracking object.
The tracking object has a target that is the point or region on or
in the object to which an emission to direct an emission.
[0041] The systems described herein also have logic for generating
a model of the tracking object and for determining a position and
orientation of the tracking object with respect to the imaging
device by aligning the model and a real-time imagery. For example,
the systems can comprise logic for determining a position and
orientation of the emission device with respect to the imaging
device, as well as logic for directing an emission from the
emission device to the target. As detailed below for particular
embodiments, the emission device can be a laser and the imaging
device can be a camera.
[0042] In some instances, the systems comprise logic for
identifying a pixel position of one or more laser spots visible to
the camera on an object, as well as logic for determining one or
more mirror angles used for directing the laser, each mirror angle
corresponding to the pixel position of each laser spot.
[0043] The systems can comprise computer vision algorithms for
determining the relative pose of an imaging device and an emission
device. For example, the system comprises logic configured to align
an image of the target to a wireframe model to generate a
keyframe.
[0044] The logics in many of these embodiments are executable code
stored on one or more memory devices. Memory devices include
storage media such as computer hard disks, redundant array of
inexpensive disks ("RAID"), random access memory ("RAM"), solid
state memory such as flash memory, and optical disk drives.
Examples of generic memory devices are well known in the art (e.g.,
U.S. Pat. No. 7,552,368, describing conventional semiconductor
memory devices and such disclosure being herein incorporated by
reference).
[0045] To further describe the systems described above, the
following non-limiting example is provided. Referring to FIG. 1, a
system 100 is shown in which a camera 110 (an imaging device in
this illustrative description) and laser 120 (the emission device,
named "focused energy" device in the figure) are arranged to allow
for viewing of a target 130 (tissue in the brain 160 of a patient
150). The system 100 includes a computer 140 that comprises memory
to store the logics for performing the tracking, calibration, and
feedback functions of the system.
[0046] With regard to an example in which a patient has a cancerous
brain tumor, healthy tissue to be ablated, or noncancerous growth,
a surgeon cannot see the tissue in the brain. A diagnostic scan 170
shows where the target tissue is located. The computer aligns the
diagnostic scan to a wireframe model 180, such that the wireframe
is overlaid on the patient and the scan location matches the actual
target tissue location. This registration can be done by matching
the surface features of the brain in the keyframe to surface
features shown in the MRI.
[0047] MLT uses the texture of the surface of the brain to align
the wireframe model 180 to the real time image of the patient. An
aiming beam from the emission device is turned on in order to
initiate the feedback. Once the aiming beam is pointing at the
correct tumor location, the treatment "focused energy" from the
emission device is directed to the tumor and ablates the tumor.
[0048] 1.3 Methodology
[0049] The following example describes how the logics stored in the
computer 140 in FIG. 1 provide tracking, calibration, and feedback
functions. Referring to FIG. 2, the various components of the
system 100 of FIG. 1 are described with respect to a scan and
treatment of a retina. Each Component is identified as follows.
[0050] FIG. 2 shows the contour model M which is being aligned to
the real-time image of the retina R (R.sub.1 and R.sub.C) via the
markerless tracking algorithm. Once the model is aligned, the
marker less tracking outputs the position and orientation of the
model in the camera coordinates. Since the model is aligned with
the real-time image, these coordinates also represent the position
and orientation of the retina. The diagnostic scan S is also
aligned to the model M such that there is accurate registration of
the diagnostic scan to the real-time retina image during tracking.
The treatment plan is represented by the pixel matrix in the
diagnostic scan. In some embodiments, the diagnostic scan is shown
overlaid on the image of the object; the diagnostic scan contains
information relating to the treatment plan. Sometimes, the camera C
and laser L have a known position and orientation relative to one
another due to a priori calibration. The camera C and the laser L
are positioned such that the laser can be directed to the retina
shown in the real-time image R.
[0051] In this example, a system generates a reference location for
the laser L to shoot using the alignment of the contour model M
with the real-time retina image R and the alignment of the
diagnostic scan S with the model M. The system obtains the
coordinates of the treatment locations in the diagnostic scan using
known coordinate transformations between S, M, C and L generated
for the laser L. In certain embodiments, the coordinates for S and
M are computed by manual alignment. The determination of C and L
coordinates are determined as shown below. The laser L steers the
beam such that it passes through the desired location in space. In
this configuration, the visual information is used as a reference
for the laser servo control. This can be described as a
feed-forward visual servo methodology. The following discussion
details the coordinate transformations that allow the use of
information from MLT to generate the reference coordinates in the
laser's L coordinate system.
[0052] Any point (v.sub.i) represented in a coordinate system
attached to object i can be represented as a point v.sub.j in a
coordinate system attached to object j via the following
transformation,
v.sub.j=.sup.jR.sub.iv.sub.i+.sup.jT.sub.i (0.1)
[0053] Where .sup.1R, represents the orientation of the
i-coordinate system in j-coordinates, v.sub.j represents the
coordinates of a point in three dimensional space in an i
coordinate system, .sup.jR.sub.i is in the case of
three-dimensional space a 3.times.3 rotation matrix that represents
the orientation of the i-coordinate system in j-coordinates. A
rotation matrix is a 3.times.3 real matrix with det(R)=+1 and
R.sup.TR=Identity. Similarly, .sup.jT.sub.i represents the
translation of the i-coordinate system in j-coordinates. Therefore
the objective of the reference generation algorithm for the laser
delivery is to update the treatment location in the laser
coordinates which was originally described in the diagnostic scan
coordinates. From equation 0.1 the algorithm computes the following
coordinate transformation:
.sup.LR.sub.Sv.sub.S+.sup.LT.sub.S (0.2)
[0054] .sup.LR.sub.S and .sup.LT.sub.S can be computed by
considering a simplified description of the tracking algorithm. The
scan and the model are aligned a priori. This is done either
manually or automatically. This establishes a fixed coordinate
transformation between the scan and the model as (.sup.MR.sub.S,
.sup.MT.sub.S). A keyframe is generated representing proper
alignment between the model and a retina image. Then as the
real-time image changes, MLT computes the coordinate transformation
between the model and the camera such that the model aligns to the
real-time image as it did in the keyframe. This is a changing
coordinate transformation between the model and the camera at each
frame update (.sup.CR.sub.M, .sup.CT.sub.M). The imaging device and
the emission device are then be calibrated such that the coordinate
transformation between the camera and the laser is known
(.sup.LR.sub.C, .sup.LT.sub.C). Using equation 0.1 and sequentially
representing the treatment locations in the scan, model, camera and
finally laser coordinate systems, it can be shown that
.sup.LR.sub.C and .sup.LT.sub.C are given by,
.sup.LR.sub.S=.sup.LR.sub.C.sup.CR.sub.M.sup.MR.sub.S
.sup.LT.sub.S=.sup.LR.sub.C.sup.CR.sub.M.sup.MT.sub.S+.sup.LR.sub.C.sup.-
CT.sub.M+.sup.LT.sub.C
[0055] The .MLT outputs (.sup.CR.sub.M, .sup.MR.sub.S,
.sup.CT.sub.M, .sup.LT.sub.C) for the reference generation
algorithm. However (.sup.LR.sub.C, .sup.LT.sub.C) is a relationship
between hardware that cannot be computed by MLT. Thus
(.sup.LR.sub.C, .sup.TT.sub.C) is calibrated each time the imaging
device and emission device hardware is modified.
[0056] 1.4 Camera/Laser Pose Computation Using Point
Correspondence
[0057] The following discussion describes a method involving the
identification of a point on an object utilizing imaging locations
and steering an emission guidance system to direct an emission to
the point. FIG. 3 discusses a certain attribute of the methodology
through the use of a representative emission device (i.e., laser)
and a representative imaging device (i.e., camera). The following
discussion is exemplary and is not limiting.
[0058] Consider a laser spot p that is in the field of view of the
camera as shown in FIG. 3. The camera C and the laser L are
positioned such that the laser L directs a beam to the target and
the camera C views the spot p. From equation 0.1, the relationship
between the representations of p in each coordinate system is as
follows.
P.sub.L=R.sub.CP.sub.C+.sup.LT.sub.C (0.3)
[0059] If P.sub.L. and P.sub.C vectors were known, a number of
measurements could be taken and (.sup.LR.sub.C, .sup.LT.sub.C)
could be computed directly. However in practice it may not be
possible to accurately know the magnitude of P.sub.L. and P.sub.C
because the object that the laser is shooting is an unknown
distance from the camera and the laser. Therefore P.sub.L. and
P.sub.C are known only up to some unknown scale factor
.lamda..sub.i.
p.sub.i=.lamda..sub.in.sub.i,i=L,C (0.4)
[0060] where n.sub.i is some vector in the direction of p in
i-coordinates. Plugging equation 0.4 into 0.3, the following
equation is obtained.
.lamda..sub.Ln.sub.L=.sup.LR.sub.C.lamda..sub.Cn.sub.C+.sup.LT.sub.C
(0.5)
[0061] In order to solve for (.sup.LR.sub.C, .sup.LT.sub.C),
.lamda..sub.L and .lamda..sub.C is be eliminated. This can be done
by multiplying on the left by [.sup.LT.sub.C].sub.x, which is the
skew symmetric matrix realizing the cross-product in R.sup.3
as,
[.sup.LT.sub.C].sub.x.sup.LT.sub.C=.sup.LT.sub.C.times..sup.LT.sub.C=0
(0.6)
Which gives:
.lamda..sub.L[.sup.LT.sub.C].sub.xn.sub.L=[.sup.LT.sub.C].sub.x.sup.LR.s-
ub.C.lamda..sub.Cn.sub.C. (0.7) [0062] Since [.sup.LT.sub.C].sub.x
n.sub.L is orthogonal to both .sup.LT.sub.C and n.sub.L.sup.T,
multiplying on the left by n.sub.L sets the left hand side of
equation 0.7 to zero, giving:
[0062]
0=n.sub.L.sup.T[.sup.LT.sub.C].sub.x.sup.LR.sub.Cn.sub.C=n.sub.L.-
sup.TEn.sub.C. (0.8)
[0063] Equation 0.8 is the well-known epipolar constraint commonly
encountered in two-view geometry. Here [.sup.LT.sub.C].sub.x
.sup.LR.sub.C is the useful matrix E. There are many algorithms to
compute E and extract (.sup.LR.sub.C, .sup.LT.sub.C) up to scale,
given enough measurements of n.sub.L and n.sub.C in general
configuration. However, in the typical two-view geometry, n.sub.L
and n.sub.C are pixel locations where here n.sub.L is a vector in
the direction of the laser which is related to the laser steering
mirror angles.
[0064] 1.5 Feedback
[0065] In certain examples, any errors in the desired location of
the emission spot and the actual location of the spot are corrected
through a methodology such as the method described herein. In this
example, a laser is used as an exemplary, non-limiting emission
device. The error between the desired location of the laser spot
and the actual location of the laser spot is determined in pixels.
Through MLT, the desired treatment location is provided, (x y
z).sup.T. The pixel corresponding to the desired treatment location
in the camera can be obtained by
[ x ' y ' z ' ] = K [ x y z ] [ x c y c ] = [ x ' z ' x ' z ' ]
##EQU00001##
[0066] where K is the well known camera calibration matrix.
[0067] The laser pixel location can be obtained by an image
processing step. Since the laser spot is much brighter than the
rest of the image, one method to accomplish this is to threshold
the image such that a binary image is computed showing only the
spot. A "center of mass" operation is then performed to give the
location of the center of the laser spot. This is one example of an
algorithm to extract the pixel location of the laser spot.
Alternatively, other algorithms in the field of image processing
can perform this task (see, e.g., Jain, Fundamentals of Digital
Image Processing, Prentice-Hall, Inc., 1989).
[0068] The vector between these two points is then calculated and
referred to as the error, e. Some feedback law would then be
implemented so that the new input to the laser is as follows:
u.sub.L=u.sub.FF+u.sub.FB
u.sub.FB=f(e)
[0069] Where UL is the laser actuator input, U.sub.FF is the
actuator input from the feed-forward section described, and
u.sub.fB is some feedback correction term that is a function of the
error. One feedback correction scheme may be the "so called"
integrator.
u.sub.FB,current=u.sub.FB,before+.gamma.e
[0070] Here the feedback correction term is the feedback correction
from the image before plus an added term that is proportional to
the error in the current image. .gamma. is a term that is chosen to
ensure stability and performance
[0071] 1.6 Therapeutics
[0072] In addition, the present methods and systems utilize
emissions for improved surgical methods for ablating tissues. The
methods comprise using an imaging device to generate a real-time
image of a tissue of the patient and obtaining a diagnostic scan of
the tissue. In certain embodiments, the tissue is a healthy tissue
that is ablated. Sometimes, the tissue contains a lesion. The
methods also comprise aligning the diagnostic scan to a model to
identify the location of the tissue to be ablated. Sometimes, the
tissue is located on the surface of the tissue. In some instances,
the tissue to be ablated is located within the tissue. In either
case, the model is overlaid on a real-time imagery of the tissue. A
determination of the position and orientation of an emission device
with respect to the imaging device is made. An emission beam is
directed to the location of the healthy tissue or lesion based on
the model alignment with the imagery of the tissue, thereby
treating the lesion.
[0073] In these methods, any tissue can be treated. In some
instances, the target for the laser is a tissue lesion. Tissue
lesions include, but are not limited to, tumors, metastatic cancer,
noncancerous growths, bacterial infections, viral infections,
fungal infections, scar tissue, and aberrant tissue growths. In
certain embodiments, such lesions are located in a body part, such
as a leg or arm, in an organ, such as the brain, liver, heart,
lung, stomach, or eyes, or in a tissue, such as lymph nodes or bone
marrow, of a subject.
[0074] As with methods described above, keyframes are generated by
aligning an image of the target to a model such as, for example, a
wireframe model. The image can be a diagnostic scan (e.g., PET
scan, MRI), a picture of the tissue, and any other medical scan.
For surgical applications, a keyframe can be generated a priori by
registering the model to a previously acquired diagnostic scan or
image taken prior to surgery.
[0075] The emission can be utilized in a medical procedure where
specific locations on anatomical structures are targeted and
ablated using the emission.
EQUIVALENTS
[0076] Those skilled in the art will recognize, or be able to
ascertain, using no more than routine experimentation, numerous
equivalents to the specific compositions and procedures described
herein. Such equivalents are considered to be within the scope of
this invention, and are covered by the following claims.
* * * * *