U.S. patent application number 12/214885 was filed with the patent office on 2009-01-01 for target location by tracking of imaging device.
Invention is credited to Calvin R. Maurer, JR., Sankaralingam Ramraj, Sohail Sayeh.
Application Number | 20090003528 12/214885 |
Document ID | / |
Family ID | 40160499 |
Filed Date | 2009-01-01 |
United States Patent
Application |
20090003528 |
Kind Code |
A1 |
Ramraj; Sankaralingam ; et
al. |
January 1, 2009 |
Target location by tracking of imaging device
Abstract
A method and apparatus for tracking a target by tracking the
location of an imaging device while the imaging device is tracking
the target is described.
Inventors: |
Ramraj; Sankaralingam;
(Sunnyvale, CA) ; Sayeh; Sohail; (San Ramon,
CA) ; Maurer, JR.; Calvin R.; (Mountain View,
CA) |
Correspondence
Address: |
ACCURAY/BSTZ;BLAKELY SOKOLOFF TAYLOR & ZAFMAN LLP
1279 OAKMEAD PARKWAY
SUNNYVALE
CA
94085-4040
US
|
Family ID: |
40160499 |
Appl. No.: |
12/214885 |
Filed: |
June 19, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60936388 |
Jun 19, 2007 |
|
|
|
Current U.S.
Class: |
378/119 ;
382/103 |
Current CPC
Class: |
A61B 8/4472 20130101;
A61B 6/527 20130101; A61B 8/4245 20130101; A61B 8/5276 20130101;
A61N 2005/1059 20130101; G06T 7/20 20130101; A61B 8/4416 20130101;
A61B 2090/378 20160201; A61B 6/4476 20130101; A61N 5/1067 20130101;
A61B 6/547 20130101; A61B 6/4405 20130101; A61B 8/4218 20130101;
A61B 34/20 20160201; A61N 2005/1051 20130101; G06T 2207/30004
20130101; A61B 6/541 20130101; A61B 6/0487 20200801; A61B 6/08
20130101; A61B 6/5247 20130101; A61B 6/4464 20130101; A61B 2090/376
20160201; A61B 8/0833 20130101; A61B 90/39 20160201; A61N 5/1049
20130101; A61B 90/36 20160201 |
Class at
Publication: |
378/119 ;
382/103 |
International
Class: |
G06K 9/00 20060101
G06K009/00; H05G 2/00 20060101 H05G002/00 |
Claims
1. A method, comprising: tracking a location of a target using an
imaging device; tracking a location of the imaging device; and
determining a location of the target relative to an global
reference point based on the tracked location of the target and the
determined location of the imaging device.
2. The method of claim 1, wherein tracking the location of the
target comprises determining a positional offset between the target
and the imaging device.
3. The method of claim 1, wherein tracking a location of the
imaging device comprises determining a positional offset between
the imaging device and the global reference point.
4. The method of claim 1, wherein the imaging device is an
ultrasound imager.
5. The method of claim 4, wherein the ultrasound imager comprises:
an ultrasonic transducer; an extension link coupled with the
ultrasonic transducer; and an external unit coupled with the
extension link, wherein the ultrasonic transducer is moveable
independently from the external unit.
6. The method of claim 1, wherein the imaging device comprises an
optical system.
7. The method of claim 1, wherein tracking the location of the
imaging device comprises capturing an image of the imaging device
using a second imaging device.
8. The method of claim 7, wherein the second imaging device is an
X-ray imager.
9. The method of claim 1, wherein the imaging device is mounted on
a robotic arm capable of motion with at least five degrees of
freedom.
10. The method of claim 9, wherein tracking the location of the
imaging device comprises receiving positional information from the
robotic arm.
11. The method of claim 1, wherein the imaging device is coupled
with a treatment couch.
12. The method of claim 11, further comprising applying the imaging
device against a skin surface of a patient using a belt coupled
with the imaging device.
13. The method of claim 1, further comprising moving the imaging
device to maintain the target within an imaging field of the
imaging device.
14. The method of claim 1, wherein the location of the target
relative to the global reference comprises a global target offset
and wherein the method further comprises maintaining an
intersection of a beam with the target using the global target
offset.
15. The method of claim 14, maintaining the intersection of the
beam with the target using the global target offset comprises
adjusting at least one of a first robotic arm coupled to a LINAC
generating the beam and a second robotic arm coupled to a treatment
couch to support a patient having the target.
16. An apparatus, comprising: an imaging device configured to track
a location of a target; a tracking device configured to track a
location of the imaging device; and a processor coupled with the
imaging device and the tracking device, wherein the processor is
configured to determine a location of the target relative to an
global reference point based on the tracked location of the target
and the tracked location of the imaging device.
17. The apparatus of claim 16, wherein the imaging device is
configured to track the location of the target relative to the
imaging device.
18. The apparatus of claim 16, wherein the tracking device is
configured to track the location of the imaging device relative to
the global reference point.
19. The apparatus of claim 16, wherein the imaging device comprises
an optical system.
20. The apparatus of claim 16, wherein the imaging device comprises
an ultrasound imager.
21. The apparatus of claim 20, wherein the ultrasound imager
comprises: an ultrasonic transducer; an extension link coupled with
the ultrasonic transducer; and an external unit coupled with the
extension link, wherein the ultrasonic transducer is moveable
independently from the external unit.
22. The apparatus of claim 16, wherein the tracking device is an
X-ray imager.
23. The apparatus of claim 16, wherein the imaging device is
mounted on a robotic arm capable of movement in at least five
degrees of freedom.
24. The apparatus of claim 23, wherein the tracking device tracks a
location of the imaging device by determining a position of the
robotic arm.
25. The apparatus of claim 16, wherein the imaging device is
mounted on a belt coupled with the treatment couch, wherein the
belt is configured to hold the imaging device against a skin
surface of a patient.
26. The apparatus of claim 25, wherein the belt includes a gel
container configured to apply gel between the imaging device and
the skin surface of the patient.
27. The apparatus of claim 16, further comprising a positioning
mechanism coupled with the imaging device, wherein the positioning
mechanism is configured to maintain the target within an imaging
field of the imaging device.
28. The apparatus of claim 16, wherein the location of the target
relative to the global reference comprises a global target offset
and wherein the apparatus further comprises a linear accelerator
(LINAC) coupled to a robotic arm, wherein the processor is coupled
to the robotic arm to adjust a position of the LINAC to maintain
intersection a LINAC beam with the target.
29. The apparatus of claim 16, wherein the location of the target
relative to the global reference comprises a global target offset
and wherein the apparatus further comprises: a LINAC to generate a
beam; and a treatment couch coupled to a robotic arm, and wherein
the processor is operatively coupled to the robotic arm to adjust a
position of the treatment couch to maintain intersection of the
LINAC beam with the target.
30. An apparatus, comprising: an ultrasonic imager configured to
track a location of a target; an X-ray imager configured to track a
location of the ultrasonic imager; and a processor coupled with the
ultrasonic imager and the X-ray imager, wherein the processor is
configured to determine a location of the target relative to a
global reference point based on the tracked location of the target
and the tracked location of the ultrasonic imager.
31. The apparatus of claim 30, wherein a transducer of the
ultrasonic imager is mounted on a belt coupled with a treatment
couch, wherein the belt is configured to hold the imaging device
against a skin surface of a patient.
32. The apparatus of claim 30, wherein the location of the target
relative to the global reference comprises a global target offset
and wherein the apparatus further comprises a linear accelerator
(LINAC) coupled to a robotic arm, wherein the processor is coupled
to the robotic arm to adjust a position of the LINAC to maintain
intersection a LINAC beam with the target.
33. The apparatus of claim 30, wherein the location of the target
relative to the global reference comprises a global target offset
and wherein the apparatus further comprises: a LINAC to generate a
beam; and a treatment couch coupled to a robotic arm, and wherein
the processor is operatively coupled to the robotic arm to adjust a
position of the treatment couch to maintain intersection of the
LINAC beam with the target.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 60/936,388, filed Jun. 19, 2007, which is
hereby incorporated by reference.
TECHNICAL FIELD
[0002] Embodiments of the present invention relate to the field of
radiation treatment, and in particular, to a system of tracking the
movement of a pathological anatomy during respiration.
BACKGROUND
[0003] One challenge facing the delivery of radiation to treat
pathological anatomies such as tumors or lesions is identifying the
location of the target (i.e. tumor location within a patient). The
most common technique currently used to identify and target a tumor
location for treatment involves a diagnostic X-ray or fluoroscopy
system to image the patient's body to detect the position of the
tumor. This technique assumes that the tumor is stationary. Even if
a patient is kept motionless, radiation treatment requires
additional methods to account for movement due to respiration, in
particular when treating a tumor located near the lungs. Breath
hold and respiratory gating are two conventional methods used to
compensate for target movement during respiration while a patient
is receiving conventional radiation treatments.
[0004] Breath hold requires the patient to hold his or her breath
at the same point in the breathing cycle and only treats the tumor
when the tumor is stationary. A respirometer is often used to
measure the tidal volume and ensure the breath is being held at the
same location in the breathing cycle during each irradiation. Such
a breath hold method takes longer than a standard treatment and
often requires training the patient to hold his or her breath in a
repeatable manner.
[0005] Respiratory gating is the process of turning on the
radiation beam as a function of a patient's breathing cycle. When
using a respiratory gating technique, treatment is synchronized to
the individual's breathing pattern, limiting the radiation beam
delivery to only one specific part of the breathing cycle and
targeting the tumor only when it is in the optimum range. Such a
respiratory gating method requires the patient to have many
sessions of training and many days of practice to breathe in the
same manner for long periods of time. A system implementing the
respiratory gating method may also require healthy tissue to be
irradiated before and after the tumor passes into view to ensure
complete coverage of the tumor.
[0006] Attempts have been made to avoid the burdens placed on a
patient from breath hold and respiratory gating techniques. Some
methods for tracking the movement of a tumor or other target use
imaging devices to capture the internal structure of a patient's
body. One imaging modality that is commonly used in medical
applications is ultrasound. Ultrasound systems create images of
internal structure by detecting reflection signatures resulting
from the propagation of high-frequency sound waves into the
internal structure.
[0007] Conventional ultrasound systems are not suitable for use in
target tracking applications because the imaging field of such
systems is typically small, so that tissue movement affecting the
imaged area is more likely to move a target out of the imaging
field. Furthermore, repositioning of the ultrasound transducer to
maintain image quality may require intervention by an operator
whose presence in a treatment room may be disruptive, particularly
during a treatment session.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present invention is illustrated by way of example, and
not by way of limitation, in the figures of the accompanying
drawings.
[0009] FIG. 1 illustrates a system for tracking motion of a target
within the body of a patient and delivering treatment to the
tracked target, according to one embodiment of the invention.
[0010] FIG. 2 illustrates components of a target tracking system,
according to one embodiment of the invention.
[0011] FIG. 3 illustrates a target tracking system utilizing an
imaging device attached to a robotic arm, according to one
embodiment of the invention.
[0012] FIG. 4 illustrates an ultrasonic imaging system that can be
used as an imaging device, according to one embodiment of the
invention.
[0013] FIG. 5 is a flow diagram illustrating a process for
administering radiation treatment while tracking the treatment
target according to one embodiment of the invention.
[0014] FIG. 6 is a flow diagram illustrating a process for tracking
a target, according to one embodiment of the invention.
DETAILED DESCRIPTION
[0015] Described herein is a method and apparatus for tracking the
movement of a target such as a pathological anatomy. The following
description sets forth numerous specific details such as examples
of specific systems, components, methods, and so forth, in order to
provide a good understanding of several embodiments of the present
invention. It will be apparent to one skilled in the art, however,
that at least some embodiments of the present invention may be
practiced without these specific details. In other instances,
well-known components or methods are not described in detail or are
presented in simple block diagram format in order to avoid
unnecessarily obscuring the present invention. Thus, the specific
details set forth are merely exemplary. Particular implementations
may vary from these exemplary details and still be contemplated to
be within the spirit and scope of the present invention.
[0016] According to one embodiment of the invention, a target
location may be tracked relative to a global reference point by
determining a positional offset between the target location and an
imaging device, then determining a positional offset between the
imaging device and the global reference point. The positional
offsets may then be added to determine a global offset between the
target and the global reference point.
[0017] The imaging device may be any device capable of locating a
target, such as a tumor, within a patient's body. For example, the
imaging device may capture images of the target using modalities
such as X-ray or computed tomography (CT). Generally, imaging
refers to the techniques and processes used to create images of an
object. Medical imaging is concerned primarily with the creation of
images of structures within the human body. An imaging device is an
apparatus used for creating images. The images can be
two-dimensional (2D) or three-dimensional (3D). If the images are
digital, the elements of 2D and 3D images are often referred to as
pixels (picture elements) and voxels (volume elements),
respectively. The images generally represent a property of the
object and in the case of medical images a property of living
tissue or agents administered to living tissue such as intravenous,
catheter, and orally administered dyes, contrast agents and
radiopharmaceuticals. The properties of living tissue are generally
inferred from an observed signal. Examples of signals include the
measurement of the transmission of x-rays through the body (the
basis for projection radiography and x-ray computed tomography),
the measurement of the reflection of ultrasound waves transmitted
through the body (the basis for ultrasonography), and the
measurement of gamma rays emitted by radiopharmaceuticals which
have been selectively deposited in the body (the basis for nuclear
medicine imaging and positron emission tomography).
[0018] In one embodiment, the imaging device may be an ultrasound
scanner, and the location of the tumor may be determined as a
positional offset between the tumor and the ultrasound scanner. The
ultrasound scanner may then be tracked by a tracking device such as
an X-ray imager, which determines the positional offset between the
ultrasound scanner and the X-ray imager. If the offset between the
X-ray imager and the global reference point is known, then the
offset between the X-ray imager and the global reference point, the
offset between the X-ray imager and the ultrasound scanner, and the
offset between the ultrasound scanner and the target may all be
added to determine the offset between the target and the global
reference point.
[0019] In a radiation treatment application, the tracked location
of the target may be used to direct a linear accelerator (LINAC)
and/or the treatment couch so that the beam of the LINAC intersects
the target, which may identify a location in a pathological
anatomy. In one embodiment, the target may be tracked periodically.
The LINAC is mounted on a robotic arm that receives the
periodically updated location of the target and adjusts the
orientation of the LINAC accordingly. Furthermore, the treatment
couch may also receive the periodically updated location of the
target and adjusted. In this way, the intersection of the LINAC
beam with the target may be maintained for a desired duration of a
treatment session despite movement of the target caused by factors
such as respiration, heartbeat, or other causes of movement.
[0020] In other embodiments of the invention, the tracking device
may be an optical system, such as a camera, or any other device
that can determine positional information. In one embodiment, the
tracking device may be an optical system that tracks the position
of the imaging device by detecting the position of light-emitting
diodes (LEDs) situated on the imaging device. Such an optical
system may include infrared cameras for detecting the position of
the LEDs, which may emit light in the infrared spectrum. In an
alternative embodiment, if the imaging device, such as an
ultrasound scanner, is mounted on a robotic arm, then the tracking
device may be implemented using sensors or mechanical encoders on
the robot arm that can determine the position of the imaging device
based on the joint orientations of the robot arm, as discussed
below in relation to FIG. 3.
[0021] FIG. 1 illustrates a treatment delivery system 100 for
delivering radiation therapy to a target area within a patient
according to one embodiment of the invention. Treatment delivery
system 100 includes tracking system 110, treatment couch 101,
robotic arm 102, and linear accelerator (LINAC) 103, which is
mounted on robotic arm 102. Tracking system 110 further includes a
processor 111, a tracking device 112, and an imaging device 113.
Treatment couch 101 may be designed to support a patient 104. A
target 105 within the patient 104 may be the site of a pathological
anatomy to receive radiation treatment.
[0022] The purpose of a radiation treatment session may be to
deliver radiation to target 105 by intersecting target 105 with a
radiation beam produced by LINAC 103. Target 105 may be moving, for
example, as a result of respiration or heartbeat of the patient
104. Thus, tracking system 110 may be used to track the location of
target 105 as it moves so that the intersection of target 105 with
the beam of LINAC 103 may be maintained. Tracking system 110 may
send positional information identifying the location of target 105
to robotic arm 102 so that robotic arm 102 can adjust the position
of LINAC 103 to maintain the intersection of the LINAC beam with
target 105. In one embodiment, tracking system 110 may send the
location of target 105 continuously to robotic arm 102.
Alternatively, the location information may be sent periodically or
may be sent only when the location of target 105 changes. In
another embodiment, the tracking system 110 may send the positional
information identifying the location of target 105 to robotic arm
106 of the treatment couch 101 so that robotic arm 106 can adjust
the position of the treatment couch 101 to move the target 105 to
maintained the intersection with the LINAC beam. Alternatively,
both robotic arms 106 and 102 may be utilized in conjunction to
maintain the intersection of the LINAC beam and target.
[0023] Tracking system 110 includes processor 111, which may be
connected to tracking device 112 and imaging device 113. Imaging
device 113 may be used to track the location of target 105 relative
to imaging device 113. For example, an image captured by imaging
device 113 may indicate a positional offset between target 105 and
imaging device 113 or another reference point, such as a fiducial
marker. Imaging device 113 may be mobile, and may be repositioned
for such reasons as maintaining image quality, for registration
purposes, or to keep target 105 within an imaging field of imaging
device 113. Tracking device 112 may then track the location of
imaging device 113. For example, tracking device 112 may determine
a positional offset between imaging device 113 and tracking device
112 or some other reference point. Information about the location
of target 105 and imaging device 113 can then be sent to processor
111, where a global position of the target 105 may be calculated.
For example, a global reference point located in the treatment room
may be used for identifying the locations of objects within the
treatment room. Accordingly, processor 111 may determine the
location of the target 105 relative to the global reference point
using positional data collected by tracking device 112 and imaging
device 113.
[0024] FIG. 2 illustrates components of tracking system 110 in
greater detail, according to one embodiment where tracking device
112 is an X-ray imaging system. In tracking system 110, X-ray
source 220 and X-ray detector 221 are components of the X-ray
imaging system operating as tracking device 112. It should be noted
that although only one X-ray detector panel 221 is illustrated in
FIG. 2, alternative embodiments may include additional detector
panels. X-ray source 220 has a tracking field 203, where objects
located within tracking field 203 may be effectively tracked.
Similarly, imaging device 113 has an imaging field 202, where
objects within imaging field 202 may be effectively captured in an
image by imaging device 113. Global reference point 201 is a
location that can be used for designating other locations,
particularly in terms of a positional offset between the global
reference point 201 and the location being designated. A positional
offset simply describes the location of one reference point
relative to another reference point. For example, a positional
offset in three-dimensional space may be represented as a vector
having x, y, and z components in a Cartesian coordinate system. The
target offset 211 is the positional offset between the imaging
device 113 and the target 105. The imaging device offset 212 is the
positional offset between the X-ray source 220 and the imaging
device 113. The global tracking device offset 213 is the positional
offset between the global reference point 201 and the X-ray source
220. The global target offset is the positional offset between the
global reference point 201 and the target 105.
[0025] In one embodiment, the global reference point 201 may be the
tracking (e.g., imaging) center of tracking device 112, which
includes X-ray source 220 and X-ray detector panel 221. Such a
tracking center may coincide with a treatment isocenter, but not
necessarily so. It should be noted that global reference point 201
has been positioned away from the other figure elements for ease of
illustration.
[0026] Imaging device 113 may in one embodiment be an ultrasound
scanner. Alternatively, imaging device 113 may be some other type
of device that is capable of locating a target, such as an X-ray
imager or an electromagnetic coil array. Imaging device 113 may be
positioned so that the imaging field 202 of imaging device 113
encompasses target 105. For example, if an ultrasound scanner is
used as imaging device 113, the transducer of the ultrasound
scanner may be placed against the skin of patient 104 near target
105. Alternatively, if another imaging modality such as X-ray
imaging is used, imaging device 113 may be placed farther away from
the patient 104, as long as the position of target 105 may still be
captured by imaging device 113.
[0027] Imaging device 113 may operate by capturing an image of
target 105. The image can then be used to determine the location of
target 105 relative to imaging device 113, which is the target
offset 211. For example, the size, position, and orientation of
target 105 as captured in an image by imaging device 113 may
indicate the position and orientation of target 105 in real space,
relative to imaging device 113. The position of target 105 may also
be determined by reference to surrounding structures having known
locations captured in an image along with target 105.
[0028] X-ray source 220 may be positioned so that tracking field
203 of X-ray source 220 encompasses imaging device 113. In one
embodiment, X-ray source 220 is mounted in a fixed position. For
example, X-ray source 220 may be mounted on a wall or ceiling of a
treatment room where a radiation treatment session is taking place.
Alternatively, X-ray source 220 may be mobile, so that X-ray source
220 can be repositioned to maintain imaging device 113 within
tracking field 203.
[0029] X-ray source 220 and X-ray detector panel 221 determine the
imaging device offset 213, which is the location of imaging device
113 relative to X-ray source 220. For example, the X-ray source 220
and X-ray detector panel 221 may capture an image of imaging device
113. The size, orientation, and position of imaging device 113 as
represented within the captured image may indicate the position of
imaging device 113 relative to X-ray source 220 in real space. The
position of imaging device 113 may also be determined by reference
to other structures having known locations captured in an image
along with imaging device 113.
[0030] The global position of the target 105 may be determined by
processor 111. Specifically, processor 111 may determine the
position of the target 105 relative to global reference point 201.
Processor 111 may base this calculation on images captured by X-ray
source 220 and X-ray detector panel 221, and also from imaging
device 113. The image data received by processor 111 in one
embodiment may be, for example, raw or processed image data.
Alternatively, the positional offsets of the target 105 and the
imaging device 113 may be transmitted to the processor, if the
positional offsets have already been determined from the raw
data.
[0031] The processor 111 can determine the global target offset 210
by adding the positional offsets, including the target offset 211,
the imaging device offset 212, and the global tracking device
offset 213. Imaging device 113 may capture an image of target 105
that may be used to determine the target offset 211. Tracking
device 112 may then capture an image or otherwise collect data that
can be used to determine the imaging device offset 212. The global
tracking device offset 213 may be determined as part of a
calibration measurement and may be measured from part of tracking
device 112 such as X-ray source 220. For example, if X-ray source
220 is mounted in a fixed location, such as on a wall or ceiling of
the treatment room, the global tracking device offset 213 may be
measured during or after the installation of X-ray source 220. The
global tracking device offset 213 may also be determined using
other imaging or tracking devices. For example, if the X-ray source
220 is movable on a track or rail, sensors on the track or rail may
be used to indicate the position of the X-ray source 220. Once the
target offset 211, imaging device offset 212, and global tracking
device offset 213 are known, they can be added to determine the
global target offset 210. This calculation may be performed by
processor 111. The global target offset can then be used, for
example, to control robotic arm 102 so that a beam of LINAC 103
intersects target 105. In one embodiment, the determination of
global target offset 210 may be repeated so that the global
location of target 105 can be continuously or periodically updated.
Alternatively, the determination of the global target offset 210
may be performed in response to detecting or anticipating movement
by target 105.
[0032] In other embodiments, a detector panel such as X-ray
detector panel 221 may not be required. For example, a camera or
other optical system in conjunction with light-emitting diodes
(LEDs) attached to imaging device 113 may be used as tracking
device 112. The camera may track imaging device 113 by capturing
images including the LEDs, without the need for detector panel 221.
Aside from X-ray imagers, cameras, or similar imaging systems,
other types of tracking devices can also be used to perform the
functions of tracking device 112.
[0033] FIG. 3 illustrates a tracking system for tracking a target
105 within patient 104 using a robotic arm system according to one
embodiment of the invention. The tracking system includes a
processor 111, an imaging device 113, and a robotic arm 301 and
determines a global target offset 210 by summing a global imaging
device offset 311 and a target offset 211. Imaging device 113 has
an imaging field 202. Objects within the imaging field 202 may be
effectively captured in an image by imaging device 113. Offsets
210, 211, and 311 may be described by vectors in three-dimensional
space.
[0034] Imaging device 113 is mounted on robotic arm 301 so that
robotic arm 301 can control the movement, orientation, and position
of imaging device 113. Depending on the type of imaging device 113
being used, robotic arm 301 may hold the imaging device 113 at a
distance from the target 105 or may contact a skin surface of
patient 104 with imaging device 113. For example, if imaging device
113 is an ultrasound scanner, robotic arm 301 may position the
ultrasound scanner so that its transducer contacts the skin surface
of patient 104. Robotic arm 301 may also be used to reposition
imaging device 113 so that target 105 remains within the imaging
field 202 of imaging device 113. An ultrasound scanner used as
imaging device 113, for instance, may have a small imaging field
202 such that movement of the patient 104 due to respiration or
heartbeat may tend to move target 105 outside imaging field 202.
Thus, robotic arm 301 may be used to compensate for the movement of
target 105. In one embodiment, processor 111 may also be used to
monitor the images captured by imaging device 113, detect when
target 105 is not within imaging field 202, and direct robotic arm
301 to move imaging device 113. Alternatively, the imaging device
may be moved according to a defined path. For example, if the
movement of target 105 can be described as a periodic pattern, the
imaging device may be moved according to that pattern. The imaging
device may also be moved for registration purposes. For example,
the imaging device may be moved to a known location in a treatment
room so that images captured by the imaging device may be
correlated with the known location for calibration purposes.
[0035] As previously described, imaging device 113 may be used to
determine target offset 211, which is the position of target 105
relative to imaging device 113. Global imaging device offset 311
may then be determined using sensors or other mechanical encoders
on robotic arm 301. For example, sensors mounted on the joints of
robotic arm 301 may indicate the orientation of each joint. The
joint orientations can then be used to calculate the position of
the imaging device 113 relative to global reference point 201. Once
the target offset 211 and the global imaging device offset 311 are
known, the global target offset 210 may be calculated by summing
the target offset 211 and the global imaging device offset 311.
This calculation may be performed by processor 111. In one
embodiment, processor 111 may receive offsets 211 and 311 from
robotic arm 301 and imaging device 113. Alternatively, processor
111 may calculate offsets 211 and 311 from raw data received from
robotic arm 301 and imaging device 113. Aside from mechanisms such
as robotic arm 301, imaging device 113 may also be positioned using
other types of positioning mechanisms.
[0036] FIG. 4 illustrates an ultrasonic imaging system that can be
positioned using a belt mechanism, according to one embodiment of
the invention. Ultrasonic imaging system 400 may be used as imaging
device 113, and includes an ultrasonic transducer 410 attached to
belt 411 at attachment point 412. Belt 411 is then attached to
treatment couch 414 by slider 413. The transducer 410 is connected
through extension link 424 to external unit 420, which includes
image processor 422 and drive circuitry 421. External unit 420 is
further connected to a monitor 423. Tracking device 112 may be
positioned so that tracking field 203 encompasses transducer 410,
so that tracking device 112 can be used to track the position of
transducer 410.
[0037] While patient 430 is lying on treatment couch 414,
transducer 410 is held in place on the skin surface of patient 430
using belt 411. Transducer 410 is attached to belt 411 at
attachment point 412, which in one embodiment, can be removed from
and reattached to belt 411 so that the position of transducer 410
can be adjusted along the x-axis 440. Alternatively, attachment
point 412 may be a sliding attachment that allows repositioning of
transducer 410 without removal and reattachment. Belt 411 may also
be attached to treatment couch 414 at slider 413. Slider 413 may
allow the belt 411 to be repositioned along the length of treatment
couch 414, along the y-axis 441. Alternatively, other types of
repositioning mechanisms may be used other than a slider. For
example, belt 411 may be repositioned by detaching belt 411 and
reattaching belt 411 at a different location. In other embodiments,
belt 411 may not be attached to treatment couch 414.
[0038] The belt assembly, including belt 411 attachment point 412,
and slider 413, keeps transducer 410 in contact with the skin
surface of patient 430 at a particular location. Transducer 410 may
then be used as imaging device 113. The location of a target 105
with respect to transducer 410 may be determined using an image of
the target 105 captured by the ultrasonic imaging system 400. The
location of transducer 410 with respect to tracking device 112 may
be determined using tracking device 112. The global position of the
target 105 with respect to the global reference point 201 can then
be determined by adding the appropriate offsets, as previously
described.
[0039] Drive circuitry 421 and image processor 422 may be kept
apart from transducer 410 so that transducer 410 can be more easily
repositioned. Thus, drive circuitry 421 and image processor 422 may
be kept in an external unit 420, which may be a box or other
enclosure. Drive circuitry 421 may be connected to transducer 410
through extension link 424 so that drive circuitry 421 can provide
the signals to the transducer 410 required to conduct the
ultrasound imaging. Image processor 422 can also be connected to
transducer 410 through extension link 424 so that image processor
422 can convert the signals received from the transducer 410 into
an image to be displayed on monitor 423. Extension link 424 may be
any medium through which signals can be transmitted, such as a
cable or a wireless link, while allowing transducer 410 to be moved
independently from external unit 420.
[0040] The ultrasonic imaging system 400 may adjust parameters such
as gain, transducer pressure, transmit frequency, receive
frequency, and dynamic range in response to input received from
other devices. For example, ultrasonic imaging system 400 may
adjust its transmit frequency based on an input received from
processor 111 requesting such an adjustment. In addition, belt 411
of ultrasonic imaging system 400 may include a gel container that
is configured to apply gel between the skin surface of the patient
430 and the transducer 410. In one embodiment, application of the
gel can be initiated by a request sent from another device. For
example, processor 111 may determine that a reapplication of gel
would improve the quality of images produced by ultrasonic imaging
system 400. Processor 111 can send an input to ultrasonic imaging
system 400 to initiate the application of gel.
[0041] FIG. 5 is a flow diagram illustrating a process for
administering radiation treatment while tracking the treatment
target according to one embodiment of the invention. At block 501
of treatment process 500, the treatment is planned and treatment
nodes are calculated. The treatment planning may include
determining such details as the radiation dosage needed to complete
the treatment or the angles at which the radiation beam will
intersect the target 105. The process may also determine a number
of treatment nodes, which represent spatial locations from which
the LINAC 103 delivers a radiation beam to the target 105.
[0042] At block 502, the patient 104 is aligned for a treatment
node. The patient 104 may be placed on a treatment couch 101 so
that the target 105 within patient 104 is positioned to receive a
radiation beam delivered from the treatment node.
[0043] With the patient 104 appropriately aligned, the position of
an imaging device 113 is adjusted in block 503 so that an image
produced by the imaging device 113 is of sufficient quality to be
used for registration with corresponding images, such as CT or
X-ray images. For example, an ultrasound scanner used as imaging
device 113 may be adjusted to maintain the target 105 within an
imaging field of the scanner, or may be adjusted to maintain an
optimal angle for imaging the target 105. The adjustment of the
position of imaging device 113 can be done manually or by an
automatic mechanism. For example, the imaging device 113 may be
automatically repositioned based on the location or orientation of
the target 105 within an image captured by imaging device 113.
[0044] Once the position of the imaging device 113 has been
adjusted, the location of the imaging device 113 is recorded as a
node for the corresponding treatment node designating the position
of LINAC 103, according to block 504. In an alternative embodiment,
other parameters may also be recorded with the imaging device node.
For example, if the imaging device 113 is an ultrasound scanner,
parameters such as gain, transducer pressure, transmit frequency,
receive frequency, and dynamic range may be recorded. The recorded
imaging device node parameters may be stored in any of a number of
storage locations. For example, the node parameters may be stored
in the imaging device itself, in another component of the treatment
delivery system 100, or in a network location such as a Digital
Imaging and Communications in Medicine (DICOM) workstation.
[0045] In block 505, if additional treatment nodes are pending,
execution proceeds back to block 502. Otherwise, if imaging device
nodes have been determined corresponding to each of the treatment
nodes, then execution proceeds to block 506.
[0046] At block 506, patient 104 is placed within range of the
treatment robot, which includes robotic arm 102 and LINAC 103. For
example, patient 104 may be placed on treatment couch 101 near
enough to LINAC 103 so that a beam of LINAC 103 can intersect
target 105.
[0047] With the patient 104 in position to receive treatment from
LINAC 103, the treatment session can begin. In block 507, the
imaging device 113 is positioned at a recorded imaging device node
corresponding to the initial treatment node. The recorded imaging
device node may also specify parameters to be used by the imaging
device 113, such as gain adjustment, transmit and receive
frequency, and dynamic range. The imaging node location and other
parameters are read, and then applied to the imaging device. In one
embodiment, where the imaging device 113 is an ultrasound scanner
having a transducer 410 attached to belt 411, the transducer 410
may be moved to the location of the imaging device node by a
positioning mechanism attached to the belt 411. Alternatively, if
the imaging device 113 is attached to a robotic arm 301, then the
imaging device 113 may be moved to the imaging device node by the
robotic arm 301. The parameters specified in the imaging device
node may be sent to imaging device 113 so that imaging device 113
may adjust its parameters accordingly. In some embodiments, imaging
device 113 may also automatically adjust its parameters in
real-time to facilitate real-time tracking of target 105.
[0048] In block 508, the position of the imaging device 113 is
adjusted to compensate for movement of target 105 caused by
respiration, heartbeat, or other tissue motion of the patient 104.
As in block 507, the imaging device may be adjusted using a robotic
arm or other positioning mechanism. The imaging device 113 is
repositioned so that the imaging device 113 can capture images of
the target 105 suitable for registration with other corresponding
images of the target 105, such as CT or X-ray images. The position
of imaging device 113 is adjusted until the quality of the images
captured by imaging device 113 is acceptable for registration,
according to block 509.
[0049] If the quality of the captured images is acceptable for
registration purposes, then execution proceeds from block 509 to
block 510, where the location of the target 105 is determined. The
location of target 105 may be determined by using an image captured
by imaging device 113 to locate the target 105 relative to the
imaging device 113. In one embodiment, the location of target 105
is tracked relative to imaging device 113 by detecting the edges of
the structures in images captured by imaging device 113,
identifying edges to be tracked, and tracking the position of the
identified edge as it moves. For example, an ultrasound scanner
used as imaging device 113 may determine the location of target 105
by tracking the edges of target 105 as they appear in images
captured by the ultrasound scanner over time. The tracking device
112 can then be used to locate the imaging device 113 relative to a
global reference point 201. The location of the target 105 relative
to the global reference point can then be determined from the
location of target 105 relative to the imaging device 113 and the
location of the imaging device 113 relative to global reference
point 201.
[0050] At block 511, the location of the target 105 determined at
block 510 is used to update the position of LINAC 103 so that the
beam of LINAC 103 will intersect target 105. With LINAC 103
properly positioned, the radiation beam is delivered to the target
105 in block 512.
[0051] At block 513, if treatment nodes are still pending, then
execution proceeds back to block 506, where the treatment process
continues. At block 506, the patient is positioned within range of
the treatment robot, if necessary. Blocks 506, 507, 508, 509, 510,
511, 512, and 513 are then repeated for subsequent treatment nodes
until no more treatment nodes are pending. When no more treatment
nodes are pending, the treatment session ends at block 514.
[0052] FIG. 6 is a flow diagram illustrating a process for tracking
a target according to one embodiment of the invention. After block
601 of target tracking process 600, the treatment session is in
progress. During the treatment session, block 508 provides for
adjustment of imaging device 113 to maintain target 105 within
imaging field 202 of the imaging device 113. The adjustment is to
maintain the quality of the image captured by imaging device 113 so
that the image can be used to locate target 105 or so the image can
be registered with other images such as CT or X-ray images. The
positional adjustment of imaging device 113 may be performed by
using a mechanical device such as robotic arm 301 to change the
orientation or position of the imaging device 113. In one
embodiment, a feedback mechanism may be used, where the robotic arm
301 adjusts the position of imaging device 113 based on an image
captured by imaging device 113. For example, if an image captured
by imaging device 113 shows that the target 105 is approaching a
boundary of imaging field 202, robotic arm may respond by moving
imaging device 113 to keep target 105 near the center of imaging
field 202. Alternatively, the positional adjustment of imaging
device 113 may be performed manually. For example, if ultrasonic
imaging system 400 is used as imaging device 113, the ultrasonic
transducer 410 may be manually repositioned using slider 413 or
attachment point 412. If target 105 is already within imaging field
202, execution of block 508 may not be necessary, and adjustment of
imaging device 113 may be avoided.
[0053] Block 602 provides for tracking the location of target 105
relative to imaging device 113. The tracking is accomplished by
using imaging device 113 to capture an image of target 105. The
position and orientation of target 105 within the captured image
can then be used to determine the location of target 105 relative
to imaging device 113. The result of this determination is target
offset 211.
[0054] Block 603 may be executed either in parallel or sequentially
with blocks 508 and 602. Block 603 provides for determining the
position of the imaging device 113 relative to the global reference
point 201. Determining the position of the imaging device 113
relative to the global reference point 201 may be accomplished by
first using the tracking device 112 to determine an imaging device
offset 212 between the tracking device 112 and the imaging device
113, then adding the imaging device offset 212 to a global tracking
device offset 213 that indicates an offset between the tracking
device 112 and the global reference point 201. For example, if an
optical device such as a camera is used as tracking device 112,
then tracking device 112 may be used to capture an image that
includes imaging device 113. The position and orientation of the
imaging device 113 relative to the tracking device 112 can then be
determined by reference to the position and orientation of the
imaging device 113 as it appears in the captured image. The
position of the imaging device 113 relative to the tracking device
112 may be represented as imaging device offset 212. The offset
between the imaging device 113 and the global reference point 201
can then be determined by adding the imaging device offset 212 and
the global tracking device offset 213. The global tracking device
offset 213 may be determined before the beginning of the treatment
session.
[0055] Alternatively, if the imaging device 113 is mounted on a
device such as robotic arm 301, positional sensors on robotic arm
301 may be used to determine the position of imaging device 113
relative to global reference point 201. The position of the imaging
device 113 relative to the global reference point 201 may be
represented as global imaging device offset 311.
[0056] When blocks 602 and 603 have been completed, execution
proceeds to block 604, where the position of the target 105 is
determined relative to the global reference point 201. The position
of target 105 relative to global reference point 201 is the global
target offset 210, which may be represented as a three-dimensional
vector. The global target offset 210 may be calculated by adding
the target offset 211, as determined in block 602, and the offset
between imaging device 113 and global reference point 201, as
determined in block 603. The resulting global target offset 210 is
the offset between the target 105 and the global reference point
201.
[0057] In block 511, the global target offset 210 is used to adjust
the beam of LINAC 103 so that the beam intersects target 105. In
one embodiment, the LINAC 103, which is mounted on robotic arm 102,
may be repositioned by robotic arm 102 to maintain an intersection
of the LINAC beam with target 105. Alternatively, the treatment
couch may be repositioned by robotic arm 106 to maintain an
intersection of the LINAC beam with target 105, or a combination of
both robotic arms 102 and 106 may be used. Global target offset
210, as determined in block 604, is used to determine how to
position LINAC 103 so that the intersection of the LINAC beam with
target 105 is maintained.
[0058] At block 513, if any treatment nodes are still pending, the
treatment is not completed and execution proceeds back to block
601, where the treatment session continues. Blocks 508, 602, 603,
604, 511, 512, and 513 are thus repeated for successive treatment
nodes until the treatment has been completed. If no treatment nodes
remain pending upon reaching block 513, then the treatment session
ends, at block 514.
[0059] Alternatively, treatment delivery system 100 may be a type
of system other than a robotic arm-based system. For example,
treatment delivery system 100 may be a gantry-based (isocentric)
intensity modulated radiotherapy (IMRT) system. In a gantry based
system, a radiation source (e.g., a LINAC) is mounted on the gantry
in such a way that it rotates in a plane corresponding to an axial
slice of the patient. Radiation is then delivered from several
positions on the circular plane of rotation. In IMRT, the shape of
the radiation beam is defined by a multi-leaf collimator that
allows portions of the beam to be blocked, so that the remaining
beam incident on the patient has a pre-defined shape. The resulting
system generates arbitrarily shaped radiation beams that intersect
each other at the global reference point to deliver a dose
distribution to the target region. In IMRT planning, the
optimization algorithm selects subsets of the main beam and
determines the amount of time that the patient should be exposed to
each subset, so that the prescribed dose constraints are best met.
In one particular embodiment, the gantry-based system may have a
gimbaled radiation source head assembly.
[0060] It should be noted that the methods and apparatus described
herein are not limited to use only with medical diagnostic imaging
and treatment. In alternative embodiments, the methods and
apparatus herein may be used in applications outside of the medical
technology field, such as industrial imaging and non-destructive
testing of materials. In such applications, for example,
"treatment" may refer generally to the effectuation of an operation
controlled by the treatment planning system, such as the
application of a beam (e.g., radiation, acoustic, etc.) and
"target" may refer to a non-anatomical object or area.
[0061] Certain embodiments may be implemented as a computer program
product that may include instructions stored on a computer-readable
medium. These instructions may be used to program a general-purpose
or special-purpose processor to perform the described operations. A
computer-readable medium includes any mechanism for storing or
transmitting information in a form (e.g., software, processing
application) readable by a computer. The computer-readable medium
may include, but is not limited to, magnetic storage medium (e.g.,
floppy diskette); optical storage medium (e.g., CD-ROM);
magneto-optical storage medium; read-only memory (ROM);
random-access memory (RAM); erasable programmable memory (e.g.,
EPROM and EEPROM); flash memory; or another type of medium suitable
for storing electronic instructions.
[0062] Additionally, some embodiments may be practiced in
distributed computing environments where the computer-readable
medium is stored on and/or executed by more than one computer
system. In addition, the information transferred between computer
systems may either be pulled or pushed across the communication
medium connecting the computer systems.
[0063] Although the operations of the methods herein are shown and
described in a particular order, the order of the operations of
each method may be altered so that certain operations may be
performed in an inverse order or so that certain operation may be
performed, at least in part, concurrently with other operations. In
another embodiment, instructions or sub-operations of distinct
operations may be in an intermittent and/or alternating manner.
[0064] In the foregoing specification, the invention has been
described with reference to specific exemplary embodiments thereof.
It will, however, be evident that various modifications and changes
may be made thereto without departing from the broader spirit and
scope of the invention as set forth in the appended claims. The
specification and drawings are, accordingly, to be regarded in an
illustrative sense rather than a restrictive sense.
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