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Description  |
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FIELD OF THE INVENTION
The invention relates to a method and apparatus for use in positioning a
patient upon a treatment table of a linear accelerator for providing
radiation therapy treatment of a lesion within a patient's body through
the use of a camera and a plurality of light emitting diodes which are
viewed by the camera.
DESCRIPTION OF THE PRIOR ART
Radiation therapy can be effective in treating certain types of cancers if
a sufficient radiation dose is delivered to the tumor, or lesion, volume;
however, complications may result from use of the necessary effective
radiation dose, due to damage to healthy tissue which surrounds the tumor,
or lesion, or to other healthy body organs located close to the tumor. The
goal of conformal radiation therapy treatment is to confine the delivered
radiation dose to only the tumor volume defined by the outer surfaces of
the tumor, while minimizing the dose of radiation to surrounding healthy
tissue or adjacent healthy organs. If the effective radiation dose is not
delivered to the proper location within the patient, serious complications
may result, whereby in the delivery of conformal radiation therapy
treatments, as well as in static radiation therapy treatments, the
position of the patient upon the treatment table is very important. The
patient usually has a radiation therapy treatment plan prepared, based
upon a diagnostic study through the use of computerized tomographic ("CT")
scanning, magnetic resonance ("MR") imaging, or conventional simulation
films, which are plain x-rays generated with the patient in the position
which will be used by the patient during the radiation therapy treatment.
Regardless of which technique, CT scanning, MR imaging, or simulation
films, is used at the time of the diagnostic study to develop the
radiation therapy treatment plan, it is necessary to relate the patient's
position at the time of the diagnostic study to how the patient will be
positioned at the time of the radiation therapy treatment. If this
relationship of the patient's position is not correct, the radiation dose
may not be delivered to the correct location within the patient's body.
Traditional techniques used in the positioning of patients during radiation
therapy treatments include: laser lights with tattoos or other markers;
non-invasive immobilization devices; and invasive immobilization devices.
When tattoos, or markers, are utilized to position the patient during the
radiation therapy treatment, the tattoos are placed on the patient's body,
while they are on the diagnostic table, in locations corresponding to the
tumor, or lesion, volume. These tattoos are aligned to wall-mounted laser
lights which cross at the isocenter of gantry rotation of the linear
accelerator which is typically used to provide the radiation therapy
treatment. The isocenter of gantry rotation is the point where the
radiation beams from the linear accelerator intersect as the gantry of the
linear accelerator carrying the radiation beam source rotates around the
patient. The position of the patient is adjusted until the tattoos are
aligned with the laser lights. The treatment table of the linear
accelerator, or other radiation device, is locked in place, and the
patient is immobilized and the radiation therapy treatment is started.
Non-invasive immobilization involves making a mold of the patient on which
tattoos, or other markers, are placed when the patient is properly
positioned upon the diagnostic table. At the time of the radiation therapy
treatment, the same mold is placed upon the treatment table, and the
patient is placed in the mold, after which the radiation therapy treatment
begins. One type of non-invasive immobilization device is disclosed in
U.S. Pat. No. 5,207,688, entitled "Non-Invasive Head Fixation Method and
Apparatus", assigned to the assignee of the present application, and this
patent is incorporated herein by reference. The device of U.S. Pat. No.
5,207,688, can be used during CT scanning or MR imaging. A radiopaque
marker on the surface of the immobilization device can be identified in
the CT scanner or MR imager. The coordinates of the marker and the tumor,
or lesion, can be generated in reference to the coordinate system of the
CT or MR device. The coordinate offsets of the tumor, or lesion, with
respect to the marker can then be generated. When the patient is
positioned on the treatment table of the linear accelerator, or other
radiation therapy treatment device, the wall-mounted laser lights in the
treatment room are first aligned with the external marker. The treatment
table may then be adjusted using the tumor, or lesion, coordinate offsets,
so that the tumor, or lesion, is brought to the isocenter of gantry
rotation of the linear accelerator. The patient then can be treated.
Invasive immobilization employees the same techniques as non-invasive
immobilization, except that the immobilization device is secured to the
patient in an invasive fashion with screws, pins, or other similar device.
The invasive immobilization device stays upon the patient for the duration
of the patient's treatment. An example of one such invasive immobilization
device is that of U.S. Pat. No. 5,163,430, entitled "Method and Apparatus
for Performing Stereotactic Surgery", commonly assigned with the present
application, and this patent is incorporated herein by reference.
Electronic systems have also been developed to check proper initial patient
positioning and to assess whether or not the patient moves during the
radiation therapy treatment. An example of one such system is the "Ottawa
system for Fractionated Stereotactic Radiotherapy". This system includes a
patient position monitoring system consisting of two charged coupled
device cameras mounted to the ceiling of the treatment room, a diode
laser, and a plurality of retroreflective targets secured to the patient.
The laser illuminates the retroreflector targets which are then viewed by
the cameras. Through the process of triangulation, the position of the
retroreflectors at any point in time can be determined by the camera
system. Another camera system, known as the Pixys, has been used for
triangulating patient position in the operating room suite and in the
radiation therapy treatment room. This system uses three unidirectional
slit cameras which are used to determine the position of light emitting
diodes attached to the patient.
There are certain disadvantages inherent in all of the foregoing patient
positioning techniques. A major problem associated with the use of
tattoos, non-invasive and/or invasive immobilization devices, is that
verification of the position of the patient is dependent upon visually
aligning the laser lights with some marker placed either on the patient or
on the immobilization device attached to the patient. Additionally, the
markers, such as tattoos or screws, may be disfiguring to the patient, or
it may be difficult to align the laser lights with such markers. Correct
alignment may also be subject to the technologist's interpretation of the
coincidence of the laser lights with the patient markers. Another
disadvantage with these techniques is that there is no means to indicate
whether or not the patient has moved after the radiation therapy treatment
has begun. Normally, the patient is positioned upon the treatment table,
and the treatment table is locked in place. The technologist leaves the
radiation therapy treatment, at which time the radiation therapy treatment
is begun. The technologist watches the radiation therapy treatment via
videocameras mounted inside the radiation therapy treatment room, which
are aimed at the treatment table. Even if close attention is paid
throughout the radiation therapy treatment, it is many times difficult for
the technologist to be, either quantitatively or qualitatively, aware of
small amounts of patient movement, which could affect the desired
radiation dose being supplied to the desired tumor, or lesion, volume.
The previously described electronic systems have certain disadvantages
associated with them. In order to function properly, the cameras have to
be rigidly secured to the ceiling of the radiation therapy treatment room,
which many times may be difficult and is a function of the construction of
the radiation therapy treatment room. Additionally, the plurality of
cameras must be situated in such a manner that each camera can
simultaneously see the retroreflective targets or light emitting diodes
which are used. If each camera cannot simultaneously see the
retroreflective targets or light emitting diodes, the necessary
triangulation cannot occur. Additionally, because the cameras are mounted
to the ceiling of the radiation therapy treatment room, which in many
instances may be low, it may be difficult for cameras to adequately view
all regions of interest. A further disadvantage associated with such
electronic systems is their cost resulting from the necessity of utilizing
multiple cameras, as well as, in one instance, a diode laser.
Accordingly, prior to the development of the present method and apparatus
for patient positioning for radiation therapy, there has been no method
and apparatus for patient positioning which: does not require the use of
disfiguring tattoos, screws, or similar markers; is easy to align, may be
used to determine undesired patient movement after the radiation therapy
treatment has begun; does not require the use of two cameras secured to
the ceiling of the radiation therapy treatment room; and is relatively
inexpensive. Therefore, the art has sought a method and apparatus for
patient positioning for radiation therapy treatments which: does not
require disfiguring tattoos, screws, or other markers; is easy to align;
permits continuous monitoring of the position of the patient during the
radiation therapy treatment; does not require multiple cameras; does not
require a diode laser; and is relatively inexpensive.
SUMMARY OF THE INVENTION
In accordance with the invention, the foregoing advantages have been
achieved through the present method and apparatus for patient positioning
for radiation therapy. The apparatus for use in positioning a patient upon
a treatment table of a linear accelerator for providing radiation therapy
treatment, the linear accelerator having a rotatable gantry, and the
treatment table having associated therewith a means for immobilizing a
portion of the patient with respect to the treatment table, in accordance
with one aspect of the present invention, includes: a plurality of light
emitting diodes, including means for mounting the plurality of light
emitting diodes with respect to the patient; at least one camera for
viewing the plurality of light emitting diodes; and means for mounting the
at least one camera to the gantry of the linear accelerator, whereby as
the gantry rotates, the at least one camera rotates with the gantry and
views the plurality of light emitting diodes from at least two different
angular positions of the gantry with respect to the treatment table.
A feature of this aspect of the present invention is that the at least one
camera may be a single camera, and the at least one camera may be a
charged coupled device camera. Another feature of this aspect of the
present invention is that the means for mounting the plurality of light
emitting diodes may include a means for mounting at least one emitting
diode in an external auditory canal of an ear of the patient. A further
feature of this aspect of the present invention is that the means for
mounting at least one light emitting diode in an ear of the patient may
include a quantity of a rapidly setting material, which is adapted to be
disposed within, and conformed to, the external auditory canal, and the
light emitting diode may be disposed within the rapidly setting material.
An additional feature of this aspect of the present invention is that the
means for mounting the plurality of light emitting diodes may include a
means for mounting at least one light emitting diode to the means for
immobilizing a portion of the patient. The means for mounting the
plurality of light emitting diodes may also include a means for mounting
at least one light emitting diode to the body of the patient.
The method for positioning a patient upon a treatment table of a linear
accelerator for providing radiation therapy treatment of a lesion within
the patient's body, the linear accelerator having a rotatable gantry, in
accordance with another aspect of the present invention, may include the
steps of: providing at least one camera mounted to the gantry of the
linear accelerator; immobilizing a portion of the patient with respect to
the treatment table with a means for immobilizing associated with the
treatment table; mounting a plurality of light emitting diodes with
respect to the patient; disposing the gantry, with the at least one camera
mounted thereto, in a first predetermined position with respect to the
patient and generating a first image of the plurality of light emitting
diodes with the at least one camera; rotating the gantry, with the at
least one camera mounted thereto, to a second predetermined position with
respect to the patient, and generating a second image of the plurality of
the light emitting diodes with the at least one camera; determining, from
the first and second images, the location of the light emitting diodes
with respect to the treatment table; and comparing the location of the
light emitting diodes, with respect to the treatment table, to a
previously determined desired location of the light emitting diodes with
respect to the treatment table, whereby if the location of the light
emitting diodes with respect to the treatment table indicates the patient
is not properly positioned, the patient may be moved whereby the light
emitting diodes will be disposed in the desired position.
A feature of this aspect of the present invention may include the step of
providing a single camera mounted to the gantry of the linear accelerator.
An additional feature of this aspect of the present invention may include
the step of mounting at least one of the light emitting diodes with
respect to the patient by mounting at least one light emitting diode upon
the patient. A further feature of this aspect of the present invention may
include the step of utilizing as the at least one camera, a charged
coupled device camera, and only one camera may be utilized.
Another feature of this aspect of the present invention may include the
step of calibrating the at least one camera with respect to the treatment
table before immobilizing at least a portion of the patient with respect
to the treatment table. A calibration fixture may be used to calibrate the
at least one camera and the calibration fixture may be provided with a
plurality of light emitting diodes disposed in a known spatial
relationship with each other. Another feature of this aspect of the
present invention may include the step of continuously monitoring the
locations of the plurality of light emitting diodes during the rotation of
the gantry while a radiation therapy treatment is provided to the patient
and the step of indicating an undesired location of at least one of the
plurality of light emitting diodes during the radiation therapy treatment.
The method and apparatus for patient positioning for radiation therapy of
the present invention, when compared with previously proposed prior art
methods and apparatus, have the advantages of being: relatively
inexpensive; not requiring the use of disfiguring markers, such as tattoos
or screws; is easy to align; able to be utilized continuously during the
radiation therapy treatment; not dependent upon the use of multiple
cameras or a diode laser; and readily utilized in existing radiation
therapy treatment rooms without mounting any equipment to the ceiling of
the radiation therapy treatment room.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a side view of a linear accelerator and apparatus for use in
positioning a patient upon a treatment table of the linear accelerator in
accordance with the present invention;
FIG. 2 is a view of the apparatus of FIG. 1 taken along line 2--2 of FIG.
1, the gantry of the linear accelerator being illustrated in two different
angular positions with respect to the treatment table after the gantry has
been rotated; and
FIG. 3 is a perspective view of a calibration fixture in accordance with
the present invention.
While the invention will be described in connection with the preferred
embodiment, it will be understood that it is not intended to limit the
invention to that embodiment. On the contrary, it is intended to cover all
alternatives, modifications, and equivalents as may be included within the
spirit and scope of the invention as defined by the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
With reference to FIGS. 1 and 2, the method and apparatus of the present
invention for positioning a patient for radiation therapy treatment will
be described. In FIGS. 1 and 2, a linear accelerator 40 is shown as
including a gantry 41 treatment table 42, which is typically mounted upon
a turntable (not shown), which causes treatment table 42 to rotate
therewith, and a conventional collimator, or means for focusing a beam of
radiation, 43 for the radiation therapy treatment. Gantry 41 is rotatable
about rotatable shaft 45 associated with gantry base member 46, as is
known to those of ordinary skill in the field of radiation therapy
treatment. Patient 50 is disposed upon treatment table 42, with patient 50
lying upon his or her back, only the head 51 of patient 50 being
illustrated for purposes of illustration.
Still with reference to FIGS. 1 and 2, the method and apparatus 60 of the
present invention for use in positioning a patient upon treatment table 42
of linear accelerator 40 for providing radiation therapy treatment of a
lesion, or tumor, 70 within the body of patient 50 will be described in
connection with method and apparatus 60 being clinically used for an
intracranial application, wherein the tumor, or lesion 70 is disposed
within the head 51 of patient 50, as shown in FIGS. 1 and 2. A portion of
patient 50, or the head 51 of patient 50, is immobilized with respect to
treatment table 42 by use of a means for immobilizing 80 a portion of
patient 50, such the patient's head 51. As illustrated in FIGS. 1 and 2,
immobilizing means 80 may be a non-invasive head fixation apparatus, such
as illustrated and described in U.S. Pat. No. 5,207,688, which includes a
frame 81 secured to treatment table 42, with frame 81 supporting a
deformable housing 83 which is adapted to overlie and contact the
patient's nasion 84, or the bridge of the patient's nose where it joins
the patient's forehead 86. Immobilizing means 80 may also include another
deformable housing 87 which restrains rotational movement of the patient's
head 51. Through the use of immobilizing means 80, the patient's head 51
is immobilized with respect to treatment table 42. Alternatively, an
invasive means for immobilizing could also be used for immobilizing
patient's head 51 with respect to treatment table 42, such as the
apparatus described in U.S. Pat. No. 5,163,430. While the use of the
immobilizing means 80 of U.S Pat. Nos. 5,207,688 and 5,163,430, are
preferred, it should be readily apparent to one of ordinary skill in the
art that other immobilizing means may be used in connection with the
method and apparatus 60 of the present invention.
Prior to patient 50 being disposed upon treatment table 42 of linear
accelerator 40, which is typically disposed in a radiation therapy
treatment room 48, a radiation treatment therapy plan would have been
generated during a CT scanning or MR imaging diagnostic study, at which
time the patient 50 would have been immobilized with respect to the
diagnostic table utilized in the CT scanning or MR imaging diagnostic
study. As will be hereinafter described, the means for immobilizing the
patient during the diagnostic study must be the same immobilizing means 80
used in connection with treatment table 42 of linear accelerator 40.
As illustrated in FIGS. 1 and 2, apparatus 60 of the present invention
further includes a plurality of light emitting diodes 90 which are mounted
with respect to the patient 50 and each light emitting diode 90 includes a
means for mounting 91 the plurality of light emitting diodes 90 with
respect to the patient 50. Apparatus 60 further includes at least one
camera 100 for viewing the plurality of light emitting diodes 90, and a
means for mounting 101 the at least one camera 100 to the gantry 41 of the
linear accelerator 40. Preferably, the at least one camera 100 is a
commercially available charged coupled device camera 102, which includes
an angle sensor 103 associated therewith. A suitable power source, or
power sources, (not shown) are provided to provide electric current for
camera 102 and the plurality of light emitting diodes 90. A small wire
(not shown) would be associated with each light emitting diode and
connected to the power source in a conventional manner. A suitable
computer 110 is operatively associated with camera 102 to process the
information and images obtained from camera 102 as will be hereinafter
described in greater detail. Preferably, the at least one camera 100 is a
single charged coupled device camera 102. However, if desired, more than
one camera 102 could be utilized, although an additional camera is not
necessary for the practice of the method of the present invention. The
second camera would also be mounted upon gantry 41 in a known fixed,
spatial relationship with respect to the other camera, or cameras. What is
important for the practice of the method of the present invention is that
the at least one camera 100 be mounted to the linear accelerator 40, and
preferably to the gantry 41.
As shown in FIG. 1, the at least one camera 100 is fixedly secured directly
to gantry 41 at an underside surface 47 of gantry 41, whereby the at least
one camera 100 has a field of view 104 of the portion, or head 51, of the
patient 50 which is being treated by the radiation therapy treatment from
linear accelerator 40. Mounting means 101 for camera 102, rigidly secures
the camera 102 to the underside surface 47 of gantry 41 as by a plurality
of bolts, screws, mounting plate, or similar type of fastening means.
Alternatively, the at least one camera 100 could be mounted to the gantry
by providing a mounting plate (not shown) which is locked into
conventional tray slots 48 associated with the collimator 43 or gantry 41
of linear accelerator 40. Such tray slots 48 are typically provided on
linear accelerators for accessories, and are known to those of ordinary
skill in the linear accelerator art. Preferably, camera 102 is
semi-permanently mounted to gantry 41 as illustrated in FIG. 1, whereby
apparatus 60 may not require to be frequently calibrated, as will be
hereinafter described in greater detail.
At least some of the light emitting diodes 90 must be mounted to the
immobilizing means 80, and preferably a minimum of three light emitting
diodes 90 are applied in a non-linear relationship to the immobilizing
means 80 in a non-coplanar, non-linear relationship as illustrated in FIG.
2, wherein two light emitting diodes 90 are disposed upon the horizontal
portion 81' of frame 81 in a spaced relationship from each other, and a
third light emitting diode 90 is disposed toward the bottom of the
vertical portion 81" of frame 81. It should be noted that the light
emitting diodes 90 mounted to immobilizing means 80 must be disposed in
the same location upon immobilizing means 80 when the patient 50 undergoes
the MR imaging or CT scanning diagnostic study. The mounting means 91 for
the light emitting diodes 90 mounted with respect to patient 50 on
immobilizing means 80 may be any suitable fastener, such as glue, epoxy,
screws, or bolts, or similar type of fastening devices, whereby the light
emitting diodes 90 associated with immobilizing means 80 are fixedly
secured to the immobilizing means 80. Some of the plurality of light
emitting diodes 90, such as light emitting diode 90' may be also mounted
to treatment table 42 by use of the same mounting means 91 previously
described.
Still with reference to FIGS. 1 and 2, preferably at least one light
emitting diode 90" is mounted in an external auditory canal 52 of patient
50. The mounting means 91 for light emitting diode 90" may be a quantity
of a rapidly setting material, such as a dental wax molding material, a
thermoplastic material, or similar material, capable of setting and curing
at room temperature and being compatible with the human body. The quantity
of rapidly setting material 93 is formed into a small ball and molded into
the patient's external auditory canal 52 of ear 53. As the rapidly setting
material 93 begins to set, light emitting diode 90" is inserted into the
material 93 so that light emitting diode 90" sets in place with the
material 93, resulting in a custom molded piece including light emitting
diode 90'. Preferably, this procedure is followed for both ears 53, and a
light emitting diode 90" is mounted within both external auditory canals
52 of ears 53. Alternatively, at least one light emitting diode 90 may be
mounted to a portion of the patient, such as head 51 of patient 50, or
some other portion of the patient's body. If a light emitting diode 90' is
mounted to the body of the patient, the mounting means 91 for such light
emitting diode 90 could be a non-disfiguring mounting means 91, such as:
surgical skin adhesive used for ostomy bags; other types of suitable
adhesive which are compatible with the human body; hook and eye material,
such as Velcro.RTM., wherein one layer of the hook and eye material is
affixed to the body and the complimentary layer of hook and eye material
is secured to the underside of the light emitting diode 90; or other
similar types of mounting means 91.
As previously described, prior to the patient receiving a radiation therapy
treatment with linear accelerator 40, a diagnostic study is conducted with
CT scanning, MR imaging, or simulation films. With the information
obtained from the diagnostic study, a radiation treatment plan may be
generated in a conventional manner. Such radiation treatment plan can
include a conformal radiation treatment plan, as are known in the art. One
such conformal radiation therapy treatment plan can be generated in
accordance with the PEACOCK.TM. Conformal Radiation Therapy Planning
System which is presently available for use from NOMOS Corporation, of
Sewickley, Penna., the assignee of the present application. During the
diagnostic study, the patient 50 is immobilized with respect to the
diagnostic imaging table of the CT or MR equipment. As previously
described, the immobilizing means used during the diagnostic study must be
the same as the immobilizing means 80 previously described in connection
with FIGS. 1 and 2, and preferably includes at least three light emitting
diodes 90 mounted to the immobilizing means 80 and may also preferably
include light emitting diodes 90" previously described. The diagnostic
study is conducted in a conventional manner and the diagnostic study will
determine the spatial coordinates of each of the light emitting diodes
with respect to the immobilizing means 80 and the patient 50 by the use of
either conventional internal imager software or through use of a
computer-based treatment planning system, such as that of the foregoing
patent applications. After the desired tumor treatment volume has been
defined by the user of the treatment planning system, the treatment
planning system determines the proper location for the patient 50 for the
radiation therapy treatment, based upon the known spatial coordinates of
the plurality of light emitting diodes 90, 90". A three dimensional offset
(x, y, z) is generated by the planning system relative to the known
location of the light emitting diodes, whereby the lesion, or tumor, 70
may be positioned at the isocenter of the linear accelerator 40 in a known
manner.
The patient 50 is then disposed upon treatment table 42 of linear
accelerator 40 as previously described in connection with FIGS. 1 and 2.
The plurality of light emitting diodes 90, 90', 90" are disposed with
respect to patient 50 in the manner previously described, and small wires
(not shown) are connected to each of the plurality of light emitting
diodes 90, 90', 90" to provide the necessary power for the light emitting
diodes. The patient 50 is then positioned upon treatment table 42 so that
the conventional wall-mounted laser lights (not shown) included with
linear accelerator 40 intersect at light emitting diodes which have been
selected by the treatment planning system in a conventional manner.
Preferably, the light emitting diodes which would be aligned with the
laser lights (not shown) would be the at least three non-coplanar light
emitting diodes 90 mounted to the immobilizing means 80. The treatment
table 42 may then be positioned in a conventional manner by moving
treatment table 42 the proper distance in the x, y and z directions,
whereby the lesion, or tumor, 70 is disposed at the isocenter of linear
accelerator 40.
With reference to FIG. 2, the gantry 41 is disposed in a first
predetermined position with respect to patient 50 as shown at location 120
in FIG. 2. An image of the plurality of light emitting diodes 90, 90', and
90" is generated by camera 102. This image is digitized by a conventional
frame grabber, and the digital information is fed into, and stored in,
computer 110. The angular disposition of gantry 41 is known from the angle
sensor 103 disposed within camera 102, which angle information is also fed
into, and stored in, computer 110. Gantry 41 is then rotated to a second
predetermined position with respect to patient 50 as indicated at 121 in
FIG. 2. Position 121, is likewise known and determined by the angle sensor
103 of camera 102. While gantry 41 is disposed in the second predetermined
position 121, a second image of the light emitting diodes 90, 90', and 90"
is generated by camera 102, which image is also processed and stored in
computer 110. A conventional triangulation algorithm is applied by
computer 100, and the location of the light emitting diodes, 90, 90', and
90", with respect to the treatment table 42 is determined. A suitable,
known three dimensional reconstruction algorithm, or triangulation
algorithm, that may be used computer 110 is that found in Mathematical
Elements for Computer Graphics, Second Edition, David F. Rogers and J.
Alan Adams, McGraw-Hill, Inc. It should be noted that the first and second
predetermined positions 120, 121 of gantry 41 illustrated in FIG. 2 have
been selected for illustrative purposes only. Preferably, the angle
between the first and second predetermined positions 120, 121 should be as
close as possible to 90 degrees since as the angle between positions 120,
121 either increases or decreases from 90 degrees, the sensitivity of
apparatus 60 may be affected.
The computer 110 has stored therein the locations, or three dimensional
coordinates, of the light emitting diodes 90, 90" from the prior
identification of their locations from the diagnostic study, and the
treatment planning system or imager software has also determined where the
tumor, or lesion, 70 is with respect to the light emitting diodes 90, 90".
The computer 110 may then compare the location of the light emitting
diodes, 90, 90", with respect to the treatment table 42 to the previously
determined desired locations of the light emitting diodes 90, 90' with
respect to treatment table 42, to determine if the light emitting diodes
90, 90" are disposed at their desired locations with respect to the
treatment table 42, which in turn will cause the tumor, or lesion, 70 to
be disposed in the proper location for treatment by linear accelerator 40.
The computer 110, after having compared the actual locations of the light
emitting diodes with the previously determined desired locations of the
light emitting diodes from the diagnostic study, can indicate to the user
of apparatus 60, either by text or a visual diagram (not shown) appearing
on the screen (not shown) of computer 110 or by an audible indication from
computer 110, whether or not the patient is positioned properly with
respect to treatment table 42 and gantry 41 of linear accelerator 40.
Computer 100 can further indicate in which direction, or directions, it is
necessary to move the patient 50 so that proper positioning of patient 50
may be achieved.
Once the proper positioning of patient 50 has been confirmed, the desired
radiation therapy treatment can begin. If the radiation therapy treatment
is a rotational therapy treatment plan, whereby gantry 41 rotates about
patient 50, camera 102 can continuously monitor the location of the
plurality of light emitting diodes 90, 90', and 90" to determine whether
or not proper patient positioning is being maintained. If the patient 50
moves, whereby the location of tumor, or lesion, 70 is changed, computer
110 can indicate to the user that the radiation therapy treatment should
be stopped, or computer 110 can automatically terminate the radiation
therapy treatment plan. Computer 110 can also be programmed to provide for
an acceptable amount of movement of patient 50, whereby if the limit of
acceptable movement is exceeded, a visual or audible indication of that
fact can be provided to the user. If a rotational radiation therapy
treatment plan is being utilized, camera 102 may generate an image of the
light emitting diodes 90, 90', and 90", at each time ga | | |
