U.S. patent application number 16/975301 was filed with the patent office on 2021-01-07 for apparatus and methods for mapping high energy radiation dose during radiation treatment.
The applicant listed for this patent is THE TRUSTEES OF DARTMOUTH COLLEGE. Invention is credited to Petr Bruza, David Gladstone, Lesley A. Jarvis, Brian W. Pogue, Irwin Tendler.
Application Number | 20210001153 16/975301 |
Document ID | / |
Family ID | |
Filed Date | 2021-01-07 |
United States Patent
Application |
20210001153 |
Kind Code |
A1 |
Pogue; Brian W. ; et
al. |
January 7, 2021 |
APPARATUS AND METHODS FOR MAPPING HIGH ENERGY RADIATION DOSE DURING
RADIATION TREATMENT
Abstract
A system for dosimetry includes a radiation source that provides
a pulsed radiation beam to a treatment zone, and a thin sheet of
scintillator disposed between the radiation source and skin of a
subject in the treatment zone. A gated camera images the
scintillator integrating light from the scintillator during
multiple pulses of the radiation beam while excluding light
received between pulses of the pulsed radiation beam; and an image
capture and processing machine that receives images from the gated
camera and performs additional corrections to provide a map of dose
received by the subject.
Inventors: |
Pogue; Brian W.; (Hanover,
NH) ; Bruza; Petr; (Lebanon, NH) ; Gladstone;
David; (Norwich, VT) ; Jarvis; Lesley A.;
(Hanover, NH) ; Tendler; Irwin; (Hanover,
NH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
THE TRUSTEES OF DARTMOUTH COLLEGE |
Hanover |
NH |
US |
|
|
Appl. No.: |
16/975301 |
Filed: |
February 22, 2019 |
PCT Filed: |
February 22, 2019 |
PCT NO: |
PCT/US19/19135 |
371 Date: |
August 24, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62634083 |
Feb 22, 2018 |
|
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Current U.S.
Class: |
1/1 |
International
Class: |
A61N 5/10 20060101
A61N005/10; G01T 1/20 20060101 G01T001/20; G01T 1/15 20060101
G01T001/15; G01T 7/00 20060101 G01T007/00 |
Goverment Interests
GOVERNMENT INTEREST
[0002] This invention was made with government support under grants
R44 CA199836 and R01 EB023909 awarded by the National Institutes of
Health. This invention was made with government support using
Shared Resources from the Norris Cotton Cancer Center core
facilities under grant P30 CA023106 awarded by the National
Institutes of Health. The Government has certain rights in the
invention.
Claims
1. A system for dosimetry, comprising: a radiation source adapted
to provide a pulsed radiation beam to a treatment zone; a thin
sheet of scintillator disposed between the radiation source and
skin of a subject, the thin sheet of scintillator being in the
treatment zone; a gated camera configured to image the sheet of
scintillator; and an image capture and processing machine coupled
to receive images from the gated camera; wherein the gated camera
is configured to capture images of light from the thin sheet of
scintillator during a plurality of pulses of the pulsed radiation
beam while excluding light received from the thin sheet of
scintillator between pulses of the plurality of pulses of the
pulsed radiation beam to form a scintillation image.
2. The system of claim 1 wherein the thin sheet of scintillator is
a conformal sheet of scintillating material in contact with skin of
the subject.
3. The system of claim 2 wherein the system further comprises a 3-D
imaging camera, and wherein the image capture and processing
machine is configured to process images from the 3-D imaging camera
into a three-dimensional model of the subject and to use the
three-dimensional model of the subject to correct the scintillation
image while determining a corrected total dose image.
4. The system of claim 1 wherein the image capture and processing
machine is configured to subtract a background image from the
scintillation image, the background image being obtained by the
gated camera at times excluding times of pulses of the pulsed
radiation beam.
5. The system of claim 4 wherein the system further comprises a 3-D
imaging camera, and wherein the image capture and processing
machine is configured to process images from the 3-D imaging camera
into a three dimensional model of the subject and to use the three
dimensional model of the subject to correct the scintillation image
while determining a corrected total dose image.
6. The system of claim 5 wherein the image capture and processing
machine further comprises a database containing calibration
information associated with individual thin sheets of scintillator,
and the image capture and processing machine is configured to
correct the scintillation image according to the calibration
information.
7.-16. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority from U.S.
Provisional Patent Application No. 62/634,083 filed Feb. 22, 2018,
which is incorporated herein by reference in its entirety.
BACKGROUND
[0003] Several technologies exist for surface dosimetry of subjects
undergoing external-beam radiotherapy; dosimetry being used to
verify the amount of radiation delivered and placement of ionizing
radiation doses delivered during external beam radiation therapy
(EBRT). Among the dominant technologies for measurement of surface
dose are film, thermo-luminescent dosimeters (TLD),
optically-stimulated luminescence dosimeters, silicon diode or
MOSFET dosimeters, or scintillator fibers; each of these
measurement approaches has issues.
[0004] Among these issues is a large burden on staff time in
reading out the measurement, especially when TLDs and film are
used. Further, application of tethered detectors decreases patient
comfort due to the necessity of affixing not only the detectors,
but also the readout fibers or wires to the patient's body.
SUMMARY
[0005] In an embodiment, a system for dosimetry includes a
radiation source that provides a pulsed radiation beam to a
treatment zone, and a thin sheet of solid scintillator disposed
between the radiation source and skin of a subject in the treatment
zone. A gated camera images the solid scintillator integrating
light from the solid scintillator during multiple pulses of the
radiation beam while excluding light received between pulses of the
pulsed radiation beam; and an image capture and processing machine
that receives images from the gated camera and performs additional
corrections to provide a map of dose received by the subject.
[0006] In another embodiment, a method for mapping skin dose of a
subject during radiation treatment performed with a pulsed
radiation beam in a treatment zone includes providing a thin sheet
of plastic scintillator in contact with skin of a subject;
positioning the subject in the treatment zone; and capturing a
scintillation image of light received from the plastic scintillator
during multiple time windows during pulses of the radiation beam
while excluding light received from the plastic scintillator
between pulses of the radiation beam. The method also includes
capturing a background image of light received during a plurality
of time windows, that are non-overlapping the radiation pulse and
that have width corresponding to the radiation pulses; and
subtracting the background image from the scintillation image.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a plan view of a treatment system and facility
illustrating key equipment used during radiotherapy, in an
embodiment.
[0008] FIG. 1A depicts a thin, rectangular, conformal sheet of
scintillator as used in the treatment system, with black border and
identifying bar code.
[0009] FIG. 1B depicts a thin, round, conformal sheet of
scintillator as used in the treatment system, with black border and
identifying bar code.
[0010] FIG. 2 is a flowchart of operation of a system for radiation
dosimetry during radiation therapy.
[0011] FIG. 3 is a flowchart of an alternative embodiment of
operation of a system for radiation dosimetry during radiation
therapy where some steps are performed in a different order than in
the embodiment of FIG. 2.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0012] A radiation treatment system 100 (FIG. 1) includes a
radiation source 102 of a beam 104 of pulsed, ionizing, radiation
of moderate to high energy such as a linear accelerator (LINAC),
cyclotron, or other particle accelerator. Beam 104 is emitted along
a beam axis 106 through a collimator 108 that may include
adjustable shielding shapes configured to determine a shape of beam
104. The beam axis 106 and beam 104 are aimed towards a treatment
zone 110 within which a subject 112 may be positioned. Shielding
113 is positioned at least behind treatment zone 110, and in
particular embodiments surrounding the entire system 100 to absorb
any radiation of beam 104 not absorbed by subject 112.
[0013] A gated electronic camera, such as an intensified
charge-coupled device (ICCD) camera 114, is positioned outside beam
104 with a field of view 116 aligned along a camera viewing axis
118; camera viewing axis 118 is aligned such that field of view 116
includes a view of most or all of treatment zone 110 including a
view of a surface of any subject 112 that may be positioned within
the treatment zone 110.
[0014] In an alternative embodiment, an image-intensified CMOS
(ICMOS) camera is substituted for ICCD camera 114; with this camera
image capture gating is performed in a manner like that described
herein for the ICCD camera. In yet another embodiment, an
electronically-gated, sensitive, CMOS (EGCMOS) camera is used in
place of ICCD camera 114 with image capture timed to coincide with
beam pulses as described herein.
[0015] For comfort of subject 112, one or more room lighting
devices 120 are provided that provide room lighting illumination
122 to the treatment zone 110 and surrounding portions of the room
in which the treatment zone 110 is located.
[0016] Pulse timing signals 130 are provided by radiation source
102 to an image capture and processing machine 132 equipped with a
display 134 and network connection 136 over which images can be
viewed and transmitted to external medical records storage systems
(not shown).
[0017] Pulse timing signals 130 are used by image capture and
processing machine 132 to synchronize time-gated imaging by ICCD
camera 114 so camera 114 captures and images light received by ICCD
camera 114 during each pulse of radiation source 102 while
excluding from images light received by ICCD camera 114 at times
between pulses of radiation source 102. In a particular embodiment,
radiation source 102 is a LINAC providing a radiation beam 104 of
high energy electrons in pulses of between three and four
microseconds width repeated at a 360 Hertz rate, a duty cycle of
approximately one in one thousand. In an alternative embodiment,
radiation source 102 is a pulsed source of a radiation beam 104 of
high-energy X-ray or gamma-ray photon radiation.
[0018] By imaging only during the short pulses of electron
radiation emitted by the accelerator, ambient background light is
suppressed by a factor of 1000, making low-intensity scintillation
imaging feasible without need to blank room lighting devices
120.
[0019] It is known that some substances, such as europium-doped
calcium fluoride or thallium-doped sodium iodide crystals,
scintillate (or emit visible light) when they absorb high-energy
charged particles or high energy photons. Some radiation detectors,
including the detectors in some gamma-ray cameras, operate by
localizing flashes of light produced by scintillation in such
crystals when radiation is absorbed. For high-energy radiation
below a saturation limit, scintillation crystals and materials emit
light proportional to both the photon or particle energy and photon
or particle quantity of high energy radiation absorbed by them. An
issue with classical scintillation crystals is that thick crystals
of high-density materials absorb most, if not all, of electron beam
radiation striking them and thereby partially or fully shield part
or all of any subject positioned behind them. As such, thick
scintillation crystals positioned in beam 104 between collimator
108 and subject 112 would block treatment of some or all of subject
112. Such crystals would also absorb a significant percentage of
photon-beam radiation such as X or gamma-ray radiation.
[0020] A plastic scintillation material, Eljen EL-240, (Eljen
Technology 1300 W. Broadway, Sweetwater, Tex.) has been formed as a
one-millimeter thin sheet, thin enough to pass a majority of beam
104, and having low enough density that the one-millimeter thin
sheet does not significantly block or absorb radiation of beam
104.
[0021] In an embodiment, a one-millimeter thick sheet 135 of EL-240
scintillator is positioned as a screen at a radiation-source side
of treatment zone 110 in a path of beam 104 from collimator 108 to
subject 112, and ICCD camera 114 is positioned to image sheet
135.
[0022] In an alternative embodiment, a flexible one-millimeter
thick sheet 137 of EL-240 scintillator is positioned in contact
with skin of subject 112 in the treatment zone, and ICCD camera 114
is positioned to image sheet 137.
[0023] In alternative embodiments, thin sheets 137 of alternative
flexible and stretchable scintillators formed of organic
scintillators or powdered inorganic scintillators suspended in a
polymer, the polymer may be a transparent plastic or synthetic
rubber, are positioned conformal to skin of subject 112; in one
alternative embodiment the scintillator is formed as a garment worn
by subject 112. For purposes of this document, a thin sheet of
scintillator is a transparent, or translucent material that either
by itself, or through a second material incorporated within the
material, emits pulses of light by any mechanism including
scintillation, fluorescence, or Cherenkov, when stimulated by
pulses of a charged particle, x-ray or gamma radiation beam, the
pulses of light emitted having a wavelength adapted to capture by
camera 114 and a decay time of less than twice a duration of pulses
of the beam, the material being formed as a sheet thin enough to
not absorb a significant portion of photons or charged particles of
the beam so that at least 80% of energy of a typical radiation
treatment beam passes through the material.
[0024] In an alternative embodiment, the conformal sheet of
scintillator has a black border of width between three and five
millimeters, inclusive.
[0025] Gated camera 114 in an embodiment is an intensified CCD
camera, such as a PI-MAX4 1024i (Princeton Instruments, N.J., USA)
camera, including an image-intensifier tube and a charge-coupled
device semiconductor image sensor. The acceleration voltage of the
image-intensifier tube is pulsed synchronous to pulses of the
radiation source so that light received from the scintillation
material sheets 135 or 137 is imaged by the gated camera during
pulses of the beam 104, while light received between pulses of the
beam 104 is ignored, to form scintillation images.
[0026] With reference to FIG. 1 and FIG. 2, in a method 200 of
operating the system of FIG. 1, in some operations of the system
reference dosimeters, which in a particular embodiment are
thermos-luminescent dosimeters (TLD dosimeters) and in another
particular embodiment are silicon-based diode or MOSFET dosimeters,
are positioned 202 on subject 112 and the thin, approximately one
millimeter thick, scintillator sheets 135 or 137 are positioned 204
between radiation source 102 with collimator 108 and subject 112.
The subject is positioned 203 in the treatment zone 110.
[0027] A background image is captured 206 and integrated during the
same number of time windows as the scintillation image, the windows
are of duration equivalent in width and frequency to the time
windows used to capture the scintillation images. The background
image windows are timed to not overlap the beam pulse, and in a
particular embodiment are delayed from beam pulses. These
background image windows are timed late in the beam-pulse to
beam-pulse gap to allow decay of any fluorescence in the
scintillator sheet.
[0028] In an alternative embodiment, the background image is
captured 206 and integrated during a greater number of wider
background capture windows than the windows during which the
scintillation images are captured. All background capture windows
are non-overlapping pulses of the beam. The total of all the
background capture windows provides a total background integration
time that is a background multiple of the total integration of each
scintillation image, in a particular embodiment being forty times
the total integration time of a scintillation image. The background
image is then divided by the background multiple to provide an
averaged background image. Averaging the background image in this
way filters the background image by signal averaging to reduce
artifacts and noise in the background image. In these embodiments,
the averaged background image is used instead of a raw background
image when background is subtracted 210 from the scintillation
image.
[0029] Radiation treatment begins and the CCD or CMOS image sensor
integration time of camera 114 is configured to integrate light
received during one or several time windows during pulses of the
beam, and in a particular embodiment 25 time windows, each time
window synchronized to occur during pulses of the beam, while
excluding light received between the time windows from the
integration, to capture 208 scintillation images.
[0030] Images captured by camera 114 representing integrated
scintillation light from scintillation material sheets 135 or 137
are received into image capture and processing machine 132 where
the background image is subtracted 210 from the scintillation
images to form an intermediate image.
[0031] The scintillation images may in some embodiments be filtered
by a rank-order filter.
[0032] During radiation treatment, intermediate images are
integrated 212 to form a total dose image.
[0033] In one embodiment, the scintillation light output, as imaged
in the scintillation images, is related to radiation dose expressed
by radiant energy fluence .PHI.s (J m.sup.-2), is proportional to
the received dose D=kD.PHI..sub.s, assuming ideal scintillator
emission isotropy, the scintillation-dose linearity, and an
electronic equilibrium established in the scintillator volume. The
dose conversion factor, kD, includes the electron mass collision
stopping power of the scintillator, as well as several other
factors that contribute to scintillator image formation.
[0034] In embodiments, the total dose image is also corrected for
scintillator-to-camera distances such as may be measured when the
subject is placed in the treatment zone.
[0035] In another embodiment, the absolute dose calculation uses a
total scintillation photon energy collected by the imaging system:
Qs=A.OMEGA.k.sub.c.PHI..sub.s where A is the scintillator area and
.OMEGA. is the solid angle projected by the imaging system
subtended by the scintillator outline in the direction of the
camera optical axis. The imaging system sensitivity is contained in
constant k.sub.c. The scintillator image shows the intensity of
scintillation radiant flux Qs, measured as a sum of all intensity
values within the thresholded image, as well as the scaled radiant
energy fluence, .PHI.s, measured as an average intensity value from
an interior region-of-interest. This approach also requires
calibration due to the projected solid angle .OMEGA., which depends
on scintillator-camera distance d and angle .theta. of scintillator
normal to camera optical axis.
[0036] The dose calibration factor k.sub.c is acquired at an angle
.theta.=0 and at a specific scintillator camera distance
d.sub.c.
[0037] An additional scintillator-camera distance calibration is
carried out to mitigate a small but non-negligible effect of lens
throughput at different focal distance values. The lens throughput
effect may be approximated to first order by a factor k.sub.1 (d),
yielding a final dose calculation formula.
[0038] The absolute dose response calibration of the scintillator
imaging system si typically performed by placing the scintillator
on a back-scattering water-equivalent phantom along with a group of
TLDs or OSLDs. The scintillator-camera distance and angle is
measured or calculated from a calibration pattern on the phantom. A
scintillation intensity-dose response is then recorded for varying
doses delivered to the phantom, and at two or more
scintillator-camera distances. We then calculate the dose
calibration factor k.sub.c at recorded scintillator distance
d=d.sub.c and observation angle .theta., assuming that the angles
.theta. and .rho. are small.
[0039] The image capture and processing machine 132 is configured
to then compensate 214 each intermediate image and, upon completion
of treatment, the total dose image, for inverse square law light
loss due to differences in lens distance from scintillation sheets
135 or 137 and camera 114 to form a second intermediate image. This
correction 214 is particularly useful with conformal sheets 137
applied to the subject.
[0040] In a particular embodiment, a 3-D imaging camera 139 is also
positioned to image conformal scintillation material sheets 137,
and image capture and processing machine 132 is configured to use
images from 3-D imaging camera 139 to form a three-dimensional
model of scintillation material sheets 137. In an embodiment, 3-D
imaging is performed in background room lighting. The
three-dimensional model is used by image capture and processing
machine 132 during compensation for inverse square law light loss.
In embodiments using the 3-D imaging camera and in which the image
capture and processing machine 132 forms a three-dimensional model
of the scintillation material sheets 137, 300 (FIG. 1A), 350 (FIG.
1B), the conformal scintillation material sheet 302, 352 may have
optional markings including a black border 306, 356 of width three
to five millimeters, inclusive, as well as a sheet-identifying
identification bar code 304, 354; in these embodiments the markings
including the black border 306, 356 aids localization of edges of
the sheet in three dimensions without significantly impairing dose
calculation, and the bar code 304, 354 identifies the sheet for
calibration purposes. Additional, slender, markings 308, 358 may
also be present on the sheet to further aid three dimensional
modeling of the scintillation material sheet. In embodiments, the
scintillation material sheets may be of rectangular 300 or round
350 shape.
[0041] Any other necessary corrections, such as corrections for the
increased thickness of scintillator sheet penetrated by beams when
sheets are oriented at angles other than perpendicular to the beam,
are then made 215.
[0042] The intermediate images and total dose images are also
compensated 216 for scintillator sheet angle relative to the beam
axis and camera angles.
[0043] Since scintillator sheets may differ in their response to
photons or charged particles of beam 104, in an embodiment each
scintillator sheet is marked with an identification code, and image
capture and processing machine 132 has access to a calibration
database having calibration information for each sheet indexed by
the identification codes of individual scintillator sheets. In a
particular embodiment the identification code is a bar code printed
on a visible corner of the sheet.
[0044] In embodiments using sheets with identification codes, the
identification code or codes of sheets in use during a treatment
session are entered into image capture and processing machine 132,
or image capture and processing machine 132 reads the
identification code, then accesses 217 a calibration record of the
database associated with the identified sheet. If a TLD or other
reference dosimeter is used during the treatment session,
calibration information derived from the reference dosimeter
readings are stored in the calibration record of the database
associated with the identified sheet. If no reference dosimeter is
used during the treatment session, averaged calibration information
obtained during prior treatment sessions or during manufacturer
calibration is used in calibration compensation for the treatment
session.
[0045] After treatment or calibration sessions where reference
dosimeters such as TLD or OSLD dosimeters are used, the TLD
dosimeters are read and used to determine 218 a calibration
adjustment that allows calculation of an actual dose 220 from the
peak intensity or integrated intensity of each scintillator image.
The calibration adjustment from prior radiation treatment sessions
performed with the same scintillator sheet or sheets may in some
embodiments also be used to provide real-time, estimated,
cumulative dose images during treatment sessions. In treatment
sessions where reference dosimeters are omitted, the total dose
image is corrected using an average calibration determined from
multiple prior sessions using the same or similar scintillator
sheets.
[0046] In a particular embodiment, in addition to a conformal
scintillator sheet 137 disposed on or worn by the subject, an
additional, calibrated, reference scintillator 139 may be
positioned in beam 104 and in view of camera 114. In this
embodiment, light emitted during treatment by reference
scintillator 139 is used to determine radiation dose available from
the beam and used in place of reference dosimeter readings to
calibrate individual scintillator sheets and to determine
calibration adjustments for the total dose image. The corrected
total dose image represents a recording of patient surface dose and
is particularly applicable to total skin electron therapy patient
dosimetry.
[0047] In an alternative embodiment, as illustrated in FIG. 3, an
intermediate image formed by subtracting 208 the background image
from the scintillation image is corrected for scintillator sheet
and camera angles, lens to sheet distance, and other effects
including calibration adjustments before integration 212 to form a
total dose image.
Combinations of Features
[0048] The features herein disclosed may be combined in multiple
ways. Among these are:
[0049] A system for dosimetry designated A, including a radiation
source adapted to provide a pulsed radiation beam to a treatment
zone; a thin sheet of scintillator disposed between the radiation
source and skin of a subject, the thin sheet of scintillator being
in the treatment zone; a gated camera configured to image the sheet
of scintillator; and an image capture and processing machine
coupled to receive images from the gated camera. The gated camera
is configured to capture images of light from the thin sheet of
scintillator during a plurality of pulses of the pulsed radiation
beam while excluding light received from the thin sheet of
scintillator between pulses of the plurality of pulses of the
pulsed radiation beam to form a scintillation image.
[0050] A system designated AA including the system designated A
wherein the thin sheet of scintillator is a conformal sheet of a
plastic scintillator in contact with skin of the subject.
[0051] A system designated AB including the system designated A or
AA further including a 3-D imaging camera, and wherein the image
capture and processing machine is configured to process images from
the 3-D imaging camera into a three-dimensional model of the
subject and to use the three dimensional model of the subject to
correct the scintillation image while determining a corrected total
dose image.
[0052] A system designated AC including the system designated A,
AA, or AB wherein the image capture and processing machine is
configured to subtract a background image from the scintillation
image, the background image being obtained by the gated camera at
times excluding times of pulses of the pulsed radiation beam.
[0053] A system designated AD including the system designated A,
AA, AB, or AC wherein the image capture and processing machine
includes a database containing calibration information associated
with individual thin sheets of scintillator, and the image capture
and processing machine is configured to correct the scintillation
image according to the calibration information.
[0054] A method designated B for mapping skin dose of a subject
during radiation treatment performed with a pulsed radiation beam
in a treatment zone including providing a thin sheet of
scintillator in contact with skin of a subject; positioning the
subject in the treatment zone; capturing a scintillation image of
light received from the thin sheet of scintillator during a
plurality of first time windows during pulses of the radiation beam
while excluding light received from the thin sheet of scintillator
between pulses of the radiation beam; capturing a background image
of light received during a plurality of second time windows delayed
after the first time windows and having width equal to the width of
the first time windows; and subtracting the background image from
the scintillation image.
[0055] A method designated BA including the method designated B or
C wherein the thin sheet of scintillator is a conformal sheet in
contact with skin of the subject and further including obtaining
3-D images of the thin sheet of scintillator using a 3-D imaging
camera, processing images from the 3-D imaging camera into a three
dimensional model of the subject, and using the three dimensional
model of the subject to correct the scintillation image while
determining a corrected total dose image.
[0056] A method designated BB including the method designated B, C,
or BA where the thin sheet of scintillator is formed of a plastic
adapted to emit light when struck by ionizing radiation.
[0057] A method designated BC including the method designated B, C,
BA, or BB and further including obtaining calibration data of light
emission versus applied radiation dose for the thin sheet of
scintillator, and adjusting the scintillation image based on the
calibration data.
[0058] A method designated BD including the method designated B, C,
BA, BB, or BC wherein the radiation beam is an electron beam.
[0059] A method designated BE including the method designated B, C,
BA, BB, BC, or BD where the thin sheet of scintillator is formed of
a plastic adapted to emit light when struck by ionizing
radiation.
[0060] A method designated BF including the method designated B, C,
BA, BB, BC, BD, or BE and including obtaining calibration data of
light emission versus applied radiation dose for the thin sheet of
scintillator and adjusting the scintillation image based on the
calibration data.
[0061] A method designated BG including the method designated B, C,
BA, BB, BC, BD, BE, or BF, wherein the calibration data is stored
in a database, the database indexed by identification information
associated with the thin sheet of scintillator.
[0062] A method designated C for mapping skin dose of a subject
during radiation treatment performed with a pulsed radiation beam
in a treatment zone including providing a thin sheet of
scintillator in contact with skin of a subject; positioning the
subject in the treatment zone; capturing a scintillation image of
light received from the thin sheet of scintillator during a
plurality of first time windows during pulses of the radiation beam
while excluding light received from the thin sheet of scintillator
between pulses of the radiation beam; capturing a time-averaged
background image of light received during a plurality of second
time windows, the second time windows excluding times of pulses of
the radiation beam; and subtracting the background image from the
scintillation image.
[0063] Changes may be made in the above methods and systems without
departing from the scope hereof. It should thus be noted that the
matter contained in the above description or shown in the
accompanying drawings should be interpreted as illustrative and not
in a limiting sense. The following claims are intended to cover all
generic and specific features described herein, as well as all
statements of the scope of the present method and system, which, as
a matter of language, might be said to fall therebetween.
* * * * *