Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CHERENKOV IMAGING SYSTEMS AND METHODS FOR DETERMINING
RADIATION DOSE
RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application
No. 62/153,417 filed April 27, 2015. Pursuant to Rule 4.11(a)(ii), this
international
application is to be treated, in the United States of America, as a
continuation-in-part of
International Application No. PCT/US14/66668 filed November 20, 2014, which
claims
priority to US Provisional Patent Application 61/906,805 filed November 20,
2013, and
as a continuation-in-part of U.S. Patent Application No. 14/118,825, with a
filing date of
May 18, 2012 and 371(c) date of November 19, 2013, which is a 371 National
Phase
Application of PCT Patent Application Serial No. PCT/U512/38609 filed May 18,
2012,
which claims priority to United States Provisional Patent Application
61/488,129 filed
May 19, 2011 and to United States Provisional Patent Application 61/585,366
filed
January 11, 2012. The disclosures of all these prior applications are
incorporated herein
by reference in their entireties.
GOVERNMENT INTEREST
[0002] This invention was made with Government support under NIH
Grant Nos.
R01CA109558 and R21EB017559, both awarded by the National Institutes of
Health. The
Government has certain rights to the inventions.
FIELD
[0003] The present document describes apparatus and methods for
imaging
and monitoring radiation treatments such as are frequently administered in
malignant
diseases.
[0004] A portion of the material disclosed herein resembles that in
the
published paper article entitled Cherenkov Video Imaging allows for the first
visualization
of radiation therapy in real time by Lesley A Jarvis, Rongxiao Zhang, David J.
Gladstone, Shudong Jiang, Whitney Hitchcock, Oscar D. Friedman, Adam K.
Glaser,
Michael Jermyn, and Brian W. Pogue, reported in the International Journal of
Radiation
Oncology, Biology and Physics Volume 89, Issue 3, pp. 615-622, on July 1, 2014
(Epub
March 28, 2014). The entire contents of this article are incorporated herein
by reference.
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[0005] This document relates to the detection and use of Cherenkov
radiation
(sometimes spelled Cerenkov radiation or (erenkov radiation) emitted as a
radiation
beam strikes tissue to observe, verify accuracy in delivery and then also
potentially
control radiation treatment machines, to ensure that medical radiation
prescription
protocols are properly followed
BACKGROUND
[0006] It is desirable when treating cancers with radiation to have a
high ratio
of energy deposited in the tumor, relative to energy deposited in normal
tissues
surrounding the tumor, resulting in a high therapeutic ratio of tumor to
normal dose.
Radiation treatments using high energy electron particle beams or high energy
photon
beams are used in the treatment of many cancers. Such beams are typically
provided by a
linear accelerator, a cyclotron, or related apparatus.
[0007] Charged particles, such us electrons, positrons, protons, or
alpha
particles, moving at greater than the effective speed of light in a medium
tend to slow
down while releasing Cherenkov radiation. Mammalian tissue, including human
tissue, is
a medium where the speed of light is reduced relative to air or vacuum due to
its
refractive index being greater than unity. Therefore fast-moving charged
particles release
Cherenkov radiation after entering such tissue. Water is also a medium where
the speed
of light is reduced relative to air or vacuum, fast-moving charged particles
in water also
release Cherenkov radiation after entering such water. Cherenkov emission has
been
detected with incident radiation in the range of 6 to 24 MeV energies for both
x-ray
photons as well as electrons. It is expected that Cherenkov radiation will
also be released
from beams of very-high-energy protons and other charged particles.
[0008] When this Cherenkov light is induced in tissue, it is
predominantly
blue in color, but with a broad spectrum which tapers off into the green, red,
and near-
infrared (NIR) with an inverse square wavelength dependence given by the Frank-
Tamm
formula. This light emitted in tissue is attenuated by absorbers in the
tissue, and can also
excite other molecular species in tissue, inducing their photo-luminescence
(fluorescence
or phosphorescence).
[0009] Prior to treating patients with high energy beams, it is
desirable to
know the shape of the beam, and to verify that the beam shape is as planned.
Additionally, when beams enter tissue it is important to accurately predict
how radiation
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beam shape varies with depth in tissue, to ensure adequate dosage to tumor
while
minimizing dosage to surrounding normal tissues. If beam shape and position is
adjusted
by positioning deflection magnets or shielding devices, it can be important to
confirm that
the resulting beam shape and dosage profile are as desired prior to exposing
patients to
the beam; radiation treatment centers may therefore desire to confirm beam
shape and
dose profile for complex beam shaping procedures for each patient, or as part
of routine
calibration and maintenance.
[0010] Manufacturers of radiation treatment devices often prepare
documentation of beam shapes and dosage profiles produced by common
configurations
of their devices for training users and guiding operators in using their
machines to treat
patients. Further, they must seek regulatory approvals of their machines, and
as part of
the regulatory approvals process they are expected to provide documentation of
beam
shapes and dosage profiles achievable by their machines. Manufacturers may
therefore
also need to accurately verify and document beam profiles for this regulatory
approval
process.
[0011] It is also desirable to monitor treatment in real-time, both
to ensure
treatment protocols are met and prevent accidental overdosing, and to image an
intersection of the beam with skin to ensure that beam profiles are as
expected for
treatment protocols.
SUMMARY
[0012] A system for providing monitored radiation therapy has a
source of
pulsed high energy radiation disposed to provide a radiation beam to a
treatment zone, the
high energy radiation of 200 keV or greater; a camera for imaging Cherenkov
light from
the treatment zone; apparatus for preventing interference by room lighting by
synchronizing the camera to pulses of the radiation beam and blanking room
lighting
during pulses of radiation; and an image processor adapted to determine
cumulative skin
dose in the treatment zone from the images.
[0013] In a particular embodiment, the processor uses a three-
dimensional
model of a subject to determine a mapping of image intensity in the images of
Cherenkov
light to radiation intensity in skin of the subject, to acquire multiple
images of Cherenkov
light, to apply the mapping to the images of Cherenkov light to map skin dose,
and to
accumulate skin dose by summing the maps of skin dose.
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[0014] In another particular embodiment, biological features apparent
in the
tissue which appear in the Cherenkov emission image can be used as landmarks
or
fiducials for verification of the beam delivery accuracy. In particular the
major blood
vessels have high Cherenkov absorption and appear as dark lines in the image,
and are
therefore apparent in the images and useful for soft tissue fiducials. These
are apparent in
successive days in fractionated therapy, so that they could be used for
patient alignment
verification on a day to day basis. The images can be recorded and saved in
the patient
record for a permanent verification of the delivered radiation treatment.
[0015] In another embodiment, a method of determining surface dose
during
radiation treatment of a first object beneath a surface of a second object to
limit dose at
the surface includes obtaining stereo images of the surface, and extracting a
three-
dimensional computer model of the surface; determining a mapping of image
brightness
at the surface in Cherenkov light images obtained by a digital camera to
radiation
intensity; recording surface brightness at the surface in a plurality of
Cherenkov light
images; and a summing step including using the mapping of image brightness at
the
surface to translate each Cherenkov light image into a surface dose image, or
summing
the surface dose images to provide a total session surface dose image. The
method
continues with summing the image brightness in each Cherenkov light image into
a total
session surface Cherenkov light image and using the mapping of image
brightness at the
surface to translate the total session surface Cherenkov light image into a
total session
surface dose image. The method concludes with displaying the total session
surface dose
image.
[0016] In an embodiment, a Cherenkov imaging system for determining
surface radiation dose for a subject undergoing radiation therapy includes (a)
a first
camera for capturing a Cherenkov image of Cherenkov radiation from a surface
region of
the subject undergoing Cherenkov-radiation-inducing radiation therapy, (b) a
second
camera for capturing a reflectance image of reflectance of optical
illumination off the
surface region, and (c) a correction module for correcting the Cherenkov image
based
upon the reflectance image to form a corrected Cherenkov image that indicates
radiation
dose for the surface region.
[0017] In an embodiment, a Cherenkov imaging method for determining
surface radiation dose for a subject undergoing radiation therapy includes
correcting a
Cherenkov image, of Cherenkov radiation from a surface region of the subject
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undergoing Cherenkov-radiation-inducing radiation therapy, using a reflectance
image, of
optical illumination reflected by the surface region, to form a corrected
Cherenkov image
that indicates radiation dose for the surface region.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is an illustration of a system for performing monitored
radiotherapy.
[0019] FIG. 2 is an approximate flowchart of a method of monitoring
radiotherapy.
[0020] FIG. 3 is an illustration of an alternative embodiment of a
system for
performing monitored radiotherapy with time-controlled room lighting and
camera
sensing of light emissions from a subject.
[0021] FIG. 4 is a block diagram of apparatus for determining beam
profiles
of high energy radiation for use in radiotherapy.
[0022] FIG. 5 is an approximate timing diagram of time windows
showing
relationships of room lighting, beam pulses, and camera shutter windows.
[0023] FIG. 6 illustrates a system utilizing a single camera, or
camera pair, on
a rotating mount for determining profiles of high energy radiation for use in
radiotherapy.
[0024] FIG. 7 illustrates the system of FIG. 3 from a different
angle.
[0025] FIG. 8 illustrates a system having multiple cameras on a fixed
mount
outside the tank.
[0026] FIG. 9 illustrates a system having multiple cameras mounted
inside the
tank.
[0027] FIG 10 illustrates a system having the beam enter the tank
from above
the tank.
[0028] FIG. 11 is a flowchart of a method of determining beam
profiles of
high energy radiation for use in radiotherapy.
[0029] FIG. 12 is an illustration having a spherical or cylindrical
tank with
internal cameras, with the tank mounted on a rotary mount.
[0030] FIG. 13 is an illustration of a radiation treatment system
having
realtime observation of skin dose using Cherenkov radiation emitted by the
interaction of
beam and skin.
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[0031] FIG. 14 is an illustration of a three-dimensional model of
tissue, such
as a breast, derived by stereovision surface extraction and used in mapping
image
intensity to skin dose.
[0032] FIG. 15 is a flowchart of operation of the system of FIG. 13
[0033] FIG. 16 is an illustration of skin dose intensity as imaged by
the system
of FIG. 13.
[0034] FIG. 17 is a photograph of a subject indicating areas of skin
damage
correlated to areas of high dose in FIG. 16.
[0035] FIG. 18 illustrates one Cherenkov imaging system for
determining
radiation dose for a surface region of a subject undergoing radiation therapy,
according to
an embodiment.
[0036] FIG. 19 is a diagram showing exemplary illumination of a
surface
region of a subject by optical illumination.
[0037] FIG. 20 is a diagram showing exemplary illumination of a
surface
region of a subject by multi-colored optical illumination.
[0038] FIG. 21 illustrates one Cherenkov imaging method for
determining
radiation dose for a surface region of a subject undergoing radiation therapy,
according to
an embodiment.
[0039] FIG. 22 illustrates another Cherenkov imaging system for
determining
radiation dose for a surface region of a subject undergoing radiation therapy,
according to
an embodiment.
[0040] FIG. 23 illustrates another Cherenkov imaging method for
determining
radiation dose for a surface region of a subject undergoing radiation therapy,
according to
an embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0041] A system 100 for providing radiotherapy and monitoring factors
known to affect the effectiveness of radiotherapy, and monitoring effects of
radiotherapy
on tissue, is illustrated in FIG. 1.
[0042] Portions of a subject 102 containing a tumor 104 requiring
radiotherapy are placed within an enclosure 106 for excluding light. The
enclosure 106
may be made of black plastic or cloth, and has a sealing portion 108 drawn
tight by an
elastomeric band such that a subject's eyes may be permitted access to ambient
light and
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thereby prevent claustrophobia while still excluding room light from optical
fibers 114. It
is anticipated that a variety of enclosures 106 may be provided to exclude
light from
various portions of a subject in various embodiments, in some embodiments
light may be
excluded from a subject's cranium, in others from a subject's chest or
abdomen,
according to location of tumor 104 within subject 102 and desired beam angles.
[0043] In an alternative embodiment, enclosure 106 is an entire room
containing the subject 102. In order to improve subject comfort, and taking
advantage of
visual persistence of the human eye and the pulsed nature of many radiation
sources such
as linear and cyclotron accelerators, a rapidly pulsed light source 107 is
used that appears
steady to the human eye. Pulses of light source 107 are timed, and appropriate
gating of
the detector 116 or camera 117 used, such that imaging or sensing of Cherenkov
radiation
is done at intervals where light source 107 is off, and radiation beam 110 is
on.
Acquisition of Cherenkov images is thereby done in synchronized room light
conditions.
[0044] An accelerator 108, or other device for providing high energy
radiation, is aimed to provide a beam 110 of radiation through normal tissue
112 to tumor
104. In all embodiments, the system herein described uses incident radiation
from
accelerator 108 at beam energies of at least 200 keV because, at beam energies
of less
than 200 keV (0.2 MeV), Cherenkov radiation is typically of insufficient
intensity for
imaging. In a particular embodiment, the accelerator 108 provides a beam of
electrons
having energy of 6 million electron volts (6 MeV) or greater, in a particular
embodiment
the beam energy lies between 6 and 24 MeV. In an alternative embodiment, the
device
for providing high energy radiation provides a beam of high energy photons,
the photons
interact with tissue or tumor to produce charged particles that in turn
produce Cherenkov
radiation. In an alternative embodiment, the accelerator 108 provides a high-
energy
proton beam. In an alternative embodiment, the radiation source is implanted
in the body,
inducing Cherenkov emission light directly as charged particles are emitted
during
radiation decay. The subject 102 and enclosure 106 is positioned within a room
having
subdued lighting.
[0045] Since high radiation doses are desired in tumors, while high
doses are
not desired in surrounding normal tissue or on skin because those tissues can
be damaged
by radiation, provisions are typically made for varying arriving beam delivery
angles by,
for example, rotating the subject and enclosure in the beam, rotating the
radiation source
about the subject and enclosure, or periodically interrupting treatment to
reposition the
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subject and enclosure. Additionally the beam is shaped either in a static
beam, or in other
embodiments the beam shape is dynamically changed while rotation is performed,
to
allow customized dose delivery to the shape of the tumor to be treated, at
each delivered
beam angles.
[0046] At least one, and in an embodiment an array of many, optical
fibers
114 are provided and positioned, such as in contact with or close to, subject
102 in
enclosure 106, for collecting any light that may be emitted from subject 102.
In an
alternative embodiment, a camera system 117, having a lens system adapted
to collecting
light from the subject and an array photosensor for detecting the collected
light,
positioned some distance from the subject is used to image light emitted from
the tissue.
[0047] Optical fibers 114 provide light to multichannel
spectrographic
detector 116. For each channel of the multichannel spectrographic detector 116
there is a
wavelength-dependent dispersive device such as a prism or diffraction grating
for
separating light according to wavelength, and an array of photosensors such as
a CCD or
CMOS sensor, an array of PIN diodes, or an array of photomultiplier tubes. In
another
embodiment, optical filters are inserted in the detection channel before the
spectrograph
to reduce ambient light and Cherenkov emission above or below a specified
wavelength
range, thus reducing the required dynamic range of the detector.
[0048] For convenience in this document, the array of optical fibers
114 and
detector 116, or camera 117, are forms of an imaging system adapted to imaging
light
from subject 102, such as Cherenkov light generated by interactions of the
beam of high
energy radiation with tissue of the subject.
[0049] Detector 116 provides information indicative of received light
amplitude at each of many wavelengths to processor 118. Processor 118 analyzes
this
information to provide indications of heme concentration in tumor, oxygen
concentration
in tumor, and other parameters (such as metabolic activity and oxygenation)
provided by
photo-luminescent emission
[0050] In an alternative embodiment, detector 116 is a spectrally
sensitive
detector constructed of a filter wheel and photodetector, providing spectral
information on
captured light from fiber 114 by alternately interposing an assortment of
filters each
having a passband at a wavelength of interest. In an alternative embodiment, a
tunable
filter is used in place of a filter wheel. In another alternative embodiment,
a filter wheel
or tunable filter is placed in front of a camera positioned some distance from
the subject.
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This embodiment allows collection of a series of images, each image of the
series
imaging light from the subject at a different wavelength band, to allow
spectral analysis
on the series of images.
[0051] In an alternative embodiment, detector 116 is timed to be
enabled in a
temporal relationship after each radiation pulse, such that the emissions from
Cerenkov
excited luminescence, such as phosphorescence or fluorescence, are captured,
allowing a
capture of images of light emitted from a secondarily-emitting chemical or
indicating
agent, such as a fluorescent or phosphorescent chemical, in or on the tissue
and as
stimulated by Cherenkov radiation emitted as radiation interacts with the
tissue. This
time sequenced signal is generated from the Cherenkov radiation, but can
provide
information regarding the bio-molecular environment of the tissue being
irradiated. The
secondarily-emitting chemical in some embodiments is a chemical intrinsic to
the body,
and in some embodiments is a drug, or a metabolite of a prodrug, that is
administered to
the subject.
[0052] In an alternative embodiment, detector 116 is replaced with a
camera
117 having similar timing characteristics and spectral sensitivity. The
imager, whether
including detector 116 and/or camera 117, in embodiments using secondarily-
emitting
substances may be sensitive to light in infrared as well as some visible
wavelengths.
[0053] In a particular embodiment, the imager is a hyperspectral
camera. For
purposes of this document, a hyperspectral camera is a camera having spectral
response
that extends beyond the visible light spectrum, such as a camera able to
respond to at least
some near-infrared light. Further, a hyperspectral camera is a camera that is
adapted to
resolve wavelengths of received light into more, and narrower, bins than the
three (red,
green, and blue) wavelength bins of a typical color electronic camera.
Hyperspectral
cameras are known in the electronic camera art that are capable of resolving
received
light into dozens of wavelength bands, including one or more infrared bands;
such
cameras may operate by using patterned filters on photosensor arrays that have
more than
the usual three colors of filters, or by using line-scanning spectrographic
techniques.
[0054] The system 100 is operated according to a method illustrated
in FIG. 2.
The subject is prepared 202 for multidose radiotherapy as known in the art of
radiotherapy; tumor 104 is localized and imaged, alignment marks may be
applied by
tattoo or in other ways, and aiming and positioning masks or frames may be
made. A
desired dose of radiation for each session is prescribed.
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[0055] Prior to each session for which monitoring is desired, in an
embodiment an enhancing and indicating agent is administered 204. In an
embodiment,
the enhancing and indicating agent is a dose of 20 milligrams per kilogram
body weight
of 5-delta-aminolevulinic acid (5-ALA), the dose being administered an
incubation time
of approximately four hours before each divided radiotherapy session begins.
[0056] In metabolically active tumor 104, some of the 5-ALA is
metabolized
to Protoporphyrin IX (PpIX). In alternative embodiments, it is expected that
other
enhancing agents may be developed or utilized. PpIX production in normal
tissue 112
and tumor 104 is due to metabolic processes in those tissues and a quantity of
PpIX
produced in those tissues is dependent on an amount of metabolic activity in
those tissues.
[0057] The subject 102 is then placed 206 in a darkened environment,
which
in an embodiment includes placing those parts of the subject to be subjected
to
radiotherapy within enclosure 106, and positioning light collecting fibers 114
to collect
light from the subject 102, as heretofore described with reference to the
enclosure.
[0058] The tumor is then treated 210 by having accelerator 108 then
provide a
beam of high energy charged particles aimed along a beam path at tumor 104 to
perform
radiotherapy of the tumor. In an embodiment, the subject 102 may be rotated
during the
session to distribute radiation absorbed by normal tissues 112 while
maintaining beam
targeting at tumor 104.
[0059] As charged particles of beam 110 decelerate in both normal
tissue 112
and tumor 104, these particles generate light by Cherenkov radiation, with
broadband
spectral constituents decreasing with wavelength to the inverse square power.
[0060] Some of the light generated by Cherenkov radiation propagates
to light
collecting fibers 114, and some may be absorbed by fluorophores (or phosphors)
within
subject 102, including fluorophores (or phosphors) within normal tissue 112
and tumor
104. Among fluorophores within subject 102 are any PpIX produced from
metabolic
activity in tissue 112 and tumor 104. Light from Cherenkov radiation that is
absorbed by
fluorophores (or phosphors) in tissue and tumor may stimulate photo-
luminescent
emission by those tissues and tumor.
[0061] Light from both Cherenkov radiation and photo-luminescent
emission
propagates from the beam path to a surface of the subject 102, intersecting
any tissue
between the tumor and the surface, and being attenuated by absorption from
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absorbers such as deoxyhemoglobin, oxyhemoglobin, proteins, lipids and water
before
being emitted from the subject.
[0062] The dominant absorption is from deoxyhemoglobin and
oxyhemoglobin, which differ in their spectral absorption, and so changes in
spectral
characteristics of the attenuated light emitted from the subject are a
reasonable measure of
oxygen saturation of the blood in the region.
[0063] Protoporphyrin IX (PpIX), formed in tissue from 5-ALA as part
of the
heme synthesis pathway that is upregulated in many tumors, absorbs across the
visible
spectrum, with a large absorption in the blue Soret band. This absorption
leads to
fluorescence emission from PpIX in the 640-720nm wavelength range. In an
embodiment, incident radiation stimulates emission of blue Cherenkov radiation
within
the subject, which in turn stimulates fluorescent light emission by PpIX; some
of the
fluorescent light from the PpIX is then emitted from the subject and imaged.
[0064] Light emitted from the subject 102, both of Cherenkov origin
as
modulated by absorption in tissue and tumor, and of fluorescent (or
phosphorescent)
origin, and attenuated by molecular absorbers in the subject, is captured 212
by fibers 114
or camera 117. This light is directed to multichannel spectrographic detector
116, which
performs a spectral analysis of received light. Electronic spectrographic
signals
indicative of light amplitude at each of several wavelengths of interest are
provided from
spectrographic detector 116 to processor 118 for processing.
[0065] In an embodiment, processor 118 utilizes a model of light
propagation
from the beam path through a model of subject 102 to determine a spatial model
of light
emitted within, and light attenuation within, subject 102 and tumor 104. It is
expected
that such an embodiment could offer enhanced accuracy over an uncorrected
system. In
an embodiment, a Monte-Carlo photon propagation model is used.
[0066] In an alternative embodiment, beam 110 is directed at tumor
104 from
multiple angles through tissue 112 within each treatment session. In such an
embodiment, processor 118 uses information regarding beam angle to correlate
measurements such that tumor oxygenation and tumor metabolic activity
determined
during one session is compared with tumor oxygenation and metabolic activity
determined along a similar beam angle in other sessions.
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[0067] Processor 118 quantifies Cherenkov emission 216 in tumor and
total
hemoglobin from an amount of light measured at one or more wavelengths to
which
oxyhemoglobin and deoxyhemoglobin are isosbestic.
[0068] Processor 118 quantifies percent oxygenation 218 of hemoglobin
in
tumor from light quantity received at 2 specific wavelength bands such as
bands centered
at 750nm and 580nm wavelengths. Alternatively the measured spectral
characteristics of
light captured by fibers 114 are curve-fit to pre-measured Cherenkov emissions
spectra
and transmission attenuation data obtained from samples of liquid with blood
and water
that have been oxygenated and deoxygenated.
[0069] Processor 118 quantifies metabolic activity 220 of tumor by
quantifying fluorescent emission from PpIX by quantifying received light from
fibers 114
in the 640-720 nanometer wavelength band, and applying any corrections
provided in the
embodiment. In alternative embodiments, these corrections may include
corrections from
a Monte-Carlo or diffusing photon propagation model of the tissue.
[0070] The stimulation of fluorescence emission by protoporphyrin IX
can be
taken as a signal which is proportional to the amount of PpIX produced, and
this is
indicative of metabolic activity in the tumor. Destruction of cellular
mitochondrial
function through radiation damage due to the applied radiotherapy would appear
in some
embodiments as a reduction of PpIX production, and hence a decrease in light
emitted at
PpIX fluorescent wavelengths versus light emitted at Cherenkov wavelengths in
the
detected spectrographic signals.
[0071] In an alternative embodiment, fluorescent emissions from
another
metabolite are used as a fluorophore for tracking metabolic activity of tumor
104, the
fluorophore being excited by the Cherenkov radiation. In alternative
embodiments, the
fluorescent emission could be used to track the activity of an alternative
enhancement
agent, such as antibodies or antibody fragments to cell surface receptors
tagged with a
fluorescent (or phosphorescent) dye. In yet other alternative embodiments,
fluorescent
emissions from NADH or NAD excited by the Cherenkov radiation are used as
indicators
of metabolic activity within tumor 104.
[0072] Since radiation damage to tumor cells during radiotherapy
involves
free radical reactions, it is expected that treatment effectiveness will
depend somewhat on
the relative oxygenation of heme at the tumor 104 as monitored by processor
118.
Further, changes in metabolic activity in tumor 104 from a first treatment
session to a
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later second treatment session as measured by PpIX or other fluorescent
emissions
measured by processor 118 are also expected to be indicative of treatment
effectiveness.
In fractionated radiotherapy subjects may receive as many as 30 to 40
fractions of a total
radiation dose, each fraction being administered on a separate day as part of
a total
treatment series. During the treatment series, changes in tumor metabolic
activity are
expected if the tumor is responsive to therapy. It is expected that metabolic
signal
changes would occur as a decrease in the fluorescent signal over time if the
patient is
responding to therapy.
[0073] These measures of treatment effectiveness are presented to a
physician
and used to adjust 222 the treatment plan, both of the radiotherapy and
following adjunct
therapies such as chemotherapy.
[0074] In an embodiment, multiple spectrographic analyzers are
provided,
each coupled to receive Cherenkov and fluorescent emissions from a different
point on
the subject through separate pickup fibers. In this embodiment, diffuse
optical modeling
or Monte Carlo modeling software executing on processor 118 allowing
reconstruction of
a shape and spectral characteristics of an emissions zone within the subject,
and for
determining spectral characteristics of light emitted within the tumor as
opposed to light
emitted elsewhere (such as in normal tissues) in the subject by compensating
for changes
due to light transport in surrounding tissues. The diffuse optical modeling
software
provides for more accurate estimation of the fluorescent emissions thereby
refining the
measurements to more directly inform about pertinent areas of tissue.
[0075] In an alternative embodiment, light emissions from the subject
are
sampled only from certain predetermined beam locations or from certain
predetermined
locations within the subject, with the goal of maximizing information from non-
tumor
tissues. Also, in an alternative embodiment, comparison of measurements of
emitted light
spectra from tumor and non-tumor regions is performed to accurately calibrate
data to the
individual subject, making interpretation of changes over different days more
reliable.
[0076] In an alternative embodiment, in addition to collecting fibers
114
placed at a surface of subject 102, there are additional optical collecting
fibers (not
shown) placed within body cavities or, in some alternative embodiments, even
directly
implanted in tumor 104. Light from such fibers is processed by spectrographic
detector
116 and processor 118 in a manner similar to that stated herein for light from
fibers 114.
Such additional collecting fibers may permit improved accuracy by enabling the
system
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to track light signals which do not propagate well in tissue, or minimizing
the spectral
distortion of light passing through tissue to the detector. In an alternative
embodiment,
implantation of fibers onto surfaces or in cavities is incorporated as part of
radiation
therapy preparation.
[0077] Measurement of emission stimulated by radiation emitted from
implanted radio-isotope sources, such as brachytherapy seeds is feasible, and
can allow
direct measurement at the tissue site where the radiation is imparting maximal
energy.
Implanting fiber optic measurements at these sites is feasible via fiber
optics or small
photodiode arrays. Following the same procedures as above, the tissue function
or blood
oxygen saturation could be probed during the prolonged delivery of radiation
during
brachytherapy radiation delivery.
[0078] Many sources of high energy charged-particle beams, including
cyclotrons and some other particle accelerators, including some linear
accelerators,
provide pulsed beams. Further, the human visual system is known to integrate
received
light, so that black intervals that are short enough, and repeated rapidly
enough, may not
be noticed by a human subject. In an alternative embodiment, therefore, the
enclosure
106 is omitted. The treatment room is sealed to exclude all natural and
uncontrolled
artificial light. Timing interfaces 120 are provided for determining intervals
of beam
transmission, and for controlling pulsed room lighting 122.
[0079] In operation, the timing interfaces 120 controls an effective
shutter
(Fig. 5) interval 200 of the spectrographic detector 116 to effectively
consider only light
received by the cameras in an interval 202 during and/or surrounding pulses
of, and
including a fluorescent decay interval 204 after, pulses 206 of the beam.
Timing
interfaces 120 also controls and pulses room lighting such that the shutter
interval does
not overlap pulses 208 of the room lighting. Light received at the
spectrographic detector
116 during multiple shutter intervals is totalized, in an embodiment at the
camera, and in
an alternative embodiment multiple images are captured and per-channel
spectrographic
light totals are totalized by processor 118.
[0080] In an alternative embodiment 150 (Fig. 3), as an alternative
to optical
fibers 114 and multichannel spectrographic detector 116, high-sensitivity
electronic
cameras 166, 168, are used to image Cherenkov light and localize locations on
the subject
where this light is emitted. In another alternative embodiment, some optical
fibers 114
and multichannel spectrographic detectors 116 are provided, with the fibers
placed in
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particular tumor locations, and electronic cameras 166 are provided for
imaging light
escaping from the subject.
[0081] A subject 102 is placed in the path of a radiation beam 160
such that
the beam intersects tumor 104. Beam 160 is provided by an accelerator 108, or
other
device for providing high energy radiation, and is typically shaped by beam-
shaping
apparatus 164.
[0082] The subject 102 is located within an environment that excludes
daylight, and light from uncontrolled sources, such as incandescent lamps, is
also
excluded.
[0083] In an embodiment, a drape or paint of a light-absorbing
material is
provided so that stray light emitted from the subject 102 and not absorbed by
a camera
166, 168 is absorbed.
[0084] In an embodiment, the accelerator 108 provides a beam of
electrons
having energy of 6 million electron volts (6 MeV) or greater, as used to
provide treatment
energy to deep tumors as opposed to treatment of surface skin. In a particular
embodiment the beam energy lies between 6 and 24 MeV. In an alternative
embodiment,
the accelerator 108 produces a photon beam of 6 MeV or greater. In another
alternative
embodiment, the accelerator 108 provides a high-energy proton beam. In an
alternative
embodiment, an electron beam having electron energy of 0.5 MeV or greater is
used.
[0085] At least one camera 166 is used to capture the images, and in
an
embodiment a second or more cameras 168, are positioned to provide multiple
images of
Cherenkov and fluorescent radiation emission from subject 102. In an
embodiment,
multiple cameras with a defined linear and angular spacing between them at
each camera
location are provided.
[0086] The cameras 166, 168 are coupled to camera interface 172 of
image
processing system 174; camera interface 172 captures and stores digital images
from the
cameras 166, 168, in memory 176 for processing by at least one processor 178
of the
image processing system 174. In addition to interfaces to the camera interface
172 and
memory 176, processor 178 interfaces with a timing interface 120 and a display
subsystem 182. Timing interface 120 is adapted to determine timing of pulses
of
radiation from the radiation beam source 108, to control pulsed room lighting
122 to
avoid interference from room lighting in the way discussed with reference to
Fig. 5, and
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to synchronize light or image capture by spectrographic detector 116 or
cameras 166, 168
at shutter intervals discussed with reference to Fig. 5.
[0087] In an alternative embodiment, instead of blanking room
lighting
during pulses of the radiation beam, room lighting is left on, but subdued.
The image
processor is configured by machine readable instructions to operate the camera
twice for
each Cherenkov-light image. The camera is operated to obtain a first image
during the
time the radiation beam is ON; this image is exposed by both room lighting and
by
Cherenkov light. A second image is then obtained during a nearby time, and for
an
equivalent shutter period, when the radiation beam is OFF, and therefore is
exposed by
room lighting alone. The Cherenkov-light image used for further processing is
determined by the image processor by subtracting the second image from the
first image,
leaving an image corresponding to an image taken under Cherenkov light alone.
[0088] In yet another alternative embodiment, during a radiation
treatment the
room lighting is replaced by a subdued, monochromatic, light at a first
wavelength or first
wavelength band. This may, for example, be light provided by light-emitting
diodes. The
Cherenkov-light images are obtained at wavelengths other than the first
wavelength by
use of a notch filter that blocks light of the first wavelength or wavelength
band. Since
Cherenkov emissions are typically broadband, albeit more intense toward the
blue end of
the spectrum, a Cherenkov-light image that excludes light of the first
wavelength, but
includes other wavelengths, is adequate for determining beam shape and
intensity of skin
irradiation. For example, the first wavelength may be a green wavelength.
Cherenkov
light emitted at the skin surface can be visualized by imaging at blue
wavelengths, and,
since heme in tissue blocks many short wavelengths of light, Cherenkov light
emitted at
deeper levels in tissue may be visualized by imaging at wavelengths in red
wavelengths.
Cherenkov-stimulated fluorescent and phosphorescent emissions may also be
visualized
by imaging at wavelengths in the infrared and red visible wavelengths.
[0089] As the beam penetrates subject 102, Cherenkov light is emitted
within
an emissions zone 125, including the tumor 104.
[0090] In an embodiment, the imaging system cameras 166, 168 are
spectrally-sensitive cameras capable of providing spectral data permitting
distinction
between Cherenkov and fluorescent light, and in a particular embodiment
permitting
distinction between oxyhemoglobin and deoxyhemoglobin. Spectrally-sensitive
cameras
suitable for this application may be implemented as black and white cameras
equipped
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with apparatus for positioning and changing filters in front of each camera,
such as
rotatable multiple-filter disks; by deposition of custom filter elements in a
pattern on pixel
sensors of a photosensor array as is common for color cameras; or in other
ways.
[0091] In embodiments, raw or de-noised images from the imaging
system are
recorded in a suitable digital memory system as documentation of the radiation
treatment.
[0092] While Cherenkov radiation is emitted during beam pulses 206
(Fig. 5),
light emitted 209 from naturally occurring, artificially administered, and
drug metabolite
fluorescent materials within a subject, including PpIX, lags the beam and
decays
exponentially after each pulse of the beam turns off as illustrated. In an
embodiment
therefore, an effective shutter interval during beam pulse 206 is used to
image light
primarily emitted by Cherenkov mechanisms, and an effective fluorescent-
emissions
shutter interval 211 is used to capture light emitted from the subject or
phantom by
fluorescent and phosphorescent mechanisms. In this embodiment, light arriving
in fibers
114 or light imaged by cameras 166, 168, is recorded as image pairs, with a
first image of
each pair indicative of light emitted during beam pulse 206 and a second image
of each
pair indicative of light emitted during the fluorescent shutter interval 211.
Processor 118
or 178 executes machine-readable instructions in associated memory, such as
memory
186 to reconstruct first tomographic image sets of the subject from the first
images of all
image pairs captured, to reconstruct second tomographic image sets of the
subject from
the second images of all image pairs captured, and the ratios or otherwise
processes the
first and second tomographic image sets to determine a tomographic image set
of
fluorophore distribution in the subject.
[0093] In embodiments, such as those where 5-ALA is administered,
where
fluorophore distribution is related to metabolic activity in the subject, the
tomographic
image set of fluorophore distribution in the subject is also indicative of
metabolic activity
in the subject. The processor 118 or 178 further executes machine readable
instructions in
memory to compare the tomographic image set of fluorophore distribution in the
subject
against a tomographic image set of fluorophore distribution obtained during a
prior
radiation treatment session to produce a tomographic image set indicative of
treatment
effectiveness.
[0094] Since both an enclosure 106 surrounding and excluding ambient
light
from the subject, and the combination of timing interfaces 120 and pulsed room
lighting
122 serve to prevent interference of room lighting from interfering with
measurement of
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Cherenkov radiation and fluorescent radiation emitted from an emissions zone
in the
subject, the term "apparatus for preventing interference by room lighting" as
used herein
shall mean either or both of an enclosure 106 surrounding and excluding
ambient light
from the subject, and the combination of timing interfaces 120 and pulsed room
lighting
122.
[009.5] Cherenkov radiation and associated fluorescent emissions are
useful
for beam profiling and calibration as well as for monitoring treatment.
[0096] A system 300 for providing radiotherapy equipped with a
subsystem
for determining beam profiles is illustrated in FIG. 4.
[0097] A beam-calibration phantom 302 is placed in a zone where it is
desired
to measure a profile of a radiation beam 310 provided by a radiation treatment
machine
312. The zone may be a volume above or beside a treatment table 306. In many
embodiments, the phantom is a fluid-filled tank, the fluid in the tank being a
transparent
fluid having an index of refraction greater than that of air; in a particular
embodiment the
transparent fluid is water. In an embodiment, the tank has transparent top and
sides such
as glass or transparent plastic. In a particular embodiment the tank has sides
constructed
of acrylic sheets; another particular embodiment has sides constructed of
polycarbonate
panels. In an embodiment, a small amount of scattering agent is added to the
liquid in the
tank to enhance scatter of Cherenkov light but not affect propagation of the
radiation
beam, overcoming directionality of Cherenkov light and allowing more light to
be
detected laterally around the tank. The treatment room may be blacked out to
prevent
interference of ambient light with measurements of the Cherenkov radiation
because a
phantom is not subject to claustrophobia like live subjects.
[0098] In an alternative embodiment, the tank is filled with a
transparent fluid
having an index of refraction greater than that of water, such as silicone
oil. In yet
another embodiment, the phantom is formed from a high-index, transparent,
material,
such as a cast high-index plastic, and may have both fluorophores and light-
scattering
additives embedded within it.
[0099] The treatment table 306 and phantom 302 are located within an
environment that excludes daylight, and light from uncontrolled sources, such
as
incandescent and fluorescent lamps, and LED indicator lights, is also
excluded. In
another embodiment, the phantom walls are coated on their interior surface
with a light-
absorbing coating except for camera viewing windows positioned in front of
each camera,
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the coating is provided to absorb both stray light originating from outside
the phantom
and to prevent Cherenkov light from being reflected from the phantom wall into
a camera
to give a false indication of beam profile.
[0100] In an embodiment, a drape of a light-absorbing material is
provided so
that stray light emitted from Cherenkov radiation zone 320 and not absorbed by
a camera
is absorbed without being scattered back to the treatment zone. The light-
absorbing drape
improves contrast in Cherenkov images by reducing stray light.
[0101] An accelerator 308, or other device for providing high energy
radiation, is aimed to provide a beam 310 of radiation through beam-shaping
apparatus
314 to phantom 302. In an embodiment, the accelerator 308 provides a beam of
electrons
having energy of 6 million electron volts (6 MeV) or greater, in a particular
embodiment
the beam energy lies between 6 and 24 MeV. In an alternatively embodiment, the
accelerator 308 produces a photon beam of 6 MeV or greater. In an alternative
embodiment, the accelerator 308 provides a proton beam. In an alternative
embodiment,
the accelerator 308 produces a beam of electrons or photons having a
substantial
percentage of electrons or photons having energy of 1 MeV or greater.
[0102] At least one camera 316 is used to capture the images, and in
an
embodiment a second or more cameras 318, are positioned to provide multiple
images of
the Cherenkov radiation emission zone 320 where beam 310 intersects the
transparent
fluid of phantom 302. In an embodiment, as illustrated in Fig. 4, a pair of
cameras is used
by providing two cameras 316 with a defined spacing between them at each
camera
location, allowing imaging of the beam with or without tomographic recovery.
In an
alternative embodiment as illustrated in FIG. 6, a single camera 316; or in a
variation as
illustrated in FIG. 7, a single camera pair 316 is provided; the embodiments
of FIG. 6 and
7 mount the camera or camera pair on a rotary, movable, mount 340 such that
single
images, or stereo pairs of images, can be made of the Cherenkov emissions zone
from
several camera positions, In the interest of simplicity, structure and
bearings for
supporting the rotary mount 340 and motor 341 has not been shown. The
embodiment of
Fig. 7 illustrates the beam entering the tank from out of the page.
[0103] While the embodiments of Figs. 6, 7, 8, and 9 illustrate the
beam
entering the tank from a side of the tank, the method is applicable to beams
entering the
tank from any angle, including by way of example a beam as illustrated in FIG.
10.where
the beam comes from above the tank.
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[0104] The cameras 316, 318 are coupled to camera interface 322 of
image
processing system 324; camera interface 322 captures and stores digital images
from the
cameras 316, 318, in memory 326 for processing by at least one processor 328
of the
image processing system 324. In addition to interfaces to the camera interface
322 and
memory 326, processor 328 interfaces with a timing interfaces 330 and a
display
subsystem 332.
[0105] In an alternative embodiment, as illustrated in FIG. 8, a
plurality of
cameras 370 are disposed on a fixed frame 372 outside the volume of the
phantom but
configured to provide images of the emissions zone 320 from several angles.
[0106] In an alternative embodiment, as illustrated in FIG. 9, a
plurality of
submersible cameras 374 are disposed within the volume of the phantom and
configured
to provide images of the emissions zone 320 from several angles. In a
particular
embodiment, submersible cameras 374 are cemented to a wall of phantom 376.
[0107] In a particular embodiment, a camera is disposed to image the
emissions zone from approximately every 60 degrees in the horizontal plane,
into which
the radiation beam is being sent. The camera field of view is designed to
capture the
relevant depth of the beam into the tank from above, and the depth of focus of
the
cameras is designed to capture light from the entire cross section of the
beam. The
angular arrangement is chosen to allow capture of the beam profile data in a
time which
matches with the temporal requirements of characterizing the beam. For
example, fast
beam profile changes or complex beam cross section shapes require more cameras
and
less mobile cameras, for fast profile imaging.
[0108] Camera numbers and viewing angles may in some embodiments be
determined according to the expected beam profile; for example standard square
beam
cross sections may only require one or two cameras to characterize the beam,
and may not
even require tomographic recovery to characterize the beam. Where imaging time
is
unconstrained, beams may be imaged with a rotation stage or rotating frame for
sequential imaging of the beam from multiple angles. A standard square beam
may be
adequately profiled by only two camera positions at 90 degrees from each
other, whereas
a non-square or non-circular beam would require more camera positions for
tomographic
recovery of the profile. If adaptive delivery of radiation such as arc therapy
or intensity
modulated radiation therapy are imaged, then multiple parallel cameras would
be
desirable to allow imaging of the complex beam cross sections in reasonable or
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time during delivery to the tank. The time constraints and complexity of the
beam
therefore determine the exact number of cameras and degree of sequential or
parallel
acquisition.
[0109] In each embodiment, as illustrated in FIG. 11, the tank is
positioned
702 in the beam, and beam adjustment devices, if any, are adjusted 704 to
provide a
particular beam profile. The cameras 316, 318, 370, 374 in all embodiments are
disposed
to provide images of the Cherenkov radiation emissions zone 320, where beam
310
intersects fluid of phantom 302, and may be repositioned 706 if movable camera
mounts
are used. It should be noted that, because cameras are likely to be damaged if
the beam
directly impinges on the camera, movable mount 340 is configured, and the
cameras are
located, to avoid direct impingement of the beam on any camera.
[0110] In each embodiment, images and/or stereo pairs of images each
are
taken by sequentially 708 turning OFF room lighting, opening effective or
physical
camera shutters, pulsing the beam, then sequentially 710 turning off the beam,
closing
shutters, and turning ON room lighting. This process results in multiple
images taken
from multiple angles of Cherenkov radiation zone 320 by cameras 316, 318, 370,
374.
Once sufficient images are captured, they are processed 712 by processor 328
to generate
a fully three dimensional image of the Cherenkov emission. These images are
then used
to tomographically reconstruct the beam profile.
[0111] Prior to reconstruction of the beam profile from the images,
the images
obtained by any cameras located outside the phantom volume (such as those of
FIGs. 4, 6,
and 8) are corrected for distortions caused by refraction as light passes from
the emissions
zone 320 through known surfaces of the phantom.
[0112] A combination of rotation angles both vertical and lateral
around the
beam may be used.
[0113] The multiple camera image formation by tomography would use a
filtered backprojection computational algorithm for recovery of the emissions
zone 320.
[0114] It is known that Cherenkov emissions from beams of intensities
used
during radiotherapy are somewhat dim, hence sensitive cameras with long,
integrated,
exposures are required, and it is also advisable to avoid interference from
extraneous
lighting sources. In an alternative embodiment, sensitive cameras take
multiple short
exposures, the multiple exposures being summed to provide an overall
integrated
exposure.
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[0115] Timing interfaces 330 are arranged to sense a timing of beam
pulses
provided by particle beam source 308 and to control room lighting 334 such
that room
lighting is pulsed and does not overlap pulses of beam 310. Similarly, timing
interface
330 is arranged to control capture of images at camera interface 322 from
stereo camera
pairs 316, 318 to capture images of light emitted at emission zone 320 during
pulses of
beam 310, and to ignore light received by camera pairs 316, 318, during pulses
of room
lighting. It is anticipated that room lighting 334 may be provided by fast-
responding
light-emitting diode arrays.
[0116] In operation, the timing interfaces 330 controls an effective
shutter
(Fig. 5) interval of the cameras or stereo camera pairs 316, 318, 370, 374 to
effectively
consider only light received by the cameras in an interval 202 surrounding
pulses of the
beam. The timing interfaces 330 also controls and pulses room lighting such
that the
shutter interval does not overlap pulses of the room lighting. Light received
at the
cameras 316, 318, 370, 374 during multiple camera intervals is totalized, in
an
embodiment at the camera, and in an alternative embodiment multiple images are
captured and pixel light totals are totalized by processor 328.
[0117] Once sufficient light is received at cameras 316, 318, 370,
374 during
the shutter intervals and totalized images prepared in or read through camera
interface
322 into memory 326, the beam is shut off. Then at least one processor 328
then
processes the images in memory 326, to construct a three-dimensional model of
light
emissions in the emission zone 320. Since the light emissions in the emissions
zone are
from Cherenkov radiation emitted as charged particles of beam 310 decelerate
in the fluid
of the phantom, with broadband spectral constituents decreasing with
wavelength to the
inverse square power, these light emissions relate directly to radiation dose
from beam
310 passing into and absorbed in the emissions zone 320. Further, since
Cherenkov
radiation is emitted from where the beam intersects fluid of the phantom in
emissions
zone 320, and not from surrounding un-irradiated fluid, the reconstructed
three
dimensional model of light emissions in emissions zone 320 provides an
indication of
beam shape.
[0118] The processor 328 then uses display subsystem 332 to provide
displayable images illustrating cross section, overall surface, and
tomographic images
representing radiation dose profile in the emissions zone 320. In a particular
embodiment, processor 328 has at least one processor as known in the art of
computing
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coupled to execute instructions from a memory system; in an embodiment the
memory
contains machine readable instructions for processing multiple sets of images
to construct
the three-dimensional models of light emissions in the emission zone 320, and
to prepare
displayable images representing radiation dose profile in the emissions zone;
the memory
containing machine readable instructions may be the same or a different memory
than the
memory 326 in which images are stored.
[0119] In an embodiment, processor 328 has calibration information in
its
memory system, and translates the determined three dimensional models of
Cherenkov
light emission in the emissions zone into three dimensional models of
radiation intensity
and/or dose.
[0120] Monte Carlo simulations are used to study the complex
directionality
of Cherenkov radiation at each spatial location within the irradiated tank.
Due to the
finite field of view of the cameras, the intrinsic proportionality between the
imparted dose
and emitted Cherenkov radiation may be distorted. Therefore necessary
calibration
factors may be sought through analysis of the system and its camera
placements.
Additional correction factors may be necessary to correct for inherent
differences
between the emitted Cherenkov light and imparted dose, specifically spatial
locations
where the relative fluence of low keV energy electrons is high.
[0121] Because fluorescent emissions are omnidirectional, a
fluorophore or
fluorescent dye in a phantom helps overcome distortions that may otherwise
result due to
the directionality of emitted Cherenkov radiation, whether the charged
particles are part
of a charged-particle radiation beam or induced by high-energy photons of a
gamma-ray
photon beam.
[0122] Since high index materials may absorb radiation differently
than does
tissue, in an embodiment processor 328 has calibration information in its
memory system
for adjustment for beam attenuation in the phantom, and translates determined
three
dimensional models of light emission in the emissions zone into three
dimensional
models of radiation dose in tissue using that calibration information.
[0123] While Cherenkov radiation is emitted during beam pulses 206
(Fig. 5),
light emitted 209 from fluorophores lags the beam and decays exponentially
after each
pulse of the beam turns off as illustrated. In an embodiment therefore, an
effective
shutter interval during beam pulse 206 is used to image light primarily
emitted by
Cherenkov mechanisms, and an effective fluorescent shutter interval 211 is
used to
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capture light emitted from the phantom by fluorescent and phosphorescent
mechanisms.
In this embodiment, light imaged by cameras 316, 318 is recorded as image
pairs, with a
first image of each pair indicative of light emitted during beam pulse 206 and
a second
image of each pair indicative of light emitted during the fluorescent shutter
interval 211.
Processor 328 therefore executes machine-readable instructions in associated
memory,
such as memory 326 to reconstruct beam shape and beam energy distribution
profiles
from the captured image pairs.
[0124] In an alternative embodiment, in order to increase sensitivity
and
improve contrast, images obtained during and after 211 multiple pulses 206 of
the beam
are summed and/or averaged.
[0125] In an embodiment, an operator may turn on the beam, and have
the
system construct a model of emissions zone 320, then turn off the beam and
view the
images provided on display subsystem 332. If the beam fails to meet
specifications 714
for a particular treatment, the operator may then use the images provided on
display
subsystem 332 to determine a different setting of beam-shaping apparatus 314
that should
provide a beam that more closely resembles a beam desired for treatment of a
patient.
The operator may then adjust beam shaping apparatus 314, following which the
beam is
turned back on while new images of Cherenkov radiation in emissions zone 320
are
captured by the cameras 316, 318, 370, 374, the beam then being turned off and
a new
three-dimensional model of the emissions zone and displayable images prepared.
Once
beam profile meets a desired beam profile, the phantom is removed and replaced
by a
patient, and the system may then be used to provide radiation of the desired
profile for
treating the patient.
[0126] In an embodiment, parameters of the three dimensional model of
the
emissions zone and the displayable images are recorded in a machine-readable
memory
system, such that the model and images may be used to document treatment, for
periodic
quality assurance and calibration, or to seek regulatory approvals. In another
embodiment, the parameters of the three dimensional model are used to satisfy
monthly
quality assurances checks on the clinical electron and x-ray photon beam
qualities.
[0127] In an embodiment, the system is utilized with optically
translucent
anthropomorphic tissue phantoms, or complex tissue phantoms to capture images
of the
beam shape in more complex geometries and tissue compositions than is possible
in
homogeneous water phantoms.
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Motion Systems for Skin Dose and Beam-Skin Intersection Tracking
[0128] As is known in the art of radiotherapy, the relative positions
of subject
and beam source is often altered during treatment. For example, a subject may
be rotated
in a radiation beam, or more commonly the radiation source is rotated about
the subject,
to irradiate a tumor within the patient from multiple angles, and thereby
spread out
radiation dose received by normal tissues of the subject. In an embodiment,
surface
images of Cherenkov emission from tissue are repetitively captured during
standard
courses of fractionated radiotherapy, and these images provide real time video
of beam
delivery on the subject's tissue, both for relatively stationary and
relatively moving beam
and subject. Further, the images can be used as real time video or integrated
to provide an
estimate for total skin dose. The images can be acquired from gated cameras
set up inside
or alongside the linear accelerator to image skin illuminated by the
accelerator or at fixed
positions within the treatment room. In embodiments utilizing fiducial markers
placed on
or in tissue, the images have both information about the delivered dose map on
the tissue
as well as biological fiducial information, and both can be used in treatment
verification.
[0129] In an embodiment, as illustrated in Fig. 13, a movable
particle
accelerator 1102 on rotary mount 1104 and counterweight 1106 with a subject
1108
positioned on a table 1110, such that the accelerator 1102 may rotate about
subject 1108
to provide radiation treatment to a breast 1112 of subject 1108. One or more
intensified
CCD (ICCD) cameras 1114 are positioned on tripods 1116, suspended from ceiling
of a
room enclosing the accelerator, or attached 1118 to the accelerator 1102. At
least two
optical cameras, such as a stereo pair of cameras 1120, are also provided.
Accelerator
1102 may be equipped with a multi-leaf collimator 1126. All cameras, including
ICCD
cameras 1114 and stereo optical cameras 1120 are interfaced (connections are
not shown
for simplicity) through a camera interface 1122 to an image processor 1124
that has
memory 1128 having recorded therein machine readable code for performing the
steps
referenced below with reference to Fig. 15. In alternative embodiments, high-
sensitivity
CMOS or other electronic cameras are used in place of ICCD cameras 1114.
[0130] An embodiment is used to provide skin dose totals over
multiple
sessions of treatment; a particular variation of this embodiment has
positioning devices or
camera mounts suitable for mounting ICCD cameras 1114 in the same position and
angle
from treatment session to treatment session such that images are comparable
from session
to session.
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[0131] In operation, as illustrated by the flowchart of Fig. 15, a
stereo pair of
images under white light is captured 1202 by stereo cameras 1120, and a three-
dimensional computer model (fig. 14), is generated 1204 of skin of breast 1112
of subject
1108 in the area to be treated. In alternative embodiments, the skin is skin
of other parts
of human or other mammal anatomy, such as skin of a head. A translation or
mapping of
image intensity at the skin surface in Cherenkov light images, as obtained by
one or more
ICCD cameras 1114, to surface radiation intensity is determined 1206. The
mapping is
based in part on ray tracing from skin as modeled in the three dimensional
model into the
ICCD camera or cameras, and a scale factor determined by calibration. A total
session-
dose image and model is then cleared 1208.
[0132] Once the beam is energized 1210 and treatment begins, a
sequence of
images of Cherenkov light emitted from skin illuminated by a radiation beam
1130 from
accelerator 1102 is obtained 1212 by at least one camera of ICCD cameras 1114
during
beam-on intervals while ambient illumination is blanked as previously
described. Each
image is then processed by applying 1214 the mapping of image intensity in
Cherenkov
light images as obtained by the ICCD cameras 1114 to surface radiation
intensity. The
mapped surface intensity is then summed into the session total skin dose 1216
image or
model. The mapped surface intensity, the session total skin dose image, and a
multisession total skin dose image obtained by summing a current session total
skin dose
image with prior session skin dose images, are provided 1218 in real time on
display
1132. In an alternative embodiment, the Cherenkov light images are summed,
then the
mapping of image intensity to surface radiation intensity is applied to
provide a session
total skin dose image. At the end of the session, the session total skin dose
and
multisession total skin dose are stored over a network 1134 in the subject's
electronic
health record (not shown), and the session total skin dose is summed into a
multisession
total skin dose.
[0133] The system permits direct observation of the effect altered
multileaf
collimator 1126 settings, and/or accelerator 1102 rotation about subject 1108,
on the areas
of skin illuminated by beam 1130. Further, the system permits determination of
both
session total and treatment total skin dose.
[0134] In an embodiment, a pre-treatment simulation of predicted skin
radiation dose versus time is copied into memory 1128. During a treatment
session,
image processor 1124 compares 1219 an image of skin dose derived from surface
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radiation intensity maps derived from Cherenkov light images to the pre-
treatment
simulation of skin radiation dose. If the skin dose determined from Cherenkov
light
images differs by more than a preset, configurable, limit from the pre-
treatment
simulation, an error 1221 is declared, the beam is turned off, and the session
is aborted.
This embodiment makes use of the Cherenkov emitted light to prevent subject
harm due
to overdose, whether from failed equipment or improper system operation.
[0135] In an embodiment, the processor 328 is provided with machine-
readable instructions in memory 326 for determining if skin and organ dose as
administered differs from planned dosage, or from prior dosage, by more than a
limit in
order to generate an error flag. Such an error flag may be generated if a
subject has shed
weight, is miss-positioned, or otherwise needs treatment replanning.
[0136] In this embodiment, in order to identify differences from
prior dosage,
during each treatment session a cumulative Cherenkov-light image is stored.
During each
treatment session other than the first treatment session, processor 328
executed machine
readable instructions in memory 326 to retrieve a first or prior Cherenkov
image from
storage for comparison with current Cherenkov images, and the processor
performs edge
detection on this first or prior image, and feature extraction on the edge-
detected prior
image to provide prior features. The processor then performs edge detection
and feature
extraction on a current Cherenkov image, and the current image features are
mapped to
prior image features.to determine correspondence points between the images. A
displacement between the features of the current image and the prior image is
computed,
and compared to limits. If the displacement exceeds the limits, the processor
then
generates an alarm to notify an operator.
[0137] In this embodiment, in order to detect differences from plan,
a
predicted skin-dosage map for dosage of, and simulated cumulative dosage
through, a
particular treatment session is generated from pre-treatment simulations and
saved in
memory 326. A do-not-exceed-without-warning dosage is determined and set as a
limit
in memory 326. A maximum difference percentage is also determined and set as a
limit
in memory 326. After each fractionated treatment session a totalized skin
dosage image
for all treatment sessions of this subject is determined, and pixels of the
totalized skin
dose are compared to the "do not exceed" skin dose and an alarm is provided to
a
treatment operator if this limit has been exceeded for any pixels. Further,
the totalized
skin dose is compared to the simulated cumulative skin dose, and if any pixels
of the
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totalized skin dose differ from the simulated skin dose by more than the
maximum
difference percentage, an alarm is generated. In order to compensate for
subject weight
loss and precise positioning, the comparison of simulated to totalized dose is
performed
by processor 328 performing edge detection in simulated skin dose at this
treatment stage,
performing edge detection in totalized skin dose as determined from Cherenkov
radiation,
determining a warping of totalized actual skin dose to simulated skin dose,
performing
image warping, and then comparing totalized actual skin dose to warped
simulation skin
dose. The images are then compared and if any pixels differ by more than a
limit, an
alarm is generated.
[0138] In an embodiment, in order to compensate for subject weight
changes
(cancer patients are often ill, have often been subjected to toxic
chemotherapies, and may
suffer additional effects due to treatment radiation) and minor differences in
subject
positioning, when totalizing skin dose across sessions, the processor executes
machine
readable instructions to determine edges and features in both the current
image, and in the
totalized image. The processor then determines edge offsets between
corresponding
features and a warping function to correctly superimpose the images. The
processor then
uses the warping function to warp the current session total image to fit the
prior images
before adding it to the totalized image in order to compensate for weight loss
or subject
position.
[0139] In another embodiment, the shape of the beam can be readily
detected
in the Cherenkov image, and if the multileaf collimators or the gantry angle
are in error
due to computer or human set up error, then the beam delivery can be halted
manually
(after display of the image to an operator) or automatically in order to avoid
erroneous or
excessive radiation dose.
[0140] In another embodiment, significant biological features of the
tissue
such as blood vessels, moles and skin variations in absorption appear in the
Cherenkov
images as variations in detected intensity, and can be used to match the
position of the
subject each day while administering daily portions of fractionated radiation
treatments.
Changes in subject position which could occur from day to day can be detected
by
changes or offsets in locations of these biological features in the images,
indicating
changes in relative position of beam and subject. These changes may result
from subject
weight changes, or differences in subject positioning. If these changes are
found and
exceed limits they can be used to alter the treatment plan or halt therapy
until a cause is
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determined, and changes in subject positioning and/or multileaf collimator
settings can be
made to compensate.
[0141] Experiments with a system of the type illustrated in Fig. 13,
operated
according to the method of Fig 15, have produced a map of multisession total
skin dose as
illustrated in Fig. 16, where high total skin dose correlates with areas of
maximal skin
damage on a human subject, as indicated in photograph Fig. 17. The system has
been
demonstrated as operable with beam energies of 6 MEV and 10 MEV.
[0142] As previously described, internal and surface biological
features
which absorb radiation and emit Cherenkov and fluorescent light, such as blood
in blood
vessels and tissue, provide information about the oxygenation of the tissue
being treated.
Further, images obtained from Cherenkov emissions may be co-registered with
prior
image data such as the contrast CT scans and MRI scans previously used for
simulation
and/or planning of treatment. These features provide an internal biological
fiducial for
treatment verification.
[0143] Cherenkov images in visible light, with infrared fluorescent
light
excluded, may show regions of high and low emission, corresponding to areas of
high and
low skin dose to a depth of up to a centimeter in tissue.
Correction of Cherenkov images to determine surface radiation dose
[0144] Cherenkov images of a surface region of subject 102 may be
used as a
tool to determine surface radiation dose during radiation therapy. However,
the signal
intensities in raw (as-captured) Cherenkov images are frequently affected by
tissue-
specific properties that produce artifacts in the Cherenkov images such that
the
Cherenkov images do not provide an accurate representation of the delivered
radiation
dose. These tissue-specific features include tissue curvature and
heterogeneities in optical
properties of the tissue such as tanned skin versus normal skin, moles,
tattoos, blood
vessels, tumor resection cavities, and optical property changes caused by skin
reactions to
prior sessions of radiation treatment. In the following, systems and methods
are disclosed,
which use a reflectance image to correct a Cherenkov image to eliminate or at
least
reduce artifacts caused by tissue-specific properties so as to generate a
corrected
Cherenkov image that provides an improved determination of surface radiation
dose.
[0145] Each of the systems and methods disclosed in FIGS. 2-13 and 15
may
be extended to implement the correction methods and/or systems discussed in
the
following.
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[0146] FIG. 18 illustrates one exemplary Cherenkov imaging system
1800 for
determining radiation dose for a surface region 1890 of subject 102 undergoing
radiation
therapy. Radiation beam 160, generated by charged particle or gamma radiation
beam
source 108, is aimed at tumor 104 and generates Cherenkov radiation in the
tissue of
subject 102. Cherenkov radiation from a surface region 1890, located at and
near the
surface of subject 102 exposed to radiation beam 160, is imaged from outside
subject 102.
Depending on the location of tumor 104 within subject 102, surface region 1890
may or
may not include at least a portion of tumor 104.
[0147] Cherenkov imaging system 1800 includes a camera system 1830
and a
correction module 1850. Camera system 1830 includes an electronic camera 1834
and a
light source 1832. Camera 1834 captures a Cherenkov image 1812 of Cherenkov
radiation emitted from surface region 1890 when subject 102 is exposed to
radiation
beam 160. Light source 1832 illuminates surface region 1890 with optical
illumination
1835. Camera 1834 captures a reflectance image 1836 of optical illumination
1835 as
reflected from surface region 1890 when light source 1832 illuminates surface
region
1890 with optical illumination 1835. Correction module 1850 corrects Cherenkov
image
1812, based upon reflectance image 1836, to produce a corrected Cherenkov
image 1852.
[0148] Light source 1832 may be monochromatic, broadband, or multi-
colored. Without departing from the scope hereof, light source 1832 may
omitted from
system 1800 and optical illumination 1835 instead be provided through ambient
illumination such as room lights 122.
[0149] In one embodiment, optical illumination 1835 generated by
light
source 1832 is diffuse, for example to reduce or avoid glare in reflectance
image 1836. In
another embodiment, optical illumination 1835 generated by light source 1832
is
polarized and camera 1834 is configured to, at least when capturing
reflectance image
1836, filter the polarization of optical illumination 1835 reflected by
surface region 1890
to deselect the polarization direction of optical illumination 1835 as
generated by light
source 1832. In one such example, light source 1832 and camera 1834 are
equipped with
polarizers that are mutually crossed such that only polarization components
orthogonal to
the polarization direction of optical illumination 1835, as generated by light
source 1832,
contribute to reflectance image 1836. The polarizer associated with camera
1834 may be
mounted on a filter wheel, or similar device, such that Cherenkov image 1812
in some
embodiments is captured by the same camera without use of the polarizer.
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[0150] Surface region 1890 scatters optical illumination 1835 in a
manner
similar to scattering of the Cherenkov radiation generated in surface region
1890. Hence,
the signal intensities in reflectance image 1836 provide a measure of the
tissue-specific
properties of surface region 1890. Correction module 1850 utilizes reflectance
image
1836 to at least partly correct artifacts caused by the tissue-specific
properties of surface
region 1890 such that corrected Cherenkov image 1852 is free of, or at least
less affected
by, these artifacts. Thus, corrected Cherenkov image 1852 provides a
determination of
surface radiation dose for surface region 1890, which is more accurate than
that provided
by Cherenkov image 1812.
[0151] Since Cherenkov image 1812 and reflectance image 1836 are
captured
by the same camera 1834, Cherenkov image 1812 and reflectance image 1836 are
inherently spatially co-registered. In addition, Cherenkov image 1812 and
reflectance
image 1836 are subject to the same camera properties. As a result, the
correction
performed by correction module 1850 may further eliminate or reduce artifacts
inherent
to camera 1834, such as optical aberrations and fixed-pattern electronic
noise.
[0152] In an embodiment, camera 1834 is a spectrally-sensitive camera
capable of providing spectral data permitting distinction between Cherenkov
radiation
and optical illumination 1835. Camera 1834 may further be able to distinguish
between
Cherenkov radiation, optical illumination 1835, and fluorescent light, and in
a particular
embodiment permitting distinction between oxyhemoglobin and deoxyhemoglobin,
as
discussed above in reference to FIG. 3. A spectrally-sensitive camera suitable
for this
application may be implemented as a black and white camera equipped with a
filter-
changer in front of the camera, or a hyperspectral camera, as discussed above
in reference
to FIG. 3.
[0153] In certain embodiments, system 1800 is configured to generate
corrected Cherenkov image 1852 in the form of a three-dimensional (3D) surface
map,
and correction module 1850 includes a surface model processor 1860 that
processes 3D
surface models and 3D surface maps. In one such embodiment, camera system 1830
further includes a light-structure encoder 1833 that encodes patterns of light
and dark,
known as structure, onto optical illumination 1835 emitted by light source
1832 while
camera 1834 captures at least one structured-light reflectance image 1838. In
this
embodiment, surface model processor 1860 uses the at least one structured-
light
reflectance image 1838 to generate a 3D surface model of surface region 1890.
In another
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such embodiment, system 1800 includes a stereo camera 1840 that captures a
stereo
image 1848. In this embodiment, surface model processor 1860 processes stereo
image
1848 to generate the 3D surface model of surface region 1890, as discussed
above in
reference to FIGS. 3, 14, and 15, for example. Whether the 3D surface model is
based
upon stereo image 1848 or the at least one structured light reflectance image
1838,
correction module 1850 may map corrected Cherenkov image 1852 onto the 3D
surface
model to output corrected Cherenkov image 1852 in the form of a 3D surface
map. In a
particular embodiment, one camera of the stereo camera does double-duty as a
Cherenkov-light imaging camera and/or as a reflectance-imaging camera.
[0154] In an embodiment, system 1800 further includes a controller
1870 that
controls timing of capture of Cherenkov image 1812 and reflectance image 1836,
and
also, if applicable, stereo image 1848 or the at least one structured
reflectance image
1838. In one example, controller 1870 pulses on light source 1832 and triggers
capture of
reflectance image 1836 by camera 1834 while light source 1832 is on.
Controller 1870
may trigger capture of Cherenkov image 1812 with timing as discussed above in
reference to FIG. 5, while also ensuring that light source 1832 is off when
camera 1834
captures Cherenkov image 1812. In embodiments that include stereo camera 1840,
controller 1870 may trigger capture of stereo image 1848 by stereo camera
1640. In
embodiments that include light-structure encoder 1833, controller 1870 trigger
may
configure light-structure encoder 1833 and trigger image capture by camera
1834 such
that (a) light-structure encoder 1833, which may be a projection cathode-ray
tube, a
multimirror display device, a liquid-crystal display device, or a slide
projector, encodes
structure of one or more sequential patterns onto optical illumination 1835
during capture
of the at least one structured reflectance image 1838 and (b) light-structure
encoder 1833
does not encode structure onto optical illumination 1835 during capture of
reflectance
image 1812.
[0155] FIG. 19 is a diagram 1900 showing exemplary illumination of
surface
region 1890 by optical illumination 1835 as performed by system 1800. Surface
region
1890 is the region of subject 102 from which Cherenkov radiation is captured
in
Cherenkov image 1812. Surface region 1890 has a characteristic depth 1910
below the
surface of subject 102. Typically, characteristic depth 1910 is in the range
between two
and six millimeters. Surface region 1890 may have shape different from that
shown in
FIG. 19, without departing from the scope hereof. It is preferred that
reflectance image
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1836 samples the same region of subject 102 as Cherenkov image 1812. Hence, it
is
preferred that the penetration depth 1920 of optical illumination 1835
substantially
matches characteristic depth 1910. Penetration depth 1920 may refer to the
distance 1901
into subject 102, at which the intensity 1902 of optical illumination 1835 has
been
attenuated to approximately 10%, 30%, or 37% (1/e) of the intensity of optical
illumination 1835 at the surface of subject 102. Typically, optical
illumination 1835 is in
the red to near-infrared spectrum to sample typical values of characteristic
depth 1910.
[0156] FIG. 20 is a diagram 2000 showing exemplary illumination of
surface
region 1890 by multi-colored optical illumination 2010 generated by a multi-
colored
embodiment of light source 1832. Multi-colored optical illumination 2010 is an
example
of optical illumination 1835. In the example shown in FIG. 20, multi-colored
optical
illumination 2010 includes two different spectral components 2012 and 2014.
Without
departing from the scope hereof, multi-colored optical illumination 2010 may
include
three or more spectral components. Since Cherenkov radiation is spectrally
broadband,
multi-colored optical illumination 2010 may be better suited, as compared to
monochromatic optical illumination, for sampling surface region 1890 in the
same
manner as the Cherenkov radiation captured in Cherenkov image 112.
Furthermore,
multi-colored optical illumination 2010 may be, or include, a spectrally broad
component,
for example with spectral width of a hundred or hundreds of nanometers.
Spectral
components 2012 and 2014 have respective penetration depths 2022 and 2024,
wherein
penetration depth 2022 is different from penetration depth 2024. It is clear
from diagram
2000 that spectral components 2012 and 2014, and optionally additional other
spectral
components, may be combined to better match the sampling intensity profile of
Cherenkov radiation from surface region 1890, as compared to the match that
may be
achieved using only a single spectral component.
[0157] FIG. 21 illustrates one exemplary Cherenkov imaging method
2100 for
determining radiation dose for surface region 1890 of subject 102 undergoing
radiation
therapy. Method 2100 is performed, for example, by Cherenkov imaging system
1800.
[0158] In a step 2110, method 2100 captures a Cherenkov image of
Cherenkov radiation from surface region 1890 of subject 102. In one example of
step
2110, camera 1834 captures Cherenkov image 1812. Step 2110 may include a step
2112
of irradiating surface region 1890 with a radiation beam that induces the
Cherenkov
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radiation. In one example of step 2112, charged particle or gamma radiation
beam source
108 irradiates surface region 1890 with radiation beam 160.
[0159] In a step 2120, method 2100 captures a reflectance image of
optical
illumination reflected by surface region 1890. In one example of step 2120,
camera 1834
captures reflectance image 1836. Step 2120 may include a step 2122 of
illuminating
surface region 1890 with the optical illumination that produces the reflected
light imaged
in the reflectance image. In one example of step 2122, light source 1832
illuminates
surface region 1890 with optical illumination 1835, such as discussed in
reference to FIG.
19 or in reference to FIG. 20. In another example of step 2122, ambient light
illuminates
surface region 1890 with optical illumination 1835.
[0160] In one embodiment, step 2122 illuminates surface region 1890
with
diffuse optical illumination. Such diffuse optical illumination may help
reduce glare in
the reflectance image and also better resemble the sampling of surface region
1890 by the
Cherenkov radiation imaged in step 2110.
[0161] In another embodiment, step 2122 illuminates surface region
1890 with
polarized optical illumination, and step 2120 further includes filtering the
reflected optical
illumination to produce the reflectance image based upon only randomly
polarized
reflected light. In one example, step 2120 may image reflected optical
illumination only
of polarization orthogonal to the polarization of the incident polarized
optical
illumination. Deselection of the incident polarization ensures that
substantially all
photons contributing to the reflectance image (or at least the majority of
such photons)
have undergone a sufficient number of scattering processes within surface
region 1890 to
be diffusely scattered by surface region 1890, the resulting reflectance image
being a
scattered-light image with a reduced surface specular reflection component.
[0162] In a step 2140, the Cherenkov image captured in step 2110 is
corrected, based upon the reflectance image captured in step 2120, to form a
corrected
Cherenkov image that indicates the radiation dose for surface region 1890, at
least with
improved accuracy over the Cherenkov image captured in step 2110. In one
example of
step 2140, correction module 1850 corrects Cherenkov image 1812 based upon
reflectance image 1836 to produce corrected Cherenkov image 1852. In an
embodiment,
step 2140 includes a step 2142 of reducing an artifact in the Cherenkov image
captured in
step 2110, wherein the artifact is caused by a tissue-specific light-
transmission property,
as discussed above in reference to FIG. 18. In an embodiment, step 2140
includes a step
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2144 of normalizing the Cherenkov image captured in step 2110 to the
reflectance image
captured in step 2120. In one example of step 2144, correction module 1850
normalizes
Cherenkov image 1812 to reflectance image 1836. This example of step 2144
benefits
from Cherenkov image 1812 and reflectance image 1836 being spatially co-
registered and
subject to the same inherent camera properties. In certain embodiments,
corrected
Cherenkov image 1852 is Cherenkov image 1812 normalized to reflectance image
1836.
[0163] Although not shown in FIG. 21, step 2140 may use a model, such
as a
Monte Carlo simulation, that describes transport of both Cherenkov radiation
(and
optionally radiation beam 160) and optical illumination within surface region
1890, so as
to account for differences in propagation through and sampling of surface
region 1890 by
the Cherenkov radiation and optical illumination. This model is formed by
independently
simulating the propagation of each of (a) Cherenkov radiation and (b) the
optical
illumination for a plurality of different conditions, such as different tissue
conditions of
subject 101 and different configurations both for the radiation beam that
induces the
Cherenkov radiation and for the optical illumination. Step 2140 may use
modification
parameters, according to this model, to compensate for the difference of
propagation
between the Cherenkov radiation and the optical illumination. The model may be
implemented as a looking up database with modification parameters for typical
combinations of optical illumination properties (e.g., intensity, beam
profile, and spectral
composition), radiation beam properties (e.g., beam energy and beam type),
geometries
(e.g., curvature of surface of subject 101 and incident angles of the
radiation beam and the
optical illumination). Optionally, the modification parameters for a specific
case
encountered in real radiation therapy are determined by interpolations within
existing
modification parameters in the database.
[0164] In an optional step 2160, method 2100 outputs the corrected
Cherenkov image generated in step 2140. In one example of step 2160,
correction module
1850 outputs corrected Cherenkov image 1852.
[0165] In certain embodiments, method 2100 includes a step 2150 of
mapping
the corrected Cherenkov image onto a 3D surface model of surface region 1890.
In one
example of step 2150, surface model processor 1860 maps corrected Cherenkov
image
1852 onto a 3D surface model of surface region 1890 to form a 3D surface
radiation dose
map. Optionally, such embodiments of method 2100 further include outputting,
in step
2160, the corrected Cherenkov image in the form of the 3D surface radiation
dose map.
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These surface model based embodiments of method 2100 may further include a
step 2130
of generating the 3D surface model. In one such embodiment, step 2130 includes
a step
2132 of capturing a stereo image, which is then processed to generate the 3D
model. In
another such embodiment, step 2130 includes a step 2134 of capturing at least
one
structured-light reflectance image, which is then processed to generate the 3D
model. In
one example of step 2130 implemented with step 2132, stereo camera 1840
captures
stereo image 1848, and surface model processor 1860 processes stereo image
1848 to
produce the 3D surface model. In one example of step 2130 implemented with
step 2134,
camera 1834 captures at least one structured-light reflectance image 1838, and
surface
model processor 1860 processes the at least one structured-light reflectance
image 1838
to produce the 3D surface model.
[0166] Without departing from the scope hereof, step 2140 may be a
stand-
alone method, for example suitable for implementation as machine-readable
instructions,
on non-transitory media, wherein these machine-readable instructions may be
executed
by a processor to perform step 2140.
[0167] FIG. 22 illustrates one exemplary Cherenkov imaging system
2200 for
determining radiation dose for a surface region 1890 of subject 102 undergoing
radiation
therapy. Cherenkov imaging system 2200 is similar to Cherenkov imaging system
1800
except that Cherenkov imaging system 2200 includes two separate cameras 2210
and
2234 that capture Cherenkov image 1812 and reflectance image 1836,
respectively. Since
Cherenkov imaging system 2200 uses two different cameras, Cherenkov image 1812
and
reflectance image 1836 are not spatially co-registered. Therefore, correction
module 1850
includes surface model processor 1860. Surface model processor 1860 maps each
of
Cherenkov image 1812 and reflectance image 1836 onto a 3D surface model of
surface
region 1890 to generate respective 3D surface maps of Cherenkov image 1812 and
reflectance image 1836. Correction module 1850 then corrects the 3D surface
map of
Cherenkov image 1812 based upon the 3D surface map of reflectance image 1836
to
produce a 3D surface radiation dose map 2252. Camera 2234 is implemented with
light
source 1832 in a camera system 2230. Each of cameras 2210 and 2234 are
electronic
cameras and may be similar to camera 1834. In addition, controller 1870 (if
included)
may trigger operation of each of cameras 2210 and 2234. As discussed in
reference to
FIGS. 18-20, optical illumination 1835 may be monochromatic, multi-colored, or
broadband, and light source 1821 may emit optical illumination 1835 as diffuse
light or as
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polarized light. Accordingly, camera 2234 may be equipped with a polarizer
that
deselects the polarization of polarized optical illumination 1835 to generate
images
emphasizing scattered light over specular reflected light.
[0168] FIG. 23 illustrates one exemplary Cherenkov imaging method
2300 for
determining radiation dose for surface region 1890 of subject 102 undergoing
radiation
therapy. Method 2300 is performed, for example, by Cherenkov imaging system
2200.
[0169] In a step 2310, method 2300 captures a Cherenkov image of
Cherenkov radiation from surface region 1890 of subject 102. In one example of
step
2310, camera 2210 captures Cherenkov image 1812. Step 2310 may include a step
2312
of irradiating surface region 1890 with a radiation beam that induces the
Cherenkov
radiation. In one example of step 2312, charged particle or gamma radiation
beam source
108 irradiates surface region 1890 with radiation beam 160.
[0170] In a step 2320, method 2300 captures a reflectance image of
optical
illumination reflected by surface region 1890. In one example of step 2320,
camera 2234
captures reflectance image 1836. Step 2320 may include a step 2322 of
illuminating
surface region 1890 with the optical illumination that produces the reflected
light imaged
in the reflectance image. In one example of step 2322, light source 1832
illuminates
surface region 1890 with optical illumination 1835, such as discussed in
reference to FIG.
19 or in reference to FIG. 20. In another example of step 2322, ambient light
illuminates
surface region 1890 with optical illumination 1835. As discussed above in
reference to
step 2120 of method 2100, step 2320 may use diffuse or polarized optical
illumination.
[0171] In a step 2330, method 2300 generates a 3D surface model. In
one
embodiment, step 2330 includes a step 2332 of capturing a stereo image, which
is then
processed to generate the 3D model. In another embodiment, step 2330 includes
a step
2334 of capturing at least one structured-light reflectance image, which is
then processed
to generate the 3D model. In one example of step 2330 implemented with step
2332,
stereo camera 1840 captures stereo image 1848, and surface model processor
1860
processes stereo image 1848 to produce the 3D surface model. In one example of
step
2330 implemented with step 2334, camera 2234 captures at least one structured-
light
reflectance image 1838, and surface model processor 1860 processes the at
least one
structured-light reflectance image 1838 to produce the 3D surface model.
[0172] In a step 2340, the Cherenkov image captured in step 2310 is
corrected, based upon the reflectance image captured in step 2320, to form a
corrected
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Cherenkov image that indicates the radiation dose for surface region 1890, at
least with
improved accuracy over the Cherenkov image captured in step 2310. Step 2340
forms the
corrected Cherenkov image in the form of a 3D surface radiation dose map. In
an
embodiment, step 2340 includes a step 2342 of reducing an artifact in the
Cherenkov
image captured in step 2310, wherein the artifact is caused by a tissue-
specific light-
transmission property, as discussed above in reference to FIG. 18.
[0173] Step 2340 includes a step 2344 of (a) mapping the Cherenkov
image
captured in step 2310 onto the 3D surface model generated in step 2330 to
produce a 3D
surface map of the Cherenkov radiation, and (b) mapping the Cherenkov image
captured
in step 2310 onto the 3D surface model generated in step 2330 to produce a 3D
surface
map of the optical illumination reflected by surface region 1890. In one
example of step
2344, surface model processor 1860 maps each of Cherenkov image 1812 and
reflectance
image 1836 onto the 3D surface model generated in step 2330. Step 2340 further
includes
a step 2346 of correcting the 3D surface map of the Cherenkov radiation, based
upon the
3D surface map of the optical illumination reflected by surface region 1890,
to form the
3D surface radiation dose map. In one example of step 2346, correction module
1850
corrects the 3D surface map of the Cherenkov radiation, based upon the 3D
surface map
of the optical illumination reflected by surface region 1890, to form 3D
surface radiation
dose map 2252. Step 2345 may include, or consist of, normalizing the 3D
surface map of
the Cherenkov radiation to the 3D surface map of the optical illumination
reflected by
surface region 1890.
[0174] Although not shown in FIG. 23, step 2340 may use a model, such
as a
Monte Carlo simulation model, that describes transport of both Cherenkov
radiation (and
optionally radiation beam 160) and optical illumination within surface region
1890, so as
to account for differences in propagation through and sampling of surface
region 1890 by
the Cherenkov radiation and optical illumination, as discussed in reference to
step 2140.
[0175] In an optional step 2350, method 2300 outputs the 3D surface
radiation
dose map generated in step 2340. In one example of step 2350, correction
module 1850
outputs 3D surface radiation dose map 2252.
[0176] Without departing from the scope hereof, step 2340 may be a
stand-
alone method, for example suitable for implementation as machine-readable
instructions,
on non-transitory media, wherein these machine-readable instructions may be
executed
by a processor to perform step 2340.
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[0177] In particular embodiments discussed herein with respect to
Fig. 18, 19,
20, 21, 22, and 23, the correction module makes use of a voxel-based light
propagation
model having scattering parameters and absorbance parameters at each voxel of
the
model. In these embodiments, the optical parameters extracted by using the
optical
illumination include the scattering parameter and an absorbance parameter at
each voxel
of the model. In particular embodiments where the optical illumination is
performed at
multiple wavelengths, the model may have multiple absorbance parameters at
each voxel
with each absorbance parameter modeling light absorbance at a particular
wavelength of
the multiple wavelengths. In embodiments where a three-dimensional model of
the
subject is determined such as by surface extraction from stereo images, the
voxel-based
light-propagation model is adjusted to conform to the three-dimensional model
by
assuming primary absorbance and scattering occurs within the subject. In
particular
embodiments, the correction module operates by adding a Cherenkov emissions
parameter to each voxel of the light propagation model, applying the
scattering and
absorbance parameters as determined under optical illumination at each voxel
of the
mode to modeled Cherenkov light, and fitting the Cherenkov emissions
parameters to
provide a best-fit to observed intensities at pixels of the Cherenkov images.
[0178] Each of system 1800, method 2100, system 2200, and method 2300
may be extended to correction of fluorescence images of fluorescence induced
by
Cherenkov radiation, such as PpIX images discussed above. For example,
Cherenkov
image 1812 may be replaced by a fluorescence image of Cherenkov-radiation-
induced
fluorescence, without departing from the scope hereof.
Combinations
[0179] The treatment recording and measuring system herein described
can be
implemented with various combinations of features, some combinations are
listed below
and some are claimed. These combinations include:
[0180] A system designated A for providing and monitoring delivery
and
accuracy of radiation therapy includes a source of pulsed high energy
radiation disposed
to provide a radiation beam to a treatment zone, the high energy radiation of
at least 0.2
MeV or greater; at least one camera configured to obtain images of Cherenkov
light from
the treatment zone; and apparatus for adapted to prevent interference by room
lighting
with the images of Cherenkov light by synchronizing the camera to pulses of
the radiation
beam, and blanking room lighting during pulses of the radiation beam. The
system also
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has an image processor adapted with machine readable code in a memory to
determine an
accuracy of actual delivered dose relative to a planned treatment from the
images of
Cherenkov light.
[0181] A system designated AA including the system designated A where
the
image processor is adapted with machine readable code to estimate cumulative
skin dose
in the treatment zone from the images of Cherenkov light.
[0182] A system designated AB including the system designated A or
AA,
where the image processor is adapted with machine readable code to resolve
patient
position relative to the treatment beam from by using vascular and skin
structures which
appearing in the emitted Cherenkov images as biological alignment features.
[0183] A system designated AC including the system designated A, AA,
or
AB, where a radiation beam extent is determined from the Cherenkov images, and
in a
system the determined radiation beam extent is used for estimation of accuracy
of
delivery of the radiation.
[0184] A system designated AD including the system designated A, AA,
AB,
or AC further comprising a positioning device configured to hold the camera in
the same
angle and position in a first fractionated radiation treatment session and a
second
fractionated radiation treatment session.
[0185] A system designated AE including the system designated A, AA,
AB,
AC, or AD wherein the memory is configured with machine readable instructions
for
using a three-dimensional model of a subject to determine a mapping of image
intensity
in the images of Cherenkov light to the radiation dose deposited in skin of
the subject.
[0186] A system designated AF including the system designated A, AA,
AB,
AC, AD, or AE wherein the image processor is configured to acquire multiple
images of
Cherenkov light during a treatment session.
[0187] A system designated AG including the system designated A, AA,
AB,
AC, AD, AE, or AF, wherein the image processor is configured with machine
readable
instructions to compare a skin dose determined from pre-treatment simulations
to a skin
dose determined from imaged Cherenkov light and to interrupt the delivery of
radiation if
the imaged Cherenkov signal disagrees with the pre-treatment simulations by
more than a
limit.
[0188] A system designated AH including the system designated A, AA,
AB,
AC, AD, AE, AF, or AG configured with machine readable code to apply the
mapping of
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image intensity from the multiple images of Cherenkov light to determine maps
of skin
dose, and to determine if changes in position have occurred and to warn an
operator if the
treatment beam design is providing excessive skin dose or excessive changes in
position
have occurred.
[0189] A system designated AK including the system designated A, AA,
AB,
AC, AD, AE, AG, or AH wherein the processor is configured with machine
readable
instructions to indicate on a display when the Cherenkov images show
significant
differences in the daily images.
[0190] A system designated AL including the system designated A, AA,
AB,
AC, AD, AE, AG, AH, or AK wherein the image processor is configured to sum
dosage
maps from a first treatment session and a second treatment session to provide
a map of
total multisession dose.
[0191] A method designated B of determining surface dose during
radiation
treatment of a first object beneath a surface of a second object to limit dose
at the surface
includes obtaining stereo images of the surface, and extracting a three-
dimensional
computer model of the surface; determining a mapping of image brightness at
the surface
in Cherenkov light images obtained by a digital camera to radiation intensity;
recording
surface brightness at the surface in a plurality of Cherenkov light images;
and summing
step including using the mapping of image brightness at the surface to
translate each
Cherenkov light image into a surface dose image, or summing the surface dose
images to
provide a total session surface dose image; and summing the image brightness
in each
Cherenkov light image into a total session surface Cherenkov light image and
using the
mapping of image brightness at the surface to translate the total session
surface
Cherenkov light image into a total session surface dose image. The method
concludes
with displaying the total session surface dose image.
[0192] A method designated BA including the method designated B and
further including summing the total session surface dose image with at least
one prior
session surface dose image to provide a total treatment surface dose image;
and
displaying the total treatment surface dose image.
[0193] A method designated BB including the method designated B or BA
and further including blanking room lighting during acquisition of the
Cherenkov light
images.
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[0194] A method designated BC including the method designated B, BA,
or
BB wherein the second object is a subject and the first object is a tumor.
[0195] A method designated BD including the method designated B, BA,
BB,
or BC and further comprising using an image selected from the group consisting
of the
total session surface dose image and the total treatment surface dose image to
modify a
radiation treatment plan for at least one radiation treatment session.
[0196] A system designated C for providing and monitoring delivery
and
accuracy of radiation therapy includes a source of pulsed high energy
radiation disposed
to provide a radiation beam to a treatment zone, with high energy radiation of
at least 0.2
MeV; at least one imaging system configured to obtain observations of light
emitted from
the treatment zone, the imaging system selected from the group consisting of
cameras
disposed to image the treatment zone, and photodetectors coupled through
optical fibers
to gather and detect light from the treatment zone; apparatus adapted to
minimize
interference by room lighting with the observations; and apparatus adapted to
record the
observations; wherein the imaging system is synchronized to pulses of the
pulsed high
energy radiation.
[0197] A system designated CA including the system designated C
wherein
the imaging system comprises at least one camera, and the observations of
light are
images, and the system further comprises an image processor.
[0198] A system designated CB including the system designated CA or C
wherein the apparatus adapted to prevent interference by room lighting with
the imaging
system comprises apparatus adapted to synchronize pulsed room lighting to
allow image
capture without ambient lighting.
[0199] A system designated CC including the system designated C, or
CA,
wherein the apparatus adapted to prevent interference by room lighting
operates through
the image processor being adapted with machine readable instructions
configured to
obtain a first image of the treatment zone during a pulse of the high energy
radiation
source, and a second image of the treatment zone at a time other than during a
pulse of
the high energy radiation source; and with machine readable instructions
configured to
subtract the second image from the first image to provide an image of
Cherenkov
emissions from the treatment zone.
[0200] A system designated CCA including the system designated C, or
CA,
wherein the apparatus adapted to prevent interference by room lighting
operates through a
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method comprising providing narrowband room lighting at a first wavelength,
and
wherein images of Cherenkov light exclude light at the first wavelength.
[0201] A system designated CD including the system designated CA, CBõ
CCA or CC wherein the image processor is adapted with machine readable code to
estimate a beam shape from the images of Cherenkov light.
[0202] A system designated CE including the system designated CD
wherein
the image processor is adapted with machine readable code to estimate a
radiation dose
map of the high energy radiation beam on a subject's skin from the images.
[0203] A system designated CF including the system designated CA, CB,
CC,
CCA, CD or CE, where the image processor is further adapted with machine
readable
code to resolve patient position relative to the treatment beam by using
vascular and skin
structures appearing in the emitted Cherenkov images as biological alignment
features.
[0204] A system designated CG including the system designated CA, CB,
CC,
CCA, CD, CE, or CF where the image processor is further adapted with machine
readable
code to compare intensity patterns from the images with images from at least
one prior
treatment session to determine if changes have occurred between sessions.
[0205] A system designated CH including the system designated CA, CB,
CC,
CCA, CD, CE, CF, or CG 10 wherein the image processor is adapted with machine
readable code to estimate a radiation dose map of the high energy radiation
beam on a
subject's skin from the images for a treatment session.
[0206] A system designated CI including the system designated CA, CB,
CC,
CCA, CD, CE, CF, or CG wherein the image processor is adapted with machine
readable
code to estimate cumulative skin dose across a plurality of a treatment
sessions in the
treatment zone.
[0207] A system designated CK including the system designated CA, CB,
CC,
CCA, CD, CE, CF, CG, CH, or CI wherein the image processor is configured with
machine readable code adapted to using a three-dimensional model of a subject
to
determine a mapping of image intensity in the images of Cherenkov light to the
radiation
dose deposited in skin of the subject.
[0208] A system designated CL including the system designated CA, CB,
CC,
CCA, CD, CE, CF, CG, CH, CI, or CK further comprising a positioning device
configured to hold the camera in a same location, angle and position in a
first fractionated
radiation treatment session and all subsequent fractionated radiation
treatment session.
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[0209] A system designated CM including the system designated CA, CB,
CC, CCA, CD, CE, CF, CG, CH, CI, CK, or CL wherein the image processor is
configured to acquire multiple images of Cherenkov light during a treatment
session.
[0210] A system designated CN, including the system designated CM,
wherein the image data is used to verify delivery as planned by comparison to
the
prescribed radiation dose.
[0211] A system designated CO including the system designated CA, CB,
CC,
CCA, CD, CE, CF, CG, CH, CI, CK, CL, or CN wherein the image processor is
configured with machine readable instructions to compare a skin dose
determined from
pre-treatment simulations to a skin dose determined from imaged Cherenkov
light and to
interrupt the delivery of radiation if the imaged Cherenkov signal disagrees
with the pre-
treatment simulations by more than a limit.
[0212] A system designated CP including the system designated C, CA,
CB,
CC, CCA, CD, CE, CF, CG, CH, CI, CK, CL, CN, or CO wherein the imaging system
is
spectrally selective such that the imaging system is adapted to capture
Cherenkov-
stimulated light emissions from tissue and to distinguish this light from
Cherenkov light.
[0213] A method designated D of determining surface dose during
radiation
treatment of a first object beneath a surface of a second object to limit dose
at the surface
includes obtaining at least two images of the surface, and extracting a three-
dimensional
computer model of the surface therefrom; determining a mapping of image
brightness at
the surface in Cherenkov light images obtained by a digital camera to
radiation intensity;
recording surface brightness at the surface in a plurality of Cherenkov light
images; and a
summing step of either using the mapping of image brightness at the surface to
translate
each Cherenkov light image into a surface dose image and summing the surface
dose
images to provide a total session surface dose image, or summing the image
brightness in
each Cherenkov light image into a total session surface Cherenkov light image
and using
the mapping of image brightness at the surface to translate the total session
surface
Cherenkov light image into a total session surface dose image; and displaying
the total
session surface dose image.
[0214] A method designated E of determining surface dose during
radiation
treatment from imaging of a fractionated radiation therapy includes obtaining
multiple
images of a surface, and extracting a three-dimensional computer model of the
surface
therefrom; synchronizing imaging to beam pulses, and obtaining Cherenkov light
images;
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determining a mapping of image brightness at the surface in Cherenkov light
images
obtained by a digital camera to radiation intensity; recording surface
brightness at the
surface in a plurality of Cherenkov light images; a summing step selected from
the group
of using the mapping of image brightness at the surface to translate each
Cherenkov light
image into a surface dose image and summing the surface dose images, or
summing the
image brightness in each Cherenkov light image into a total session surface
Cherenkov
light image, and using the mapping of image brightness at the surface to
translate the total
session surface Cherenkov light image into a total session surface dose image;
and
displaying the total session surface dose image.
[0215] A method designated EA including the method designated D or E
and
further including blanking room lighting during acquisition of the Cherenkov
light
images.
[0216] A method designated EB including the method designated D or E
further including correcting Cherenkov light images for ambient light by
subtracting an
ambient light image from an image obtained during a pulse of the beam.
[0217] A method designated EC including the method designated D, E,
EA, or
EB and further including summing the total session surface dose image with at
least one
prior session surface dose image to provide a total treatment surface dose
image; and
displaying the total treatment surface dose image.
[0218] A method designated ED including the method designated D, E,
EA,
EB, or EC wherein the surface is normal tissue and a deeper region is a tumor.
[0219] A method designated EE including the method designated D, E,
EA,
EB, EC, or ED wherein the radiation treatment is a fractionated radiation
treatment and
further comprising using an image selected from the group consisting of the
total session
surface dose image and the total treatment surface dose image to modify a
radiation
treatment plan for at least one radiation treatment session.
[0220] A Cherenkov imaging system designated F for determining
surface
radiation dose for a subject undergoing radiation therapy, comprising: a
camera system
comprising at least one digital camera, the camera system adapted to capture a
Cherenkov
image of Cherenkov radiation from a surface region of the subject undergoing
Cherenkov-radiation-inducing radiation therapy, and to capture a reflectance
image of
reflectance of optical illumination off the surface region; a light source
adapted to
generate the optical illumination, and a correction module for correcting the
Cherenkov
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image based upon the reflectance image to form a corrected Cherenkov image
that
indicates radiation dose for the surface region.
[0221] A Cherenkov imaging system designated FA including the
Cherenkov
imaging system designated F, further comprising a controller for controlling
(a) timing of
image capture by the first camera to capture the Cherenkov image to minimize
room light
interference and (b) timing of image capture by the second camera to capture
the
reflectance image when the surface region is exposed to the optical
illumination.
[0222] A Cherenkov imaging system designated FB including the
Cherenkov
imaging system designated F or FA, the light source being configured to
generate the
optical illumination as diffuse optical illumination.
[0223] A Cherenkov imaging system designated FC including the
Cherenkov
imaging system designated F, FA, or FB, the light source being configured to
generate the
optical illumination as polarized optical illumination, the camera system
including a filter
for deselecting a polarization component of the polarized optical illumination
to ensure
that substantially all photons contributing to the reflectance image have been
diffusely
scattered by the surface region.
[0224] A Cherenkov imaging system designated FC including the
Cherenkov
imaging system designated F, FA, or FB, the optical illumination having
wavelength such
that penetration depth of the optical illumination into the subject
substantially matches
maximum depth of the Cherenkov radiation imaged by the first imaging module.
[0225] A Cherenkov imaging system designated FD including the
Cherenkov
imaging system designated F, FA, FB, or FC, the optical illumination having
wavelength
such that the penetration depth is between two and six millimeters.
[0226] A Cherenkov imaging system designated FE including the
Cherenkov
imaging system designated F, FA, FC, or FD, the light source being a multi-
colored light
source for generating the optical illumination at a plurality of different
wavelengths to
sample a respectively plurality of different depths of the subject so as to
match depth-
sampling properties of the Cherenkov radiation.
[0227] A Cherenkov imaging system designated FF including the
Cherenkov
imaging system designated FE, the reflectance image being a composite image
based
upon a plurality of wavelength-specific reflectance images, the Cherenkov
imaging
system further comprising: a controller for controlling the second camera to
capture a
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plurality of wavelength-specific reflectance images using the plurality of
different
wavelengths, respectively.
[0228] A Cherenkov imaging system designated FG including the
Cherenkov
imaging system designated F, wherein the camera system is adapted to use a
single
camera for capturing the Cherenkov image and the reflectance image.
[0229] A Cherenkov imaging system designated FH including the
Cherenkov
imaging system designated F, FA, FC, or FD, the correction module being
configured to
generate the corrected Cherenkov image by normalizing the Cherenkov image to
the
reflectance image.
[0230] A Cherenkov imaging system designated FJ including the
Cherenkov
imaging system designated F, FA, FC, FD, or FE wherein the camera system is
further
adapted to capture a stereo image of the surface region under optical
illumination, and
further comprising a surface model processor adapted to (a) process the stereo
image to
produce a three-dimensional surface model of the surface region and (b) map
the
corrected Cherenkov image onto the three-dimensional surface model to generate
a three-
dimensional surface radiation dose map.
[0231] A Cherenkov imaging system designated FK including the
Cherenkov
imaging system designated F, FA, FC, FD, FE, or FH further comprising: a light-
structure
encoder for encoding structure onto the optical illumination to produce
structured light to
be used by the camera system to capture at least one structured-light
reflectance image;
and a surface model processor adapted to (a) process the at least one
structured-light
reflectance image to produce a three-dimensional surface model of the surface
region and
(b) map the corrected Cherenkov image onto the three-dimensional surface model
to
generate a three-dimensional surface radiation dose map.
[0232] A Cherenkov imaging system designated FL including the
Cherenkov
imaging system designated F, FA, FC, FD, FE, or FH, the correction module
being
configured to generate the corrected Cherenkov image in form of a three-
dimensional
surface radiation dose map by correcting a three-dimensional surface map of
the
Cherenkov radiation based upon a three-dimensional surface map of the
reflectance of the
optical illumination; the camera system being further configured to capture a
stereo image
of the surface region; and further comprising: a surface model processor for
(a)
processing the stereo image to produce a three-dimensional surface model of
the surface
region, (b) mapping the Cherenkov image onto the three-dimensional surface
model to
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generate the three-dimensional surface map of the Cherenkov radiation, and (c)
mapping
the reflectance image onto the three-dimensional surface model to generate the
three-
dimensional surface map of the reflectance of the optical illumination.
[0233] A Cherenkov imaging system designated FM including the
Cherenkov
imaging system designated F, FA, FB, FC, FD, FE, or FH, the correction module
being
configured to further take into account discrepancies between light transport
properties of
the Cherenkov radiation and the optical illumination within the subject when
correcting
the Cherenkov image.
[0234] A Cherenkov imaging system designated FN including the
Cherenkov
imaging system designated F, FA, FB, FC, FD, FE, FG, FH, FJ, FK, FL, or FM,
wherein,
the correction module is configured to use a voxel-based light propagation
model having
scattering parameters and absorbance parameters at each voxel of the model;
the optical
parameters extracted by using the optical illumination including the
scattering parameter
and an absorbance parameter at each voxel of the model.
[0235] A Cherenkov imaging system designated FO including versions of
the
Cherenkov imaging system designated FN where the optical illumination is
performed at
multiple wavelengths, the voxel-based light propagation model having multiple
absorbance parameters at each voxel with each absorbance parameter modeling
light
absorbance at a particular wavelength of the multiple wavelengths.
[0236] A Cherenkov imaging system designated FP including versions of
the
Cherenkov imaging system designated FN or FO wherein the correction module
operates
by adding a Cherenkov emissions parameter to each voxel of the light
propagation model,
applying the scattering and absorbance parameters as determined under optical
illumination at each voxel of the mode to modeled Cherenkov light, and fitting
the
Cherenkov emissions parameters to provide a best-fit to observed intensities
at pixels of
the Cherenkov images.
[0237] A Cherenkov imaging method designated G for determining
surface
radiation dose for a subject undergoing radiation therapy, comprising:
correcting a
Cherenkov image, the Cherenkov image being an image of Cherenkov radiation
emitted
from a surface region of the subject undergoing Cherenkov-radiation-inducing
radiation
therapy, the correcting comprising using a reflectance image, the reflectance
image being
an image of optical illumination reflected by the surface region, to form a
corrected
Cherenkov image that indicates radiation dose for the surface region.
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[0238] A Cherenkov imaging method designated GA including the
Cherenkov
imaging method designated G, the step of correcting comprising reducing
artifact in the
Cherenkov image caused by tissue-specific light transmission properties.
[0239] A Cherenkov imaging method designated GB including the
Cherenkov
imaging method designated G or GA, further comprising: capturing the Cherenkov
image; illuminating the surface region with the optical illumination; and
capturing the
reflectance image.
[0240] A Cherenkov imaging method designated GC including the
Cherenkov
imaging method designated G, GA, or GB, in the step of illuminating, the
optical
illumination being diffuse.
[0241] A Cherenkov imaging method designated GD including the
Cherenkov
imaging method designated G, GA, GB, or GC wherein: in the step of
illuminating,
illuminating the surface region is done with polarized illumination; and in
the step of
capturing the reflectance image, a polarization component of the polarized
illumination is
deselected in the camera system to ensure that substantially all photons
contributing to the
reflectance image have been diffusely scattered by the surface region.
[0242] A Cherenkov imaging method designated GE including the
Cherenkov
imaging method designated G, GA, GB, GC, or GD further comprising irradiating
the
surface region with a beam that induces the Cherenkov radiation.
[0243] A Cherenkov imaging method designated GF including the
Cherenkov
imaging method designated G, GA, GB, GC, GD, or GE comprising: in the step of
capturing the reflectance image, capturing the reflectance image using same
camera as
used to capture the Cherenkov image in the step of capturing the Cherenkov
image, such
that the reflectance image and the Cherenkov image are spatially co-
registered; and in the
step of correcting, normalizing the Cherenkov image to the reflectance image.
[0244] A Cherenkov imaging method designated GG including the
Cherenkov
imaging method designated G, GA, GB, GC, GD, GE, or GF further comprising:
generating a three-dimensional surface model of the surface region; and in the
step of
correcting:(a) mapping the Cherenkov image onto the three-dimensional surface
model to
produce a three-dimensional surface map of the Cherenkov radiation, (b)
mapping the
reflectance image onto the three-dimensional surface model to produce a three-
dimensional surface map of the reflectance, and (c) generating the corrected
Cherenkov
image in form of a three-dimensional surface radiation dose map by correcting
the three-
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dimensional surface map of the Cherenkov radiation based upon the three-
dimensional
surface map of the reflectance of the optical illumination.
[0245] A Cherenkov imaging method designated GH including the
Cherenkov
imaging method designated G, GA, GB, GC, GD, GE, GF, or GG, the step of
generating
comprising: capturing a stereo image of the surface region; and processing the
stereo
image to determine the three-dimensional surface model.
[0246] [0241] A Cherenkov imaging method designated GJ including the
Cherenkov imaging method designated G, GA, GB, GC, GD, GE, GF, GG, or GH the
step of generating comprising: capturing a second reflectance image of
structured light
incident upon the surface region; and processing the second reflectance image
to
determine the three-dimensional surface model.
[0247] A Cherenkov imaging method designated GK including the
Cherenkov
imaging method designated G, GA, GB, GC, GD, GE, GF, GG, GH or GK further
comprising generating the reflectance light image by: (a) illuminating the
surface region
with the optical illumination, and (b) capturing the reflectance image using a
camera; and
the step of capturing the second reflectance image comprising: (a) encoding
structure onto
the optical illumination to produce the structured light, and (b) capturing
the second
reflectance image using the camera.
[0248] A Cherenkov imaging method designated GL including the
Cherenkov
imaging method designated G, GA, GB, GC, GD, GE, GF, GG, GH or GK, in the step
of
illuminating, the optical illumination having wavelength such that penetration
depth of
the optical illumination into the subject substantially matches a maximum
depth of the
Cherenkov radiation of the Cherenkov image.
[0249] The Cherenkov imaging method designated GL, wherein, in the
step of
illuminating, the optical illumination having wavelength such that the
penetration depth is
between two and six millimeters.
[0250] A Cherenkov imaging method designated GM including the
Cherenkov imaging method designated G, GA, GB, GC, GD, GE, GF, GG, GH, GK, GH,
or GL, wherein in the step of illuminating, the optical illumination including
a plurality of
different wavelengths such that the optical illumination samples a
respectively plurality of
different depths of the subject to match depth-sampling properties of the
Cherenkov
radiation.
CA 03022122 2018-10-24
WO 2016/176265
PCT/US2016/029458
[0251] The Cherenkov imaging method designated GM, comprising: in the
step of illuminating, illuminating the surface region with optical
illumination of a
plurality of wavelengths; and in the step of capturing the reflectance image:
(a) capturing
a respective plurality of wavelength-specific reflectance images, and (b)
composing the
reflectance image from the plurality of wavelength-specific reflectance
images.
[0252] While the invention has been particularly shown and
described with
reference to a preferred embodiment thereof, it will be understood by those
skilled in the
art that various other changes in the form and details may be made without
departing
from the spirit and scope of the invention. It is to be understood that
various changes may
be made in adapting the invention to different embodiments without departing
from the
broader inventive concepts disclosed herein and comprehended by the claims
that follow.
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