scintillation dosimetry: review, new innovations and...
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Scintillation dosimetry: Scintillation dosimetry: Review, new innovations and Review, new innovations and
applicationsapplications
Sam Beddar, Ph.D., Sam Beddar, Ph.D., ProfessorProfessor
Department of Radiation Physics, UT MD Anderson Cancer Center Department of Radiation Physics, UT MD Anderson Cancer Center & UT Graduate School of Biomedical Sciences& UT Graduate School of Biomedical Sciences
&&
Luc Beaulieu, Ph.D., Luc Beaulieu, Ph.D., Associate Professor Associate Professor
Department of Physics, Department of Physics, UniversitUniversitéé Laval & Laval & Department of Radiation Department of Radiation Oncology, CHU de QuebecOncology, CHU de Quebec
OOUTLINEUTLINE
•• IntroductionIntroduction
•• Properties of plastic Properties of plastic scintillation detectorsscintillation detectors
•• ApplicationsApplications–– Daily QADaily QA–– RadiosurgeryRadiosurgery–– Clinical prototypeClinical prototype–– Proton therapyProton therapy–– Works in progressWorks in progress
•• ConclusionsConclusions
IINTRODUCTIONNTRODUCTION • Introduction• Properties• Applications• Conclusion
•• In the last 20 years, significant advances have been made In the last 20 years, significant advances have been made in scintillation dosimetryin scintillation dosimetry
•• They have a unique set of advantagesThey have a unique set of advantages
•• With the increasing complexity of radiotherapy treatments, With the increasing complexity of radiotherapy treatments, scintillation detectors could be used for quick and accurate scintillation detectors could be used for quick and accurate dose measurements even in complex geometriesdose measurements even in complex geometries
The purpose of this presentation is to show the advantages The purpose of this presentation is to show the advantages of of scintillatonscintillaton dosimetry and to explain how it can be used dosimetry and to explain how it can be used in modern radiotherapyin modern radiotherapy
INTRODUCTION • Introduction• Properties• Applications• Conclusion
•• In scintillation detectors:In scintillation detectors:
•• Impinging particles or photons will excite atoms or Impinging particles or photons will excite atoms or molecules of the scintillating medium.molecules of the scintillating medium.
•• Electron beams: Interacting electrons are not the same as Electron beams: Interacting electrons are not the same as the ionization electronsthe ionization electrons
•• The decay of these excited states will produce The decay of these excited states will produce photons in the visible part of the spectrum.photons in the visible part of the spectrum.
•• Photon beams: Interacting photons are not the same as the Photon beams: Interacting photons are not the same as the detected photonsdetected photons
•• These photons will be guided to a These photons will be guided to a photodetectorphotodetector and and then converted in an electric signal.then converted in an electric signal.
IINTRODUCTIONNTRODUCTION • Introduction• Properties• Applications• Conclusion
•• Two types of scintillators:Two types of scintillators:
A.A. Inorganic materialsInorganic materials-- NaINaI, , NaI(TlNaI(Tl), ), CsICsI, , CsI(TlCsI(Tl), ), CsI(NaCsI(Na), ), CsFCsF, BaF, BaF22, ,
CdWOCdWO44, , ……-- Advantages for stopping particles: high Z and Advantages for stopping particles: high Z and
high density (up to 8high density (up to 8--9 g/cm9 g/cm33))•• Disadvantage for dosimetryDisadvantage for dosimetry
-- Need an activator: Need an activator: e.g. e.g. TlTl ((ThaliumThalium))•• NaINaI: 330 nm: 330 nm•• NaI(TlNaI(Tl): 410 nm): 410 nm
INTRODUCTION • Introduction• Properties• Applications• Conclusion
•• Two types of scintillators:Two types of scintillators:
B.B. Organic materials (e.g. plastics) Organic materials (e.g. plastics)
-- Lower density Lower density …… and!!! nearly equivalent to waterand!!! nearly equivalent to water•• Density on the order of 1.03Density on the order of 1.03--1.06 g/cm1.06 g/cm33
•• (Generally) No high Z materials content.(Generally) No high Z materials content.
-- Excitation and emission spectra are similar in Excitation and emission spectra are similar in solid, liquid or vapor statessolid, liquid or vapor states
•• Core (bulk solvent)Core (bulk solvent)–– PolyvinyltoluenePolyvinyltoluene ((plastic scintillatorsplastic scintillators))–– Polystyrene (Polystyrene (plastic scintillating fibersplastic scintillating fibers))
•• Cladding (scintillating fibers)Cladding (scintillating fibers)–– PolymethylacrylatePolymethylacrylate (PMMA)(PMMA)–– Improves transmission of light to optical fiberImproves transmission of light to optical fiber
PPLASTICLASTIC SSCINTILLATINGCINTILLATING MMATERIALSATERIALS • Introduction• Properties• Applications• Conclusion
Dose deposition and scintillation
C.P. Interactions(keV to MeV)
De-excitation Processes
Energy Absorption
Energy Deposition
Ionization - Excitation
Light Emission(a few eV)
SSCINTILLATION CINTILLATION PPROCESSROCESS • Introduction• Properties• Applications• Conclusion
• Prompt fluorescence following excitation (10-9 – 10-7 s) important for radiation detection
• Introduction• Properties• Applications• Conclusion
SSCINTILLATION CINTILLATION PPROCESSROCESS
SCINTILLATION PROCESS • Introduction• Properties• Applications• Conclusion
• At room temperature, e- almost all in S00
– ΔE S1-S0 about 3-4 eV>> 0.025 eV
• S1 band (about 0.15 eV apart) decay radiation-less to the S1 base state
– Photon emitted only to S0 states
• T1 band: lower energy and longer process
SCINTILLATION PROCESS • Introduction• Properties• Applications• Conclusion
• Aromatic molecules– Large number of “shared”
electrons (π-electrons)» 4n+2» Anthracene has 14 of
such electrons.
– Excitation of π-electrons in S states = fast fluorescence.
– Ionization of π-electrons = mostly T states.
– Excitation or ionization of other electrons (σ-electrons) = no fluo or temporary / permanent damage
SCINTILLATION PROCESS • Introduction• Properties• Applications• Conclusion
• Since all photons come from the S10
– Shift in the emission spectrum to lower energy than the excitation (absorption) spectrum
– Mostly transparent to its own emitted photons!
From Knoll
• Organic fluors (scintillating materials) are used with a bulk solvent: two components system
– BC400: >97% PVT, < 3% organic fluors» e.g. p-TERPHENYL (C6H5 C6H4 C6H5)
– Energy deposited in the solvent is transfered to the organic fluor molecules
» Emission is typically peaked in the violet-blue region.
• “Wavelength shifters” or three component system– A third (organic) component can also be used to absorb
the organics fluors emitted photons and re-emit at a longer wavelength
» POPOP [1,4-bis(5-phenyloxazol-2-yl) benzene] to get scintillators emitting in the green or yellow region.
FLUORS • Introduction• Properties• Applications• Conclusion
SCINTILLATOR SPECTRA
Scintillators with Scintillators with longer wavelengths longer wavelengths have lower light have lower light emission emission
Archambault L, Arsenault J, Archambault L, Arsenault J, GingrasGingras L, Beddar A S, Roy R, Beaulieu L, "Plastic scintillation L, Beddar A S, Roy R, Beaulieu L, "Plastic scintillation dosimetry: Optimal selection of scintillating fibers and scintildosimetry: Optimal selection of scintillating fibers and scintillatorslators““, Med. Phys 32: 2271, Med. Phys 32: 2271--2278, 2278, 2005.2005.
• Introduction• Properties• Applications• Conclusion
• Only a small portion of the incident kinetic energy lost is converted in fluorescent energy
– For plastic scintillating fibers like BCF-12 about 8000 photons/MeV
This means about 125 eV / scintillation photon.The total energy of visible light produced (at 430 nm or ~ 2.9 eV) represents an efficiency of 2.4% (97.6% goes in phonons!)
– The light output depends on the LET (i.e. CP type)
SCINTILLATION EFFICIENCY • Introduction• Properties• Applications• Conclusion
• A decrease from the optimal scintillation efficiency, or quenching, can occur under various conditions
– For organic scintillators, little thermal quenching• Constant between -60 ºC and +20 ºC• 5% variation max between +20 ºC and +60 ºC
– Radiation damage can decrease the efficiency(Ionizations lead to temporary and/or permanent molecular damage)
• Increased absorption due to defects (plastics turn yellow)• Need > kGy accumulated doses (104 to 105 Gy)
QUENCHING EFFECT • Introduction• Properties• Applications• Conclusion
• Quenching also occurs for highly ionizing radiation
– Overlapping excitation sites and molecule damages.
– Provides alternate radiationless de-excitation processes.
– Non-linearity of Light (L) to Energy (E) response.
QUENCHING EFFECT • Introduction• Properties• Applications• Conclusion
• The relationship between the specific energy loss (ionization density) and the light output is given by the Birks’ formula:
S: Scintillation efficiencyB(dE/dx): Density of damaged
molecules along the particle trackk: fraction of damage contributing to
quenching
– For electrons above 125 keV: dL/dx = S dE/dx» Thus L = SE !
– For large dE/dx, saturation can occurs along the track» dL/dx = S / (kB) (usualy for ion particles)
BIRKS’ FORMULA • Introduction• Properties• Applications• Conclusion
dLdx
=S dEdx
1+ kB dEdx
Archambault L, Beddar S, Sahoo N, Archambault L, Beddar S, Sahoo N, PoensichPoensich F, Gillin M, Mohan R, " Experimental Proof and F, Gillin M, Mohan R, " Experimental Proof and Feasibility of a 3D RealFeasibility of a 3D Real--Time Detector System for Therapeutic Proton Beams Time Detector System for Therapeutic Proton Beams ““, Med. Phys. 35: , Med. Phys. 35: 2905, 2008. (Abstract).2905, 2008. (Abstract).
• Organic (plastic) scintillators are:– Made of low Z materials.
– Light output is directly proportional to the exciting energy.» Linear with deposited energy for e-,γ.» …for electron above 100-125 keV.
– (Mostly) Transparent to its emitted photons.
– The gap is wide enough to be insensitive to a wide range of temperatures.
– Fast time response (physics of orbital transitions).
• Introduction• Properties• Applications• Conclusion
SCINTILLATION PROCESS: SUMMARY
• Scintillation efficiency is not the collection efficiency.
» These photons must be detected.
» Linearity must be preserved throughout the complete detection chain
» Light must be calibrated to Dose.
• Introduction• Properties• Applications• Conclusion
SCINTILLATION PROCESS: SUMMARY
• JB Birks, The Theory and Practice of Scintillation Counting, Pergamon Press Book, MacMillan, New York, 1964. [Chapters 3 and 6]
• GF Knoll, Radiation Detection and Measurement, 3rd Edition, John Wiley and Sons, 2000. [Chapter 8]
• WR Leo, Techniques for Nuclear and Particle Physics Experiments, 2nd edition, Springer-Verlag, 1992. [Chapter 7]
• FH Attix, Introduction to Radiological Physics and Radiation Dosimetry, John Wiley and Sons, 1986. [Chapter 15]
• Introduction• Properties• Applications• Conclusion
SCINTILLATION PROCESS: REFERENCES
• Linear response to dose
• Dose rate independence
• Energy independence
• Temperature independence
• Spatial resolution
ADVANTAGES OF PLASTIC SCINTILLATORS
• Introduction• Properties• Applications• Conclusion
WATER EQUIVALENCE• W-E is achieved by:
– Media-matching (walls and sensitive volume)– Density state of the sensitive volume (gaseous vs.
condensed)
• W-E depends on:– Mass energy-absorption coefficients– Mass collision stopping powers– Size of the sensitive volume (according to Burlin
cavity theory)
H: 11.19O: 88.81
H: 7.74C: 92.26
H: 8.47C: 91.53
Composition (by weight %)
3.3433.2383.272Electron density(1023 e-/g)
1.0001.0601.032Density (g/cm3)WaterPolystyreneScintillatorParameter
• Introduction• Properties• Applications• Conclusion
WATER EQUIVALENCE
0.005 0.980 ±=med
sci
DD
According to Burlin cavity theory, above 125 keV:
Beddar A S, Mackie T R, Beddar A S, Mackie T R, AttixAttix F H, "WaterF H, "Water--equivalent plastic scintillation detectors for highequivalent plastic scintillation detectors for high--energy beam dosimetry: I. energy beam dosimetry: I. Physical characteristics and theoretical considerationsPhysical characteristics and theoretical considerations““, Phys. Med. Biol. 37: 1883, Phys. Med. Biol. 37: 1883--1900, 1992. 1900, 1992.
• Introduction• Properties• Applications• Conclusion
Scintillator Fiber light guide Photodetector
εacceptεcouple1
εtransmitεcouple2
• Introduction• Properties• Applications• Conclusion
DETECTOR CONFIGURATION
Plastic scintillating fibers offer a good alternative to regular plastic scintillators:
• Increased light capture due to cladding (>internal reflection) • The cladding is also water-equivalent/ no perturbation
ORIGINAL PROTOTYPE
• High sensitivity (PMT)• Remove Cerenkov with background subtraction
Beddar, A S, Mackie, T R, and Attix, F H, "WaterBeddar, A S, Mackie, T R, and Attix, F H, "Water--equivalent plastic scintillation detectors for highequivalent plastic scintillation detectors for high--energy energy beam dosimetry: I. Physical characteristics and theoretical consbeam dosimetry: I. Physical characteristics and theoretical considerations," Phys. Med. Biol. 37: 1883iderations," Phys. Med. Biol. 37: 1883--1900, 1992. 1900, 1992.
• Introduction• Properties• Applications• Conclusion
LINEARITY
Light production is proportional to the dose deposited
• Introduction• Properties• Applications• Conclusion
DOSE RATE INDEPENDENCE
Not affected by dose rate variations
• Introduction• Properties• Applications• Conclusion
ENERGY DEPENDENCE
• Detecting volumes: intermediate cavities• Best energy dependence relative to other dosimeters
used in radiotherapy
• Introduction• Properties• Applications• Conclusion
Beddar A S, Mackie T R, Beddar A S, Mackie T R, AttixAttix F H, "WaterF H, "Water--equivalent plastic scintillation detectors for highequivalent plastic scintillation detectors for high--energy beam dosimetry: I. energy beam dosimetry: I. Physical characteristics and theoretical considerationsPhysical characteristics and theoretical considerations““, Phys. Med. Biol. 37: 1883, Phys. Med. Biol. 37: 1883--1900, 1992. 1900, 1992.
TEMPERATURE
No temperature dependence between 18ºC and 30ºC
• Introduction• Properties• Applications• Conclusion
CERENKOV EMISSION
Although the light spectrum due to Cerenkov emission is differenAlthough the light spectrum due to Cerenkov emission is different t from the scintillation spectrum, de Boer et al have shown that sfrom the scintillation spectrum, de Boer et al have shown that spectral pectral filtration is not sufficient to remove completely the Cerenkov lfiltration is not sufficient to remove completely the Cerenkov light.ight.
• In plastics like polystyrene, electrons with energies 146 keV and higher produce a blue light due to Cerenkov emission
• This light is superposed on the scintillation signal• If a large amount of clear optical fiber is in the radiation
field, Cerenkov emission can be significant (>15 %)
de Boer S F, Beddar A S Rawlinson J F "Optical filtering and spde Boer S F, Beddar A S Rawlinson J F "Optical filtering and spectral measurement of radiationectral measurement of radiation--induced light in plastic scintillator dosimetryinduced light in plastic scintillator dosimetry““, Phys Med , Phys Med BiolBiol 38: 94538: 945--958, 1993. 958, 1993.
• Introduction• Properties• Applications• Conclusion
CERENKOV EMISSIONTechniques to remove the Cerenkov effect:
Background subtraction
Dsci ∝M −Mcrkv
Simple filtering
Find the optimal S(λ)that max. N(λ) and min. 1/λ2
Chromatic filtration
Note: requires 2 optical fibers
With 2 different wavelength filter S1(λ) and S2(λ),
mi = kDsciN(λ) +Cλ2
⎛ ⎝ ⎜
⎞ ⎠ ⎟ e−x / l(λ)
0
∞∫ Si(λ)dλ i = 1,2
⇒ Dsci = Am1 + Bm2
Where A and B are fixed by calibration under 2 different conditions
FontbonneFontbonne J M, J M, IltisIltis G, Ban G, G, Ban G, BattalaBattala A, A, VernhesVernhes J C, J C, TillierTillier J, J, BellaizeBellaize N, le N, le BrunBrun C, C, TamainTamain B, B, Mercier K, Mercier K, MotinMotin J C, "Scintillating fiber dosimeter for radiation therapy J C, "Scintillating fiber dosimeter for radiation therapy accleratoracclerator““, IEEE Trans. , IEEE Trans. NuclNucl. . Sci. 49: 2223Sci. 49: 2223--2227, 2002. 2227, 2002.
• Introduction• Properties• Applications• Conclusion
• Commercialized product• Rugged and simple to construct• Good stability and reproducibility• Independent of temperature and pressure• No high-voltage bias• Remote operation and reset• Easily used by trained technical staff• Cost effective
Beddar S, Beddar S, ““A new scintillator detector system for the quality assurance of A new scintillator detector system for the quality assurance of 6060Co and highCo and high--energy therapy energy therapy machinesmachines””. Phys Med . Phys Med BiolBiol 39: 25339: 253––263, 1994. 263, 1994.
A DAILY QA DETECTOR SYSTEM • Introduction• Properties• Applications• Conclusion
Stability of the QA device over time
Beddar A S, Beddar A S, ““A new scintillator detector system for the quality assurance of A new scintillator detector system for the quality assurance of 60Co and high60Co and high--energy energy therapy machinestherapy machines””, Phys Med , Phys Med BiolBiol 39: 25339: 253––263, 1994. 263, 1994.
A DAILY QA DETECTOR SYSTEM • Introduction• Properties• Applications• Conclusion
SCINTILLATION FIBER ARRAYPROTOTYPE
• Alta U2000c• Interline• Color• Cooled @ -20º
• Fixed focal• f/# = 1.4
• PMMA
• BCF12 (blue)
• Subtract Cerenkov contamination with chromatic removalArchambault L, Beddar S, Archambault L, Beddar S, GingrasGingras L, Roy R, Beaulieu L, "Measurement accuracy and Cerenkov L, Roy R, Beaulieu L, "Measurement accuracy and Cerenkov removal for high performance, high spatial resolution scintillatremoval for high performance, high spatial resolution scintillation dosimetryion dosimetry““, Med. Phys. 33: 128, Med. Phys. 33: 128--135, 135, 2006. 2006.
• Introduction• Properties• Applications• Conclusion
LacroixLacroix F, Archambault L, F, Archambault L, GingrasGingras L, Beddar AS, and Beaulieu L. Clinical prototype of a plastic wL, Beddar AS, and Beaulieu L. Clinical prototype of a plastic waterater--equivalent scintillating fiber dosimeter matrix for IMRT QA applequivalent scintillating fiber dosimeter matrix for IMRT QA applications, Med Phys 35 (2008) 3682ications, Med Phys 35 (2008) 3682--3690.3690.
• Introduction• Properties• Applications• Conclusion
SCINTILLATION FIBER ARRAYDETECTOR FOR QA
30
50
70
90
110
130
150
0 25 50 75 100 125 150 175 200 225 250 275 300
Depth (mm)
Rel
ativ
e D
ose
Scint. 10x10CC13 10x10
• Introduction• Properties• Applications• Conclusion
DEPTH DOSE
1.6%
LacroixLacroix F, Archambault L, F, Archambault L, GingrasGingras L, Beddar AS, and Beaulieu L. Clinical prototype of a plastic wL, Beddar AS, and Beaulieu L. Clinical prototype of a plastic waterater--equivalent scintillating fiber dosimeter matrix for IMRT QA applequivalent scintillating fiber dosimeter matrix for IMRT QA applications, Med Phys 35 (2008) 3682ications, Med Phys 35 (2008) 3682--3690.3690.
• Introduction• Properties• Applications• Conclusion
BEAM PROFILE
LacroixLacroix F, Archambault L, F, Archambault L, GingrasGingras L, Beddar AS, and Beaulieu L. Clinical prototype of a plastic wL, Beddar AS, and Beaulieu L. Clinical prototype of a plastic waterater--equivalent scintillating fiber dosimeter matrix for IMRT QA applequivalent scintillating fiber dosimeter matrix for IMRT QA applications, Med Phys 35 (2008) 3682ications, Med Phys 35 (2008) 3682--3690.3690.
0
20
40
60
80
100
-175 -125 -75 -25 25 75 125 175Position (mm)
Rel
ativ
e D
ose
CC13 20x20 CC13 10x10CC13 4x4Scint. 20x20Scint. 10x10Scint. 4x4
EBRT
Accurate for electron measurements:
• Introduction• Properties• Applications• Conclusion
Depth in Water (cm)
Dep
th D
ose
(%)
Depth in Water (cm)
6 MeV 18 MeV
Beddar, A. S., Mackie, T. R., and Attix, F. H., "WaterBeddar, A. S., Mackie, T. R., and Attix, F. H., "Water--equivalent plastic scintillation detectors for highequivalent plastic scintillation detectors for high--energy beam dosimetry: II. Properties and measurements," Phys. Menergy beam dosimetry: II. Properties and measurements," Phys. Med. Biol. 37, 1901ed. Biol. 37, 1901--1913 (1992) c1913 (1992) c
SPATIAL RESOLUTION • Introduction• Properties• Applications• Conclusion
Beddar, A. S., Mackie, T. R., and Attix, F. H., "WaterBeddar, A. S., Mackie, T. R., and Attix, F. H., "Water--equivalent plastic scintillation detectors for highequivalent plastic scintillation detectors for high--energy beam dosimetry: II. Properties and measurements," Phys. Menergy beam dosimetry: II. Properties and measurements," Phys. Med. Biol. 37, 1901ed. Biol. 37, 1901--1913 (1992) c1913 (1992) c
SPATIAL RESOLUTION • Introduction• Properties• Applications• Conclusion
Archambault L, Beddar S, Archambault L, Beddar S, GingrasGingras L, Lacroix F, Roy R, Beaulieu L, Lacroix F, Roy R, Beaulieu L, "L, "WaterWater--equivalentequivalentdosimeterdosimeter arrayarray for for smallsmall--fieldfield externalexternal beambeam radiotherapyradiotherapy", Med ", Med PhysPhys 34: 158334: 1583––1592, 1592, 2007.2007.
A12A16Scint Diode
DOSIMETRY FOR STEREOTACTICRADIOSURGERY
• Introduction• Properties• Applications• Conclusion
DOSIMETRY FOR STEREOTACTICRADIOSURGERY
• Introduction• Properties• Applications• Conclusion
Beddar S, Beddar S, KinsellaKinsella T J, T J, IkhlefIkhlef A, Sibata C H, A, Sibata C H, ““Miniature 'ScintillatorMiniature 'Scintillator--FiberopticFiberoptic--PMT' detector PMT' detector system for the dosimetry of small fields in stereotactic system for the dosimetry of small fields in stereotactic radiosurgeryradiosurgery””, IEEE Trans. Nucl. Sci. 48: , IEEE Trans. Nucl. Sci. 48: 924924--928, 2001.928, 2001.
MONTE CARLO SIMULATIONS FOR PROTON BEAMS• Use Geant4 for a complete simulation
– Electromagnetic and hadronic processes– Production and tracking of visible light (scintillation and
Cerenkov)• Understand the behavior of a plastic scintillator
irradiated with protons• Optimize light collection efficiency
• Introduction• Properties• Applications• Conclusion
MONTE CARLO SIMULATIONS OF PROTON BEAMS
Water equivalence preserved for most clinical proton energies
• Introduction• Properties• Applications• Conclusion
Archambault L, Archambault L, PolfPolf J C, Beaulieu L, Beddar S, J C, Beaulieu L, Beddar S, ““Characterizing the response of miniature Characterizing the response of miniature scintillation detectors when irradiated with proton beamsscintillation detectors when irradiated with proton beams””, Phys Med , Phys Med BiolBiol 53: 186553: 1865--1876, 2008.1876, 2008.
Monte Carlo accurately predicts quenching and can therefore be used for determining correction factors
0.0
0.2
0.4
0.6
0.8
1.0
Rel
ativ
e D
ose
-10 -8 -6 -4 -2 0 2
Unquenched – ion chambermeasurements & simulation
Quenched – scintillationmeasurements & simulation
Depth (cm)
QUENCHING (PROTONS ONLY) • Introduction• Properties• Applications• Conclusion
SCINTILLATION SCREEN
• Rapid, but requires correction for light propagation• Similar to a-Si dosimetry, but takes advantage of the
water equivalence of the plastic scintillator• Not as accurate as point-like scintillation dosimeters• See Petric et al. for more information
PetricPetric M P, M P, RobarRobar J L, Clark B G, J L, Clark B G, ““Development Development and characterization of a tissue equivalent plastic and characterization of a tissue equivalent plastic scintillator based dosimetry system,scintillator based dosimetry system,”” Med Phys 33: Med Phys 33: 9696--105, 2006.105, 2006.
• Introduction• Properties• Applications• Conclusion
BRACHYTHERAPY
• Scintillator irradiated with low energy (< 125 keV) photons is less water equivalent than megavoltage photons
• Chemical composition of plastic scintillator may be changed for a better response (Williamson et al., Kirov et al.)
• Kirov et al. have developed a 3D scintillation detector for the characterization of Ru-106 eye plaques
Kirov A S, Kirov A S, PiaoPiao J Z, J Z, MathurMathur N K, Miller T R, N K, Miller T R, DevicDevic S, S, trichtertrichter S, S, ZaiderZaider M, M, SoaresSoares C G, C G, LoSassoLoSasso T, T, ““ThreeThree--dimensional scintillation dimensional scintillation dosimetry method: test for a 106Ru plaque dosimetry method: test for a 106Ru plaque applicatorapplicator””, Phys Med , Phys Med BiolBiol 50: 306350: 3063--3081, 3081, 2005.2005.
see also Williamson J F, Dempsey J F, Kirov A S, Monroe J I, see also Williamson J F, Dempsey J F, Kirov A S, Monroe J I, BinnsBinns W R, W R, HedtjHedtjäärnrn, , ““Plastic scintillator Plastic scintillator response to lowresponse to low--energy photonsenergy photons””, Phys Med , Phys Med BiolBiol 44: 85744: 857--871, 1999.871, 1999.
• Introduction• Properties• Applications• Conclusion
IN VIVO DOSIMETRYFOR PROSTATE RADIOTHERAPY
• Direct measurement of the dose delivered to organs, critical structures, and within the vicinity of a tumor is feasible and can be used to verify treatment plan delivery.
• We believe this can be done using an in vivoscintillation detector composed of multiple probes arranged in an application-specific design that can monitor true in vivo dose in real time.
NCI Grant No. 1R01CA120198-01A2
• Introduction• Properties• Applications• Conclusion
Adam Melancon (MDACC)
INTRAFRACTIONAL MOTION • Introduction• Properties• Applications• Conclusion
Adam Melancon (MDACC)
INTRAFRACTIONAL MOTIONGASEOUS BUILDUP
• Introduction• Properties• Applications• Conclusion
Before Before TxTx After After TxTx
OUR GOAL: ACCURACY & PRECISION
Prostate
Detector
• Introduction• Properties• Applications• Conclusion
RECTAL DETECTOR
Rectal balloons are part of the standard treatment for radiation therapy at MDACC
Capillaries where scintillation probescan be inserted
• Introduction• Properties• Applications• Conclusion
URETHRAL DETECTOR
Foley Catheter
Urethral detector consisting of a capillary containing line and point probes for measurement of dose at the urethra. The outer diameter of the catheter is 2 mm (6F).
• Introduction• Properties• Applications• Conclusion
CLINICAL INNOVATION: REAL-TIME HDR DOSIMETRY
• Introduction• Properties• Applications• Conclusion
#1 #2#3
#4 #5 #6
#7#8 #9
#10
#11#12
A single PSD is placed in an empty standard prostate plastic catheter. The remaining 12 catheters are used for planning and delivery The PSD is read in real-time to monitor the treatment delivery.
CLINICAL INNOVATION: REAL-TIME HDR DOSIMETRY
• Introduction• Properties• Applications• Conclusion
13.7±274.54Scintillator*274.5PLATOcGy
* Results of 5 measurements
SUMMARY
• Scintillation dosimeters possess a unique set of advantages
– Water equivalence, linear dose response, energy and temperature independence, spatial resolution, etc…
• Several types of scintillation detectors have been developed in the last 15 years
• Main applications:– Conventional EBRT (photons and electrons)– Quality assurance device (daily and IMRT)– Radiosurgery– Protons– Brachytherapy
• Introduction• Properties• Applications• Conclusion
CONCLUSIONS
• Scintillation dosimetry will be increasingly used in radiotherapy.
• Their advantages make them ideal for measuring complex dose distributions such as those produced by IMRT.
• They can compete with other dosimeters in terms of measurement accuracy, convenience and can be economical.
• Introduction• Properties• Applications• Conclusion
ACKNOWLEDGEMENTS
L. Archambault L. Archambault F.H. AttixF.H. AttixS.F. de BoerS.F. de BoerT.M. BriereT.M. BriereL. Gingras L. Gingras M. M. GuillotGuillotA. Ikhlef A. Ikhlef T.J. T.J. KinsellaKinsellaF. F. LacroixLacroix
T.R. MackieJ.F. RawlinsonJ.F. RawlinsonR. RoyR. RoyC.H. SibataC.H. SibataJ.V. J.V. SiebersSiebersF. F. ThThéériaultriault--ProulxProulxM. VilleneuveM. VilleneuveN. N. SuchowerskaSuchowerskaS. LawS. Law
…… and all others who have contributed to the field of and all others who have contributed to the field of scintillation dosimetryscintillation dosimetry
CoCo--authorsauthors