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Optically Stimulated Luminescence p y(OSL) dosimetry in radiotherapy
Joanna E.Cygler1 and Eduardo Yukihara2yg
1The Ottawa Hospital Regional Cancer Centre, Ottawa, Canada2Department of Physics, Oklahoma State University, Stillwater, Oklahoma
The Ottawa L’HopitalHospital d’OttawaHospital d OttawaRegional Cancer Centre
DisclosureDisclosureDisclosureDisclosure
The authors have received research support from Landauer Incsupport from Landauer Inc.
OutlineOutline• Principles of OSL dosimetry • OSL readers and stimulation methods• Optically Simulated Luminescence Dosimeters (OSLDs)• Optically Simulated Luminescence Dosimeters (OSLDs)• Dosimetric characteristics of Al2O3:C OSLDs for
radiotherapy applications– Environmental corrections– Linearity of dose response– Dose-rate dependence– Energy dependence– Directional dependence– Fadingg
• Advantages and disadvantages• Clinical dosimetry applications
Summary• Summary
OSL dosimetry OSL dosimetry -- IntroductionIntroductionOSL dosimetry OSL dosimetry IntroductionIntroduction
OSL known for more than 50 years• OSL known for more than 50 years
• Widely used in luminescence dating
• Highly sensitive Al2O3:C introduced in 90’s
• Developed for personal dosimetry at Developed for personal dosimetry at
Oklahoma State University
OSL dosimetry OSL dosimetry -- IntroductionIntroductionOSL dosimetry OSL dosimetry IntroductionIntroduction
• Used in the LuxelTM and Used in the Luxel and InLightTM dosimetry systems (Landauer Inc.)
• >1.5 million users (25% of world market)
• Used in space by NASA• Starting to be adopted in g p
radiotherapy and diagnostic radiology
LuxelTM (Landauer Inc.)
Introduction to luminescence Introduction to luminescence dosimetrydosimetry
EXPOSURE
Radiation
Radiation sensor(insulating crystal)\
Introduction to luminescence Introduction to luminescence d i td i tdosimetrydosimetry
READOUT
Light emissionLight emission (e.g., blue, UV)
Thermal ti l tistimulation
(heating)
Introduction to luminescence Introduction to luminescence d i td i tdosimetrydosimetry
READOUT
Light stimulation(e.g., green) Light emissionLight emission
(e.g., blue, UV)
Introduction to luminescence Introduction to luminescence d i td i tdosimetrydosimetry
READOUT
Optically Stimulated Luminescence detectors (OSLD )
Light stimulation(e.g., green) Light emission(OSLDs):
Al2O3:C (TLD500)Light emission (e.g., blue, UV)
Thermal ti l ti
Thermoluminescence detectors (TLDs): stimulation
(heating)(TLDs):LiF:Mg,Ti, CaF2
OSL readout systemOSL readout systemOSL readout systemOSL readout system
PMTLight source
Detection filters
OSL
Detection filters
StimulationStimulation filters
Dosimeter(OSLD)
Methods of OSL stimulationMethods of OSL stimulationMethods of OSL stimulationMethods of OSL stimulation
• CW-OSL (continuous wave OSL)( )
POSL ( ls d OSL)• POSL (pulsed OSL)
• LM-OSL (linearly modulated OSL)
CWCW--OSL readout methodOSL readout methodCWCW OSL readout methodOSL readout method
400
300constantun
its)
200
constant
arbi
tratry
u
100
W-O
SL (a
0 100 200 300 400 500 6000
CW
Time (s)
POSL readout methodPOSL readout methodPOSL readout methodPOSL readout methodon
inte
nsity
0 50 100 150 200 250 300 350 400 450 500 550
Stim
ulat
io
on
Stat
e
off
Gat
e S
0 50 100 150 200 250 300 350 400 450 500 550
Time (s)
Commercial OSL dosimetry systems Commercial OSL dosimetry systems (L d I )(L d I )(Landauer Inc.)(Landauer Inc.)
InLightTM
• One manufacturer
• Two types of readers MicroStarTMTwo types of readers
• CW- stimulation readout
D t t f L d • Detectors from Landauer Inc. only
www.Landauer.com, www.osldosimetry.com
Characteristics of AlCharacteristics of Al22OO33:C OSLDs :C OSLDs for radiotherapy applicationsfor radiotherapy applications
Ideal detector•Small size
•Good reproducibility
•None or well defined environmental correctionsNone or well defined environmental corrections
•Dose linearity
D t i d d•Dose rate independence
•Energy independence
•No directional dependence -isotropic response to radiation
OSLD reproducibility OSLD reproducibility
40
30
35
% n
umbe
r
20
25
5
10
15
Relative sensitivity
0
5
0.94 0.96 0.98 1.00 1.02 1.04 1.06 1.08
Courtesy of C. Yahnke
y
Environmental correctionsEnvironmental correctionsEnvironmental correctionsEnvironmental corrections
Temperature dependence• During irradiation• During irradiation• During readout
OSL temperature dependence OSL temperature dependence during irradiationduring irradiationduring irradiationduring irradiation
Jursinic, Med. Phys. 34(12), 4594-4604, 2007
Temperature effect during OSL Temperature effect during OSL ti l ti ( d t)ti l ti ( d t)stimulation (readout)stimulation (readout)
Andersen et al, Radiation Measurements, 43, 948 – 9532008
OSLD dose linearity, 6 MVOSLD dose linearity, 6 MV
1000
1200
800
1000y
units
)
400
600
g (a
rbitr
ary
200
400
Rdg
00 100 200 300 400 500
Dose / cGyDose / cGy
Viamonte et al Med. Phys. 35(4), 1261-6, 2008
OSL dose supralinearity at OSL dose supralinearity at hi h dhi h dhigher doseshigher doses
Schembri V and Heijmen BJM. Med. Phys. 2007; 34:2113-2118.
Absorbed dose energy dependence f(Q) for Al2O3:C and LiF TLD
QCoOAl F
32
QCoLiF FEnergy Mean Energy
(keV)Ratio
60Co gamma rays 1250 1.000 1.000 1.00
/LiFOAl 32
50 kV X-rays 29 3.219 ± 0.3% 1.463 2.20
100 kV X-rays 60 2.861 ± 0.3% 1.376 2.08
150 kV X-rays 105 1.607 ± 0.3% 1.245 1.29
250 kV X-rays 170 1.449 ± 0.3% 1.192 1.19
6 MV X 2020 0 990 ± 0 3% 0 987 1 006 MV X-rays 2020 0.990 ± 0.3% 0.987 1.00
10 MV X-rays 3050 0.983 ± 0.3% 0.976 1.00
15 MV X-rays 4180 0.980 ± 0.3% 0.976 1.00
25 MV X-rays 6600 0.973 ± 0.3% 0.976 1.00
Mobit et al. Radiat Prot Dosim 119, 497-499, 2006).
Absorbed dose sensitivity relative Absorbed dose sensitivity relative yyto 6 MV photons as a function of to 6 MV photons as a function of
beam quality for Albeam quality for Al OO :C:Cbeam quality for Albeam quality for Al22OO33:C:C
OSLD 60Co: Viamonte et al 2008, Reft, 2009
Jursinic, Med. Phys. 34(12), 4594-4604, 2007 Yukihara et al, Phys Med Biol 53, R351-R379, 2008
OSL LET dependence in carbon OSL LET dependence in carbon bbbeambeam
Reft, Med. Phys. 36(5), 1690-9, 2009
Fading of OSL signal Fading of OSL signal Fading of OSL signal Fading of OSL signal 1.2
1.0
0 80.8
0.6
)/Q
(1min)
0.2
0.4
Q(t)
Time / min2 4 6 8 10 12
00
Reft, Med. Phys. 36(5), 1690-9, 2009
Fading of signal with timeFading of signal with timeFading of signal with timeFading of signal with time
kteBA)t(S
Jursinic, Med. Phys. 34(12), 4594-4604, 2007
OSL dosimetryOSL dosimetryAd t Ad t di d tdi d t
Advantages Disadvantages
Advantages Advantages vs. vs. disadvantagesdisadvantagesAdvantages• High sensitivity• High precision• Size
Disadvantages• Sensitivity to light• Non-tissue equivalent – energy
d d• Size• Convenience• Readout flexibility• Fast non destructive readout
dependence• Only 1 material currently
available (only 1 provider)• Fast, non-destructive readout• Narrow stimulating beams may
could allow dose mapping• No significant fading dose • No significant fading - dose
storage• No need for annealing• Although it can be bleached Although it can be bleached
and re-used if needed*
Clinical dosimetry applicationsClinical dosimetry applications
• In phantomIn phantom
− PDD
ROF− ROF
−IMRT QA
• In vivo
−external beam (entrance, exit dose)
−brachytherapy
6060Co relative output factorCo relative output factor
Viamonte et al Med. Phys. 35(4), 1261-6, 2008
The small AlThe small Al22OO33:C crystals:C crystalsThe small AlThe small Al22OO33 C crystalsC crystals
M Aznar Phys Med Biol 49 1655–69 2004
courtesy of C. Andersen, Risø
M. Aznar, Phys. Med. Biol. 49, 1655 69, 2004
Riso OSLRiso OSL--optical fibre dosimetry optical fibre dosimetry ttsystemsystem
tdecOSL τt
dtecOSL t
t f C A d RiBoth RL and OSL signals are seen
th t courtesy of C. Andersen, Risøon the computer screenM. Aznar, Phys. Med. Biol. 49, 1655–69, 2004
In In -- vivo measurements for vivo measurements for b h h b h h a brachytherapy patienta brachytherapy patient
• Cervix recurrence just above the vaginal wall• Cervix recurrence just above the vaginal wall
• Treated in 15 needles – OSL crystals in 2 needles
• 30 Gy delivered in 50 pulses over 50 hours
courtesy of C. Andersen, Risø
Stability of the Risø systemStability of the Risø system• OSL measured pulse dose between each pulse• RL signal integrated to give pulse doseg g g p• TPS with +/- 1 mm uncertainty
courtesy of C. Andersen, Risø
Remote dosimetry applicationRemote dosimetry applicationRemote dosimetry applicationRemote dosimetry application
• Recently evaluated by Radiological Physics Center (RPC) for remote dosimetry applicationy pp
• OSL dosimeters were irradiated in an acrylic mini-phantomp
• Results indicated that the precision of OSL dosimeters is comparable to that provided by dosimeters is comparable to that provided by TLDs used for remote dosimetry
SummarySummary• OSLD have linear dose response and good
reproducibility (screened) for standard clinical doses • Minimal energy dependence in megavoltage photon
beamsbl f d • Suitable for accurate dosimetric measurements
– individual calibration factorsC b d i i t f li i l li ti• Can be used in variety of clinical applications– surface dose detectors
t d it d t– entrance and exit dose measurements– brachytherapy
dose mapping– dose mapping• Are suitable for remote dosimetry
AcknowledgementsAcknowledgementsAcknowledgementsAcknowledgements
• Claus Andersen, Risø National Laboratory
• Cliff Yahnke, Landauer Inc.