oppytically stimulated luminescence (osl) dosimetry in radiotherapy

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

STORAGE


READOUT

Light emissionLight emission (e.g., blue, UV)

Thermal ti l tistimulation

(heating)


READOUT

Light stimulation(e.g., green) Light emissionLight emission

(e.g., blue, UV)


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

OSL dosimetersOSL dosimeters

Dot nanoDot

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.

DoseDose--rate dependencerate dependence

6 MV6 MV


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 dependenceOSL LET dependenceOSL LET dependenceOSL LET dependence

Yukihara et al. 2006

OSL LET dependence in carbon OSL LET dependence in carbon bbbeambeam

Reft, Med. Phys. 36(5), 1690-9, 2009

Directional dependenceDirectional dependence


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


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


In vivo dosimetryIn vivo dosimetryyy

J Danzer* et al AAPM 2007

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


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


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.

Thank youThank youThank youThank you

Energy dependenceEnergy dependenceAl2O3:C Zeff=10.2

water Zeff=7.2

LMLM--OSL readout methodOSL readout methodLMLM OSL readout methodOSL readout methodni

tsar

bitr

ary

unLM

-OSL

Time (s)

oppytically stimulated luminescence (osl) dosimetry in radiotherapy

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