Large-area Two-Dimensional Thermoluminescence Dosimetry System in Ion Beam Quality Assurance

Transcription

1 Large-area Two-Dimensional Thermoluminescence Dosimetry System in Ion Beam Quality Assurance J. Gajewski1, M. Kłosowski1, S. Greilich2, P. Olko1 Institute of Nuclear Physics, Kraków, Poland German Cancer Research Center, Heidelberg, Germany rd Annual Conference of the Particle Therapy Co-operative Group (PTCOG 53) 13th June, 2014, Shanghai, China

2 Introduction Position (X,Y) Size (sigma) Presently used systems: Kodak EDR2 Gafchromic EBT2 IBA LynX (IBA Dosimetry) Weaknesses low resolution disposable non-linear dose response Symmetry (eccentricity) The goal is to test 2D TLD system for measurements of spot parameters

3 Outline of the presentation Materials and methods 2D TL Reader TL foils FlatView software Dose and beam quality response National Center for Hadron Therapy at Institute of Nuclear Physics in Kraków Results Comparison with Kodak EDR2 Comparison with IBA LynX Application in scanning gantry acceptance tests in Kraków IBA dedicated Gantry

4 The principle of 2D TL Dosimetry Resolution: 1024 x 1024 px2 (pixel size ~0.2 mm) heater size: 20 x 20 cm2 Automated heating and cooling process easy and safe to use Movable Developed at IFJ by: Mariusz Kłosowski Łukasz Czopyk Paweł Olko Barbara Marczewska

5 TL foils Foil composition: LiF:Mg,Cu,P + ETFE (polymer) Water resistant and flexible Area up to 20 x 20 cm2 Thickness mm Reusable Resolution ~0.2 mm 1mmTLD = 1.64mmH2O Zeff = 8.1 by courtesy of Saveta Miljanic

6 FlatView software for image analysis Automatic image acquisition from TLD reader Noise and geometrical corrections, additional filters Basic analysis: Area histograms Line profiles Specific analysis: Circular shapes analysis Spot parameters Individual Reference Image matching Universal software for image analysis from disparate sources

7 Dose and beam quality response Co-60 6MV X-ray 6MV X-ray 1 p 41.4 MeV (1.4 kev/μm) J. Gajewski et al, The Response of 2D TL Foils After Doses of Co-60 Gamma-Ray, 6MV X-Ray and 60 MeV Proton Beams Applied In Radiotherapy, Acta Physica Polonica B, vol 6, no. 4, p Kodak EDR2 (Co-60) Gafchromic EBT2 (6MV X-ray) 2D TLD (6MV X-ray) Reinhardt, S., Hillbrand, M., Wilkens, J. J., & Assmann, W. (2012). Comparison of Gafchromic EBT2 and EBT3 films for clinical photon. Medical Physics, 39(August), Dose response of 2D TLD linear up to 20 Gy

8 Methods of spot analysis Sigma from spot profiles Absolute spot distances Relative spot distances Spot positions Relative sigma of X and Y profiles

9 Spot positions and profiles 2D TLD vs. Kodak EDR2 Carbon spot example Difference of relative spot positions measured with Kodak film and 2DTLD foils in relation to Kodak measurement Irradiations made at Heidelberg Ion-Beam Therapy Center Kodak EDR2 film 2D TLD foil Difference of spot sigma measured with Kodak film and 2DTLD foils in relation to Kodak measurement Spot position measured with 2D TLD agree within 1% with those measured with Kodak ERD2 Spot sigma measured with 2D TLD agree with sigma measured with Kodak ERD2 within 10%

10 Spot positions and shapes 2D TLD vs. LynX (IBA Dosimetry) 0º 315º 270º 45º Irradiations made at Proton Beam Therapy Center in Prague Difference of spot positions measured with LynX and 2DTLD 90º Gantry Angle [ ] Difference of spot sigma measured with LynX and 2DTLD 225º 135º 180º Different gantry angle with one TL detector Absolute spot positions consistent with LynX within 0.1 mm Sigma the same within 0.1 mm Gantry Angle [ ]

11 Proton beam matching to X-ray 2D TLD vs. Gafchromic EBT2 Irradiations made at Bronowice Cyclotron Center in Kraków Example of 2DTLD result Circular pattern irradiation Metal ball positioned in isocenter Irradiated ring area Distance between centres of two circles [mm] Det. nr EBT2 2DTLD DP DP D TLD DP-140 Proton beam matches to the X-ray system within mm Results obtained by IBA with Gafchromic films are comparable to those obtained with 2D TLD system

12 Summary and Plans 2D TL dosimetry system has been developed at Institute of Nuclear Physics in Kraków The measurements made at different particle therapy facilities shown that the 2D TLD system is suitable for measurements of spot properties The FlatView software was prepared for analysis of images from 2D TLD system. Images from other systems can be analysed (Gafchromic, LynX, OmniPro I'mRT) The system will be applied for spot quality control of IBA dedicated gantry at National Center for Hadron Therapy at Institute of Nuclear Physics in Kraków

13 Thank you for your attention Special thanks to colleagues from: German Cancer Research Center, Heidelberg Heidelberg Ion-Beam Therapy Center, Heidelberg Institute of Nuclear Physics, Prague Proton Therapy Center, Prague