Two-Dimensional Thermoluminescence Dosimetry System for Proton Beam Quality Assurance

Transcription

1 Two-Dimensional Thermoluminescence Dosimetry System for Proton Beam Quality Assurance Jan Gajewski Institute of Nuclear Physics, Kraków, Poland German Cancer Research Center, Heidelberg, Germany

2 Existing methods used in dosimetry 1-dimensional 2-dimensional Films TL pellet diamond OSL ionization chamber semiconductor diode 3-dimensional Gafchromic Radiographic TLD foils matrix of ionisation chambers strip and pixel semiconductor detectors Fricke gel 3-D scintillators TLD personal badge Strip semiconductor detector 3-D Scintillator

3 Presentation plan Principle of operation 2D Thermoluminescence System TL Foils Readers Dosimetric properties 2D TL system for broad beam Quality Assurance TL foils and LET-painting technique Summary and plans for future

4 The principle of 2-D TL Dosimetry Preparation of foil Irradiation Heating Collection of emitted light Data analysis

5 Dosimetric system TLD foils Two types of foils: LiF:Mg,Cu,P (MCP-2D) CaSO :Dy 4 Water resistance and flexibility Up to 20 x 20 cm2 Reusability Zeff MPC-2D CaSO Resolution below 0.1 mm2 Linearity of dose response: Gy

6 Dosimetric system hardware Laboratory Reader: detector size 50 x 50 mm2 resolution 640 x 480 px2 fully adjustable Laboratory reader Clinical Reader: detector size 200 x 200 mm2 resolution 1024 x 1024 px2 easy and safe to use Clinical reader

7 Dosimetric properties uniformity 20 cm After corrections the uniformity of readouts is around 2%

8 Dosimetric properties dose response f(d) f(d) Linearity Index D was constant within ±5% measured with the Laboratory Reader. For the Clinical Reader it is ±2% Laboratory Reader Clinical Reader f(d) D ±2% f(d) D

9 Dosimetric properties Reproducibility More than 20 equivalent irradiations and readouts Repeatability was found below 2% For previous reader and software it was 5% For radiochromic films it is 1-6% [1] McLaughlin et al. Methods Phys. Res. A 302 [2] N. V. Klassen et al. Med. Phys. 24

10 Beam cross-section in PMMA phantom Diode TLD Irradiations have been performed with 60 MeV proton beam at IFJ PAN in Kraków (AIC-144 cyclotron)

11 Profile of proton beam PBP Experimental setup Beam 25 mm collimator PMMA plates TLD foil Pristine Bragg Peak

12 Profile of proton beam SOBP Experimental setup Beam SOBP wheel PMMA plates TLD foil 25 mm collimator Spread Out Bragg Peak

13 Profile of proton beam summary About 100 beam cross-sections have been measured Measured flatness of dose profiles is in 5-12% range (for diode it is 2-3%) Penumbra is broader with deeper location in phantom (difficult to measure with diode) Experiments conducted at IFJ PAN in Kraków show that 2D TLD system is a good tool for proton beam Quality Assurance Dose profiles of beam measured with TL foils and photodiode are comparable 3D visualisation of a cross-section of a proton broad beam

14 MCP-2D relative efficiency η TL response depends not only on dose but also on ionization density.

15 LET-painting with TL foils Biological response depends on ionisation density. Determination of LET is very important for ion radiotherapy. The idea Set of two foils: MCP-2D + CaSO4:Dy Beam MCP-2D CaSO4:Dy Difference in relative efficiency Energy response for CaSO4:Dy foils needs to be verified

16 Plans for future Incoming experiments (HIT-Heidelberg) Energy response for 12 C and p+ ions Tests of QA of scanning beam Calibration curve for dose/let dosimetry Validation of the dose/let response in clinical conditions Other TL foils properties: transparency, angular response, fading, etc. 2D TLD system will be used for QA of therapeutic scanning beam at Bronowice Cyclotron Center in Kraków (C-235 IBA cyclotron)

17 Thank You for Your attention