Basic dosimetric data for treatment planning system

Transcription

1 Measurement of relative output factors for Leksell Gamma Knife Perfexion, BrainLAB m3 multi-leaf collimator and Accuray CyberKnife fixed and Iris collimators by PTW MicroDiamond detector J. Novotny Jr. 1,2,3,4, T. Veselsky 1,2,3, V. Pastykova 1,3, P. Kozubikova 1,2,3,, J. Pipek 3, J.P. Bhatnagar 4, M. F. Desrosiers 5, M. S. Huq 4, B. Otáhal 6, L. Knýbel 6 1Na Homolce Hospital, Prague, Czech Republic 2University Hospital in Motol, Prague, Czech Republic 3CTU in Prague, Faculty of Nuclear Sciences and Physical Engineering, Department of Dosimetry and Application of Ionizing Radiation, Prague, Czech Republic 4University of Pittsburgh Cancer Institute, Pittsburgh, USA 5National Institute of Standards and Technology, Gaithersburg, USA 6Faculty Hospital Ostrava, Czech Republic

2 Basic dosimetric data for treatment planning system Output calibration Dose profiles and depth dose curves Relative output factors Other factors (wedge factors, tray factors and etc.)

3 Objective The purpose of this study was to perform measurement of relative output factors for Leksell Gamma Knife Perfexion, BrainLAB m3 multi-leaf collimator and Accuray CyberKnife collimators by PTW MicroDiamond detector and compare results with existing reference data, Monte Carlo simulation and measurements performed by other detectors

4 Crucial parameters and sources of errors Detector positioning and phantom set up Detector volume!!!!

5 Leksell Gamma Knife Perfexion

6 Method and materials Leksell Gamma Knife Perfexion (Na Homolce Hospital) Output factors for 4 mm a 8 mm collimators measured, normalized to 16 mm collimator Measurements performed in Elekta spherical ABS plastic phantom

7 Method and materials Following detectors were used and tested for ROFs measurements: i) two types of micro ion chambers: Exradin A16 (volume cm 3 ) and PTW PinPoint 3D (volume cm 3 ) ii) two types of diode detectors: IBA dosimetry PFD (diameter 2.00 mm, thickness 0.06 mm) and IBA dosimetry SFD (diameter 0.60 mm, thickness 0.06 mm) iii) MicroDiamond PTW detector (volume mm 3 ) iv) three different film dosimeters: Kodak EDR2, Gafchromic EBT and Gafchromic MD-V2-55 v) radiochromic gel dosimeter based on Turnbull blue dye (TB gel) vi) alanine dosimeters: mini pellets (diameter 3.0 mm, thickness 3.0 mm) Independent MC simulation was performed with: Geant4 simulation toolkit (Agostinelli et al 2003), version 9.6

8 ROF Relative output factor for 8 mm collimator Elekta s default value 0.95 Results 8 mm collimator ROF Exradin A16 ion chamber Measured values are compared with measurements of other commonly used dosimeters, with ELEKTA recommended value and Monte Carlo (MC) calculation 0.9 Alanine dosimeter PTW PinPoint 3D ion chamber 0.85 TB gel dosimeter IBA dosimetry PFD diode detector 0.8 IBA dosimetry SFD diode detector Kodak EDR2 film 0.75 Gafchromic MD-V2-55 film Gafchromic EBT film Fig.3: ROF for 8 mm 0.7 collimator Detector Sensitive Volume [mm 3 ] MicroDiamond MC Geant4 calculated

9 ROF Relative output factor for 4 mm collimator Elekta s default value 4 mm collimator ROF 0.85 Exradin A16 ion chamber PTW PinPoint 3D ion chamber 0.8 Alanine dosimeter Detector Sensitive Volume [mm 3 ] TB gel dosimeter IBA dosimetry PFD diode detector IBA dosimetry SFD diode detector Kodak EDR2 film Gafchromic MD-V2-55 film Gafchromic EBT film MicroDiamond MC Geant4 calculated Vendor's recommended value

10 Relative output factor for 8 a 4 mm summary Detector Measured Measured Deviation to vendor s values [%] 4 mm ROF 8 mm ROF 4 mm ROF 8 mm ROF ELEKTA value 0,814 0,900 Exradin A16 ion chamber 0,675 ± 0,009 0,869 ± 0,006-17,1-3,4 PTW PinPoint 3D ion chamber 0,616 ± 0,015 0,873 ± 0,009-24,3-3,0 Alanine dosimeter 0,705 ± 0,004 0,894 ± 0,004-13,4-0,7 TB gel dosimeter 0,746 ± 0,004 0,874 ± 0,005-8,4-2,9 IBA dosimetry PFD diode detector 0,767 ± 0,026 0,890 ± 0,024-5,8-1,1 IBA dosimetry SFD diode detector 0,812 ± 0,029 0,893 ± 0,032-0,2-0,8 Kodak EDR2 film 0,769 ± 0,010 0,904 ± 0,012-5,5 0,4 Gafchromic MD-V2-55 film 0,819 ± 0,009 0,906 ± 0,018 0,6 0,7 Gafchromic EBT film 0,810 ± 0,007 0,917 ± 0,014-0,5 1,9 MC Geant4 calculated 0,826 ± 0,006 0,918 ± 0,004 1,5 2,0 MicroDiamond 0,831 ± 0,001 0,900 ± 0,001 2,1-0,1

11 Varian Clinac 600C + BrainLab m3 micromlc

12 Method and materials Varian Clinac 600C 4MV + BrainLab m3 micromlc (Motol University Hospital) Measurement of output factors performed based on BrainLab commissioning requirements SSD = 100 cm, depth 10 cm Measurement for each collimator performed for 50 MU, comparison with PinPoint ion chamber IBA CC01 as reference detector (used in 2009 during commissioning) Measurements repeated also with diode detector PTW type E

13 Relative Output Factor Relative output factors Varian Clinac 600C + BrainLab m3 micromlc for 6x6 to 100x100 mm2 1,05 BrainLab m3 micromlc Collimator 0,95 0,85 0,75 MicroDiamond 0,65 0,55 Dosimetry Diode E PinPoint Chamber 0, Field Size [mm]

14 Relative output factors Varian Clinac 600C + BrainLab m3 micromlc for 6x6 to 100x100 mm2 Jaws [mm 2 ] MLC [mm 2 ] Mean Response [pc] ROF Ref. Value Difference [%] 98x98 100x , x80 80x80 569,705 0,963 0,947 1,715 60x60 60x60 541,007 0,915 0,889 2,902 44x44 42x42 509,320 0,861 0,832 3,512 20x20 18x18 452,863 0,766 0,737 3,829 14x14 12x12 433,543 0,733 0,689 6,342 8x8 6x6 366,150 0,619 0,487 27,082

15 Accuray CyberKnife

16 Method and materials Accuray CyberKnife (University Hospital Ostrava) Measured relative output factors for 5 50 mm, normalized to reference field of diameter 60 mm for both fixed and Iris collimators Obtained values were compared with configuration data in the treatment planning system (measured by diode detector PTW type E) and composite data (data obtained from vendor based on measured mean values from a few worldwide CyberKnife centers)

17 Relative Output Factor Relative output factors for Accuray CyberKnife for fixed collimators 5 to 50 mm 1,05 CyberKnife Fixed Collimators 1,00 0,95 0,90 0,85 0,80 0,75 MicroDiamond Dosimetry Diode E Composite Data 0,70 0, Field Size [mm]

18 Relative Output Factor Relative output factors for Accuray CyberKnife for Iris collimators 5 to 50 mm 1,05 CyberKnife Iris Collimator 0,95 0,85 0,75 0,65 MicroDiamond Dosimetry Diode E Composite Data 0,55 0, Field Size [mm]

19 Relative output factors for Accuray CyberKnife for fixed collimators 5 to 50 mm Field Size [mm] Mean Response [pc] ROF Difference [%] 60 1, ,137 0,996 0, ,131 0,991 0, ,127 0,988 0, ,122 0,984 0, ,116 0,979 0, ,103 0,967 0, ,079 0,946 0,195 12,5 1,054 0,924 0, ,013 0,888-0,292 7,5 0,960 0,841-0, ,789 0,691-1,915

20 Conclusions PTW MicroDiamond detector appears to be a promising tool for small field dosimetry tasks Measured relative output factors on Leksell Gamma Knife Perfexion, BrainLAB m3 multi-leaf collimator and Accuray CyberKnife fixed and Iris collimators demonstrated good agreement with experimental values determined by other reasonable small field dosimetry detectors, Monte Carlo calculations and reference values

21 DĚKUJI ZA POZORNOST!