Page 50 - Fisica In Medicina n° 1/2017
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^Äëíê~Åí=cáëáÅá= =Characterization of a commercial Optically Stimulated Luminescence dosimetry in High Dose Range for SBRT TreatmentsCA V ALLI1, E. BONANNO1, N. RICOTTONE1, G. PISASALE1, A.N.D’AGOSTINO1, A. GIRLANDO1, C. MARINO11 HUMANITAS-Centro Catanese di Oncologia, CATANIA, ITALYIntroductionA commercial Optically Stimulated Luminescence (OSL) dosimetry system was studied to analyze the possibility of its using for SBRT planning checks. OSL dosimetry system was characterized and tested in high dose range (10-33 Gy). The verification of SBRT treatment plans were performed for two cases regarding lung and spine lesions.Materials and MethodsThe used OSL detectors (NanoDots by Landauer®), matched with readout system MicroSTARiiTM, are made of carbon-doped aluminum oxide Al2O3:C, which show extremely sensitive 40-60 times the TL sensitivity. The characterization of NanoDots included: signal decrease for repeated readings; angular dependence; energy and dose-rate dependence. To establish the relation between “known” delivered dose and reader photomultiplier tube counts, a calibration curve was obtained in the high dose range 10-33 Gy, using a solid RW3 phantom and 10MV energy photon with dose rate of 600 UM/min. The verification of SBRT treatment plans were performed with a Varian TrueBeam 2.5 in RW3 phantom. Plans, regarding lung and spine lesions, were designed and optimized with VMAT technique, 10 FFF energy photon beam and dose rate of 2400 MU/min. They were calculated using the algorithm Acuros XB, version 13.6.23. The Nanodots measurements in RW3 were compared with the pin point values. In fine to perform measurements in anthropomorphic phantom, in a future work, it was evaluated the Nanodot signal caused by CBCT, necessary to improve the positioning accuracy of the phantom before delivering treatment plans.ResultsThe OSLD, exposed to 26 Gy of 10 MV x rays and read for 10 times, showed a maximum deviation from the first reading of 3%. In the range 10-33 Gy, the OSLDs exhibited a linear response with41
