P03.07.B DOSIMETRIC ACCURACY OF CYBERKNIFE STEREOTACTIC RADIOSURGERY FOR BENIGN PERIOPTIC TUMOR

Abstract

Abstract BACKGROUND The Cyberknife (CK) SRS delivers a highly focused ablative radiation dose to tumors to effectively control tumors with minimized radiation toxicity to surrounding normal tissues. This study aimed to evaluate the dosimetric accuracy of Cyberknife (CK) for benign perioptic tumor using patient specific head phantom. METHODS Patient specific head phantoms was fabricated using a 3D-printer to be dosimetrically equivalent to actual target regions of benign perioptic tumor case treated via Cyberknife radiosurgery. Head phantom QA plan was produced using the original CK contour set (target and optic nerve). The head phantom containing the Gafchromic EBT3 film was irradiated using Cyberknife 6D skull tracking method. The dose distributions calculated by MultiPlan Treatment Planning System (version 5.6) was compared with those measured by film dose using gamma analysis method. After moved rotating (1 degree) and translating (1-5mm) the couch table prior to beam delivery, we checked the 6D skull tracking accuracy according to the beam irradiation. RESULTS Gamma passing rates for the 2%/1 mm and 2%/2 mm criteria was found to be 84.11 ± 2.12% and 93.61±1.39% greater than the acceptance criteria 80% and 90%. The difference between measured and calculated dose to the optic nerve in contact with the tumor was less than 3%. CONCLUSION Dosimetric verification with patient-specific head phantoms could be successfully implemented as the evaluation method for CK perioptic tumor radiosurgery delivery with 6D skull tracking system.