SU-E-T-601: Patient Specific QA Check for Radiotherapy with Carbon Beam at SAGA HIMAT.

PURPOSE: To verify a patient specific QA for a prescribed dose per monitor unit (MU) and range check of carbon ion radiotherapy with a beam wobbling method at SAGA HIMAT.

METHODS: The dose distribution in a water phantom was recalculated with a treatment plan made by XiO-N (Mitsubishi Electric Corporation, Tokyo). The depth dose distributions at central axis were compared with measurements using pinpoint ionization chamber (PTW31014). Measured data were analyzed for dose and distance difference with criteria of 3% and 2mm. To check for the MU and range, analysis data were used at center and distal end of a spread out bragg peak (SOBP) depth, respectively.

RESULTS: Treatment plan of 1400 beams in 500 patients were used for analysis. The pass rate of the MU and range was about 98% and 74%, respectively. The rate of both was 73%. The plan data passed only the MU check were verified depth dose profile. The data passed only the range and failed of both were compared depth dose distributions at off axis. If it was failed, we discussed with physicians.

CONCLUSION: Most of patient specific QA check for a prescribed MU and range check at SAGA HIMAT were passed.