SU‐C‐BRCD‐04: Development of An Efficient and Effective Patient Specific QA Program for IMPT

Purpose: Intensity modulated proton therapy (IMPT) patient specific quality assurance (QA) program based on measurement alone could be very time consuming due to highly modulated dose distributions of IMPT fields. In this work, we present our efforts for developing an efficient and effective patient specific QA program for IMPT. Methods: The improved QA program, based on a previously reported one for single field uniform dose (SFUD), consists of three components: measurements, independent dose calculation and analysis of patient specific treatment delivery log files. Measurements included two‐dimensional (2D) measurements for each field delivered at the planned gantry angles with electronic medical record (EMR) system in the QA mode and the accelerator control system (ACS) in the treatment mode and additional depths for each field with ACS in physics mode without using the EMR. Dose distributions in a water phantom for each field were calculated independently using a recently developed in‐ house pencil beam algorithm and compared with the results of TPS. The treatment log file for each field was analyzed in terms of deviations in delivered spot positions from their planned positions using various statistic analysis methods. Results: With the improved patient specific QA program, we are able to verify (1) the dose calculation of TPS, (2) integrity of the data transfer from TPS to EMR to ACS and (3) treatment delivery including dose delivered and spot positions. We estimated that the in‐room measurement time required for each complex IMPT patient like head and neck patients would be less than 2 h. Conclusions: We have developed an efficient and effective QA program for IMPT patients with the equipment and resources available in our clinic.