SU‐E‐T‐361: Three Dimensional Dose Verification in Proton Therapy Using EBT2 Film Array

Purpose: The purpose of this study was to determine whether a three dimensional (3D) film based quality assurance verifies patient‐specific characteristics such as dose distribution, beam range and compensator all together for the passively scattered and uniform scanning proton beams. Methods: Three passively scattered and one uniform scanning proton beams were irradiated to a 3D phantom based on 5 mm thick acrylic slabs with Gafchromic EBT films. The measured 3D dose distributions with proton beam range data were compared with data provided by a protontreatment planning system (TPS). Results: For passively scattered and uniform scanning proton beams, the gamma index for the dose‐distribution comparison for treatment fields was less than 1.0 for 97.2% and 98.1% of total pixels for a 3% dose tolerance and 3 mm distance‐to‐dose agreement, respectively. The experimental proton beam ranges based on 3D film measurement also shows good agreement with the calculated beam ranges from TPS. Conclusions: Our results show that both the dose distribution and the proton range based on 3D EBT film measurement are well matched with planned data. These results indirectly show that 3D film data can be also used for the quality assurance method for physically manufactured proton range compensators.