Spot-Scanning Proton Therapy Patient-Specific Quality Assurance: Results from 309 Treatment Plans

Purpose: We report the outcomes of patient-specific quality assurance (PSQA) for spot-scanning proton therapy (SSPT) treatment plans by disease site. Patients and Methods: We analyzed quality assurance outcomes for 309 SSPT plans. The PSQA measurements consisted of 2 parts: (1) an end-to-end test in which the beam was delivered at the prescribed gantry angle and (2) dose plane measurements made from gantry angle 270°. The HPlusQ software was used for gamma analysis of the dose planes using dose-tolerance and distance-to-agreement levels of 2%, 2 mm and 3%, 3 mm, respectively. Passing was defined as a gamma score