Commissioning of 360⁰ Rotational Single Room ProBeam Compact™ (Varian Medical) Pencil Beam Scanning Proton Therapy System

A clinical commissioning of the first 360 rotational compact Varian ProBeam scanning proton pencil beam (Varian Medical, Palo Alto, CA) system was conducted at the South Florida Proton Therapy Institute (SFPTI). The beam dosimetry and characterizations were the vital section used to verify the consistency of the treatment planning system (TPS) outputs. The integrated depth dose curves were acquired with AP CAX in water phantom utilizing a large PTW Bragg peak chamber; the dose output factors measurements were performed by using IBA PCC05 chamber at 1.5 cm water depth applying a single layer 10×10 cm2 beams and 1.1 RBE offset as recommended in TRS 398 report. Widths of the Bragg peaks ranges (Rb80-Ra80) were from 4.07 cm to 30.51 cm for the energy range 70 MeV to 220 MeV. Beam optics such as spot sizes and spot profiles were acquired in-air by using Logos scintillators with a CCD camera and the result data were from 2.33 mm to for 77 MeV to 9.70 mm for 220 MeV. In different field sizes, a comparison between the dose measured using PTW Semiflex and the AcurosPT estimated dose were performed to study the halo effect. All the measured dosimetric parameters showed that the design specifications were well achieved, and the results are suitable for being used as a part of the clinical commissioning and quality assurance program for treating patients.