Characterization of proton pencil beam dosimetry and optics of the first 360 degree rotational single room ProBeam Compact™ (Varian Medical)

Among all types of radiotherapy, proton therapy has a great potential to deliver a high dose to the tumor volume with a minimum of dose to the surrounding tissues. Knowledge of therapeutic proton beam characteristics is therefore essential for its successful management in cancer treatment. The purpose of our work is to characterize the dosimetry and optics for the scanning pencil proton beam of the first 360 degree rotational Varian™ ProBeam compact machine at South Florida Proton Therapy Institute. The characterizations used for the commissioning of the provided Treatment Planning System (TPS) and include integrated depth doses (IDDs), absolute dose measurements, and in air spot profiles. The widths of Bragg peaks (R_b80 -R_a80) of IDDs were from 2.33 mm for 70 MeV to 9.70 mm for 220 MeV within the specifications. The surface beam Spot profiles were fitted by single Gaussian distributions using in-house Python code. The average beam spot sigma ranged from 5.89 mm to 3.32 mm for 70 MeV to 220 MeV. Characterization of the pencil scanning proton beam dosimetry and optics are presented in this investigation for Varian first ProBeam Compact™ scanning proton therapy machine.
Key words: beam characterization, commissioning, proton therapy