Upgrade of gamma electron vertex imaging system for high-performance range verifi cation in pencil beam scanning proton therapy

In proton therapy, a highly conformal proton dose can be delivered to the tumor by means of the steepdistal dose penumbra at the end of the beam range. The proton beam range, however, is highly sensitiveto range uncertainty, which makes accurately locating the proton range in the patient difficult. In-vivorange verification is a method to manage range uncertainty, one of the promising techniques beingprompt gamma imaging (PGI). In earlier studies, we proposed gamma electron vertex imaging (GEVI),and constructed a proof-of-principle system. The system successfully demonstrated the GEVI imagingprinciple for therapeutic proton pencil beams without scanning, but showed some limitations underclinical conditions, particularly for pencil beam scanning proton therapy. In the present study, weupgraded the GEVI system in several aspects and tested the performance improvements such as forrange-shift verification in the context of line scanning proton treatment. Specifically, the system showedbetter performance in obtaining accurate prompt gamma (PG) distributions in the clinical environment. Furthermore, high shift-detection sensitivity and accuracy were shown under various range-shift conditionsusing line scanning proton beams. KCI Citation Count: 0