A Study of The Clinical Viability of A Prototype Compton Camera for Prompt Gamma Imaging Based Proton Beam Range Verification

Abstract We present Compton camera (CC) based PG imaging for proton range verification at clinical dose rates. PG emission from a tissue-equivalent phantom during irradiation with clinical proton beams was measured with a prototype CC. Images were reconstructed of the raw measured data and of data processed with a neural network (NN) trained to identify “true” and “false” PG events. From these images, we determine if PG images produced by the prototype CC could provide clinically useful information about the in vivo range of the proton beams delivered during proton beam radiotherapy. NN processing of the data was found necessary to allow identification of the proton beam path from the PG images. Furthermore, to allow the localization of the end of the proton beam range with a precision of ≤ 3mm with the prototype CC, ~1 x 109 protons would need to be delivered, which is on the order of magnitude delivered for a standard proton radiotherapy treatment field. To obtain higher precision in beam range determination and to allow imaging a single proton pencil beam delivered within the full treatment field, further improvements in PG detection rates by the CC, NN data processing, and image reconstruction algorithms are needed.