Detector conceptual design and image reconstruction of a compton camera system used for verification of proton beam dose distribution during proton therapy

Abstract

In this study, a Compton camera imaging system containing several scatterer layers made of Si and a LYSO detector as an absorber layer were designed and simulated using Geant4 code. At first, the efficiency of the system according to the number of scatterer layers was optimized using a gamma point source with various energies. After finding the best structure of the system which contains 10 layers of scatterer, two similar setup of Compton camera were placed perpendicularly to the proton beam around the phantom to take image of the position of the prompt gamma emission resulted from the nuclear interaction of the proton beam with the phantom. In order to imaging the gammas, information such as interaction positions and deposited energies in the scatterers and absorber were recorded by Geant4 code in a root file. Then, using a Compton camera reconstruction algorithm, production position profile of gammas was reconstructed in a MATLAB software. A Comparison of the gamma photon distribution and dose distribution showes that this Compton camera structure is able to measure the proton beam range with less than 7 mm error, which proves the capability of prompt gammas detection for verification of the proton beam range during proton therapy.

Keywords

• proton therapy
• compton camera
• image reconstruction
• geant4 code