Monitoring of Dose Distribution in Photon Therapy with Multiple-Scattering Compton Camera: A Monte Carlo Simulation Study

This study evaluated the performance of a multiple-scattering Compton camera (MSCC) for in vivo monitoring of the dose distribution of therapeutic photons in various phantoms. When 6-MV photons interacted with materials in the phantom, most photons deposited part of their energies on the voxels and were scattered out of the phantom. The 3D distribution of the scattered photons detected by the MSCC was reconstructed by using image processing methods based on Compton kinematics. The optimized design parameters from previous studies were used in the current system. In order to verify the accuracy of dose estimation by using MSCC, the results of depth-dose distribution curves in the phantom were compared with theoretical values calculated by MCNPX for various phantoms. The dose distribution of scattered photons showed similar trends to the deposited dose of incident photons in various phantoms. For realistic visualization, the reconstructed Compton images were combined with Computed Tomography (CT) images of the phantom. The results of this study demonstrated the feasibility of using Compton imaging as a means of monitoring the 3D dose distribution of the therapeutic photons in radiation therapy. The combination of Compton and CT images of the human phantom highlighted the effectiveness of our MSCC for monitoring patient doses in 3D photon therapy.