Development of 3D Image Reconstruction Method for Beam Online PET Using Irradiation Log Data

In radiation therapy, confirming that the dose distribution has been formed as planned is necessary. The proton dose distribution cannot be measured since it forms the Bragg peak and stops inside the body. The beam online positron emission tomography (PET) onboard the proton therapy device is used to measure the deposited dose distribution by the proton beam. In this study, it is described that the 3D image reconstruction method from an opposed detector data of OnlinePET using the irradiated log data as time-of-flight (TOF) information. This method was confirmed by Monte Carlo simulation using Geant4. In the image obtained by projecting the 3D reconstructed image, it is possible to discriminate between the irradiated and non-irradiated areas. This study demonstrated the possibility of estimating dose distribution from 3D images reconstructed by OnlinePET data.