Monte Carlo PET camera modelling for proton range evaluation in proton therapy

Proton therapy is a conformal method for dose delivery in sensitive regions. Offline PET monitoring has been proposed as proton irradiation produces positron emitters such as 11C and 15O [1]. Generally, the proposed methods consist in comparing a Monte Carlo simulation of the positron emitters produced during irradiation with PET measurements. Simulations can be performed using FLUKA [2] or GEANT4 [3] toolkit. Simulations are then convolved by a Gaussian function to account for the PET acquisition process. Such method assumes that the point spread function is constant within the tomograph field of view and that the PET camera is detecting all decay events. However the PET sensitivity is generally close to few percent. The aim is to investigate the contribution of the PET camera modelling either using a Monte-Carlo modelling of the PET camera with GATE [4] toolkit or a Gaussian post filtering of the distribution of the positron emitters for proton monitoring using PET. Experimental data were obtained from two single Bragg peaks in plexiglass. As expected the image statistics differs between the two camera modelling. However the range difference estimation observed was the same in homogeneous phantoms.