Low statistics positron activity reconstruction methods for proton therapy

Positron emission tomography (PET) is one of the most mature techniques for monitoring in ion beam therapy. PET allows to reconstruct the β$^{+}$ activity generated in the patient by the nuclear interaction of the ions. Taking advantage of the spatial correlation between positron emitters created along the ions path and the dose distribution, it is possible to perform a quality control of the treatment. Usually, to reconstruct the activity generated within the irradiated volume, standard 3D PET reconstruction techniques are implemented. In this work, we explore a new reconstruction method (Straight Forward Reconstruction) particularly useful for reconstructing activity distribution generated by mono-energetic pencil beams. The method was validated by measuring the produced activity distribution with the DoPET system. Irradiations performed with mono-energetic pencil beams on phantoms mimicking human tissues were used for this study. Both reconstruction methods reach an accuracy in the reconstruction of the activity distribution width of the order of 1.5 mm for 2⋅10$^{8}$ primaries.