The CPPM in Marseille developed recently a new demonstrator of small animal CT-scan PIXSCAN2 and an hybrid PET/CT Scan ClearPET/XPAD. The last one is designed to record images for both modalities CT and PET simultaneously. Moreover the use of a new generation of detectors which are not affected by dark noise leads to model the measurements with pure Poisson noise. Proximal algorithms can be used to solve the inverse problem in CT and they demonstrate on real data very good reconstruction properties at low radiation dose in 2D as well as in the context of CT spectral acquisitions. In this talk we will study their properties in the 3D case.