Monte-Carlo simulations for an endoscopic time-of-flight PET detector

The EndoTOFPET-US collaboration develops a novel multimodal device for Ultrasound (US) Endoscopy and Positron Emission Tomography (PET) for detecting and quantifying novel morphologic and functional biomarkers for pancreas and prostate oncology. The detector is based on scintillating crystals with Silicon Photomultiplier (SiPM) read-out, aiming at a time of flight coincidence time resolution of 200 ps and a spatial resolution of ≈ 1 mm to allow for more sensitive, more precise and lower radiation-dose imaging than whole-body devices. We develop a framework, which is built around the Geant4-based simulation toolkit GAMOS, to simulate and reconstruct realistic imaging scenarios with this asymmetric PET detector. Both attenuation and activity DICOM data from e.g. PET/CT scans can be incorporated as phantoms in the simulations. The framework takes care of distributing jobs on a computing grid which is crucial for running large-scale simulations on voxelised phantoms. A set of studies on simple simulated phantoms quantifies the influence of acquisition time and detector movement on the spatial image resolution and overall image quality. A scan time of approx. 10 min and small rotation of around 10° yields a sufficient image quality. We further present qualitative studies of the expected performance of the EndoTOFPET-US detector using voxelised patient PET/CT DICOM datasets. The studies suggest that the endoscopic approach is able to separate the prostatic lesion well from the background radiation from prostate and bladder.