Conceptual design of a combined CLI/PET scanner via all event-by-event readout

A combined Cerenkov Luminescence Imaging (CLI) and Positron Emission Tomography (PET) scanner for in-vivo imaging of small animals is conceptually designed via all event-by-event readout and multiple-coincidence processing. Strategies and concepts for the design of the combined CLI/PET scanner based on the list-mode scheme are analyzed and modeled in terms of Monte Carlo approach. This allows for a proper inclusion of imaging via CLI modality, PET modality and combined CLI/PET modality. In the CLI modality, photons are collected in event-by-event mode, which has been widely adopted in PET or SPECT instrument and scientifically proven to be effective to reject background and unrelated radiation. In the combined CLI/PET modality, the Cerenkov events in CLI are taken in account for the coincidence processing of the gamma pairs in the PET modality without image fusion after reconstruction. The comparative testing results of the image quality among the CLI only, PET only and combined CLI/PET are shown after the simulation on a Derenzo phantom. The reconstructed CLI image shows evident blurring in the center of phantom, while the reconstructed PET image is noisy. The combined CLI/PET scanner results in dramatically improved image quality, which is evident from visual inspection of the reconstructed images as well as a quantitative evaluation in Peak Signal to Noise Rate (PSNR), Mean Square Error (MSE), and Maximum Error (ME). The MSE of CLI/PET image has an order of magnitude lower than CLI only or PET only image, and then demonstrated the performance advantages of the proposed CLI/PET imaging system with modality fusion at the original data stage and in the event level.