High-definition positron emission tomography using restored sinograms

Resolution recovery becomes an important technology for high-resolution and high-sensitivity Positron Emission Tomography (PET) cameras. High-definition PET images can be created after correcting detector parallax errors using point-spread functions. Many studies have demonstrated that better resolution and quantitative accuracy can be achieved by iterative reconstruction method with system respond function (SRF). In this paper, we use the SRF to restore sinograms first and then reconstruct images using the restored sinograms with conventional reconstruction methods. SRF is derived from Monte Carlo simulations with GEANT software. We modeled the SRF for the detector geometry of our prototype animal PET camera (RRPET) and human PET camera (HOTPET) for the evaluation. Na-22 point source experiment results demonstrated that resolution degradations in both cameras were eliminated. As expected, with sinogram restoration method the image quality was dramatically improved in the small animal PET system evaluated with micro-deluxe phantom and rat data. However, there was no improvement of Hoffman brain-phantom image in the human PET with rotatable gantry, which may relate to the detector gaps and scatter background existing in the original sinograms.