@article { author = {Jozi, Hanieh Sadat and Ghafarian, Pardis}, title = {Quantitative evaluation of TOF benefits indifferent tumor regions of Overweight patients in clinical PET/CT scanner}, journal = {Iranian Journal of Medical Physics}, volume = {15}, number = {Special Issue-12th. Iranian Congress of Medical Physics}, pages = {84-84}, year = {2018}, publisher = {Mashhad University of Medical Sciences}, issn = {2345-3672}, eissn = {2345-3672}, doi = {10.22038/ijmp.2018.12362}, abstract = {Introduction: Using TOF information in image reconstruction reduce the noise propagation along the LOR during forward and back projection of the data, and improve the image signal-to-noise ratio (SNR) of PET scanners. This improvement is dependent on the scintillator decay time, time response of coincidence circuits and front-end electronics. The goals of this study were to evaluate the benefits of time of flight (TOF) in clinical PET/CT images of overweight patients in relation to the tumor-to-background ratios, and to determine what SNR gains in PET performance could be achieved. Materials and Methods: 32 overweight patient studies with normal 18F-fluoro-deoxyglucose (18F-FDG) uptake were chosen. FDG-PET/CT imaging was performed on the LYSO-based PET component of Discovery RX PET/CT scanner. Various tumor sizes in different locations of the thorax and abdomen in PET images have been investigated. The PET data were reconstructed with the baseline ordered-subsets expectation maximization (OSEM) algorithm+ PSF model and OSEM + PSF + TOF model. The image quality was evaluated using AMIDE to estimate the SNR, contrast, coefficient of variation(COV), and the standardized uptake values (𝑆𝑈𝑉𝑚𝑎𝑥). The results were then subjectively analyzed as a function of patient body-mass index (25