First results on kinetic modelling and parametric imaging of dynamic 18 F-FDG datasets from a long axial FOV PET scanner in oncological patients

Purpose To investigate the kinetics of 18 F-fluorodeoxyglucose ( 18 F-FDG) by positron emission tomography (PET) in multiple organs and test the feasibility of total-body parametric imaging using an image-derived input function (IDIF). Methods Twenty-four oncological patients underwent dynamic 18 F-FDG scans lasting 65 min using a long axial FOV (LAFOV) PET/CT system. Time activity curves (TAC) were extracted from semi-automated segmentations of multiple organs, cerebral grey and white matter, and from vascular structures. The tissue and tumor lesion TACs were fitted using an irreversible two-tissue compartment (2TC) and a Patlak model. Parametric images were also generated using direct and indirect Patlak methods and their performances were evaluated. Results We report estimates of kinetic parameters and metabolic rate of glucose consumption (MR FDG ) for different organs and tumor lesions. In some organs, there were significant differences between MR FDG values estimated using 2TC and Patlak models. No statistically significant difference was seen between MR FDG values estimated using 2TC and Patlak methods in tumor lesions (paired t -test, P = 0.65). Parametric imaging showed that net influx (K i ) images generated using direct and indirect Patlak methods had superior tumor-to-background ratio (TBR) to standard uptake value (SUV) images (3.1- and 3.0-fold mean increases in TBR mean , respectively). Influx images generated using the direct Patlak method had twofold higher contrast-to-noise ratio in tumor lesions compared to images generated using the indirect Patlak method. Conclusion We performed pharmacokinetic modelling of multiple organs using linear and non-linear models using dynamic total-body 18 F-FDG images. Although parametric images did not reveal more tumors than SUV images, the results confirmed that parametric imaging furnishes improved tumor contrast. We thus demonstrate the feasibility of total-body kinetic modelling and parametric imaging in basic research and oncological studies. LAFOV PET can enhance dynamic imaging capabilities by providing high sensitivity parametric images and allowing total-body pharmacokinetic analysis.