Abstract
BACKGROUND: Dynamic whole-body (D-WB) FDG PET/CT is a recently developed technique that allows direct reconstruction of multiparametric images of metabolic rate of FDG uptake (MR(FDG)) and "free" FDG (DV(FDG)). Multiparametric images have a markedly different appearance than the conventional SUV images obtained by static PET imaging, and normal values of MR(FDG) and DV(FDG) in frequently used reference tissues and organs are lacking. The aim of this study was therefore to: (1) provide an overview of normal MR(FDG) and DV(FDG) values and range of variation in organs and tissues; (2) analyse organ time-activity curves (TACs); (3) validate the accuracy of directly reconstructed MR(FDG) tissue values versus manually calculated K(i) (and MR(FDG)) values; and (4) explore correlations between demographics, blood glucose levels and MR(FDG) values. D-WB data from 126 prospectively recruited patients (100 without diabetes and 26 with diabetes) were retrospectively analysed. Participants were scanned using a 70-min multiparametric PET acquisition protocol on a Siemens Biograph Vision 600 PET/CT scanner. 13 regions (bone, brain grey and white matter, colon, heart, kidney, liver, lung, skeletal muscle of the back and thigh, pancreas, spleen, and stomach) as well as representative pathological findings were manually delineated, and values of static PET (SUV), D-WB PET (K(i), MR(FDG) and DV(FDG)) and individual TACs were extracted. Multiparametric values were compared with manual TAC-based calculations of K(i) and MR(FDG), and correlations with blood glucose, age, weight, BMI, and injected tracer dose were explored. RESULTS: Tissue and organ MR(FDG) values showed little variation, comparable to corresponding SUV variation. All regional TACs were in line with previously published FDG kinetics, and the multiparametric metrics correlated well with manual TAC-based calculations (r(2) = 0.97, p < 0.0001). No correlations were observed between glucose levels and MR(FDG) in tissues known not to be substrate driven, while tissues with substrate driven glucose uptake had significantly correlated glucose levels and MR(FDG) values. CONCLUSION: The multiparametric D-WB PET scan protocol provides normal MR(FDG) values with little inter-subject variation and in agreement with manual TAC-based calculations and literature values. The technique therefore facilitates both accurate clinical reports and simpler acquisition of quantitative estimates of whole-body tissue glucose metabolism.