Quantitative F-18 FDG uptake in patients undergoing cardiac viability and sarcoid imaging and patients undergoing tumor imaging

Objectives PET imaging with F-18 FDG is used for the identification inflammatory heart diseases (InfHD) as well as myocardial viability. Metabolic preparation of patients (Pts) undergoing these protocols vary significantly. The objective of this study was to evaluate quantitative differences in background FDG uptake (liver and blood pool) and peak myocardial uptake in three protocols: (1) high fat preparatory diet (HFPD)+heparin used to minimize uptake in normal myocardial tissue imaging inflammatory heart disease, (2) glucose loading CLAMP in viability (VIAB) imaging, and (3) fast (FAST) preparation for tumor imaging.

Methods Study population consisted of 74 Pts including 24 with known or suspected InfHD (sarcoidosis), 29 with coronary disease for VIAB testing, and 21 with known or suspected cancer. Imaging was performed using 8-10 mCi F-18 FDG with Siemens mCT PET-CT (Siemens Medical Solutions, USA, Knoxville, TN). Images were analyzed for standardized uptake values (SUV) using Corridor4DM software (INVIA, Ann Arbor, MI). For statistical purposes, p<0.05 was considered significant.

Results Peak myocardial uptake varied widely depending on protocol and disease activity. Pts studied with HFPD+heparin had the lowest peak uptake (5.74±3.92, range 0.91-12.55), significantly lower than VIAB protocol (14.54±4.28, range 7.05-24.32, p<0.01), and lower than FAST preparation (9.4±4.3, range 1.3-17.0, p<0.05). Background uptake in blood and liver were much less variable with all three protocols although mean blood pool and liver uptake were significantly higher with both HFPD+heparin and FAST preparation compared to CLAMP, p<0.0001.

Conclusions Quantitative myocardial and background FDG uptake varies depending on disease activity and metabolic preparation. Although highly variable in the myocardium, relatively predictable patterns of background uptake were demonstrated depending on protocol. These differences may have important bearing on image interpretation and quantification.