The Impact of Energy Substrates, Hormone Level and Subject-Related Factors on Physiologic Myocardial (18)F-FDG Uptake...

In a whole-body (18)F-FDG PET/CT, non-specific (18)F-FDG uptake of the myocardium is a common finding and can be very variable, ranging from background activity to intense accumulation and inhomogeneity. We investigated the effect of energy substrates and plasma/serum hormones that may have an influence on myocardial (18)F-FDG uptake.

F-FDG PET/CT was performed on 100 normal volunteers from November 2007 to August 2008. Blood samples were taken just before (18)F-FDG injection from all subjects. Myocardial (18)F-FDG uptake was measured as the mean (SUVmean) and maximal (SUVmax) standardized uptake value. The myocardium was delineated on the PET/CT image by a manual volume of interest (VOI). We analyzed the influence of age, sex, presence of diabetes, fasting duration, insulin, glucagon, fasting glucose, lactate, free fatty acid (FFA), epinephrine (EPi), norepinephrine (NEp), free triiodothyronine (T3), free thyroxine (T4), thyroid-stimulating hormone (TSH) and body mass index (BMI).

Overall, 92 subjects (mean age 50.28 ± 8.30, male 57) were enrolled. The average of myocardial SUVmean was 2.08 and of myocardial SUVmax was 4.57, respectively and there was a strong linear correlation between SUVmean and SUVmax (r = 0.98). FFA and fasting duration showed significant negative correlation with myocardial (18)F-FDG uptake, respectively (r = -0.40 in FFA; r = -0.41 in fasting duration). No significant relationships were observed between myocardial uptake and age, sex, presence of diabetics, insulin, glucagon, fasting glucose, lactate, EPi, NEp, free T3, free T4, TSH and BMI.

Myocardial (18)F-FDG uptake decreases with longer fasting duration and higher FFA level in normal humans. Modulating myocardial uptake could improve (18)F-FDG PET/CT imaging for specific oncologic and cardiovascular indications.