Can you predict myocardial uptake of F-18 fluoro-deoxy-glucose (FDG) from fasting plasma glucose?

Positron emission tomography (PET) using F-18 fluoro-deoxyglucose (FDG) has become a very powerful tool for myocardial viability determination. Plasma glucose is usually determined prior to myocardial imaging with FDG. Some centers routinely use insulin-clamp (insulin after a glucose load) while others rely on fasting glucose. The purpose of this investigation was to determine if the fasting glucose can predict myocardial uptake of FDG. This study population included 49 patients (mean age 60 [+ or -] 14 years) who had undergone FDG whole body PET scans for variety of indications. The mean injected activity of FDG was 18 [+ or -] 2.5 mCi. These images were retrospectively analyzed to determine myocardial uptake of FDG. The LV region of interest was demarcated and average selective uptake value (SUV) was determined and correlated with the fasting plasma glucose levels. The data analysis showed no correlation between fasting glucose and average SUV. The fasting plasma glucose ranged from 50-354 mg/dl (mean of 103 [+ or -] 42). The SUV ranged from 1.14 to 9.71 (mean 2.92 [+ or -] 1.89). A regression coefficient of -0.008 indicated no correlation between fasting glucose and average SUV. For further analysis, the patients (pts) were divided into two groups based on plasma glucose. In group A, there were 29 pts with glucose level 50-100, and in group B, there were 20 pts with glucose level 100-354. The mean SUV was 3.22 [+ or -] 2.17 and 2.49 [+ or -] 1.27 in groups A and B, respectively, and the difference was statistically significant (P = 0.03). However, this small difference in SUV is probably clinically insignificant. We conclude that fasting plasma glucose measured prior to myocardial imaging with FDG do not predict myocardial uptake of FDG. We question the usefulness of the practice of using fasting plasma glucose and prefer to use insulin clamp technique, with excellent results.

Amolak Singh, MD, FACP, FACNM, and Aju Thomas, MD. University of Missouri Health Care, Columbia, MO.