To evaluate the relationship between fasting blood sugar, period of fasting, age of the patient and degree of non-pathological uptake of fluorodeoxyglucose in myocardium.

Positron emission tomography with 18F-fluorodeoxyglucose (FDG-PET) is a method used widely for the evaluation of various malignancies. Increased uptake of FDG in myocardium is frequently observed on clinical studies, which is not related to the disease. Such physiological uptake may interfere with correct image reading. In the present study we tried to evaluate the role of patient related factors like fasting blood sugar level (FBSL), fasting period (FP) and age of the patient that may have an influence on this phenomenon. Literature reveals many reports with controversial results on this subject.

We evaluated 61 non-diabetic patients with malignant diseases who underwent wholebody FDG-PET studies at RMC. Estimation of FBSL in all patients was done prior to injection of FDG. Total fasting period and age was noted by making inquiry with the patient. Qualitative analysis of the images was carried out by experienced Nuclear Medicine Physician. All patients were classified into four grades of myocardial uptake according to the visual interpretation of the FDG image. Out of 61 patients, 22 showed no uptake in myocardium (Gr0). The variation in FP, FBSL and Age was 14.18+/− 2.85 hrs, 93.86+/− 11.6mg% and 45.13+/− 14.25 years respectively. Grade-I (equal to normal liver tissue) uptake was noted in 8 cases (FP-12.62 +/− 2.77 hrs, FBSL - 99.37 +/− 2.77 mg% and Age-44.87+/− 20.32 years). Twenty-one patients were having Grade-II (>liver but < brain) uptake in the heart (FP-13.66+/− 3.66 hrs, FBSL - 87.09 +/− 9.24 mg% and Age-43.23 +/− 20.22 years). We found 10 patients with intense FDG uptake (Grade-III-equivalent to brain) in myocardium (FP-12.9 +/− 1.66hrs, FBSL-890.9 +/− 14.6 mg% and Age - 37.3 +/− 18.1 years). As the results of 61 patients indicate, it is difficult to predict the degree of physiological uptake of FDG in the myocardium from the data regarding fasting period, fasting blood sugar level or age of the patient. Probably it is more a patient specific factor or some other factors like the type of malignancy and treatment. It needs further exploration including a large number of patients and factors.