Assessing effect of various blood glucose levels on ¹⁸F-FDG activity in the brain, liver and blood pool

Abstract

Objective: Studies have extensively analyzed the effect of hyperglycemia on ¹⁸F- fluorodeoxyglucose (¹⁸F-FDG or FDG) uptake in normal tissues and tumor. In this study, we measured standardized uptake value (SUV) in the brain, liver and blood pool in normoglycemia, hyperglycemia and hypoglycemia to understand the effect of blood glucose (BG) on FDG uptake and to develop a formula to correct SUV. Material and Methods: Whole body FDG positron emission tomography/computed tomography (PET/CT) images of adults were selected for analysis. Brain SUV_max, blood pool SUVmean and liver SUVmean were measured for the BG ranges of 61-70, 71-80, 81-90, 91-100, 101-110, 111-120, 121-130, 131-140, 141-150, 151-160, 161-170, 171-180, 181-190, 191-200, and 201 mg/dl and above. In each BG range, ten (10) PET images were analyzed (total 150). Mean ± SD of SUV of brain, liver and blood pool in each BG range was calculated and BG/SUV curves were generated. As brain and tumors show high expression of GLUT1 and GLUT3, based on % reduction in brain SUV_max with increasing BG, we generated a formula to correct SUV. Results: Mean brain SUV_max gradually reduced with increasing BG starting after BG level of 110 mg/dl. Approximate % reduction in brain SUV_max was 20%, 35%, 50%, 60%, and 65% for the BG ranges of 111-120, 121-140, 141-160, 161-200, and ≥ 201 mg/dl, respectively. In the formula we generated, measured SUV_max is multiplied by reduction factor of 1.25, 1.5, 2, 2.5 and 2.8 for the BG ranges of 111-120, 121-140 , 141-160 , 161-200 and ≥ 201 mg/dl, respectively, to correct SUV. Brain SUV_max was not different in hypoglycemics as compared to normoglycemics (p>0.05). SUVmean in the blood pool and liver were lower in hypoglycemics (P < 0.05) and not different in hyperglycemicss (p>0.05) as compared to normoglycemics. Conclusion: Hyperglycemia gradually reduces brain FDG uptake starting after BG of 110 mg/dl. Hyperglycemia doesn’t affect FDG activity in the liver and blood pool. Hypoglycemia doesn’t seem to effect brain FDG uptake but appears to reduce liver and blood pool activity. The simple formula we generated can be used to correct SUV in hyperglycemic adults in selected cases.