Effects of administration route, dietary condition, and blood glucose level on kinetics and uptake of 18F-FDG in mice

Abstract

The effects of dietary condition and blood glucose level on the kinetics and uptake of 18F-FDG in mice were systematically investigated using intraperitoneal and tail-vein injection. Methods: Dynamic PET was performed for 60 min on 23 isoflurane-anesthetized male C57BL/6 mice after intravenous (n = 11) or intraperitoneal (n = 12) injection of 18F-FDG. Five and 6 mice in the intravenous and intraperitoneal groups, respectively, were kept fasting overnight (18 ± 2 h), and the others were fed ad libitum. Serial blood samples were collected from the femoral artery to measure 18F-FDG and glucose concentrations. Image data were reconstructed using filtered backprojection with CT-based attenuation correction. The standardized uptake value (SUV) was estimated from the 45- to 60-min image. The metabolic rate of glucose (MRGlu) and 18F-FDG uptake constant (Ki) were derived by Patlak graphical analysis. Results: In the brain, SUV and K i were significantly higher in fasting mice with intraperitoneal injection, but MRGlu did not differ significantly under different dietary states and administration routes. Cerebral Ki was inversely related to elevated blood glucose levels, irrespective of administration route or dietary state. In myocardium, SUV, Ki, and MRGlu were significantly lower in fasting than in nonfasting mice for both routes of injection. Myocardial SUV and Ki were strongly dependent on the dietary state, and Ki did not correlate with the blood glucose level. Similar results were obtained for skeletal muscle, although the differences were not as pronounced. Conclusion: Intraperitoneal injection is a valid alternative route, providing pharmacokinetic data equivalent to data from tail-vein injection for small-animal 18F-FDG PET. Cerebral Ki varies inversely with blood glucose level, but the measured cerebral MRGlu does not correlate with blood glucose level or dietary condition. Conversely, the Ki values of the myocardium and skeletal muscle are strongly dependent on dietary condition but not on blood glucose level. In tissue in which 18F-FDG uptake declines with increasing blood glucose, correction for blood glucose level will make SUV a more robust outcome measure of MRGlu. Copyright © 2011 by the Society of Nuclear Medicine, Inc.