Magnetic resonance imaging of perfusion in rat cerebral 9L tumor after nicotinamide administration

Purpose: To investigate the effect of nicotinamide on normal brain and 9L t umor blood Row in the rat using magnetic resonance imaging (MRI) and arteri al spin tagging. Methods and Materials: Using MRI at 7 Tesla, measurements of blood perfusio n were determined from two-dimensional maps of intracerebral 9L rat tumors and normal Fischer rat brains. The spatial and temporal influence of nicoti namide, 500 mg/kg i.p., on cerebral blood flow (CBF) was studied in normal brain and tumors between 5 and 21 days after tumor implantation, The MRI CB F measurements employed a variable tip-angle-gradient-recalled echo (VTA-GR E-CBF) readout of the magnetization of the tissue slice. The VTA-GRE-CBF re quired 8 minutes for a blood Row image with inplane resolution of 250 mu m x 500 mu m x 2 mm. Results: Normal brain blood Row decreased following the administration of n icotinamide. In contrast, tumor blood flow remained unaffected in the time following nicotinamide administration, Consequently, the blood flowing in t he tumor relative to that in normal brain demonstrated a significant and se lective increase in response to nicotinamide administration. Relative tumor blood flow increased at 10 minutes after nicotinamide injection compared w ith predrug levels and remained elevated for at least 1 hour. Conclusion: The results suggest that nicotinamide will not enhance radiosen sitivity of brain tumors. The results support the use of nicotinamide to im prove delivery of anticancer therapeutics through its ability to selectivel y increase tumor blood how relative to that in normal brain. (C) 1999 Elsev ier Science Inc.