ASSESSMENT OF CHANGES IN MURINE TUMOR OXYGENATION IN RESPONSE TO NICOTINAMIDE USING F-19 NMR RELAXOMETRY OF A PERFLUOROCARBON EMULSION

The oxygen dependencies of the 19F NMR spin‐lattice relaxation rates (R1 = 1/T1) of a perfluorocarbon emulsion sequestered in a murine tumor model has been used to evaluate nicotinamide, a radiosensitizer believed to act through enhanced tissue oxygenation. Fluorine‐19 NMR spectroscopic measurements from solid Radiation‐Induced Fibrosarcoma (RIF‐1) tumors in C3H mice showed a statistically significant improvement in tumor pO2 for a Nicotinamide‐treated group, with a ΔpO2 = 4.7 ± 3 torr (=mm Hg) (Mean ± SEM) at t = 60 min (P <.01), and 4.5 ± 3 at t = 70 min post intraperitoneal injection (P < 0.02) as compared with saline‐treated Controls, while several other time points for which t > 30 min were significant at the P < 0.05 level. Both groups had n = 10, and the statistics were based on Student's one‐tailed group t test. By comparison, in another study group where breathing gas was switched from air to 100% O2, a statistically insignificant increase of 2 torr was realized in tumor pO2 (n = 9). The maximal treatment effect occurs at a delay of 60 to 70 min, consistent with results obtained by other investigators using radiobiology techniques. Fluorine‐19 spectroscopic relaxometry can measure therapeutically meaningful changes in in vivo tumor pO2 and represents an improvement in expenditures of time, animal resources, and statistical power over conventional radiobiological methods. Copyright © 1993 Wiley‐Liss, Inc., A Wiley Company