REGIONAL TUMOR OXIMETRY - F-19 NMR-SPECTROSCOPY OF HEXAFLUOROBENZENE

Purpose: An accurate method for monitoring oxygen tension (pO(2)) of i ndividual tumors could be valuable for optimizing treatment plans. We have recently shown that F-19 nuclear magnetic resonance (MMR) spin-la ttice relaxometry of hexafluorobenzene (HFB) provides a highly sensiti ve indicator of tumor oxygenation. We have now refined the methodology to provide enhanced precision, and applied the method to investigate dynamic changes in tumor oxygenation. Methods and Materials: Dunning p rostate adenocarcinoma R3327-AT1 was grown in the form of pedicles on the foreback of male Copenhagen rats. When the tumors reached similar or equal to 1 cm diameter, HFB (20 mu l) was administered, either cent rally or peripherally, by direct intratumoral (IT) injection. Local pO (2) was determined using pulse-burst saturation recovery (PBSR) F-19 N MR spectroscopy on the basis of the spin-lattice relaxation rate, R1. Results: Interrogation of the central region of tumors provided typica l values in the range pO(2) = 1.4-6.4 mmHg, with a typical stability o f +/-2 mmHg over a period of 20 min, when rats breathed 33% O-2. Alter ing the inhaled gas to oxygen or carbogen (95% O-2/5% CO2) produced no significant change. In contrast, interrogation of tumor periphery ind icated baseline pO(2) in the range 7.9-78.9 mmHg, Altering inspired ga s produced significant changes (p < 0.0001) with O-2 or carbogen, alth ough the change was generally greater with carbogen, In each case, pO( 2) returned to baseline within 16 min of returning the inhaled gas to baseline. Conclusion: We believe this method provides a valuable new a pproach with the requisite precision and accuracy to investigate tumor pO(2). (C) 1998 Elsevier Science Inc.