Rapid monitoring of oxygenation by 19F magnetic resonance imaging: Simultaneous comparison with fluorescence quenching.

The aim of this study was to develop an MRI fluorocarbon oximetry technique using snapshot inversion recovery and compare it with fluorescence quenching fiber-optic probe oximetry (OxyLite) performed simultaneously in experimental mouse tumors. The oxygen reporter probe hexafluorobenzene (HFB) was injected directly into the tumors, along with the insertion of the OxyLite probe. Tumor oxygenation (pO(2)) was modified using carbogen or lethal doses of the anesthetic gas. MRI pO(2) maps were generated in 1.5 min with an in-plane spatial resolution of 1.88 mm. MRI and OxyLite showed consistent baseline and postmortem pO(2) values. Increases in tumor pO(2) during carbogen breathing showed similar kinetics for the two methods. The pO(2) values observed using the OxyLite corresponded with relatively hypoxic values observed by MRI. The apparent discrepancy between mean values might be due to the difference in sampling volumes of the techniques and the observation of multiple locations using (19)F MRI versus a single location using the large optical fiber. Overall, the present method provides a rapid way to map the tumor oxygenation and is particularly suitable to monitor acute changes of pO(2) in tumors.