In vivo oxygen tension and temperature: Simultaneous determination using ¹⁹F NMR spectroscopy of perfluorocarbon

A novel technique is presented to measure in vivo simulataneously oxygen tension and temperature using ¹⁹F NMR spectroscopy of perfluorocarbon. This work examines the variation with oxygen tension (pO₂) and temperature of the individual spin lattice relaxation rates (R₁) of the ¹⁹F resonances of the perfluorocarbon emulsion Oxypherol‐ET. A linear relationship between R₁ and pO₂ is confirmed for all the resonances at any specific temperature in the range 27–50°C. Similarly, a linear relationship is determined between R₁ and temperature at any specific pO₂ in this temperature range. Each resonance behaves uniquely with respect to temperature and pO₂ and consideration of 2 or more resonances uniquely defines pO₂ and temperature simultaneously, and unambiguously. This concept is demonstrated in vivo in a murine tumor and perfused rat heart, where pO₂ and temperature were both determined without prior knowledge.