Measurement of Oxygen Tensions in the Abdominal Cavity and in the Skeletal Muscle Using 19F-MRI of Neat PFC Droplets

Abstract

Perfluorochemicals (PFCs) are not only of interest as artificial oxygen carriers but also as 19F-NMR (19F nuclear magnetic resonance) contrast agents for the determination of partial oxygen pressuresin vivo. Since the longitudinal relaxation rate R₁ increases linearly with the partial oxygen pressure (pO²), pO² values can be determined in regions of PFC accumulation. After the i.v. injection of a PFC emulsion, pO₂ measurements are possible in large vessels until most of the PFC particles are removed from the circulation by macrophages. Then intracellular pO₂ measurements can be performed in regions with high macrophage concentration, i.e. in the liver and spleen, and in pathological tissues with high macrophage activity, e.g. in tumors and in regions of inflammation. In many studies with PFC emulsions, negative apparent pO₂ values were reported under hypoxic conditions (F₁O₂ < 0.21) [1-7]. Purpose of this work was to measure extracellular pO₂ values in a depot of neat PFC in the abdominal cavity and in the skeletal muscle under hyperoxic, normoxic and hypoxic conditions, and further to determine whether neat PFC also yields negative apparent pO₂ values under hypoxic conditions.