Quantitative Po₂ Imaging in Vivo with Perfluorocarbon F-19 NMR: Tracking Oxygen from the Airway Through the Blood to Organ Tissues

Abstract

The physiological redistribution of perfluorocarbon (PFC) compounds to liver, spleen, bone marrow, and lung after intravenous (IV) or intraperitoneal (IP) administration of PFC emulsions affords the unique opportunity for non-invasive monitoring of oxygenation status of these organs and tissues utilizing fluorine (F-19) nuclear magnetic resonance (NMR) imaging techniques. PFCs also may be introduced directly into the pulmonary airways by procedures such as liquid ventilation, intratracheal instillation, or aerosol inhalation. Considerations of importance when establishing methodology for accurate quantitation of oxygen partial pressure (pO₂) in vivo using F-19 NMR include: 1.) error analysis of the calibration curves which relate pO₂ to the measured PFC F-19 relaxation rate, 2.) optimization of the NMR pulse sequence for efficient oxygen sensitive data acquisition and, 3.) fluorine signal independence from emulsion aqueous phase bioconstituents. The porcine model was investigated at 0.14T following IV or IP administration of the PFC emulsion containing perfluorotributylamine (FC-43) to demonstrate the capability for tracking oxygen with F-19 NMR from the lung through the blood to selected organ tissues. Quantitative pO₂ projection images and isobaric contour graphs were derived for the liver, spleen, and lungs as a function of inspired oxygen. Blood pO₂ levels in aorta, pulmonary artery, and hepatic vein were monitored simultaneously with NMR imaging for correlative analysis.