MR imaging of the lung using liquid perfluorocarbons

Certain perfluorocarbon (PFC) compounds, commonly used as the oxygen transport components of "blood substitutes," may be breathed as neat liquids with survival because of their chemical inertness and their high solubility for oxygen and carbon dioxide. In addition, the paramagnetism of oxygen reduces the fluorine T1 value according to an inverse relationship allowing a potential method of monitoring PO2 gradients in vivo. This article presents the results of magnetic resonance (MR) imaging of the lungs of mice and rats following breathing of four PFC liquids (FC-43, FC-75, PFOB, APF-215). The images presented were obtained at two magnetic field strengths (0.66 and 0.14 T) under conditions of breathing either ambient air or pure oxygen. Spin-lattice relaxation times (T1) for the PFCs are measured both in vitro and in vivo (in the lungs) as a function of the state of oxygenation. A MR image signal strength enhancement of up to 90% is demonstrated in vivo under conditions of pure oxygen breathing.