IN-VIVO PO(2) IMAGING IN THE PORCINE MODEL WITH PERFLUOROCARBON F-19 NMR AT LOW-FIELD

Quantitative pO(2) imaging in vivo has been evaluated utilizing F-19 N MR in the porcine model at 0.14 T for the lungs, liver, and spleen fol lowing IP administration of the commercial perfluorotributylamine (FC- 43)-based perfluorocarbon (PFC) emulsion, Oxypherol-ET. Calculated T-1 maps obtained from a two spin-echo saturation recovery/inversion reco very (SR/IR) pulse protocol are converted into quantitative pO(2) imag es through a temperature-dependent calibration curve relating longitud inal relaxation rate (1/T-1) to pO(2). The uncertainty in pO(2) for a T-1 measurement error of +/- 5% as encountered in establishing the cal ibration curves ranges from +/- 10 torr (+/- 40%) at 25 torr to +/- 16 torr (+/- 11%) at 150 torr for FC-43 (37 degrees C), However, additio nal uncertainties in T-1 dependent upon the signal-to-noise ratio may beintroduced through the SR/IR calculated T-1 pulse protocol, which mi ght severely degrade the pO(2) accuracy. Correlation of the organ imag e calculated pO(2) with directly measured pO(2) in airway or blood poo ls in six pigs indicate that the PFC resident in lung is in near equil ibrium with arterialized blood and not with airway pO(2), suggesting a location distal to the alveolar epithelium, For the liver, the strong est correlation implying equilibrium was evident for venous blood (hep atic vein), For the spleen, arterial blood pO(2) (aorta) was an unreli able predictor of pO(2) for PFC resident in splenic tissue, The result s have demonstrated the utility and defined the limiting aspects of qu antitative pO(2) imaging in vivo using F-19 MRI of sequestered PFC mat erials.