Quantitative Tissue Oxygen Measurement in Multiple Organs Using 19F MRI in a Rat Model

Measurement of individual organ tissue oxygen levels can provide information to help evaluate and optimize medical interventions in many areas including wound healing, resuscitation strategies, and cancer therapeutics. Echo planar 19F MRI has previously focused on tumor oxygen measurement at low oxygen levels (pO2) <30 mmHg. It uses the linear relationship between spin-lattice relaxation rate (R1) of hexafluorobenzene (HFB) and pO2. The feasibility of this technique for a wider range of pO2values and individual organ tissue pO2 measurement was investigated in a rat model. Spin-lattice relaxation times (T1= 1/R1) of hexafluorobenzene were measured using 19F saturation recovery echo planar imaging. Initial in vitro studies validated the linear relationship between R1 and pO2 from 0 to 760 mmHg oxygen partial pressure at 25, 37, and 41°C at 7 Tesla for hexafluorobenzene. In vivo experiments measured rat tissue oxygen (ptO2) levels of brain, kidney, liver, gut, muscle, and skin during inhalation of both 30 and 100% oxygen. All organ ptO2 values significantly increased with hyperoxia (P < 0.001). This study demonstrates that 19F MRI of hexafluorobenzene offers a feasible tool to measure regional ptO2 in vivo, and that hyperoxia significantly increases ptO2 of multiple organs in a rat model. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.