Comparison of Normal Tissue R1 and R2* Modulation by Oxygen and Carbogen

Magnetic resonance imaging has shown promise for evaluating tissue oxygenation. In this study differences in the tissue longitudinal relaxation rate (R-1) and effective transverse relaxation rate (R-2*), induced by inhalation of pure oxygen and carbogen, were evaluated in 10 healthy subjects. Significant reductions in R-1 were demonstrated following both oxygen and carbogen inhalation in the spleen (both P < 0.001), liver (P = 0.002 air vs. oxygen; P = 0.001 air vs. carbogen), skeletal muscle (both P < 0.001), and renal cortex (P = 0.005 air vs. oxygen; P = 0.008 air vs. carbogen). No significant change in R-2* occurred following pure oxygen in any organ. Howeve R-1 a significant increase in R-2* was observed in the spleen (P < 0.001), liver (P = 0.001), skeletal muscle (P = 0.026), and renal cortex (P = 0.001) following carbogen inhalation, an opposite effect to that observed in many studies of tumor pathophysiology. Changes in R-1 and R-2* were independent of the gas administration order in the spleen and skeletal muscle. These findings suggest that the R-1 and R-2* responses to hyperoxic gases are independent biomarkers of oxygen physiology. Magn Reson Mad 61:75-83, 2009. (C) 2008 Wiley-Liss, Inc.