IN-VIVO MEASUREMENT OF ARTERIAL AND VENOUS OXYGENATION IN THE RAT USING 3D SPECTRAL-SPATIAL ELECTRON-PARAMAGNETIC-RESONANCE IMAGING

Electron paramagnetic resonance imaging (EFRI) instrumentation, enabli ng the performance of three-dimensional spectral-spatial images of fre e radicals, has been developed to study spatially defined differences in tissue metabolism and oxygenation. Using this instrumentation 3D im ages of nitroxides in rat tail were obtained. The images visualize the arterial and venous vasculature in the tail segment. Based on the exc hange broadening influence of oxygen on the EPR linewidth of nitroxide s, we performed localized oxygen measurements in the in vivo rat. An o xygen concentration of 300 +/- 30 mu M was measured in the arteries an d 50 +/- 20 mu M in the veins. These results demonstrate the feasibili ty of performing in vivo, non-invasive measurements and mapping of loc alized oxygenation in small animals using spectral-spatial EPR imaging techniques.