Blood oxygen saturation assessment in vivo using T 2 * estimation

The feasibility of noninvasively assessing hemoglobin oxygen saturation of deep blood vessels in vivo by measuring blood T 2 * is investigated. Techniques for blood T 2 * measurements in major arteries and veins in the presence of pulsatile blood flow are presented and validated using a flow phantom. Images of multiple TEs were collected in a paired fashion. Cardiac triggering was used to eliminate image artifacts caused by pulsatile arterial blood flow. Using these techniques, it was found that the T 2 * of arterial blood (199 ± 8 ms) is significantly greater than that of venous blood (108 ± 6 ms) in 10 volunteers, consistent with the fact that the oxygen saturation level of arterial blood is much larger than that of venous blood. Various oxygen saturation levels were created in vivo in a pig and the blood T 2 * was shown to increase with oxygen saturation levels over a wide range. Preliminary results of this study indicate that it is feasible to assess local oxygen saturation by measuring blood T 2 * using the proposed techniques.