Importance of oxygenation in the appearance of acute subarachnoid hemorrhage on high field magnetic resonance imaging.

The ability to detect acute hemorrhage by magnetic resonance (MR) is related to the oxygen saturation of hemoglobin. This experiment measured the relaxation times of solutions of cerebrospinal fluid containing a 5 per cent hematocrit at various pO2's on a 1.4 tesla (T) MR imaging system. The results demonstrate that the state of oxygen saturation of hemoglobin determines the extent of T2 relaxation at this field strength. The T2 relaxation rate varies quadratically with the concentration of deoxyhemoglobin. There were no significant changes in the T1 relaxation rate with variations in pO2. These findings may, in part, explain the inability of MR to detect subarachnoid hemorrhage, and the MR appearance of blood in intratumoral hemorrhage, hemorrhagic cortical infarction and neonatal hemorrhage.