The effect of hyperoxygenation on T1 relaxation time in vitro

Rationale and Objectives. Ventilation with high oxygen (O-2) concentrations has been shown to decrease T1 in blood and tissues of patients. This study aims to assess the effect of hyperoxygenation on the T1 relaxation time of blood and other physiologic solutions. Materials and Methods. Varied gaseous mixtures of 0.2 and air between 21% and 100% O-2 were created using an experimental circuit at room temperature, and used to saturate human blood, plasma, or normal saline. The samples were studied using an 8.45-Tesla magnetic resonance (MR) system and a 1.5-Tesla clinical MR scanner. Results. MR spectroscopy at 8.45 Tesla showed that the percentage of O-2 chosen for saturation correlated negatively with T1 (R-2 = 1.00 for blood, 0.90 for plasma, and 1.00 for normal saline). The reduction in T1 between solutions saturated with 21% and 100% 02 was 487 milliseconds (22% of the baseline T1 value) for blood, 391 milliseconds (15,70) for plasma and 622 milliseconds (19%) for saline. Similarly, MR measurements at 1.5 Tesla showed T1 reduction with increasing 02 concentration. Conclusion. The decreasing T1 in blood depends strongly on the fraction of dissolved 02 in solution and is largely independent of the hemoglobin content.