Changes in T1 and T2 observed in brain magnetic resonance imaging with delivery of high concentrations of oxygen.

Objective: The aim of this study was to clarify the relative contributions of the amount of oxygen in the blood, and vasoconstriction/dilation responsible for changes in T1 and T2 observed in brain during hyperoxia.
Methods: T1 and T2 values of the cerebral cortex and pituitary gland in mice were determined in room air. After room air was changed to either 100% oxygen (n = 8) or carbogen (n = 8), T1 and T2 values were again determined. Changes in each value with both gases were compared.
Results: In both challenges, T1 values of the cerebral cortex decreased, whereas significant T2 prolongation of the cerebral cortex and pituitary gland was demonstrated. However, both cortex and pituitary gland displayed similar responses in T1 and T2 values when exposed to 100% oxygen or carbogen.
Conclusions: Reduction of T1 was introduced by the increased amount of dissolved oxygen in blood, and the increased fraction of oxyhemoglobin caused T2 prolongation. The contribution of vasoconstriction/dilation by carbogen to changes in T1 and T2 may be negligible.