Assessment of R2* Dependence on Oxygenation Across Field Strength.

Paula L. Croal¹, Emma Louise Hall¹, Ian D. Driver¹, Susan T. Francis¹, Penelope A. Gowland¹

The power law () relating blood oxygenation and tissue R2* is yet to be tested experimentally in humans. This is important as models and simulations do not accurately depict intravascular effects. Cross-field studies which use neuronal activation or hypercapnia are confounded by changes in CBV (ΔCBV) which also modulate R2*. Here, isocapnic-hyperoxia is used to measure the dependence of R2* on oxygenation, and the effect of ΔCBV simulated. Experimental and simulation results support a reduction of  with field strength. For a given field, β will not have a significantly impact on CMRO2 estimations within a normal physiological range.