Air pressure‐induced susceptibility changes in vascular reactivity studies using BOLD MRI

Abstract

To investigate whether compressed air during air-cuff inflation in vascular reactivity studies could induce aberrant blood oxygenation level-dependent (BOLD) signal change. Magnetic resonance imaging (MRI) experiments were performed on a whole-body 3 T scanner. The pattern of T2* signal change measured from a phantom simulating the lower limb was assessed while a thigh cuff was inflated and deflated. MR spectroscopy was performed on a head phantom wrapped using a hand-cuff to determine the relationship between water peak linewidth and applied cuff pressure. Calf muscles from 14 normal subjects were examined to identify aberrant T2* signal changes in the occluded and nonoccluded legs. A sudden T2* signal drop was observed in the phantom on initiation of cuff inflation with subsequent signal change being dependent on cuff pressure. Water peak linewidth increased linearly with cuff pressure (r(2) = 0.94). Aberrant T2* signal changes were observed in both the occluded and nonoccluded legs. Compressed air due to cuff inflation directly affects local magnetic field susceptibility. The T2* sequence is sensitive to local field disturbances induced by an inflated cuff. Muscle BOLD results are affected by high-pressure air, with a sudden drop in T2* signal being a characteristic feature of this induced effect.