More than meets the eye: significant regional heterogeneity in human cortical T1☆

Segmented k-space acquisition of data was used to decrease the acquisition time and to increase the imaging resolution of the precise and accurate inversion recovery (PAIR) method of measuring T1. We validated the new TurboPAIR method by measuring T1 in 158 regions of interest in 12 volunteers, using both PAIR and TurboPAIR. We found a 3% difference between methods, which could be corrected by linear regression. After validation, the TurboPAIR method was used to test a hypothesis that there is significant regional heterogeneity in cortical T1. We measured cortical gray matter T1 in 11 right-handed volunteers, in 48 regions of interest scattered over frontal and parietal cortex, and in 46 ROIs along the central sulcus (CS). We found that T1 in the CS is less than T1 elsewhere in the cortex (p < 0.001), and that there is considerable hemispheric asymmetry in T1 in gray matter, but not in white matter. In central gray structures (caudate, thalamus, nucleus pulvinarus), and in the posterior CS (sensory cortex), right hemisphere T1 was significantly greater than left hemisphere T1 (p ≤ 0.004). In cortical gray matter of the frontal lobe and anterior CS (motor cortex), left hemisphere T1 was significantly greater than right hemisphere T1 (p ≤ 0.003). These findings demonstrate that there is considerable regional heterogeneity in human cortical T1 that is unexplained by differences in tissue iron content, but may be evidence of an inherent anatomic asymmetry of the brain.