Inverse T₂ contrast at 1.5 Tesla between gray matter and white matter in the occipital lobe of normal adult human brain

T₂ of cortical gray matter is generally assumed to be longer than that of white matter. It is shown here that this is not the case in the occipital lobe, but that this effect is often obscured at lower resolution and concealed in standard T₂-weighted images. Using a high-resolution (1 × 1.3 × 2 mm³) segmented EPI CarrPurcell-Meiboom-Gill sequence,T₂ relaxation times of the brain were measured at 1.5 T for eight healthy adult volunteers. The average T₂ values of cortical gray and white matter were found to be 88 ± 2 and 84 ± 3 msec in the frontal lobe, 84 ± 2 and 83 ± 3 msec in the parietal lobe, and 79 ± 1 and 87 ± 3 msec in the occipital lobe, respectively. This unexpected occipital T₂ contrast between gray and white matter is attributed to regional differences in iron concentration.