Inverse Consistent Image Registration of MR Brain Scans: Handedness in Normal Adult Males

Abstract

Brain shape differences between right and left-handed normal adults were evaluated by inverse-consistent linear-elastic image registration (ICLEIR) applied to MRI scans from two groups. The study populations were 9 right-handed and 9 left-handed adult males from ages of 24 to 51 years old. The mean brain shape of each population was computed and used as the reference shape for detecting shape differences. Nonrigid, ICLEIR transformations that registered the mean brain image with the brain images from the pooled populations were used to detect local brain population shape differences. Following the approach of Thirion et al., asymmetry maps between the left and right hemispheres of a brain image were computed by registering each brain image with their mirror images. Local statistical shape differences between the two populations were determined using one and two-tailed t-tests at each voxel in the coordinate system of the mean brain shape. Four t-tests were computed and compared which included the log-Jacobian and magnitude-divergence of the individual-to-pooled-average (IPA) correspondence map and the log-Jacobian and magnitude-divergence of the asymmetry maps. Local shape differences between populations were evaluated to determine the location of asymmetries due to handedness. Statistically significant (α=0.01) shape differences were found in this small pilot study with a sample size of 9 for each group. Although the populations were too small to draw conclusions regarding neuromorphological differences between left and right handed individuals, the method shows promise for detecting brain shape differences between different populations.