Mid-sagittal Plane and Mid-sagittal Surface Optimization in Brain MRI Using a Local Symmetry Measure

摘要

This paper describes methods for automatic localization of the mid-sagittal plane (MSP) and mid-sagittal surface(MSS). The data used is a subset of the Leukoaraiosis And DISability (LADIS) study consisting of threedimensionalmagnetic resonance brain data from 62 elderly subjects (age 66 to 84 years). Traditionally, themid-sagittal plane is localized by global measures. However, this approach fails when the partitioning planebetween the brain hemispheres does not coincide with the symmetry plane of the head. We instead propose touse a sparse set of profiles in the plane normal direction and maximize the local symmetry around these using ageneral-purpose optimizer. The plane is parameterized by azimuth and elevation angles along with the distanceto the origin in the normal direction. This approach leads to solutions confirmed as the optimal MSP in 98percent of the subjects. Despite the name, the mid-sagittal plane is not always planar, but a curved surfaceresulting in poor partitioning of the brain hemispheres. To account for this, this paper also investigates an optimizationstrategy which fits a thin-plate spline surface to the brain data using a robust least median of squaresestimator. Albeit computationally more expensive, mid-sagittal surface fitting demonstrated convincingly betterpartitioning of curved brains into cerebral hemispheres.