A method for finding consistent mid-sagittal planes (MSPs) in a pair of 3D image head scans of a same patient includes, for each image, selecting a 2D transverse localizer image from a middle slice along a transverse view of the 3D image, fitting an ellipse to the transverse localizer image to locate a head position (x, y), where the y-coordinate is indicative of a position of a 2D coronal localizer image in the 3D image, fitting an ellipse to the coronal localizer image to locate a head position (x, y) in the coronal localizer image, calculating a middle line in the transverse localizer image and a middle line in the coronal localizer image, calculating an MSP from the middle lines, and determining a new set of slope and intercept parameters for one MSP that maximizes a similarity measure between the one MSP and the other MSP.