Systems and methods for automatic symmetry identification and for quantification of asymmetry for analytic, diagnostic and therapeutic purposes

摘要

Methods and related computational techniques are presented for analyzing images from various scan modalities, such as computerized tomography ("CT"). The methods convert image values to relative differences, to highlight side-to-side asymmetry. The conversion may be performed by comparing a small region of the scan to the corresponding region in the contralateral hemisphere, quantifying the degree of relative difference using statistical techniques, and representing this quantity of relative difference in a two dimensional or three dimensional relative difference map. In exemplary embodiments the method involves assigning an axis or plane of symmetry to a medical image, computing, using the image data, at least one relative difference map based on a comparison of two substantially symmetrical areas around the axis of symmetry, and generating a representation of any relative difference between the two symmetrical areas. In exemplary embodiments of the present invention the 3D orientation of a volumetric representation of an organ or anatomical area can be realigned within a scanner co-ordinate system. An inertia matrix can be computed on the sampled organ or structure, and principal axes can be can be derived from the eigenvectors of the inertia matrix. In alternate exemplary embodiments of the present invention, a volume, such as, for example, of a brain, can be represented as a re-parameterized surface point cloud. The interior contents can be removed, thus decomposing a symmetry plane computation problem into a surface matching routine. A search for a best matching surface can be implemented in a multi-resolution paradigm so as to optimize computational time. Subsequent to processing using either technique, in exemplary embodiments of the present invention a spatial affine transform can be applied to rotate the 3D images and align them within the co-ordinate system of the scanner. The corrected organ volume, for example, a brain, can then be re-sliced such that each planar image represents the organ at the same axial level.