The measurement of left ventricular function will be greatly enhanced when the Three-dimensional (3-D) shape of the ventricle can be closely assessed by biplane angiocardiograms taken from two perpendicular X-ray camera sets. The ventricle shape at a given time may be reconstructed by dividing each of the two orthogonal projection images into corresponding slices, processing each pair of corresponding slices to form a binary cross-sectional image, and stacking up these parallel cross-sectional images. Existing methods of reconstructing cross sections often involve assumptions of elliptic shape or convex symmetry. Recently a new approach was proposed to reconstruct each cross section by estimating an equal-divisor curve instead of estimating the boundary directly; it works well as long as a certain regularity condition (a much relaxed assumption) is satisfied. In this correspondence, we extend the notion to the equal-divisor surface of a 3-D object with two orthogonal projections, and develop a method of direct 3-D reconstruction of the left ventricle instead of piling up the parallel reconstructed two-dimensional (2-D) cross sections.
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