Three-dimensional automatic image warping in cardiac SPECT

This study presents a new tool for the visualization and analysis of three-dimensional (3-D) cardiac single-photon emission computed tomography (SPECT). The first step consisted of computing the 3-D pseudo-skeleton of a binarized myocardium and, using the skeleton points, to design a bullet model (half ellipsoid prolonged by a cylinder). Afterwards, this model was used to drive the warping of the 3-D myocardium, initially egg-shaped, into a thick, flat disc using the thin-plate splines as deformation method. Hence, instead of achieving several rotations of the initial egg-shaped volume to have an idea on the myocardial outer face (epicardial) only, the whole myocardium is seen by looking either on top of the disc-shaped transformed myocardium (epicardial surface) or underneath for the inner face (endocardial). This new shape permitted us to localize any type of defect and to evaluate its extent and depth just by a single glance. A detailed analysis, achieved after stripping away this shape in about 10 layers, allowed us to evaluate the defect extent layer by layer and to determine whether the defect involves the totality of the myocardium layers. Finally, its flattening following the ventricular long-axis led to a summed bull's eye.