An automated temporal alignment technique for the translational and rotational correction of digital radiographic images of Bjork-Shiley heart valves

An accurate technique for the temporal registration of digital radiographic valve images is an integral process in the objective quantification of single leg separation (SLS) in Bjork-Shiley Convexo Concave heart valves. The authors have developed a fully automated technique for the translational and rotational correction of sequential valve images based on the principal axes of the valve. This technique was chosen for ease of implementation, speed, and accuracy. The first step of the alignment procedure is to correct for translational and rotational motion by aligning the centroids of segmented valve images according to their principal axes. The second step involves a rotational correction for each leg of the outlet strut using a linear cross-correlation of data sampled along a specified are about the centroid. This technique has been successfully applied to a preliminary set (10 patients) of digital radiographic data (8-16 sequential frames). This technique was determined accurate to within 2 pixels at a spatial resolution of 139 μm/pixel