Correction of image intensifier distortion for three-dimensional x-ray angiography

An algorithm has been developed to correct spatial distortion in image intensifier-based projections for three-dimensional (3D) angiographic reconstruction. A piecewise spatial warping technique is used to calculate a set of correction lookup tables which store the row and column subpixel spatial shifts, based on a reference grid image. Pixel amplitudes in the corrected image are determined from bilinear interpolation of the four surrounding pixels in the observed image. The method has been tested using an x-ray imaging chain with a 30-cm image intensifier positioned at various angular orientations and x-ray source distances. Prior to distortion correction, the maximum error between observed and expected reference point locations was found to be 14 mm. After correction, the maximum and mean errors were 0.23 mm and 0.053 mm, respectively.