In 1992 IEEE Nuclear Science Symposium and Medical Imaging Conference Record, pages 1339-1341, Orlando, Florida, 29-31 October 1992.
An automated procedure is described for accurately correcting the distortion present in x-ray image intensifiers. An image of a rectilinear grid of wires is acquired. The wire crossing point positions are determined to sub-pixel accuracy without operator intervention. The points are then associated with their true coordinates. Following this association procedure, a piecewise affine transformation is found. Each output pixel point needed is mapped to the corresponding location in the distorted image. If it is not at a true acquired pixel location, bilinear interpolation is done to estimate the gray level at that point. After calibration data is analyzed, all subsequent images are corrected using a fast and simple table lookup algorithm. High accuracy is achieved for applications requiring sub-pixel registration.