Abstract
A distortion correction table compression method based on polynomial fitting has been developed for implementation in a commercial volume-CT system. To achieve the fastest processing rates, distortion correction tables must fit into the limited memory present in hardware. The number of elements in raw lookup tables is approximately 2 X Ni X Nj X N(theta ), where Ni X Ni is the image dimensions in pixels, and N(theta ) is the number of frames. Two- dimensional (2D) compression fits 4th-order polynomials to columns and rows of the raw table, reducing table size to 2 X 5 X 5 X Nf. Three-dimensional (3D) compression further compresses 2D tables in the angle dimension; reducing table size to 2 X 5 X 5 X 5. Tradeoffs between table size, accuracy, speed, and amount of distortion were investigated with data acquired from 7', 9', 10', 12', 14', and 16' IIs. The mean error was approximately 0.11, 0.20, and 0.20 pixels for raw table, 2D and 3D corrected data; with standard deviations of 0.08, 0.12, and 0.12 pixels.
