Analysis and correction of spatial distortions produced by the gamma camera.

Summary Spatial distortions introduced to radionuclide images from a gamma camera/PDP-8/I computing system have been investigated by analyzing the response of the system using a 4,000-hole technetium collimator to a defined orthogonal grid source of 99mTc. The 50 × 50 data matrix of the grid image was first corrected for nonuniform sensitivity response, and the nonlinearities in the image were analyzed using programs developed for an IBM 1800 computing system. Spatial distortions ranged from −7.8 to 5.8 mm with 30% of the data matrix points distorted more than 3.2 mm. Spatial errors were consistent, both in magnitude and location, over the camera face during a 5-month period. A software routine has been developed for the IBM 1800 which either shifts each data point in any radionuclide image to its correct location, leaving the count content unchanged, or, leaving each data point in its original position, calculates the correct number of counts for the location in question. The latter alternative maintains the uniform intervals between the digitized data points and hence is more convenient for display of clinical data by an output device. These techniques may be applied to any digitized clinical image to correct for spatial distortions.