Correction for field nonuniformity in scintillation cameras through removal of spastial distortion

A method to correct for the spatial distortions of gamma cameras has been developed. The method consists of two parts: measuring spatial distortions and repositioning events during accumulation. Distortions are measured using a pattern consisting of parallel slits on 15-mm centers with slit-pattern images obtained in two orthogonal orientations. Slit locations are used to determine X and Y displacements. In repositioning camera events, X and Y event coordinates are digitized and correction displacements added. The procedure is implemented in hardware that replositions each event in real time without introducing additional dead time. Distortion removal offers considerable advantage over other uniformity-improvement schemes, since it correctly compensates for the major cause of nonuniformity, spatial distortion. The method may be used for quantitative studies, because it does not change the number of detected events.