Abstract: Registration of organ images, such as myocardial images obtained by myocardial perfusion scintigraphy, is performed by an elastic transformation which includes a rigid transformation, a global affine transformation, and local transformations. The elastic transformation eliminates normal morphological variances such as variances in orientation, size and shape, so that the remaining differences represent important functional differences. The method may be used to register a patient's organ against a template obtained by averaging organ images from many patients. For scintigraphic images the boundary of the organ is determined by a "segmentation" procedure involving the analysis of spatial derivatives of the count density. After the elastic transformations of the surface of the organ, the scintigraphic count densities are redistributed. The method decreases the effects of operator variability and increases the reliability of diagnoses of organ irregularities.