central ray (CR), 1. the portion of the x-ray beam with minimal divergence of the beam rays. It is directed toward the center of the image receptor or of the object being imaged. See also elongation, image foreshortening, cone cutting. 2. ▪ METHOD: when utilizing the paralleling technique of image requisition, the central ray should be perpendicular to the long axes of both the tooth and the image receptor. If the central ray is not positioned correctly, the resulting image is distorted or missing.
