For the past several years a small group within the Division, which now constitutes the Image Analysis Section of the Medical Physics Branch, has been developing analytical methodology for evaluating the imaging performance of medical diagnostic x-ray systems. This includes the development and evaluation of a wide variety of methods of analysis for appraising the health impact of radiation exposure. Many aspects of this performance have substantial impact on the patient radiation dose required for a given amount of diagnostic information and on the amount and quality of that information which can be obtained. As a result of our early work, and studies of the literature in this field, we concluded that an international symposium devoted exclusively to this topic was in order. This present volume represents the culmination of our efforts toward that end. Kenneth E: Weaver, M.S. and Robert F. Wagner, Ph.D. of the Image Analysis Section and Assistant Professor David J. Goodenough, Ph.D. of The Johns Hopkins Medical Institutions.