The need for a book on medica1 imaging techniques became evi- dent to the editors of this vo1ume at the 1976 Engineering Founda- tion Conference on Non-Invasive Medica1 Diagnosis. This conference treated imaging of the thorax, abdomen, brain, and extremities using ultrasound, radiology, computed tomography, and nuc1ear medi- cine. During 1976 and 1977 the editors solicited participants in the conference for contributions to this vo1ume. Other sources were also sought in special areas of interest in medical imaging beyond those individua1s who had been conference participants. Most of the writing and editing was done in late 1977 and in 1978 resu1ting in this 25-chapter book which is organized into sections on (1) Systems Considerations, (2) C1inical Results, (3) Research Topics, and (4) Tutorials. A short survey of the book is contained in the Introduction. The editors wish to acknowledge the United States National Science Foundation, particularly J. C. Aller, Program Manager, for partial financia1 support of the conference and of the publication of this book under Grant APR76-24161. The exce11ent typing services of Caroline Wadhams's organization (Report Production Associates, Cambridge, Massachusetts) and her staff, particu1ar1y Susan Dunham, are acknowledged as weIl as the efforts of Meg Grant and Winnie Garcia (Tucson, Arizona) who assisted with the subject index. The splendid cooperation of the staff of Plenum Press, in particular Stephen Dyer (Assistant Managing Editor) and Derrick Mancini (Editor), has been inva1uab1e. K. Preston, Jr.