This book is a supplement to Volume V /1 in the present series, Diag­ nostic Radiology, published in 1962. Despite the relatively long period of time which has elapsed since its publication, that comprehensive vol­ ume is still essentially valid, even though further developments have of course occurred in certain fields. In recent years the developments in nuclear medicine and ultrasonic techniques have led to a number of new methods of medical investigation, which, in different ways, complement diagnostic radiology. Functional disorders of the urinary tract can often be detected by means of radioiso­ topes. Since morphologic changes are almost always preceeded by func­ tional disturbances, radionuc1ide techniques in many instances produce an earlier diagnosis than radiography. Disturbances of renal blood flow, slight ureteric obstruction, and ureteric reflux are examples of pathologic states which can be detected early by the'}' scintillation camera. Bone scans, i.e., imaging of the skeletal system using a radionuc1ide, are used extensively to diagnose bone metastases now that it has been demonstrated that such metastatic growths are identified both earlier and with greater accuracy by scintigraphy than by radiographic tech­ niques.