In recent decades imaging has proved one of the most rapidly expanding areas of medicine. The present day trainees entering radiology are no longer trained by radiologists who cover and are well informed on most aspects of their specialty as was the case with previous generations. Instead they encounter a confusing array of subspecialists divided both by systems and by techniques. The system specialists include neuroradiologists. vascular radiologists. gastrointestinal radiologists. chest radiologists. and skeletal radiologists. Technique specialists include experts in nuclear medicine. ultrasound. computed tomography and magnetic resonance. and there are subspecialists in both groups. not to mention others like pediatric radiologists who fit into neither classification. It is our experience that this plethora of experts each with his own individual approach is bewildering and intimidating to the novice radiologist. The numerous monographs on individual subjects and tech niques and the large textbooks so valuable to the more advanced radiologist are also confusing and unhelp ful to the new recruit. It was for these reasons that we decided to embark on this new Short Textbook. The aim was to produce a concise and integrated volume which could provide the beginner with a balanced and realistic view of the true place of different imaging techniques in current practice. Details of technique are generally excluded; most will be inevitably absorbed with increasing practical experience. The emphasis throughout is on clinical usage. and the relative and often changing importance of different methods in specific clinical contexts.