The last decade has witnessed an unprecedented and explosive expansion of new modalities in diagnostic imaging. To a great extent this is the result of the investment of governments in weapons research and space and energy exploration. These have produced significant break throughs and advances in microcomputers, microcircuits, telecommunications and miniaturisation of equipment. The impact of the application of the new imaging modalities has been significant. The patient flow is changing from predominantly in-patient to largely ambulatory as diagnostic examinations have become less and less invasive. Even some therapeutic procedures have shifted from the operating room, where anaesthesia was required, to the high-technology imaging suite where interventional radiologists remotely control instruments, with the help of one of the imaging modalities. These changes are accelerating as technological advances continue and the benefits are so obvious that even the most severe critics are challenging not their benefits but their affordability in view of their rapid dissemination and high price.Furthermore, the advances in imaging technology are occurring in an atmosphere of retrenchment in expenses and a determination on the part of society in the USA and elsewhere rigidly to control the cost of medicine.In 1984 $387.4 billion were spent on all types of health care in the US (Waldo&Lazenby, 1985).