Three Domains in Diagnostic Radiology

S ince the discovery of X-rays in 1895, the applications of radiation in medicine have broadened tremendously in scope. Three specialties have emerged during the last 50 years; namely, diagnostic radiology, therapeutic radiology, and nuclear medicine. Nowadays, these specialties are established worldwide in clinical practice with board certification, and in education, training, and research, although some loose interrelationships still remain in some countries. In diagnostic radiology, subspecialization has evolved either by organ system or by technology. Even though they were met with a tremendous enthusiasm in their early stages, we have witnessed the eventual decline of subspecialties for angiography and CT, and technology oriented subspecialization seems unrealistic and self limited. Interventional radiology is a relatively young subspecialty of diagnostic radiology and the role of interventional radiologists in patient care is quite different from that of traditional image interpretation-oriented radiologists. Interventional radiology is increasingly expanding its role replacing surgery as a treatment of choice in various diseases. Recently, with the advance of new MR technology, the clinical application of functional MR imaging, spectroscopy, diffusion and/or perfusion imaging is increasingly applied in daily practice. Furthermore, imaging of immunological process and imaging at the gene level is being explored. This means that the scope of diagnostic imaging is expanding from detection and characterization of organ or tissue level pathology, to characterization of disease at the cellular or molecular level. Consequently, we could define three domains of diagnostic radiology (1, 2) as