Computed tomography and magnetic resonance imaging of the skull and brain.

The role of magnetic resonance imaging (MRI) and computed tomography (CT) in the evaluation of the central nervous system and spine has been intensely studied over the past 10 years. However, MRI is still undergoing rapid technologic evolution including new image-acquisition techniques and the development of paramagnetic contrast agents. Since the first description of MR imaging in humans in 1977, many papers have described the “usefulness” of this new technology. Prior to FDA approval of Diasonics, Picker, and Technicare units in 1984, all studies were performed on clinical research protocols that were not reimbursed by insurance companies or Medicare. Since 1984, Technicare Diasonics General Electric, Fonar, Siemens, Philips, El Stint, and other manufacturers have been granted approval by the FDA, and the number of MRI installations has mushroomed, exceeding 1000 in 1988. Many states attempted to limit the proliferation of MRI devices using certificate of need (CON) regulations mainly affecting the number of institutional units. However, in many states, including New York, CON regulations have no jurisdiction over acquisition of medical equipment for private offices or imaging centers, thus encouraging hospital-based radiologists to establish off-campus MRI sites sometimes in direct competition with units owned by self-referring clinicians or nonmedical investors.