The diffusion of MRI: patterns of siting and ownership in an era of changing incentives.

The rate and pattern of magnetic resonance imaging (MRI) siting and ownership are examined in the context of the current turbulent health-care environment. By the end of 1984, 151 MRI units were located at 134 different sites. There was one MRI unit for every 1.55 million Americans. Most of the largest metropolitan areas had at least one unit. Overall, however, the diffusion rate of MRI has lagged behind that of computed tomography (CT). Trends in magnet preference, siting, and ownership are evolving. While the majority of all units are located within hospitals, the diffusion of nonhospital-based MRI units is accelerating. The deployment of hospital-based units is progressing at a slower rate, largely limited to academic institutions and urban centers. Purchase of superconducting and permanent magnets is accelerating, while that of resistive units is decreasing. Likewise, there is a trend toward adoption of intermediate (0.5 T-0.6 T) and large (1.0 T or 1.5 T) magnets. Ownership arrangements are highly varied and characterized by increased efforts at risk-sharing, trends that reflect a more competitive, profit-oriented medical-care environment. An analysis of recent health-policy initiatives and evolving market factors helps to explain some of these observations. Increased cost-consciousness, prospective reimbursement systems, loopholes in current regulations, and increased competition among health-care providers are influencing the diffusion of MRI and may herald the fate of other expensive medical technologies in the near future.