Influence of magnetic resonance imaging on diagnosis and therapeutic intention

We assessed the contribution of magnetic resonance (MR) imaging to diagnostic and therapeutic decision making.

In a before-after observational study, we collected information from clinicians before and after patients were given MR examinations. We studied 406 cases selected from consecutive referrals to a single MR imaging facility in Manitoba between November 1, 1991, and October 30, 1992, for diagnosis of suspected brain, spinal column, or large-joint disorder. We examined changes in diagnoses, changes in clinician diagnostic confidence, and changes in therapeutic intentions after MR examinations.

Overall, MR imaging findings contributed to a change in referring physicians' diagnoses or diagnostic confidence in 76% of the cases. Referring physicians reported a change in provisional diagnosis in 42% of the cases. In 67% of these cases, the referring physician's provisional diagnosis was ruled out by normal examination findings; in the remaining 33% of the cases, an alternate diagnosis was offered by the consulting radiologist. In the 58% of the cases in which the provisional diagnosis was not altered by MR imaging findings, clinical confidence in the provisional diagnosis increased in 46% of the cases and decreased in 12% of the cases. Management plans were reported to be altered in 54% of the cases; in 24% of the cases, therapeutic intentions changed from lower to higher levels of intervention.

Although MR imaging had a substantial influence on clinicians' decisions concerning diagnoses, the influence of MR imaging findings on therapeutic decision making, and therefore on patients' health status, was more moderate.