Study Objective: Evaluation of demonstrated clinical efficacy of magnetic resonance (MR) imaging in the central nervous system.
Design: Information synthesis of studies before January 1987.
Setting: Reports were classified by the level of clinical efficacy studied (technical capacity, diagnostic impacts, and therapeutic or patient outcome impacts) and were judged by the validity of their methods, especially avoidance of diagnosis review, test review, and work-up biases.
Main Results: Magnetic resonance imaging probably is superior to computed tomography for detection and characterization of posterior fossa lesions and spinal cord myelopathies, imaging in multiple sclerosis, detecting lesions in patients with refractory partial seizures, and detailed display for guiding complex therapy, as for brain tumors. In other diseases, the efficacy of MR imaging is similar to that of computed tomography (cerebrovascular, radiculopathy, and infection). Magnetic resonance imaging is less invasive than intrathecal or intravenous contrast-enhanced computed tomography and costs 20% to 300% more than computed tomography, although avoidance of hospital stays may offset some costs. Generally, the quality of MR images probably exceeds that of computed tomographic (CT) scans. However, published evidence does not show that the clinical efficacy of MR imaging is generally superior to that of existing imaging modalities such as computed tomography. Only six studies avoided major methodologic biases, and lower true-positive rates for MR imaging were reported in these studies than reported in multiply biased studies. Few studies of the potential of MR imaging for false-positive diagnosis have been done.
Conclusions: Use of standards for quality of evidence leads to more conservative conclusions than those of reports describing the clinical potential of MR imaging. Some applications of MR imaging were confirmed by rigorous studies, whereas others were not well supported by reports free of methodologic biases. If the diagnostic alternative is invasive (for example, myelography and cisternography), MR imaging is preferred, but adequate diagnosis for many conditions (head trauma, simple stroke, and dementia) may not require the detail of an MR imaging study. In general, more rigorous clinical research studies are needed for new technologies such as MR imaging. Because the field of MR imaging is changing, review of its clinical efficacy will need to be revised frequently.