CLINICAL INDICATIONS Despite its status as the least used imaging modality of the ED, MRI is a continually evolving technology that may one day be indispensable to the ED physician. The combination of superior contrast and resolution frequently provides more sensitive and specific diagnoses of abdominal pathology, relative to CT (1-3). MRI also carries the additional, and perhaps more important, benefit of producing its images by measuring the effect of a radiofrequency pulse on tissue within a static magnetic field (4). The clinical relevance of this is that high-quality images can be obtained without the use of ionizing radiation. In May 2005, the U.S. Food and Drug Administration released a report stating that the amount of radiation exposure from a single CT scan of the abdomen may be enough to increase the lifetime probability of a fatal cancer by 1 chance in 2,000 (5). As MRI becomes faster and increasingly cost effective, it is not unreasonable to predict that it may eventually supplant CT scanning as first-line imaging in many indications. Today, however, the American College of Radiology (ACR) offers a very specific list of indications for MRI of the abdomen (Table 42.1). Although these are useful, they do not become compelling without the presence of a strong contraindication for CT scanning.
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