MRI and CT of the mediastinum: comparisons, controversies, and pitfalls.

The evolving roles of MR and CT in mediastinal imaging are of keen interest to both the radiologist and the clinician. This article has illustrated the usefulness of both CT and MRI in evaluating the mediastinum. The potential pitfalls and limitations of each modality have been reiterated to help gain a perspective for further application of these technologies. Although MRI has a completely different physical basis compared with CT, current (proton) imaging is still predominantly an anatomic study. If one focuses on the image quality and the information gain (see Table 1), as has been appropriately done in comparison studies, MRI and CT are roughly equivalent imaging techniques. At present, however, technical and economic factors combine to mitigate against MRI. MRI will need to be clearly better than CT to overcome those disadvantages. The two major advantages of MRI, absence of ionizing radiation and lack of necessity for intravenous contrast material, are not important enough factors for most clinical imaging situations. Because of its current disadvantages, primarily the length of examination time, MRI serves predominantly as a second-order problem-solving technique in the mediastinum. CT currently maintains its role as the examination of choice for performing tomography of the mediastinum in the overwhelming majority of clinical situations.