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MRA for diagnosis of venous thromboembolism.

Direct imaging of pulmonary embolism (PE) and deep vein thrombosis (DVT) with CT, and potentially with MR, will continue to replace V/Q scintigraphy. Venous imaging with MR far detecting DVT is used in a few centers, and their published accuracy figures are impressive. Recent studies of MR pulmonary angiography for PE reported that sensitivity of MRA was 85-100%, specificity 95-96%, but this data must be confirmed in other centers and patient populations. MR has advantages compared with CT, which make it worthwhile to continue MR development. Ionizing radiation and iodinated contrast material are not used. Imaging the pulmonary arteries and then imaging whichever venous region is of clinical interest is practical in a single examination. Repeated examinations can be performed safely. New contrast materials will facilitate the practicality and accuracy of the MR technique and perfusion imaging may increase sensitivity. MR also has disadvantages compared with CT. It does not image effectively the non-vascular compartment of the lungs. It is more expensive, patient monitoring is more cumbersome, and a routine technique, which embodies all of MR's potential advantages, has not been packaged and tested. Accordingly, helical CT is a realistic option in clinical management of patients with suspected PE in most centers, while clinical application of MR is limited to centers with appropriate MR expertise and technology. However, MR has a number of fundamental characteristics that make it a potentially ideal modality for evaluating patients with suspected acute venous thromboembolic disease and further clinical research with MRA is warranted.