Magnetic Resonance for Evaluation of the Thorax: Pulmonary VascularityPulmonary Vascularity
Since the introduction of MR there has been some interest in the use of MR in the evaluation of the pulmonary arteries in order to allow detection of pulmonary embolism and/or thrombus. Studies have been performed both in the animal model and in humans presenting with pulmonary embolus and/or thrombus.’ The experiments in dogs showed MR allowed detection of all blood clots greater than 3 mm and only three of 20 blood clots less than 3 mm. Other studies in the animal model showed MR was also capable of demonstrating the larger pulmonary emboli, especially those centrally located. read more

However, central emboli in this series also was mistaken for hilar fat. The studies performed in patients have shown MR can detect thrombus as intraluminal signal within the pulmonary arteries and MR may show resolution of this signal on repeat examinations after clot lysis. Currently, MR is not the modality of choice for determination of pulmonary emboli whether centrally or peripherally located. The above studies delineate some of the capabilities of MR in this respect. In a patient where there is an absolute contraindication to contrast and an equivocal ventilation-perfusion scan, perhaps a MR may supplement these data by demonstrating emboli.

If it is utilized, MR would be better suited for detection of central rather than peripheral emboli.
An area where MR may be useful is in the evaluation of the mediastinal and thoracic inlet vessels and in those patients presenting with obstruction of these vessels. MR has been found to provide detailed information in regard to the precise site and extent of venous obstruction. When evaluating the capabilities of CT in relation to MR it has been seen that CT with an intravenous contrast infusion can provide information similar to that available with MR. However, in those studies where an inadequate bolus of contrast is given, CT may not provide the same degree of information as MR.