Pulmonary embolism: comparison of MR images with radionuclide and angiographic studies

To assess the accuracy and potential of magnetic resonance (MR) imaging in evaluation of patients in whom pulmonary embolism is suspected.

Blinded, prospective interpretations of multiphasic, cardiac-gated spin-echo MR images were compared with retrospective chart review in 86 patients in whom pulmonary embolism was suspected. In 64 patients, the presence or absence of pulmonary emboli was established with x-ray angiography (n = 34) or ventilation-perfusion (V-P) scans and concurrent clinical impression (n = 30).

In the subgroup with angiographic proof, MR imaging had a sensitivity of 90%, specificity of 77%, positive predictive value of 86%, and negative predictive value of 83%. In 21 patients with intermediate probability of pulmonary embolism on V-P scans and angiograms, MR images enabled diagnosis of pulmonary embolism in 12 of 12 patients (sensitivity, 100%) and absence of pulmonary embolism in seven of nine patients (specificity, 78%).

MR imaging reliably depicts large and medium-size pulmonary emboli, regardless of infiltrates or effusion; hence, it may clarify findings on V-P scans that show intermediate probability of pulmonary embolism or are at variance with the clinical impression.