Newer modalities for detection of pulmonary emboli.

Pulmonary embolism (PE) is the third most common cardiovascular disease after myocardial infarction and stroke in the United States. Early and accurate diagnosis of this condition is imperative because many patients die within hours of presentation. Clinical and laboratory tests can be used to accurately determine the pretest probability of PE. When necessary, imaging techniques are then used to exclude or diagnose PE. Pulmonary angiography is the reference standard for the diagnosis of PE, but it is invasive and has a high morbidity and mortality rate. Ventilation and perfusion (V/Q) scanning in the past has been recommended as the initial diagnostic test for PE; however, this technique also has limitations. Recently, new modalities for the diagnosis and exclusion of PE have been evaluated. These techniques include V/Q single photon emission computed tomography (SPECT), single- and multi-detected computed tomography, and magnetic resonance angiography (MRA) including gadolinium-enhanced MRA, real-time magnetic resonance imaging (RT-MR), and magnetic resonance perfusion imaging.