MR-angiography in the diagnosis of pulmonary embolism

Summary

 The purpose of this article is to describe the role of 3 dimensional (3D), breathhold, contrast enhanced magnetic resonance angiography (MRA) in the diagnosis of acute pulmonary embolism. In a volunteer study, two MRA techniques were adopted. One of which enabled acquisition of the pulmonary vasculature in 18 s. The other technique was coupled with a higher spatial resolution, leading to a scan time of 23 s. Additionally, the impact of breathing motion on vessel delineation was assessed. The breathheld 23 second scans revealed excellent image quality and near complete visualization of central and segmental, as well as 81% of subsegmental, pulmonary arteries. Imaging time can be shortened to 18 seconds with only marginal loss in visualization performance (p<0.05). Respiratory motion was found to cause significant worsening of image quality and vessel detectability. To maintain relevance in a clinical setting, imaging time can be minimized at the cost of a reduction in spatial resolution. According to data available from patient studies, the sensitivity, specificity, positive and negative predictive values of 3D MRA in comparison to conventional angiography amounts to 100, 95, 87, and 100%, respectively.

However, breathhold duration and spatial resolution need further optimization if 3D MRA should replace conventional angiography as the gold standard in the future.

Conclusion: The preliminary experience suggest that gadolinium-enhanced, three dimensional, breathhold, magnetic resonance angiography shows promise as a safe, rapid, accurate and cost-effective imaging technique for the diagnosis of pulmonary embolism. In combination with its ability to perform deep venous studies and the potential aspect of MR-perfusion studies of the lung parenchyma, pulmonary MRA might in the future turn out to be the “one stop shop” for diagnosing pulmonary embolism.