Magnetic Resonance Imaging

Pulmonary emboli appear as intermediate to low signal defects on spin echo T1-weighted images (figure 1) and low signal defects surrounded by enhanced blood pool on MRA images (figure 2).


Figure 1. MRI for PE

Coronal spin echo T1-weighted image through the thorax shows intermediate signal abnormalities occupying the left and right pulmonary arteries, consistent with PE.

Find the embolus in the left pulmonary artery.

Find the embolus in the right pulmonary artery.


Figure 2. MRA for PE

Coronal MRA image through the thorax shows an abnormality with very low signal occupying the main and left pulmonary arteries, representing PE.

Find the embolus.

A = aorta

IVC = inferior vena cava

MRA has recently been compared to conventional angiography [1].


1. Oudkerk M, van Beek E, Wielopolski P, van Ooijen P, Brouwers-Kuyper E, Bongaerts A, Berghout A. Comparison of contrast-enhanced magnetic resonance angiography and conventional pulmonary angiography for the diagnosis of pulmonary embolism: a prospective study. Lancet 2002; 359:1643-1647. Abstract

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Embolus in left pulmonary artery
































Embolus in right pulmonary artery
































Embolus in main and left pulmonary arteries