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Contrast Enhanced MRA of the Pulmonary Arteries, Demonstrating Pulmonary Embolism
authors, Henrik Michaely, MD, Ulrike Attenberger, MD

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Clinical History:
This 23-year-old woman presented to the emergency room with chest pain and slightly elevated D-dimers. Her past medical history was relevant for a prior pulmonary embolus two years ago.

Diagnosis:
A large pulmonary embolus is visualized within the right pulmonary artery, extending into the right upper and lower lobe arteries.

MR Technique:
Scans were acquired at 1.5 T on a Siemens Avanto system, using one body matrix coil in combination with the spine coil. Bolus timing was used, employing 1 ml of contrast. For the exam itself, 14 ml of gadolinium chelate was administered at a rate of 1.5 ml/sec. This was followed by a 25 ml saline flush, administered at the same rate. The scan parameters (for the 3D volume gradient echo acquisition) were TR/TE 3.24 msec/1.08 msec, with a voxel size of 1.0 x 1.2 x 1.5 mm3 and a scan time of 21 seconds (acquired during breath-holding). Parallel imaging was utilized (GRAPPA), with an acceleration factor of 2. The scan was acquired twice, once during the arterial and once during the early venous phase (A). A MIP was performed of the contrast-enhanced acquisition in the arterial phase (B).

Imaging Findings:
In the coronal early venous phase image (A), a saddle embolus of the right pulmonary artery can be appreciated. There is only a faint residual lumen of the right lower pulmonary artery demonstrated. The right upper lobe artery is subtotally occluded. This is nicely reflected in the full thickness MIP (B) by the complete lack of vascularization of the right lung.