Blood Clots in the Lung Become Clearer

MRI techniques improve pulmonary embolism detection

(RxWiki News) New Magnetic Resonance Imaging (MRI) techniques are improving pulmonary embolism detection without the radiation of a Computer Tomography (CT) scan.

Two new MRI techniques led to improved detection of pulmonary embolisms. Using contrast-enhanced volumetric interpolated breath-hold examination (VIBE) and non-contrast true fast imaging with steady-state precession (true FISP) with MR pulmonary angiography (MRPA), provided a radiation-free alternative to a CT scan.

"Ask your doctor about signs of a pulmonary embolism."

The study was led by Diego R. Martin, M.D., Ph.D., head of the Department of Radiology at the University of Arizona College of Medicine. Originally MRPA, which uses MRI techniques, was used for pregnant women and patients whose kidneys may be damaged by CT scan radiation to detect a pulmonary embolism. It was recommended that only centers with extensive experience using MRPA should use it for pulmonary embolism detection. The two new MRI techniques could create more widespread use of MRPA.

A pulmonary embolism is a blood clot that blocks a pulmonary artery in the lungs. The blood clot commonly has traveled from the leg into the lungs. This blockage can lead to lung damage, low oxygen levels in the blood and could possibly be fatal.

MRPA is not widely used due to recommendations stemming from the Prospective Investigation of Pulmonary Embolism Diagnosis III (PIOPED III) study. The PIOPED III study was unable to get satisfactory image quality using MRPA, thus not making it viable to use for pulmonary embolism detection.

VIBE adds gray to the MRPA to distinguish between the blood clot and the lung. Using the MRPA without VIBE it was hard to tell the difference between the lung and the clot because both appeared dark. True FISP does not require a contrasting element to be added to the patient nor does it require the patient to hold their breath. Both tests are not time-sensitive which makes using the MRPA easier.

Researchers examined 22 patients who were diagnosed with a pulmonary embolism using a CT scan. Individually, VIBE, True FISP and MRPA were only adequate in detecting a pulmonary embolism, with VIBE faring the best out of the three. When combined, pulmonary embolism was able to be detected 84 percent of the time.

The use of these MRI techniques may be a viable alternative to current CT scans for detecting a pulmonary embolism. MRPA with VIBE and True FISP do not use radiation and the whole process takes just 15 minutes to set up. Dr. Martin hopes these techniques and the positive results will lead to a revised PIOPED III recommendation. 

No funding information was provided.

This study was published in the March edition of Radiology.

Review Date: 
March 22, 2012