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New Guideline: MRI, Not CT, For Stroke

July 13, 2010
Written by: , Filed in: Diagnostic Imaging, Emergency Radiology, Neuroradiology
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Diffusion MRI beats CT for diagnosing acute ischemic stroke, according to a new guideline from the American Academy of Neurology published today in the journal Neurology.

CT is the de facto standard for stroke diagnosis. But newer MRI techniques, such as diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI), are more accurate, the article said.

“While CT scans are currently the standard test used to diagnose stroke, the academy’s guideline found that MRI scans are better at detecting ischemic stroke damage compared to CT scans,” said lead guideline author Peter Schellinger, MD, of the Johannes Wesling Clinical Center in Minden, Germany. Schellinger was quoted in an academy news release.

Ischemic strokes (resulting from lack of blood flow to the brain rather than hemorrhage) constitute about 87 percent of all strokes. In the United States, stroke is the third-leading cause of death and the leading cause of permanent disability.

The new guideline resulted from a study in which a team of neurologists, neuroradiologists, and radiologists analyzed literature dating from 1966 to January 2008. They particularly cited a study that compared the accuracy of CT and DWI in 356 consecutive potential patients at a hospital emergency department over an 18-month period. Two neuroradiologists and two stroke neurologists, blinded to clinical information and CT-DWI pairings, interpreted the scans independently.

According to the article:

In the subset of 221 patients scanned within 12 hours of onset, the majority of readers correctly diagnosed acute ischemic stroke by MRI more often than by CT (94 vs. 22).

The study also found that MRI more accurately detected lesions from stroke and helped identify the severity of some types of stroke or diagnose other conditions with similar symptoms.

“This guideline gives doctors clear direction in using MRI first, ultimately helping people get an acute stroke diagnosis and treatment faster,” said Dr. Schellinger. “However, one situation in which CT may still be used first is when a person needs an emergency injection of drug therapy (also known as intravenous thrombolytic therapy) to break up blood clots, if MRI is not immediately available, to avoid delays in starting this treatment. MRI can be added later if more information is needed. Otherwise, MRI should be used first.”

Related seminar: National Diagnostic Imaging Symposium

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