Diagnostic Imaging Online
November 19, 2002
CT may equal MRI for emergency room evaluation of stroke
A combined CT protocol could be just as good as MRI to assess acute stroke, according to German researchers. The technique could make emergency room evaluation faster and more accurate.
A team of investigators at the University of Heidelberg and the University of Kiel found in a study of stroke patients that nonenhanced CT, contrast-enhanced CT angiography, and CTA source images (CTA-SI) matched up well against diffusion-weighted imaging (DWI) and MR angiography for diagnosing acute stroke.
Researchers examined 20 stroke patients who underwent CT and diffusion-weighted MRI within six hours of the onset of symptoms. Both modalities confirmed vessel occlusion in 16 patients, with no significant volume difference and a high outcome correlation between CTA-SI and DWI.
The research team also found that CTA-SI could be as reliable as DWI for assessing the extent of ischemia, detecting hemorrhage, assessing vessel status, and estimating brain tissue at risk. The trial was published in the October issue of Stroke.
"Acute stroke imaging can be done with CT and CTA with a quality comparable to DWI," said Dr. Peter Schramm, a neuroradiologist at the University of Heidelberg.
Although they are difficult to perform in emergency settings, diffusion and perfusion MRI studies are preferred by many radiologists for assessing patients with acute stroke. The combined CT/CTA/CTA-SI technique, however, should be considered a reliable approach in an emergency room setting, where CT is likely to be more readily available than MRI, Schramm said.
"One does not need MRI to detect large middle cerebral artery infarctions that should be treated with thrombolysis. Considering the availability of this method, a CT-based imaging modality in acute stroke patients is necessary," he said.
Previous studies indicate that combined perfusion and diffusion MRI data analysis, referred to as PWI/DWI mismatch, may identify brain tissue at risk of infarction that could be saved with revascularization. According to Schramm, some specific CT and CTA criteria, such as poor collateral flow and a smaller infarct volume than the brain area corresponding to the localization of the vessel occlusion, may be considered analogous to the PWI/DWI mismatch criteria.
Using CTA to detect vessel occlusion and CTA-SI to see the extent of the infarct core offers a reliable, CT-based diagnostic tool, and the protocol can be applied on most CT equipment, he said.
"CT angiography can be done on almost every spiral CT scanner, even single-slice," Schramm said.
-- By Harold Abella
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