Improved imaging of carotid artery bifurcation using helical computed tomographic angiography.

Although duplex scan and magnetic resonance angiography (MRA) provide reliable and noninvasive tests for detecting extracranial carotid artery disease, they sometimes fail to differentiate between high-grade stenosis and total carotid occlusion. Helical computed tomographic angiography (CTA) is a safe, noninvasive technique that allows the rapid acquisition of data that can be reconstructed into two- and three-dimensional images. Axial images can be magnified and provide a cross-sectional view of the carotid vessel and the atherosclerotic plaque. Maximal intensity projection technique allows data to be reconstructed into images that closely resemble conventional arteriograms. Helical CTA has previously been shown to have a diagnostic accuracy approaching 90%. We present two case reports demonstrating the utility of helical CTA in carotid artery imaging when duplex scan and MRA results are ambiguous. These cases illustrate improved carotid imaging with helical CTA. Duplex scan results are unreliable in the presence of thick calcified plaques, and severe stenoses can be misread as occlusion by duplex and MRA due to low blood flow. Thus, helical CT angiography should be considered as a confirmatory test, before arteriography, when duplex scan or MRA results are equivocal.