Report from ISET: Sonoelastography breaks through in carotid imaging

Following a stream of new clinical applications for ultrasound elastography, researchers at New York Medical College have announced new evidence suggesting the technology is sensitive and accurate for characterization of carotid artery plaque. Sonoelastography could help prevent strokes and other vascular ischemic diseases, according to investigators.

Evidence pointing at carotid artery plaque composition rather than stenosis degree as more predictive of stroke continues to accumulate in the clinical literature. In addition to other imaging modalities, B-mode and 3D Doppler sonography of the carotids have shown value for the characterization of vulnerable plaque. The test has also been proposed as an alternative to invasive intravascular ultrasound.

Calcified plaque hinders the accuracy of conventional ultrasound, however. European and Canadian researchers have considerable experience testing whether intra- and extravascular elastography can overcome this limitation. The largest prospective in vivo study thus far to compare Doppler and elastographic sonography suggests that sonoelastography can characterize vulnerable carotid plaque accurately and more cost-effectively than other modalities, according to principal investigator Dr. Robert L. Bard, an associate professor of radiology at New York Medical College.

"What makes this technology special is it can actually image the arterial wall in people with calcified plaque, whereas a regular sonogram would not do it at all, and the test would be inconclusive," said Bard in an interview with Diagnostic Imaging.

In Bard's study, 44 patients with proven carotid plaque underwent conventional real-time 3D power Doppler and elastographic angiography. All patients underwent conventional and elastographic imaging at the same time. Researchers found elastography could image the entire arterial lumen even in the presence of the calcified plaque that had undermined Doppler sonography.

Bard released findings in January at the 2009 International Symposium on Endovascular Therapy in Hollywood, FL.

Twenty-four of the 44 patients had anterior calcified plaque that limited study of posterior wall disease on conventional high-resolution sonography. Elastography allowed accurate visualization and analysis of 20 of these patients, 15 of whom were later confirmed by MR angiography as having greater than 50% stenosis undetected by conventional ultrasound.

The technique developed at the Curie Institute in Paris has proven particularly useful for the characterization of ulcerated plaque, which can break off and lead to ischemia, according to Bard. Ongoing research on future applications includes diagnosis of arteriovenous malformations and peripheral vascular disease in diabetic patients.

One of the most promising areas, however, could be the characterization of thrombosis. Sonoelastography may be able to differentiate between chronic and life-threatening acute thrombosis, which led Bard to choose the topic as the focus of his next study.

Thanks to the development of volumetric ultrasound scanning, the technique is not operator-dependent and can be performed quickly. Sonoelastography could become a cheaper alternative to MR vascular studies and a safer alternative to fluoro or CT angiography. Overall, vascular ultrasound elastography might have important implications for patients and clinical practice, according to Bard.

"It will give patients an accurate diagnosis and peace of mind. Sometimes, they are told their disease is much worse than it actually is," he said. "And it will give clinicians not only a better mapping tool, but it will help them look at intimal thickness -- a predictor of stroke and heart attack -- in a different way."

For more information from the Diagnostic Imaging archives:

Sonoelastography breaks new ground in musculoskeletal imagingThree-D MRI zeroes in on stroke-inducing carotid artery diseaseVessel imagers focus on plaque characterization