Ultrasound elastography reduces need for breast biopsy

March 20, 2006

A decade has passed since luminaries began generating promising clinical results using ultrasound elastography, which measures the elastic properties of tissue. Two years ago, Hitachi Medical began commercializing this technology. Now that company’s experience with its EUB Logos 8500 and pioneering work with a modified Siemens Allegra suggest that efforts to push elastography forward could soon begin paying dividends for vendors, customers, and patients.

A decade has passed since luminaries began generating promising clinical results using ultrasound elastography, which measures the elastic properties of tissue. Two years ago, Hitachi Medical began commercializing this technology. Now that company's experience with its EUB Logos 8500 and pioneering work with a modified Siemens Allegra suggest that efforts to push elastography forward could soon begin paying dividends for vendors, customers, and patients.

Promising results reported at the European Congress of Radiology indicate that elastography may have a major impact in breast imaging, where the difference in acoustic impedance is small, and tumors are often difficult to image clearly.

In a multicenter prospective study of 345 breast lesions in 314 patients, French researchers achieved sensitivity of 80%, specificity of 93%, positive predictive value of 85.3%, and negative predictive value of 90.3% using the elastography function on Hitachi's EUB Logos. Sensitivity was best for lesions smaller than 5 mm (90%), while specificity was best for lesions larger than 10 mm (95%). For lesions in BI-RADS categories 3 and 4, sensitivity was 68% and specificity was 90%.

Researchers also reported 16 false positives (e.g., fibrous mastopathy and sclerosis adenosis) with elastography and 26 false-negative findings (e.g., DCIS).

Dr. Anne Tardivon of the Institut Curie in Paris described elastography as easy to perform, once practitioners are trained in its application. She said the technology provides good visualization, describing its use as "not time-consuming."

"Elastography does not replace standard B-mode imaging, but clearly, it is a useful complementary tool and may reduce biopsies of benign lesions," Tardivon said.

SonoElastography, built into Hitachi's EUB Logos, transforms information about the relative stiffness of tissue into color maps and overlays them on standard B-mode images. These overlays appear to be helpful in distinguishing between malignant and benign tumors, a distinction that often requires invasive techniques as needle biopsy or cytodiagnosis.

U.K. researchers reported that ultrasound elastography helped a British breast cancer screening program slash the rate of biopsies of benign lesions by half. The results were based on four years of experience with Siemens' Allegra ultrasound system outfitted with standard breast probes and specialized elastography software.

"This has great importance, given the increased incidence of screening abnormalities picked up on breast ultrasound," said Dr. William Svensson, an honorary senior clinical lecturer at the division of investigative science at Imperial College London.

The clinical results show that benign lesions have smaller elasticity profiles, compared with malignant lesions, which appear larger in gray scale than benign lesions.

"Our hypothesis proved true: that the size of a cancer is larger in elasticity imaging than in B-mode," Svensson said. "With benign lesions, the reverse is the case."

The British study included women who were referred for breast ultrasound because of focal breast abnormalities. In cases where abnormalities were identified on ultrasound, women underwent breast strain imaging.

Of 260 lesions identified, 71 were malignant, nine were intermediate with malignant potential, and the majority, 180 lesions, were benign.

The British researchers determined that lesions with a certain elasticity to gray-scale ratio were benign. Based on this ratio, all of the malignant lesions - aside from a few intermediate ones - would have been identified. That equates to a sensitivity of 96%.

Specificity was just 53%, meaning that applying the ratio could cut the number of benign lesions needing to be biopsied in half, Svensson said. In addition to the obvious clinical value, there are also economic advantages.

"Benign biopsies cost us a lot of money and if we can reduce them, that would bring significant savings for the health service," he said.