Breast ultrasound elastography scores in new studies

49-year-old woman presents for screening mammogram. Area of architectural distortion is seen in left superior breast. Ultrasound-guided biopsy reveals grade 3 intraductal carcinoma. (Provided by Dr. Stamatia Destounis, Elizabeth Wende Breast Clinic)

Judging by large clinical trials on two different imaging platforms, breast ultrasound elastography is moving closer to mainstream use as a means of helping prevent biopsies of benign lesions.

Elastography refers to the measurement of elastic properties of tissues, based on the well-established principle that malignant tissue is harder and less elastic than benign tissue. On elastography images, obtained while the region of interest is compressed, malignancies appear to be larger relative to conventional ultrasound images.Dr. Richard Barr presented multisite trial results at the RSNA meeting, with real-time freehand ultrasound elastography on the Siemens Antares unit, as a follow-up to a positive single-center study presented at RSNA 2006.The new trial involved patients scheduled for ultrasound-guided biopsy at six sites. It took about one to two additional minutes to perform obtain the elastography image and measure the lesion size. The images were interpreted before pathology results were known.Of 649 biopsy-proven lesions ranging in size from 3 mm to 2 cm, 427 were benign and 222 were malignant. In five of six sites, radiologists recently trained in elastography correctly characterized all of the cancers based on lesion size on elastography images. In one site, radiologists missed three malignancies, including one case of ductal carcinoma in situ, said Barr, a professor of radiology at Northeastern Ohio Universities College of Medicine in Rootstown.Across the six sites, sensitivity averaged 98.2%, whereas specificity ranged from 67% to 95%, with an average of 85%. By comparison, in the single-center study of 100 patients presented last year, elasticity imaging correctly identified all 17 malignant lesions and 105 of 106 benign lesions, for a sensitivity of 100% and a specificity of 99%. "Hopefully, we can decrease the number of biopsies," Barr said.Radiologists were more likely to classify benign lesions as malignant when the lesion blended in with dense breast tissue on elastography images, making it difficult to make accurate size measurements, Barr said. Researchers are now working to correct this problem. Although ultrasound elastography has mostly proven itself for masses, it is also promising for evaluating suspicious microcalcifications picked up during screening mammography, according to a different study from Seoul National University Hospital in Korea.In one study at Seoul National University, conventional ultrasound and elastography images were obtained on the EUB-8500 scanner from Hitachi Medical. Researchers examined results for 50 women who underwent ultrasound-guided biopsy, including 25 DCIS lesions and 25 fibrocystic changes. Unlike Barr's study, the Korean researchers used color indications of stiffness and softness, rather than lesion size, to determine malignancy. Therefore, it was not necessary to see and measure a lesion.Elastography video clips were shown in random order to different radiologists who were blinded to the mammography results and pathology findings. These radiologists then rated the elastography images for likelihood of malignancy.

Based on this study, real-time freehand elastography achieved the following results, according to Dr. Nariya Cho, a clinical assistant professor of radiology:

• sensitivity, 96%
• specificity, 68%
• positive predictive value, 75%
• negative predictive value, 94%

"In the near future, ultrasound elastography has potential to improve accuracy of gray-scale ultrasound detection and differentiation of breast lesions associated with suspicious microcalcifications," Cho said.

In another study of 130 cases (80 benign and 50 malignant) presented by the Korean team, three radiologists had moderate to substantial interobserver agreement and substantial to perfect intraobserver agreement. The malignant cases included 36 invasive cancers and 16 DCIS lesions. Results did not differ by lesion size, the researchers said.For more information from the Diagnostic Imaging archives:

Ultrasound could overcome flaws and play supplemental role in breast screening

Strain imaging identifies benign breast masses without biopsy

Emerging technologies for ultrasonic breast cancer diagnosis: ultrasound elastography

Elastography stretches the horizons of breast imaging