Breast ultrasound technique edges toward acceptance

November 29, 2006

Automated whole-breast ultrasound (ABUS) helps find additional lesions in the screening setting and its performance in diagnostic studies alongside mammography is roughly equal to handheld ultrasound, according to studies presented on Wednesday at the RSNA meeting.

Automated whole-breast ultrasound (ABUS) helps find additional lesions in the screening setting and its performance in diagnostic studies alongside mammography is roughly equal to handheld ultrasound, according to studies presented on Wednesday at the RSNA meeting.ABUS systems are commercially available in the U.S. but to date, trial data have been limited. Breast ultrasound is notoriously operator dependent and scanning practices are highly variable. Automated versions promise to level the playing field.

Two RSNA studies examined the performance of the SomoVu system from U-Systems. In one multicenter trial of 177 breasts in 165 patients, findings on mammography with automated ultrasound agreed with mammography plus handheld ultrasound in 94% of breasts analyzed. This study updates results released last year in 40 cases with a similar level of agreement.Another study performed at the Elizabeth Wende Breast Clinic in Rochester, NY, found that in women with dense breasts, ABUS helps spot additional findings that otherwise would go undetected in mammography screening.With handheld ultrasound, a technologist performs the scan with input and/or monitoring from the physician, or the physician personally performs the ultrasound study. But wide variability exists in practice, as some users image only the area of concern, others scan just one breast, and still others routinely fully scan all areas of both breasts. With ABUS, parameters are preset, technologists perform the scan and the radiologist reads the cases on a workstation later after the patient leaves the premises. Dr. Stamatia Destounis, the study's lead author, noted the potential manpower benefits of the device."The bottom line is, there are not enough of us to go around," she said. "Mammography is not well reimbursed and not enough young people are entering breast imaging fellowships. Breast imagers are already overworked and we have to get smarter about how do to things."Researchers at Elizabeth Wende are currently performing three views per breast, which takes six minutes per breast. It might be possible to reduce scan time by selecting the best two views. It takes about two minutes reading time per breast with the automated device, although there is a learning curve involved in achieving this speed, she added.In the screening trial at Elizabeth Wende, researchers examined use of automated ultrasound as an adjunct to screening mammography in 292 breasts of 147 women. Mean age was 49 and most patients had dense breasts and had been undergoing regular breast exams.Ultrasound yielded 95 findings, most of which researchers determined were benign, often with the help of prior imaging studies and case histories. Cysts comprised the predominant findings. Six patients were recalled for further assessment and two were biopsied. A larger patient population is needed to assess the value of ABUS in screening, but these results are promising, Destounis said. Ultrasound will make a difference by finding cancers at earlier stages, before they are palpable, with obvious benefits for prognosis. Given the manpower issues, it would be more challenging to implement handheld ultrasound in the screening setting.Automated ultrasound has been a works-in-progress for some years now. Previously, the technology suffered from insufficient sensitivity. Earlier versions of the SomoVu system imaged the patient while standing, but since then it has become evident that visualization is better when the patient is lying down. There have also been multiple software upgrades. Now, the test appears to be edging toward clinical acceptance in some quarters."If [vendors] keep on improving quality, which has already come a long way, automated breast ultrasound will become a helpful additional tool for screening for breast cancer detection," said Destounis.Aside from the SomoVu systems, a number of other automated breast ultrasound devices have been in development. At the RSNA meeting, researchers presented results with the Philips investigational Whobus system, in which women are imaged standing up with breast compression. Results were compiled by Dr. Robert Schmidt, professor of radiology at the University of Chicago and Dr. Bruce Porter, medical director at First Hill Diagnostic Imaging in Seattle. Researchers at the two sites analyzed the ability of Whobus to detect known lesions in a nonrandomized pilot study funded by Philips. Out of 38 lesions, Whobus had 82% sensitivity for malignant lesions and only 50% sensitivity for benign findings. The 12 lesions not seen with Whobus included lesions close to the chest wall and immediately behind the nipple. Furthermore, handheld ultrasound proved more accurate in measuring lesion size.Due to the poor results, researchers stopped the study, even though they had intended to look at 100 cases, and recommended changes in system design. Many of the problems in performance were related to breast slippage in compression due to the coupling gel and limitations in visualization of the nipple and chest wall.