3D Digital Mammography Could Reduce False-Positive Findings

Two-dimensional (2D) X-ray mammography, the existing primary screening technique for early detection of breast cancer in women, is a helpful approach but has some drawbacks. Surrounding normal tissue can hide lesions, and 2D views do not provide direct data about the volumetric appearance (the 3D physical shape) of an identified tumor.

Stereoscopic digital mammography (SDM) handles these hurdles by imitating the manner in which human eyes work in conjunction to form a 3D image. The approach utilizes digital mammography equipment that has been customized to allow the X-ray tube to move separately from the cassette. The ensuing images are viewed on two monitors mounted one above the other.

“Our eyes see the world from two slightly different perspectives,” said Carl J. D'Orsi, MD, from the department of radiology and imaging sciences at Emory University School of Medicine and the Winship Cancer Institute at Emory University (both in Atlanta, GA, USA). “In this technique, the X-ray tube functions as the eyeball, with two different images providing slightly different views of the internal structure of the breast.”

By using new workstation and polarizing lens technology, SDM has the ability to identify tumors at varying depths within the breast volume, possibly decreasing both false-positive findings and recalls while enabling more effective diagnoses. Dr. D'Orsi and colleagues recently compared SDM to 2-D digital mammography in 779 patients at an increased risk of developing breast cancer because of personal or family history. Patients received both exams in a single visit, and two experienced radiologists independently interpreted a total of 1,298 exams. Imaging findings were correlated with findings of one-year follow up or biopsy.

The study showed that SDM considerably improved the accuracy of cancer detection. The specificity of 91.2% was better than the 87.8% rate for 2D digital mammography; and the accuracy of 90.9%, compared with 87.4% for 2D digital mammography, was also a statistically significant improvement. “We found that the stereoscopic technique could significantly decrease the need for calling women back for additional exams,” Dr. D'Orsi said.

Dr. D'Orsi and colleagues are expanding their studies to evaluate SDM with a lower radiation dose in the general screening population. The radiation dose used in the study was about twice the standard dose for mammography. “In this study, we used a high-risk population to get an adequate number of cancers, and we acquired each of the images comprising the stereo pairs with a full standard X-ray dose,” he concluded. “Now that we know the technique is worthwhile, we’re repeating the study in the general population with a dose comparable to routine screening mammography.”

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Emory University School of Medicine