Radiology: Hybrid scanner makes headway into breast cancer detection
A pilot clinical evaluation of a hybrid scanner that uses dual-modality tomosynthesis (DMT) and technetium 99m sestamibi to provide co-registered anatomic and 3D functional breast images suggests that it is a feasible and accurate method with which to detect and diagnose breast cancer, according to a study published in the April edition of Radiology.

Mark B. Williams, PhD, department of radiology at the University of Virginia in Charlottesville, and colleagues evaluated the DMT scanner, and determined that systems such as this scanner designed specifically for 3D multimodality breast imaging could advance tumor detection, localization and characterization of breast cancer that are now being observed with whole-body 3D hybrid systems, such as PET/CT or SPECT.

The HIPAA-compliant prospective evaluation of the scanning method included 17 women, with an age range of 44-67 years, who were scheduled to undergo breast biopsy between April 2008 and May 2009. X-ray tomosynthesis imaging was performed first, followed by MBI tomosynthesis. Thirteen of the study participants had one lesion each, four had two lesions and the researchers evaluated all 21 biopsy-sampled lesions. The results of DMT scanning were compared with histopathologic results for the 21 lesions, they wrote.

All images were read by a board-certified mammography radiologist with five years of experience and the reader was blinded to biopsy results, as well as to all clinical mammographic, ultrasound and MRI, explained the authors.

The x-ray tomosynthesis images alone were presented in a random sequence, followed by the MBI tomosynthesis images alone which were presented in a different random sequence. Then, the matched DMT data sets were presented to the reader, said the researchers. In all three reading sessions, all findings were rated by using a five-point scale: 1, definitely benign; 2, probably benign; 3, indeterminate; 4, suggestive of malignancy; and 5, highly suggestive of malignancy, they wrote.

Williams and colleagues found that of the 21 lesions, 14 could be classified as benign and seven were malignant. Ten of the 13 subjects that had one lesion had negative biopsy results and the remaining three had positive results.  The authors also found that of the four participants with two lesions, the biopsy results were as follows: bilateral in one, both negative; bilateral in one, both positive; unilateral in two, one positive and one negative.

In addition, the DMT scanning yielded a sensitivity rate of 86 percent; specificity, 100 percent; positive predictive value, 100 percent; negative predictive value, 93 percent; and the overall accuracy of the scanning method was determined to be 95 percent.

Noting the strength of the DMT approach, the authors said: “The MBI tomosynthesis scan depicted a clinically occult lesion in a region of radiographically dense fibroglandular tissue, and the fused x-ray tomosynthesis images yielded an anatomic reference with which to identify exactly which region of the breast contained the lesion, thereby permitting subsequent localization and biopsy by means of ultrasound.”

Williams and colleagues noted that integrated, multimodal, 3D breast imaging systems are being developed by other investigators.

While the authors called the results of their pilot study “encouraging,” they acknowledged: “It is a small study, and more experience with DMT breast scanning will be necessary to optimize subject positioning and acquisition protocol, as well as to assess more precisely the incremental benefit of DMT relative to x-ray tomosynthesis alone.”