Hybrid breast imaging unit melds molecular and x-ray tomo

By Kate Madden Yee, AuntMinnie.com staff writer

April 5, 2010 -- Digital mammography tomosynthesis is one of the hottest new breast imaging technologies, but what if you added a molecular-based functional tomosynthesis capability to it? University of Virginia researchers did just that, and reported on their findings in a new study published in the April issue of Radiology.

In the study, the research team describes what they call dual-modality tomosynthesis (DMT), which combines a 3D digital mammography breast tomosynthesis system developed by Dexela of London with a molecular breast imaging (MBI) gamma camera that also moves across the breast to collect 3D functional tomosynthesis images. The camera was supplied by Jefferson Laboratory of Newport News, VA, while the university supplied the x-ray detector and gamma camera positioning mechanism (Radiology, April 2010, Vol. 255:1, pp. 191-198).

The DMT system is intended to improve on the shortcomings of x-ray mammography and ultrasound in detecting early cancers in women with dense breast tissue by acquiring anatomical 3D tomo images and 3D functional images of a technetium-99m sestamibi-based tracer with one device, according to Mark Williams, Ph.D., from the University of Virginia. The DMT unit sequentially scans patients who are seated upright and gathers both types of images with the breast in the same, immobilized position.

In a pilot study of the system, Williams and colleagues compared DMT results with biopsy results in 17 women with 21 lesions. Of the 21 lesions, seven were malignant and 14 were benign. Among 13 women with one lesion each, three had positive biopsy results and 10 had negative biopsy results.

DMT detected one missed cancerous lesion and corroborated every benign diagnosis from biopsy results.

Diagnostic performance of breast tomo modalities
X-ray tomo only MBI tomo only X-ray + MBI tomo
Sensitivity 86% 86% 86%
Specificity 57% 100% 100%
Positive predictive value 50% 100% 100%
Negative predictive value 89% 93% 93%
Accuracy 67% 95% 95%

In an e-mail to AuntMinnie.com, Williams acknowledged that the findings demonstrated equivalence between MBI tomosynthesis alone and MBI tomosynthesis combined with x-ray tomo, a finding he said could be due to the small number of lesions in the study.

He added that the significance of the study was its novel use of MBI tomosynthesis, which could offer an improvement over planar MBI with dedicated breast cameras. At least one planar MBI camera has already received U.S. Food and Drug Administration (FDA) approval.

Tomosynthesis full-field digital mammography systems are about to hit the U.S. market, and they are likely to replace an increasing number of existing conventional digital mammography units over the next 10 years, according to Williams. An adjunct compact gamma camera capable of MBI tomosynthesis could be mounted on an upright x-ray tomosynthesis mammography unit relatively inexpensively, he wrote.

By Kate Madden Yee
AuntMinnie.com staff writer
April 5, 2010

Can DBT unseat MRI for screening high-risk women? March 22, 2010

Adding DBT to mammo increases cancer detection in dense breasts, January 18, 2010

DBT reduces false-positive rate by 41% in screening setting, December 1, 2009

Digital breast tomosynthesis cuts recall rate by 30%, August 4, 2009

ECR delivers new findings on digital breast tomosynthesis, March 7, 2009

Copyright © 2010 AuntMinnie.com


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