In the first study, researchers compared standard plain film mammography to TOMO. Forty patients were included in the study. Radiologists detected 16 of 22 malignant lesions on mammography and 18 of 22 malignant lesions on TOMO, says Elizabeth Rafferty, MD, lead author of both studies. TOMO was superior to plain film mammography in detecting masses and architectural distortions, which results from a tethering or pulling in of the tissue, says Dr. Rafferty. Calcifications were not as conspicuous on the tomosynthesis imaging during the pilot study, she says. "We are currently implementing a solution to this challenge and will have data on this soon," she adds.
In the second study, 45 patients were reviewed. All patients had been called back for a second mammogram because their first showed a possible abnormality; "30 of them were subsequently found by additional mammographic views to have breast tissue overlap accounting for their possible abnormality," she says. Fifteen patients went on to biopsy. "We asked radiologists to look at the TOMO study (without knowing the results of the second mammogram or biopsy) and indicate whether they would have called these patients back for additional evaluation," says Dr. Rafferty. They indicated that they would have only called back five of the 30 patients who had breast tissue overlap. "If we could have used TOMO on these patients initially, it would have saved 25 women the anxiety they felt and the inconvenience they experienced of being called back for additional tests," notes Dr. Rafferty.
The radiologists indicated that they would have recalled 14 of the 15 patients who had a biopsy, says Dr. Rafferty. A single reader missed one cancer, she says. "This is well within the standard interobserver variability seen with conventional mammography," she adds.
"TOMO allows us to take multiple projections of the breast at different angles. These projections are then reconstructed into a three-dimensional data set. We can then look at each slice individually and assess each area of the breast without confusing overlap from surrounding structures," Dr. Rafferty says. "The ability to look at individual slices of the breast is a real asset," she says.
TOMO is more comfortable for the patient. The patient's breasts only need to be compressed once (compared to twice for the standard two-view mammogram); the patient sits during the procedure, and the overall radiation dose is lower, says Dr. Rafferty. Dr. Rafferty cautions, however, that "full-field digital tomosynthesis is still in its infancy." However, she predicts, "this technique will only get better." Researchers at Massachusetts General Hospital conceived, developed, and patented full-field breast tomosynthesis, and, in conjunction with General Electric, built the only prototype currently in clinical use. To date, more than 350 clinical tomosynthesis studies have been performed at Massachusetts General Hospital under research protocols.
Dr. Rafferty will present the results of her studies on May 8 during the American Roentgen Ray Society Annual Meeting in San Diego.
Contact: Keri J. Sperry (703) 858-4306
Danica Laub (703) 858-4332
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