FDA has approved the first 3-D mammography imaging system (Selenia Dimensions System) for breast cancer screening and diagnosis. The 3-D mammogram, when used in conjunction with 2-D systems, may improve accuracy in breast cancer detection and diagnosis.
Because of the limitations of 2-D x-ray imaging, about 10% of women undergo additional testing after the initial mammogram for abnormalities that are later determined to be noncancerous. According to Helen Barr, MD, Director of the Division of Mammography Quality and Radiation Programs with the Center for Devices and Radiological Health at FDA, “Overlapping breast tissue makes it difficult for radiologists to make out potentially cancerous findings when using 2-D imaging.
“What dedicated breast tomography [3-D imaging] does is take slices through the breast to cut down on the overlap of tissue. This allows the radiologist to see lesions and will hopefully decrease additional testing.”
FDA reviewed results from 2 studies where 25 board-certified radiologists were asked to review 2-D and 3-D images from more than 300 mammography exams. In both studies, radiologists viewing a combination of the 2-D and 3-D images obtained a 7% improvement in their ability to distinguish between cancerous and noncancerous cases as compared to viewing 2-D images alone.
The combination of 2-D and 3-D images approximately doubled the radiation dose the patient received, due to twice as many images being taken. However, it improved the accuracy with which radiologists detected cancers, decreasing the number of women recalled for a diagnostic work-up.
“There is a large uncertainty for radiation risk estimates,” said Robert Ochs, PhD, who was involved in the FDA approval of the Selenia device. “The increase in cancer risks from having both a 2-D and 3-D breast exam is expected to be very small [less than 1.5%] compared to the natural cancer incidents for breast cancer, which is already about 1 in 8 women, so we don’t see this having a large increase.”
The Mammography Quality Standards Act requires that all health care professionals obtain 8 hours of training prior to using new mammography technology on patients. FDA also requires that the manufacturer provide each facility with a manual clearly defining the tests required for initial, periodic, and yearly quality control measures.
The Selenia Dimensions System is marketed by Hologic Inc (Bedford, MA) and is an upgrade to the company’s 2-D system.
Source: FDA (www.fda.gov)
The Female Patient — April 6, 2011