Tomosynthesis provides new tool in fight against breast cancer
From Parkwest Medical Center
If you are one of the nearly 40 percent of women who have “dense” breast tissue, then the 3-D mammography is for you. In Knoxville, tomosynthesis, or 3-D mammography, is only available at Parkwest Medical Center.
Women whose breasts are comprised of less fat and more glandular tissue have “dense” breasts, according to doctors. On a mammogram, this dense tissue appears white. Cancerous tumors also appear white, making it nearly impossible to “see” the tumor. In comparison, a fatty breast is radiolucent, meaning it produces a dark background which makes a small, white tumor relatively easy to see.
“It’s like looking for a single snowflake in the middle of a snowstorm,” said Parkwest Radiologist Amanda Squires, M.D., describing the difficulty of finding cancer in a dense tissue breast with a regular mammogram. “With traditional mammography, we only have the two images of each breast. With tomosynthesis, we can scroll through the series of images, much like watching a movie. It’s gives much clearer images and more of them to work with. Tomosynthesis makes it easier to detect cancer early, and also allows for fewer false positive results.”
Ball versus circle
Digital tomosynthesis creates a 3-D picture of the breast using X-rays. It is different from a standard mammogram in the same way a ball differs from a circle. The ball is 3-D; the circle is flat.
Two-dimensional mammography usually only takes two X-rays of each breast from different angles: one from top to bottom and one from side to side. The breast is pulled away from the body, compressed, and held between two glass plates to ensure that the whole breast is viewed. The compression also causes overlapping of the breast tissue. A breast cancer can be hidden in the overlapping tissue and not show up on the mammogram. 3-D mammography eliminates this potential problem.
Digital tomosynthesis takes multiple X-ray pictures of each breast from many angles. The breast is positioned the same way it is in a conventional mammogram, but only a little pressure is applied — just enough to keep the breast in a stable position during the procedure. The X-ray tube moves in an arc around the breast while 11 images are taken during a 7-second examination. Then the information is sent to a computer, where it is assembled to produce clear, highly focused 3-dimensional images throughout the breast.
“Tomosynthesis builds upon the success of existing mammography,” Squires said. “Over time, we expect that 3-D mammography will become the new standard in breast cancer screening and detection.”
Squires said the radiation dose for the combined exam (standard mammogram plus tomosynthesis at the same time) is essentially equivalent to the prior non-digital mammograms that were used for more than 30 years.
The study is completed in about five minutes, which is much faster than whole breast ultrasound. The FDA thoroughly considered the radiation issue before approving tomosynthesis for use in screening and diagnostic exams and ruled that the benefit of the additional information available to the radiologist outweighs any potential risk.
For now, tomosynthesis will be used as a complement to existing mammography and will be performed along with a conventional mammogram — at the same time on the same scanner. This technology is currently being performed at facilities such as Duke, Emory, Harvard, Johns Hopkins and Yale.
While it has received FDA approval, 3-D mammography is not yet covered by all insurance plans. The cost of the procedure is $125.