September 1, 2007 — Radiologists have devised a better way to perform a mammogram, called digital tomosynthesis. An X-ray tube moves in an arc around the breast, capturing several images. The information is then sent to a computer, which produces clear, highly focused 3-dimensional images of the breast.
One out of seven women will develop breast cancer in her lifetime. Up until now, a mammogram has been the best hope for early detection. But mammograms can be uncomfortable and difficult to read. Now, new technology may change all that.
For most women, the prospect of getting a mammogram is scary.
"I think for many radiologists, the prospect of interpreting mammography is a very scary thing," said Elizabeth Rafferty, a radiologist at Massachusetts General Hospital.
That's because 50-percent of women have dense breast tissue and on a mammogram, that density looks similar to cancer.
"It's really like a 'Where's Waldo.' I'm trying to find the thing I'm interested in, but it looks like everything else in the sea of normal structures," Rafferty said. But a new technology called tomosynthesis is helping radiologists pinpoint cancer as small as two millimeters. Tomosynthesis builds on digital mammography by taking multiple images. An x-ray tube moves in an arch around the breast at different angles. A computer then combines the information into a 3-D image.
"The radiologists can look at it like pages of a book, looking at one area of the breast in isolation," Rafferty said.
Traditional mammograms only take two angles of the breast. Depending on breast size, tomosynthesis takes at least 11 different angles. Another bonus -- tomosynthesis uses less compression than traditional mammograms and that means less pain for the patient. Doctors are awaiting FDA approval. The cost of the test is expected to be about the same as a traditional mammogram.
The American Association of Physicists in Medicine and the Optical Society of America contributed to the information contained in the TV portion of this report.
BACKGROUND: Digital tomosynthesis is a new kind of breast imaging that is anticipated to replace regular mammography because it makes breast cancers easier to find in dense breast tissue, and makes the procedure much more comfortable. The technique is currently being reviewed by the FDA and should be commercialized within the year. It is easy to implement in any centers that currently provide mammography, with no necessary extra training for technicians to interpret results.
HOW IT WORKS: In digital tomosynthesis, the breast is positioned the same way as with a conventional mammogram, but only a little pressure is applied -- just enough to keep the breast in a stable position during the procedure. An X-ray tube moves in an arc around the breast while several images (11) are taken in seven seconds. The information is then sent to a computer and assembled to produce clear, highly focused 3D images throughout the breast. Breast cancer is denser than most healthy nearby breast tissue, and will appear on the image as irregular white areas. With conventional mammography, the breast is pulled away from the body, compressed, and held between two glass plates to ensure that the whole breast is viewed. Two X-rays of each breast are taken from different angles, top to bottom and side to side. Mammography is a good imaging technique, but it has some limitations. It is uncomfortable for women, making some reluctant to get the test regularly. It also causes overlapping of the breast tissue, which can hide a cancer. Mammography also only provides a limited number of views.
ABOUT BREAST CANCER: Breast cancer is a type of cancer in which cells in the breast become abnormal and grow and divide uncontrollably, eventually forming a mass called a tumor. Some tumors are benign, meaning that they do not invade other types of tissue, although if they become big enough, they can interfere with some bodily functions, such as the flow of blood or urine. Malignant tumors have cells that can invade nearby tissues. When a cancer "metastasizes," cells from the original tumor break off and travel to other parts of the body via the blood or lymph systems. More than 75 percent of breast cancers begin in the milk ducts within the breast. The next most common site is in the glandular tissue that makes the milk.
DO-IT-YOURSELF BREAST EXAM: Although it is not a substitute for regular tests by your doctor, women can perform a basic breast self-exam at home. In fact, more than 90 percent of all breast lumps are found by the women themselves. Breast tissue is shaped like a comma with the tail curving up toward the armpit, and normally has a lumpy feel. Bring to the attention of your doctor any changes in your breasts that last over a full month's cycle, or seem to get worse or more obvious over time. Because hormones can affect the breast tissue, the best time to examine your breasts is a few days after your period ends, when hormone levels are stable.
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.
Note: This story and accompanying video were originally produced for the American Institute of Physics series Discoveries and Breakthroughs in Science by Ivanhoe Broadcast News and are protected by copyright law. All rights reserved.
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