Breast ultrasound (US)
Ultrasound uses sound waves rather than x-rays (like mammography) to identify structures in the breast that could be tumors. Most ultrasound devices are hand-held. On our breast ultrasound page you'll find every recent news article and medical journal abstract on the use of breast ultrasound for the detection of tumors in dense breast tissue. Advantages of US are that it's relatively inexpensive (usually a few hundred dollars), widely available and doesn't cause discomfort. Hand-held ultrasound, though, requires a skilled practitioner and it will result in more false positives than mammography.
Automated breast ultrasound (ABUS)
The main advantage of automated compared to hand-held ultrasound is that enables a less labor intensive, operator-dependent workflow. The main (only?) system being marketed in the United States is the somo-v INSIGHT by U-Systems (Sunnyvale, CA). It has regulatory clearance as an adjunct to mammography and is seeing more use, particularly in Connecticut and Texas, states that recently passed dense breast tissue laws and that therefore are seeing increased demand for ultrasound screening.
3-D Mammography
Also called breast tomosynthesis and stereo digital mammography (SDM). The only FDA-approved system on the market in the United States is the Selenia Dimensions System by Hologic, Inc. (Bedford, MA). It was approved in February of this year and is becoming more available. In 3-D mammography, an x-ray imager moves around the breast, taking 15 images from different angles (standard mammography takes two images). These 15 images are then assembled using software to create the 3-D depiction. Imaging from different angles decreases the odds that a tumor will be completely hidden by dense breast tissue. I recommend the August 14th news story from the Boston Globe. The link is on LATESTBreastCancer.com's 3-D Mammography page. All links are conveniently listed in reverse chronological order.
Breast MRI
Along with breast ultrasound, breast MRI is the most commonly mentioned supplemental screening method for women with dense breast tissue. MRI uses a strong magnetic field to excite nuclear particles in breast tissue. A contrast agent chemical (gadolinium-DPA) is first injected into the bloodstream. This agent helps visualize areas containing blood vessel networks, which are suggestive of a tumor. MRI is highly sensitive but does generate a high rate of false positives. It is also very expensive ($2000-6000). The most recent news articles and medical journal articles on breast MRI can be found on our Breast MRI page. Among those are articles that discuss its use as a supplemental screening method for women at high risk, including women with dense breast tissue.
Molecular breast imaging (MBI) systems
Molecular breast imaging is "functional" imaging. It looks at metabolic activity in the breast tissue. This makes is complementary to "anatomical" imaging methods like mammography and ultrasound that look at tissue structures. MBI methods include BSGI (Breast-specific gamma imaging) and PEM (Positron emission mammography). Both generate fewer false-positives than breast MRI and so results in fewer unnecessary biopsies. They are also less expensive than MRI. BSGI and PEM are based on the same principle but use different radioactive tracer molecules and imaging systems. In both, the tracer is absorbed by cells throughout the body. Cancer cells, due to their increased rate of metabolic activity, absorb a greater amount than healthy cells and so appear as dark "hot spots" on the image. The major problem with MBI is that it results in greater exposure to radioactivity.
No comments:
Post a Comment