Breast cancer screening
Screening for breast cancer screening can be one of the hardest things to do. Currently, mammography is the best technique available to look for breast cancers in women who don't have any symptoms. On average, screening mammograms correctly identifies 80 percent to 85 percent of women who have cancer and about 90 percent of women who don't. Despite this being the most successful form of screening, scientists are still always on the hunt for new technologies to improve screenings and reduce the number of cancer cases which are missed.
The LA Times has taken a look at the various forms of technology in screening, some of which are available now, and some of which are currently going through clinical trials.
The screening mammography we get today takes X-ray images - usually two of each breast - looking for abnormalities that can't be felt in a physical exam. These include small tumors and tiny deposits of calcium, called microcalcifications, which, in clusters, may be a sign of cancer.
In digital mammography, which was approved by the Food and Drug Administration in 2000, images are stored in a computer instead of on film.
Digital mammography has its advantages as images can be enhanced, and they're easier to store and transmit.
Despite the positives though, digital mammography is not available everywhere. Digital mammography systems cost approximately 1.5 to four times as much as standard film mammography systems. While procedural time saved by using digital mammography over standard film mammography justifies part of the cost for facilities that perform several thousand mammograms each year, its not currently known if the high cost is justifiable in terms of its benefits in detecting breast cancer, Imaginis cites.
When it comes to reading mammograms, evidence shows that two radiologists are better than one - improving detection rates by about 10 percent on average. Double-reading is standard practice in many European countries but is used only in 25 percent to 30 percent of US readings.
In this approach, a radiologist reviews the mammogram, then a detection device scans it, marking suspicious areas. The radiologist then compares his or her analysis with the computer's and decides if further evaluation is needed.
Previous research hasn't always found the benefits with computer-aided detection, but a large clinical trial published in 2008 did. Among more than 31,000 women who had conventional mammograms in England, computer-aided detection identified 87.2 percent of breast cancers, pretty much on a par with double-radiologist readings.
Scientists have discovered that by adding the right kind of noise (interference) to a mammogram image, they can make the image clearer. In a study of 75 images published last year, researchers found they could detect cancers as well or better than mammography alone, while reducing the number of false alarms by as much as 36 percent.
Digital tomosynthesis takes at least 11 x-ray images of the breast at different angles, which a computer combines into three-dimensional images. Digitaltomosynthesis is a new kind of test that's trying to overcome the problems associated with mammograms.
While mammography pulls the breast away from the body and squeezes it between two glass plates, tomosynthesis uses just enough pressure to hold the breast still - so it doesn't hurt the way mammography can. And because it doesn't squeeze the breast,tomosynthesis doesn't create overlaps in tissue that hide cancers. As a result of this, it could cause fewer false alarms.
Ultrasound can distinguish solid tumors from fluid-filled cysts, but it's not useful for routine screening because it misses too many cancers, includingmicrocalcifications, and comes up with too many false alarms. Still, it's sometimes used for screening patients with dense breasts (generally younger women), usually in addition to mammography. Ultrasound imaging of the breast produces a picture of the internal structures of the breast.
Magnetic resonance imaging (MRI)
MRI produces precise images of internal organs and tissues based on differences in water content and distribution. A breast MRI produces hundreds of images from multiple directions.
MRI is not used for routine breast cancer screening because it's expensive and tends to give a lot of false alarms, although the rate of these is decreasing. MRI can detect cancers which are very small though.
Although MRI is very good at finding small lumps in the breast, it's less good at determining whether the lumps are cancerous or not.
Electrical impedance scanning (EIS)
Electrical impedance can be used to locate breast cancers because malignant breast tissue conducts electricity better than normal breast tissue. Not currently approved for use as a screening device, it is approved for follow-up use when doctors aren't sure from mammograms if a biopsy should be done. Some studies have suggested that electrical impedance scanning may be useful for identifying young,premenopausal women at increased risk for breast cancer.
Scintimammography (molecular breast imaging)
In scintimammography, a radioactive tracer is injected into the patient, after a special camera locates where the radiation accumulates in the breasts. It is not used as a screening test but has proved a useful complement to mammography in diagnosing cancers when they're large enough. Some studies suggest that a newly developed "high resolution dedicated breast camera" may be useful with smaller cancers too.
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