The Future of Breast Cancer Screening
An array of high-tech detection techniques and devices is on the scientific horizon.
Digital mammography, which takes the X-ray image on computer
rather than on film, is gradually becoming available. There are now about 300
such units in use around the country, according to the American Cancer
The instrument "offers enormous potential" because the
pictures can be manipulated, says Robert A. Smith, PhD, head of screening at
the American Cancer Society.
Much like digital photographs currently taken by consumer
digital cameras, breast images taken by digital mammography can be magnified,
and the resolution can be adjusted to get a clearer picture.
While easier to use, digital mammography is not more successful
at finding cancers than traditional mammograms -- and the cost of each machine
tends to be prohibitive.
Computer-Aided Detection Devices (CAD)
Smith says the digital imaging technology could especially
improve with better-programmed computer-aided detection (CAD) devices, which
are now used by some labs to analyze standard mammograms and act as
second-opinion readers for radiologists.
Early tests show CAD can help point out cancers otherwise
missed by experts. Yet there is an ongoing debate about whether a machine can
sufficiently replace a second radiologist in reviewing test results.
Medical experts who want to evaluate problems first found
during a mammogram or a physical exam often turn to ultrasound technology. An
ultrasound device releases sound waves into the body, and creates a picture of
the breast from the bouncing back of the waves. The idea is that sound echoes
differently of off masses of various consistencies, such as fluid-filled cysts,
solid tumors, or normal tissue.
Ultrasound has been around for decades, but improvements to the
technology promise to make it more helpful in looking for cancer. One advance
of note is still in the experimental stages: an ultrasound that takes 3-D
images of the breast as opposed to 2-D ones.
Another breast detection technique that scientists have
gradually enhanced over the years is magnetic resonance imaging (MRI). In this
method, a large magnet, radio waves, and a computer work together to produce
what experts consider a very clear, cross-sectional picture of the breast.
Furthermore, experts can examine specific areas by injecting a dye in the
veins, which collects in problematic tissues, making them more visible in the
Similar techniques are now under investigation, such as
magnetic resonance elastography (MRE), which draws an image of the breast based
on the elasticity of vibrating tissue.
Toward a Better Image (of Breasts)
Many methods to check for breast cancer are still experimental
right now. Often, women at high risk of developing the disease turn to clinical
trials of these imaging devices in an effort to ease their concerns.
Some of these experimental methods are:
Positron emission tomography (PET). This technology makes use of the
notion that a tumor has a higher metabolism than normal tissue. When a
radioactive substance is injected into a patient's vein, it travels to rapidly
dividing cancerous cells, which have greater nutrient needs. Ideally, a PET
scanner would detect the activity and produce an image of it.
Ductal lavage and ductoscopy. The idea behind these two methods is
that certain cancers begin in the milk ducts of the breasts. In ductal lavage,
a catheter is inserted through the nipple and into the milk ducts. A saline
solution is emptied into the ducts, and then withdrawn. Then the cells washed
out from the ducts are checked under a microscope. In ductoscopy, a catheter
with a light at the tip is inserted through the nipple into the ducts and a dye
is injected. The dye outlines the shape of the duct and an X-ray ideally shows
whether there is an abnormal growth in the area.
Electrical impedance spectral imaging (EIS). Low-frequency
electrical currents are applied to the breast, and an image is formed based on
the theory that normal tissue and cancerous masses conduct electricity in
Microwave imaging spectroscopy (MIS). This device uses microwave
energy that is similar to cell phone frequencies (but at a much lower level).
The technique is particularly sensitive to water, and can detect areas where
there is more of it. Tumors are thought to have more water and blood than
Near infrared (NIR) spectral imaging. This method is based on the
idea that infrared light is sensitive to blood, creating an image of hemoglobin
inside the breast. Knowledge of vascular activity is believed to help spot
early tumor growth, and determine its stage.