Breast Cancer Detection and Diagnosis

by National Cancer Institute

The National Cancer Institute (NCI) is funding numerous research projects to improve conventional mammography (an x-ray technique to visualize the internal structure of the breast) and develop other imaging technologies to detect, diagnose, and characterize breast.

High-quality mammography is the most effective technology presently available for breast cancer screening. Efforts to improve mammography focus on refining the technology and improving how it is administered and x-ray films are interpreted. NCI is funding research to reduce the already low radiation dosage of mammography; enhance mammogram image quality; develop statistical techniques for computer-assisted interpretation of images; enable long-distance, electronic image transmission technology (telemammography/teleradiology) for clinical consultations; and improve image-guided techniques to assist with breast biopsies. (A breast biopsy is the removal of cells or tissues to look at under a microscope to check for signs of disease). NCI also supports research on technologies that do not use x-rays, such as magnetic resonance imaging (MRI), ultrasound, and breast-specific positron emission tomography (PET) to detect breast cancer. The following information describes the latest imaging techniques that are in use or being studied.

Ultrasound

Ultrasound, also called sonography, is an imaging technique in which high-frequency sound waves that cannot be heard by humans are bounced off tissues and internal organs. Their echoes produce a picture called a sonogram. Ultrasound imaging of the breast is used to distinguish between solid tumors and fluid-filled cysts. Ultrasound can also be used to evaluate lumps that are hard to see on a mammogram. Sometimes, ultrasound is used as part of other diagnostic procedures, such as fine needle aspiration (also called needle biopsy). Fine needle aspiration is the removal of tissue or fluid with a needle for examination under a microscope to check for signs of disease.

During an ultrasound examination, the clinician spreads a thin coating of lubricating jelly over the area to be imaged to improve conduction of the sound waves. A hand-held device called a transducer directs the sound waves through the skin toward specific tissues. As the sound waves are reflected back from the tissues within the breast, the patterns formed by the waves create a two-dimensional image of the breast on a computer.

Ultrasound is not used for routine breast cancer screening because it does not consistently detect certain early signs of cancer such as microcalcifications (tiny deposits of calcium in the breast that cannot be felt but can be seen on a conventional mammogram). A cluster of microcalcifications may indicate that cancer is present.

Digital Mammography

Digital mammography is a technique for recording x-ray images in computer code instead of on x-ray film, as with conventional mammography. The images are displayed on a computer monitor and can be enhanced (lightened or darkened) before they are printed on film. Images can also be manipulated; the radiologist (a doctor who specializes in creating and interpreting pictures of areas inside the body) can magnify or zoom in on an area. From the patient's perspective, the procedure for a mammogram with a digital system is the same as for conventional mammography.

Digital mammography may have some advantages over conventional mammography. The images can be stored and retrieved electronically, which makes long-distance consultations with other mammography specialists easier. Because the images can be adjusted by the radiologist, subtle differences between tissues may be noted. The improved accuracy of digital mammography may reduce the number of followup procedures. Despite these benefits, studies have not yet shown that digital mammography is more effective in finding cancer than conventional mammography.

The first digital mammography system received U.S. Food and Drug Administration (FDA) approval in 2000. An example of a digital mammography system is the Senographe® 2000D. Women considering digital mammography should talk with their doctor or contact a local FDA-certified mammography center to find out if this technique is available at that location. Only facilities that have been certified to practice conventional mammography and have FDA approval for digital mammography may offer the digital system. A list of conventional mammography facilities is available by calling the Cancer Information Service at 1-800-4-CANCER (1-800-422-6237), or by visiting the FDA Web site at http://www.accessdata.fda.gov.

Computer-Aided Detection

Computer-aided detection (CAD) involves the use of computers to bring suspicious areas on a mammogram to the radiologist's attention. It is used after the radiologist has done the initial review of the mammogram.

In 1998, the FDA approved a breast imaging device that uses CAD technology. Others are in development. An example of a breast imaging device that uses CAD technology is the ImageChecker®. This device scans the mammogram with a laser beam and converts it into a digital signal that is processed by a computer. The image is then displayed on a video monitor, with suspicious areas highlighted for the radiologist to review. The radiologist can compare the digital image with the conventional mammogram to see if any of the highlighted areas were missed on the initial review and require further evaluation. CAD technology may improve the accuracy of screening mammography. The incorporation of CAD technology to digital mammography is under evaluation.

MRI

In magnetic resonance imaging (MRI), a magnet linked to a computer creates detailed pictures of areas inside the body without the use of radiation. Each MRI produces hundreds of images of the breast from side-to-side, top-to-bottom, and front-to-back. The images are then interpreted by a radiologist.

During an MRI of the breast, the patient lies on her stomach on the scanning table. The breast hangs into a depression or hollow in the table, which contains coils that detect the magnetic signal. The table is moved into a tube-like machine that contains the magnet. After an initial series of images has been taken, the patient may be given a contrast agent intravenously (by injection into a vein). The contrast agent is not radioactive; it is sometimes used to improve the visibility of a tumor. Additional images are then taken. The entire imaging session takes about 1 hour.

Breast MRI is not used for routine breast cancer screening, but clinical trials (research studies with people) are being performed to determine if MRI is valuable for screening certain women, such as young women at high risk for breast cancer. MRI cannot always accurately distinguish between cancer and benign (noncancerous) breast conditions. Like ultrasound, MRI cannot detect microcalcifications.

MRI is used primarily to evaluate breast implants for leaks or ruptures, and to assess abnormal areas that are seen on a mammogram or are felt after breast surgery or radiation therapy. It can be used after breast cancer is diagnosed to determine the extent of the tumor in the breast. MRI is also sometimes useful in imaging dense breast tissue, which is often found in younger women, and in viewing breast abnormalities that can be felt but are not visible with conventional mammography or ultrasound.

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