Advances in mammography and breast imaging - information

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Mammography

What is mammography?
How is mammography performed?
How mammography works
Benefits of mammography
Limitations of mammography
History of mammography

What is mammography?

Mammography is an X-ray of the breast, used to detect breast cancer in women with no signs or symptoms of the disease. Mammography can detect small changes in the breast that are too small to be felt either by the woman herself or by a doctor.

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How is mammography performed?

Mammography is performed using a low-dose X-ray system designed specifically for imaging the breasts. Each breast is lightly compressed between two flat plates with an X-ray film placed underneath. Compressing the breast helps by spreading the breast tissue out to obtain a clearer picture whilst using the lowest possible dose. X-rays pass through the breast and onto the film beneath.

For a screening mammogram, usually two X-rays are taken of each breast, from two different angles. The films are developed and interpreted by a radiologist, who compares left and right images to each other and to previous mammograms.

Right and left side views (left) and top views (right).

Side view right Side view left Top view right Top view left

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How mammography works

The breast is made up of fat, fibrous tissue and glands. During mammography, as the X-rays pass through the breast they are stopped to differing degrees by the different tissues they encounter. Fat is very dense and stops a great deal of the X-rays and appears as black regions on a mammogram film. Benign and cancerous breast masses appear as white regions on a mammogram film. Everything else, including fibrous tissues, glands and other abnormalities such as microcalcifications, appear as various levels of white on a mammogram.

In general, it is difficult to see a clear separation between normal functioning fibrous and glandular tissues and cancerous tissue since their X-ray stopping powers are very similar. In older women, the fibrous and glandular tissues diminish, leaving only fatty tissues. Mammography in these fatty breasts is very effective since even small cancers show up well against fat.

Right and left side views of fatty (left) and dense breasts (right).

Fatty breast side view right Fatty breast side view left Dense breast side view right Dense breast side view left

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Benefits of mammography

It improves the chances of detecting tumours when they are small and effective treatment and cure are more likely.
It is excellent at imaging microcalcifications.

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Limitations of mammography

Not all cancers of the breast can be seen using mammography.
Interpreting mammograms can be difficult because of differences in the appearance of the normal breast for each woman.
It cannot always distinguish cancerous from non-cancerous tumours.
It is not routinely used for screening women under 50 as younger women tend to have more dense breast tissue making it more difficult to detect breast cancer using mammography.
Breast implants can affect the accuracy of mammography because silicone implants are not transparent on X-rays and can block a clear view of the tissues behind them.

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History of mammography

1895	William Roentgen, a German physicist discovers X-rays.
1913	Albert Solomon, a surgeon in Berlin, uses a conventional X-ray machine to visualise breast cancers in 3000 mastectomy specimens.
1940s	Stafford Warren, in New York, develops a stereoscopic system for tumour identification.
1949	Uruguayan Raul Leborgne emphasises the need for breast compression to identify calcifications.
1956	Robert Egan, a radiologist in Houston, introduces dedicated film for mammography to produce simple and reproducible images with improved detail. Egan also identified the need to train technologists to produce high quality images and radiologists to provide accurate and consistent readings of these images.
1966	The first dedicated mammography machine is developed.
1970s	X-ray mammography finds widespread application in imaging the breasts as several manufacturers begin selling dedicated mammography systems.
1980s-1990s	Major improvements in mammography equipment including reduced radiation dosage, better film, digital imaging and computer-aided detection.

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