A diagnostic mammogram is essentially a low dose X-ray of the breast which has been used for screening since the 1980s.
How does mammography work?
For a short time the breast is compressed into two different positions and then X rays of the breast are taken. This examination takes about 10 minutes and sometimes a radiologist may require additional images in order to include all the breast tissue completely. Due to the compression the amount of radiation required to penetrate the tissue is reduced and the breast tissue is spread out which enhances the quality of images. Due to compression the motion is also reduced which prevents the image from getting blurred and also prevents important findings to be missed. In a mammogram you can see cancers as masses, areas if tissue asymmetry, calcifications and/or areas of distortion. However, skill is required to study mammograms because many noncancerous conditions also produce masses and calcifications and normal tissues can also appear as areas of asymmetry. At the same time, a mammography is unable to differentiate between normal and cancerous tissues in cases of dense breast tissue.
Mammography is of two types – 2D mammography and 3D mammography. 2D mammography is also known as Full Field Digital Mammogram or analog mammogram.
3D mammogram is also known as tomosynthesis or tomo. In this method a dedicated electronic detector system is used to obtain multiple projection images which are then synthesized with the help of the computer to create thin slices of the breast.
In this method specially equipped digital mammography machines are used to acquire images at multiple angles. Here again the breast is compressed to get better quality of images and reduce the amount of radiation required. The benefit of this method is that when combined with standard digital mammography, tomo is able to reveal 1 to 2 additional cancers per thousand women in the first round of screening.