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What is Digital Mammography and Breast Tomosynthesis?

Amber Nason • Mar 16, 2017

Traditionally, mammography  produced images of your breast tissue on film. Today, this technique has been largely replaced with digital mammography in most parts of Canada.

Digital mammography uses the same procedure as the traditional mammography whereby the breast is compressed to spread the tissue apart for an accurate image taken by low-dose X-rays. The difference is that instead of processing the images on screen-film, digital mammography uses a computer to capture a digital image (mammogram) of the breast tissue. This method is much more accurate, much faster, and makes it easier to share the images between health care practitioners and save them on your electronic health record. The Canadian Breast Cancer Foundation encourages women to choose digital mammography whenever possible.

Digital Breast Tomosynthesis is often referred to as 3D mammography or just tomosynthesis. It is a newer technology that is not yet widely available for use in Canada. Like digital mammography, it uses low-dose X-rays to capture images of the breast tissue. However, with Digital Breast Tomosynthesis the X-ray machine rotates in an arc to capture multiple images of the tissue from many different angles, which are then processed to create a three-dimensional (3D) image of the breast. This produces a more detailed image, since a standard mammography takes images only from the front and side.


According to the Toward Optimized Practice Breast Cancer Screening Clinical Practice Guideline, mammography is the recommended method of breast cancer screening for the average risk population because it reduces breast cancer mortality. However, sometimes the compression can cause overlapping in the breast tissue which decreases the accuracy of the image.  Similarly, if a patient has very dense breasts the sensitivity of mammography is decreased

Digital Breast Tomosynthesis, on the other hand, may be especially useful for higher risk patients. For example, over 40 percent of women in Canada, age 40 and over, have dense breast tissue which is a risk factor for breast cancer. Specifically, smaller tumours are harder to see among dense breast tissue in digital mammography. Evidence suggests that Digital Breast Tomosynthesis is better able to detect smaller breast cancers with more accuracy and fewer false-positives.

For more information on dense breasts, read our articles: What are Dense Breasts? and Advances in Breast Imaging.


As a patient, the most important thing to do is thoroughly discuss your options with your health care practitioner. At Mayfair, all of our Screening Mammography exams include Digital Breast Tomosynthesis technology. Breast imaging exams are listed on our General Requisition under Breast Imaging, your physician would simply check the appropriate box. Click here to download the requisition. Your doctor can also check off the “Complete Breast Assessment” check box and we will determine the appropriate breast exams for you to have based on your history and breast density.


CADTH (2015) “Tomosynthesis (3D Mammography) for Breast Cancer Screening.” Issues in Emerging Health Technologies. May, 135

Canadian Cancer Society (2014) Breast Screening Technology. Taken from:

Dudley, Susan, et al. (2016) “Should I “upgrade” to digital or 3D? A mammography guide.” Cancer Prevention and Treatment Fund. Taken from:

Government of Alberta (2017) Mammogram: Test Overview. Taken from:

Haas, B.M., et al. (2013) “Comparison of Tomosynthesis Plus Digital Mammography and Digital Mammography Alone for Breast Cancer Screening.” RSNA News. December, 269(3), Department of Diagnostic Radiology, Yale University School of Medicine

Public Health Agency of Canada (2009) Information on Mammography for Women Aged 40 and Older: A Decision Aid for Breast Cancer Screening in Canada. The Chronic Disease Management Division, Centre for Chronic Disease Prevention and Control

Svahn, T. M., et al. (2012) “Breast tomosynthesis and digital mammography: a comparison of diagnostic accuracy.” British Institute of Radiology. November, 85(1019): e1074–e1082

Breast Health, Your Clinic Visit, Disease Prevention