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When is Breast MRI appropriate?

More women are surviving a breast cancer diagnosis thanks to early detection and more effective treatment options. In 2017, 87% of women diagnosed with breast cancer were still alive after five years.

While it’s easy to understand the importance of breast screening when looking at survival rates, understanding the different breast screening technologies and when to use them can be confusing. Mammography, breast ultrasound, and breast magnetic resonance imaging (MRI) can all be used to help diagnose breast cancer, or other breast diseases.


A mammography exam takes X-ray images – mammograms – of the breast to look for abnormalities. It provides a detailed view of breast tissue with a very small dose of radiation and can reveal changes that may be too small for you or your doctor to feel. It is the gold standard for breast screening, and is usually the first step in the screening process.

Breast ultrasound uses sound waves to check breast tissue from a different perspective than mammography. It can be handheld or an Automated Breast Ultrasound, which uses 3D ultrasound technology to offer a fast and reproducible look at the breast from a variety of angles. Breast ultrasounds are often requested when you or your health care practitioner feel a lump, see nipple discharge, or your mammogram shows new findings or high breast density. They are often performed as a supplement to a mammography exam.

Breast MRI uses a powerful magnetic field and radio waves to take a very detailed look at the soft tissues of the breast. Although mammography is still the standard first method of detecting abnormalities in breast tissue, Breast MRI can be a powerful screening and diagnostic tool for women at high risk of breast cancer. It can also be used to assess the extent of breast tumors after a cancer diagnosis, for further examination of concerns when mammography and/or ultrasound are negative, or as a follow up after treatment to look for recurrence of breast cancer. Women with extremely dense breast tissue may also benefit from a Breast MRI.


Your risk for breast cancer depends on a number of factors including your personal medical history, age, genetics, lifestyle, etc. Discussing your risk factors with your health care practitioner will help you gauge your risk level.

The following are considered high risk factors:

  • Personal history of breast, ovarian, or uterine cancer.
  • First-degree relative (parent, sibling, child) diagnosed with breast cancer.
  • Yourself or first-degree relative with a BRCA1 or BRCA2 gene mutation.
  • Chest wall radiation at an age younger than 30.
  • History of lobular carcinoma in situ or atypical hyperplasia on previous breast biopsy.

Another risk factor for breast cancer that should be considered is breast density. Your breasts are made up of different types of tissue: fibroglandular (dense) tissue, and fat (not dense tissue). Dense breasts have less fatty tissue, more fibroglandular tissue, and a higher risk of cancer. Fatty tissue appears dark on a mammogram while both abnormalities and fibroglandular tissue appear white, making abnormalities harder to find.

Dense breasts are quite common, but they can only be determined by a mammogram. At Mayfair Diagnostics all of our mammography machines are equipped with software that classifies breast density, which is included in reports to referring doctors. It’s important to know your breast density and discuss it with your doctor since women with dense breast tissue often benefit from regular mammograms supplemented by ultrasound or Breast MRI.

How mammography, breast ultrasound, and Breast MRI work together and whether they would all be appropriate depends on your personal circumstances and will need to be determined by your doctor.

For more information about breast imaging, please visit our services page.


Canadian Cancer Society (2018) “Breast Cancer Statistics.” Accessed on October 1, 2018.

Engmann et al. (2017) “Population-Attributable Risk Proportion of Clinical Risk Factors for Breast Cancer.”  JAMA Oncology. 2017; 3(9) 1228-36.

Huizen, J. (2017) “Breast MRI: What you need to know.” Medical News Today. Accessed on October 1, 2018.

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