Breast MRI vs. Mammography

By Helen Mrose, MD, PhD

Bay Radiology Breast Imaging Center

. https://bay-radiology.com/#

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Breast MRI vs. Mammography

Recent reports that the diagnosis of breast cancer in 36-year-old actress Christina Applegate was made by MRI, not mammography, have piqued public interest in breast cancer diagnostic testing.
Several questions arise from this recent news, including
What is an MRI, and how does it differ from a mammogram?
Why was this young woman being tested for breast cancer when usual testing begins at age 40 and
Why was this particular patient offered testing with MRI in addition to mammography?
These are important questions.
MRI (magnetic resonance imaging) was developed in the 1980's. It is a powerful imaging technology that utilizes a high field strength magnet, radiofrequency waves and computer technology to generate cross sectional images of the human body. In contrast to mammography, no ionizing radiation is used with MRI.
Breast MRI technology has improved dramatically over the past ten years, making it possible to find tiny breast tumors that may be missed by mammography, ultrasound and physical examination. Breast MRI for cancer diagnosis requires use of the contrast agent gadolinium, which causes tumors to “light up”.
Studies have shown that breast MRI is more sensitive than mammography in many cases, meaning it shows more cancers. However, some cancers found by mammography are not shown by breast MRI. Breast MRI should not replace mammography (imaging using x-rays). In addition, breast MRI is so sensitive that many benign (non-cancerous) conditions light up and mimic cancer, leading to “false positive” scan results.
The American Cancer Society currently recommends that breast MRI be used in conjunction with mammography for women who are at very high risk for breast cancer (20 to 25% lifetime risk). There are models available to calculate risk for breast cancer; genetic counselors are best able to determine who is at elevated risk.
Women who have the genetic mutation BRCA1 or BRCA2 are at extremely high risk for breast cancer, and qualify for yearly screening with mammography and MRI, usually beginning earlier than women with average risk (for whom yearly mammography screening beginning at 40 is recommended). Breast MRI is also routinely recommended for women with a new diagnosis of breast cancer, to help with surgical planning.
It was reported that Christina Applegate tested positive for the
genetic mutation in BRCA1. This
mutation puts her in one of the highest risk categories, with a lifetime risk for developing breast cancer of
approximately 85%. Current recommendations for a young woman with this mutation are to begin screen-
ing between the ages of 20 to 30, and that mammography be used in addition to MRI.
Breast MRI requires a high field strength magnet, a specialized “breast coil”, and the use of gadolinium. High quality MRI imaging is difficult to obtain, requiring experienced, specially trained personnel and meticulous attention to detail and excellent equipment. Finally, no matter how good the quality of the images, diagnostic accuracy depends on the expertise of the radiologist interpreting the MRI.