December 16, 2018
Woman getting a mammogram
Ask the Experts

Should You Use a Thyroid Shield During a Mammogram?

by Berkeley Wellness  

Q: Should I use a thyroid shield when I get a mammogram? What about a lap shield? I see them in the exam room.

A: These lead-containing shields minimize exposure to radiation during imaging tests that use X-rays, like mammograms. But you don’t need a thyroid shield (also called a thyroid collar) despite rumors about an increased risk of thyroid cancer from the scattering of radiation. Several years ago, Dr. Oz created a commotion and needless worry when he speculated—without any scientific support—that mammograms are contributing to the rise in thyroid cancer in women.

The American College of Radiology, the Society of Breast Imaging, and other medical groups have recommended against the use of thyroid shields, citing a lack of evidence of benefit, as well as possible harm. Mammogram machines are designed for safety with internal shields that minimize scatter. As a result, negligible radiation reaches the thyroid gland—equivalent to what you would get from natural background sources when standing outside for 30 minutes. According to the American Thyroid Association “any risk to the thyroid is much lower than the benefit of mammography.”

Moreover, thyroid shields are cumbersome and can interfere with proper positioning during the exam. This can compromise image quality, necessitating repeat imaging, which would result in greater radiation exposure to the breasts.

Lap shields, worn around the waist like an apron, are also unnecessary, since the amount of radiation that scatters to abdominal organs is also minimal. (Actually, most of that radiation comes via scattering of X-rays from within the breast tissue, so a lead apron wouldn’t stop it anyway.) These shields don’t interfere with the exam, however, so there’s no downside to wearing one if you want to. And women who are or may be pregnant can wear one for extra safety. According to a paper in Radiology in 2008 that looked at radiation doses to internal organs during the procedure, “if a patient underwent a standard mammogram not knowing that she was in the early stages of pregnancy, our findings suggest that the dose to the fetus is minimal. If, however, a patient is known to be pregnant and a mammogram is deemed necessary, a lead apron can lower this low amount of dose to the fetus by at least one half.”

If you want to wear a lap shield during your exam, you will likely have to request it, since technicians do not routinely offer them to patients, even pregnant women.

Also see When to Have Mammograms: No Consensus.