Thyroid guard: Do I need one during a mammogram?
Medically reviewed by Drugs.com. Last updated on Apr 2, 2019.
Probably not, as there is little chance that the exposure from the radiation from breast X-ray (mammogram) will cause thyroid cancer. In addition, a thyroid guard could interfere with the accuracy of your mammogram.
A thyroid guard or thyroid shield is a lead collar that wraps around your neck to block the radiation that's generated in making X-ray images.
During an X-ray, the majority of radiation needed to create the images goes exactly where it's aimed. In the case of a mammogram, most radiation exposure occurs in your breast. But the rest of your body is exposed to small amounts of what's called scatter radiation. Scatter radiation during a mammogram is a fraction of the natural radiation (known as background radiation) you'd receive in one day.
One study estimated that during a mammogram, which involves two X-rays per breast, a woman's thyroid is exposed to the equivalent of 30 minutes of natural radiation. Even over many years of annual mammograms, this amount of additional radiation is considered tiny.
Still, don't let a fear of thyroid cancer keep you from having a mammogram. If you choose to use a thyroid guard, many facilities have them available. Call ahead to make sure one is available at your facility.
Discuss the benefits and risks of thyroid guards with your radiologist or breast-imaging specialist. Thyroid guards can sometimes interfere with getting good images of the breast tissue, which could make the mammogram images incomplete. Thyroid guards can also distort the appearance of the mammogram. In these cases, you may be called back to have additional mammogram images.