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Thyroid shields in mammography

Patient information A-Z

The aim of this leaflet is to help answer some of the questions you may have about not using a thyroid shield during a mammogram examination.

About thyroid shielding

What is thyroid shielding?

A thyroid shield is a small, covered piece of leaded vinyl worn around the neck to protect the thyroid from radiation exposure. During some medical imaging examinations this shielding is worn by members of staff and/or patients to reduce the amount on radiation to the thyroid gland.

Why is a thyroid shield not required for a mammogram?

During a mammogram, the thyroid is not exposed to the direct x-ray beam. Mammography machines are designed to ensure patient safety, incorporating internal radiation shielding, which prevents stray radiation. Thyroid shields can interfere with positioning the breast, meaning the images may be incomplete. It may also result in artefacts – shadows that might appear on the mammography image. Both of these factors could reduce the quality of the image and interfere with diagnosis.

For these reasons the National Breast Screening Programme and its National Physics Advisory Board does not recommend the use of thyroid shields. As we comply with the National Breast Screening Programme, we do not give thyroid shields to women.

What are the risks of radiation from a mammogram to my thyroid?

During a mammogram the radiation needed to create the images goes where it is aimed, ie to the breast that is being imaged. The rest of the body is exposed to small amounts of what is called scatter radiation. Scatter radiation during a mammogram is a fraction of the natural radiation (known as background radiation) you would receive in one day.

Background radiation fills the universe and is there in every direction, but cannot be seen with the naked eye. Created shortly after the universe came into being, background radiation was the first radiation detected. One study estimated that during a mammogram a woman's thyroid is exposed to the equivalent of 30 minutes of natural background radiation. Even over many years of annual mammograms, this amount of additional radiation is considered tiny.


There are no current alternatives at present in line with current guidelines.

Contacts/ further information

If you have any further questions please call 01223 217627 and ask to speak to the Director of Breast Screening, Kathryn Taylor.

References/ sources of evidence

Our policy is in line with those of other international organisations, such as that of the American Thyroid Association, who also do not recommend thyroid shields during mammography.

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Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151