Sir, the American Thyroid Association (ATA) has recently published1 its recommendations that thyroid protection should be provided to all patients undergoing head and neck radiography in order to reduce the risk to the thyroid gland from ionising radiation: 'With regards to dental X-rays, the ATA recommends the reduction of thyroidal radiation exposure as much as possible without compromising the clinical goals of dental examinations.'

The risk to the thyroid gland from ionising radiation has been well documented. Dr Elaine Ron of the Radiation Epidemiology Branch, National Cancer Institute, USA, and her colleagues in their enormous 1995 study of thyroid cancer2 following exposure to external radiation of the head and neck region concluded that: 'The thyroid gland in children has one of the highest risk coefficients of any organ.'

Whilst a relatively rare disease (2,300 cases are diagnosed in the UK each year), the number of thyroid cancer cases in the UK continues to rise, with the highest rate of increase being in the cohort of young females (15-35 years of age).3

Current US,4,5 European6 and UK7 guidelines appear to be clear and unequivocal on the necessity for shielding the thyroid gland during dental radiography. In the course of delivering radiography and radiation protection training ('IR(ME)R' courses) throughout the UK, I encounter a widespread lack of knowledge amongst my dental colleagues either that such a risk exists or that national and European guidelines recommending the use of thyroid collars during routine dental radiography are still extant – despite no longer requiring the use of 'lead aprons'.

In light of the recent publication of the ATA's recommendations, is it perhaps time for us as a profession to review the necessity of using thyroid protection on our patients whilst undertaking diagnostic imaging? (See Fig. 1.)

Figure 1: Upper anterior periapical radiograph.
figure 1

The likelihood of illuminating the thyroid gland in the primary beam increases if the patient has a shallow palate or raises their head

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