Thyroid shields and neck exposures in cephalometric radiography
1 Department of Dental Public Health Sciences, School of Dentistry University of Washington, Seattle, USA
2 Department of Epidemiology, School of Public Health University of Washington, Seattle, USA
3 Radiology Clinic, Oral Medicine, School of Dentistry University of Washington, Seattle, USA
4 Department of Orthodontics School of Dentistry University of Washington, Seattle, USA
5 Environmental Health and Safety, Hall Health Center, University of Washington, Seattle, USA
BMC Medical Imaging 2006, 6:6 doi:10.1186/1471-2342-6-6Published: 13 June 2006
The thyroid is among the more radiosensitive organs in the body. The goal of this study was twofold: (1) to evaluate age-related changes in what is exposed to ionizing radiation in the neck area, and (2) to assess thyroid shield presence in cephalometric radiographs
Cephalometric radiographs at one academic setting were sampled and neck exposure was related to calendar year and patient's gender and age.
In the absence of shields, children have more vertebrae exposed than adults (p < 0.0001) and females have more neck tissue exposed inferior to the hyoid bone than males (p < 0.0001). The hyoid bone-porion distance increased with age (p <0.01). Thyroid shields were visible in 19% of the radiographs and depended strongly on the calendar year during which patient was seen (p-value <0.0001). Compared to adults, children were less likely to wear thyroid shields, particularly between 1973 and 1990 (1.8% versus 7.3% – p-value < 0.05) and between 2001 and 2003 (7.1% versus 42.9% – p-value < 0.05).
In the absence of a thyroid shield, children have more neck structure exposed to radiation than adults. In agreement with other reports, thyroid shield utilization in this study was low, particularly in children.