Thyroid shields for radiation dose reduction during cone beam computed tomography scanning for different oral and maxillofacial regions

Aims: To evaluate the radiation dose level during cone beam computed tomography (CBCT) scanning for the different oral and maxillofacial regions with and without thyroid collar shielding. Materials and methods: Average tissue-absorbed dose for a DCT PRO CBCT was measured using thermoluminescent dosimeter chips in a phantom with or without applying thyroid collars. Effective organ dose and total effective dose were derived using International Commission on Radiological Protection (ICRP) 2007 recommendations. Results: The total effective doses for large, middle and small field of view (FOV) were 254.3 mu Sv, 249.0 mu Sv and 180.3 mu Sv, respectively, when no thyroid collar was used. Applying one thyroid collar around the front neck can reduce the total effective doses to 208.5 mu Sv (18.0% reduction), 149.1 mu Sv (40.1% reduction) and 110.5 mu Sv (38.7% reduction), respectively. When two thyroid collars were used around the front and back neck, the total effective doses were reduced to 219.1 mu Sv (13.8% reduction), 142.0 mu Sv (43.0% reduction) and 105.5 mu Sv (41.5% reduction), respectively. Conclusions: Thyroid collar can reduce the radiation dose during CBCT scanning for the oral and maxillofacial regions. The dose reduction becomes more significant when middle or small FOV is chosen. (C) 2011 Elsevier Ireland Ltd. All rights reserved.