Comparison of thyroid absorbed dose and image quality in panoramic radiographs with and without Nanocomposite shields
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Background: The thyroid gland, eyes, and salivary glands are organs that are sensitive to radiations and are in the main radiation field in maxillofacial radiographic examinations.However, the use of lead shields results in artifacts and the loss of diagnostic data in the mandible.In the present study, shields containing nanocomposite materials were used to decrease the mean dose of the transmitted radiation and increase the percentage of the radiation absorbed by the shield with no effect on the diagnostic accuracy of the radiographs in the mandible and thyroid gland area. Methods: Shields with different concentrations of different nanoparticles, were used to evaluate the protective efficacy of these nanoparticles for the thyroid gland during panoramic radiography in three statuses: no shield, and shields containing bismuth oxide nanoparticles (10%), shields containing bismuth oxide nanoparticles (5%) + lead oxide (5%), shields containing bismuth oxide nanoparticles (5%) + ferric oxide (5%), shields containing silver oxide (5%) + lead oxide (5%), and shields containing ferric oxide (5%) + lead oxide (5%) 0.5-mm and 1-mm shields. Results: The maximum decrease in the dose in the thyroid area occurred with the shield containing 10% bismuth oxide with 1-mm thickness, followed by the bismuth oxide with a decrease in thyroid dose up to 0.29 mGy.Concerning the comparison of image quality with the CNR and visual quality, the best images were achieved with 0.5-mm bismuth oxide, followed by 1-mm bismuth oxide.An increase in the nanocomposite shields’ thickness from 0.5 mm to 1 mm further decreased the transmitted dose up to 0.272 mGy and further increased the percentage of the absorbed dose up to 72.24% by the shield, indicating the efficacy of the shields. Conclusion: Evaluation of panoramic radiographs taken with and without the suggested shields in the thyroid gland area and visual comparison of the images showed that these shields could be used to decrease the radiation dose of the phantom without affecting the diagnostic accuracy of the images.