Absorbed doses in salivary and thyroid glands from panoramic radiography and cone beam computed tomography

Abstract Introduction: Panoramic radiography and cone beam computed tomography (CBCT) are very important in the diagnosis of oral diseases, however patients are exposed to the risk of ionizing radiation. This paper describes our study aimed at comparing absorbed doses in the salivary glands and thyroid due to panoramic radiography and CBCT and estimating radiation induced cancer risk associated with those methods. Methods Absorbed doses of two CBCT equipment (i-CAT® Next Generation and SCANORA® 3D) and a digital panoramic device (ORTHOPANTOMOGRAPH® OP200D) were measured using thermoluminescent dosimeters loaded in an anthropomorphic phantom on sublingual, submandibular, parotid and thyroid glands. Results Absorbed doses in the i-CAT® device ranged between 0.02 (+/-0.01) and 2.23 mGy (+/-0.03), in the SCANORA™ device ranged from 0.01 (+/-0.01) to 2.96 mGy (+/-0.29) and in the ORTHOPANTOMOGRAPH® OP200D ranged between 0.04 mGy and 0.78 mGy. The radiation induced cancer risk was highlighted in the salivary glands, which received higher doses. The protocols that offer the highest risk of cancer are the high resolution protocols of CBCT equipment. Conclusion CBCT exposes patients to higher levels of radiation than panoramic radiography, so the risks and benefits of each method should be considered. The doses in CBCT were dependent on equipment and exposure parameters, therefore adequate selection minimizes the radiation dose.

摘要 引言：全景放射摄影与锥形束计算机断层扫描（cone beam computed tomography，CBCT）在口腔疾病诊断中具有核心应用价值，但患者会面临电离辐射暴露风险。本研究旨在对比全景放射摄影与CBCT在唾液腺及甲状腺中的吸收剂量，并评估这两种检查方式相关的辐射诱发癌症风险。
方法 采用热释光剂量计，将其安置于拟人体模的舌下腺、下颌下腺、腮腺及甲状腺位点，对两台CBCT设备（i-CAT® Next Generation与SCANORA® 3D）及一台数字全景摄影设备（ORTHOPANTOMOGRAPH® OP200D）的吸收剂量进行实测。
结果 i-CAT®设备的吸收剂量区间为0.02(±0.01)至2.23 mGy(±0.03)，SCANORA™设备为0.01(±0.01)至2.96 mGy(±0.29)，ORTHOPANTOMOGRAPH® OP200D则介于0.04 mGy至0.78 mGy之间。研究显示，唾液腺因接收更高辐射剂量，其辐射诱发癌症风险更为显著；其中CBCT设备的高分辨率扫描协议对应的癌症风险最高。
结论 相较于全景放射摄影，CBCT会使患者接受更高剂量的辐射，因此临床需权衡每种检查方式的风险与获益。由于CBCT的辐射剂量取决于设备型号及曝光参数，合理选择扫描参数可有效降低辐射暴露水平。