Mazonakis Michalis, Tzedakis Antonis, Damilakis John, Gourtsoyiannis Nicholas
Department of Medical Physics, Division of Radiology, University Hospital of Iraklion, P.O. Box 1352, 71110, Iraklion, Crete, Greece.
Eur Radiol. 2007 May;17(5):1352-7. doi: 10.1007/s00330-006-0417-9. Epub 2006 Sep 21.
This study was conducted to estimate thyroid dose and the associated risk for thyroid cancer induction from common head and neck computed tomography (CT) examinations during childhood. The Monte Carlo N-particle transport code was employed to simulate the routine CT scanning of the brain, paranasal sinuses, inner ear and neck performed on sequential and/or spiral modes. The mean thyroid dose was calculated using mathematical phantoms representing a newborn infant and children of 1year, 5 years, 10 years and 15 years old. To verify Monte Carlo results, dose measurements were carried out on physical anthropomorphic phantoms using thermoluminescent dosemeters (TLDs). The scattered dose to thyroid from head CT examinations varied from 0.6 mGy to 8.7 mGy depending upon the scanned region, the pediatric patient's age and the acquisition mode used. Primary irradiation of the thyroid gland during CT of the neck resulted in an absorbed dose range of 15.2-52.0 mGy. The mean difference between Monte Carlo calculations and TLD measurements was 11.8%. Thyroid exposure to scattered radiation from head CT scanning is associated with a low but not negligible risk of cancer induction of 4-65 per million patients. Neck CT can result in an increased risk for development of thyroid malignancies up to 390 per million patients.
本研究旨在估算儿童期常见头颈部计算机断层扫描（CT）检查所致的甲状腺剂量以及诱发甲状腺癌的相关风险。采用蒙特卡罗N粒子输运代码模拟对大脑、鼻旁窦、内耳和颈部进行的常规顺序扫描和/或螺旋扫描CT。使用代表新生儿以及1岁、5岁、10岁和15岁儿童的数学体模计算平均甲状腺剂量。为验证蒙特卡罗模拟结果，使用热释光剂量仪（TLD）对物理人体模型进行剂量测量。头CT检查对甲状腺的散射剂量在0.6 mGy至8.7 mGy之间，具体取决于扫描区域、儿科患者年龄和所采用的采集模式。颈部CT期间甲状腺的一次照射导致吸收剂量范围为15.2 - 52.0 mGy。蒙特卡罗计算结果与TLD测量结果之间的平均差异为11.8%。头CT扫描的甲状腺散在辐射暴露与每百万患者4 - 65例的低但不可忽视的癌症诱发风险相关。颈部CT可导致每百万患者高达390例的甲状腺恶性肿瘤发生风险增加。
