Brady Z, Cain T M, Johnston P N
Applied Physics, RMIT University, Melbourne, VIC, Australia.
Australas Phys Eng Sci Med. 2012 Jun;35(2):117-34. doi: 10.1007/s13246-012-0134-4. Epub 2012 Apr 11.
Computed tomography (CT) is the single biggest ionising radiation risk from anthropogenic exposure. Reducing unnecessary carcinogenic risks from this source requires the determination of organ and tissue absorbed doses to estimate detrimental stochastic effects. In addition, effective dose can be used to assess comparative risk between exposure situations and facilitate dose reduction through optimisation. Children are at the highest risk from radiation induced carcinogenesis and therefore dosimetry for paediatric CT recipients is essential in addressing the ionising radiation health risks of CT scanning. However, there is no well-defined method in the clinical environment for routinely and reliably performing paediatric CT organ dosimetry and there are numerous methods utilised for estimating paediatric CT effective dose. Therefore, in this study, eleven computational methods for organ dosimetry and/or effective dose calculation were investigated and compared with absorbed doses measured using thermoluminescent dosemeters placed in a physical anthropomorphic phantom representing a 10 year old child. Three common clinical paediatric CT protocols including brain, chest and abdomen/pelvis examinations were evaluated. Overall, computed absorbed doses to organs and tissues fully and directly irradiated demonstrated better agreement (within approximately 50 %) with the measured absorbed doses than absorbed doses to distributed organs or to those located on the periphery of the scan volume, which showed up to a 15-fold dose variation. The disparities predominantly arose from differences in the phantoms used. While the ability to estimate CT dose is essential for risk assessment and radiation protection, identifying a simple, practical dosimetry method remains challenging.
计算机断层扫描（CT）是人为辐射源中最大的电离辐射风险因素。减少这一来源的不必要致癌风险需要确定器官和组织的吸收剂量，以估计有害的随机效应。此外，有效剂量可用于评估不同照射情况之间的相对风险，并通过优化来促进剂量降低。儿童受辐射致癌的风险最高，因此对接受儿科CT检查的患者进行剂量测定对于解决CT扫描的电离辐射健康风险至关重要。然而，临床环境中尚无常规且可靠地进行儿科CT器官剂量测定的明确方法，并且有多种方法用于估算儿科CT有效剂量。因此，在本研究中，对11种用于器官剂量测定和/或有效剂量计算的计算方法进行了研究，并与使用置于代表10岁儿童的物理人体模型中的热释光剂量计测量的吸收剂量进行了比较。评估了三种常见的儿科临床CT检查方案，包括脑部、胸部和腹部/盆腔检查。总体而言，对完全和直接受照射的器官和组织计算得到的吸收剂量与测量的吸收剂量显示出更好的一致性（约在50%以内），而对分布器官或扫描体积周边器官的吸收剂量则显示出高达15倍的剂量差异。这些差异主要源于所使用模型的不同。虽然估计CT剂量的能力对于风险评估和辐射防护至关重要，但确定一种简单、实用的剂量测定方法仍然具有挑战性。
