Kalender Willi A
Institute of Medical Physics, University of Erlangen-Nuernberg, Henkestr. 91, D-91052 Erlangen, Germany.
Phys Med Biol. 2014 Feb 7;59(3):R129-50. doi: 10.1088/0031-9155/59/3/R129. Epub 2014 Jan 17.
Radiation dose in x-ray computed tomography (CT) has become a topic of high interest due to the increasing numbers of CT examinations performed worldwide. This review aims to present an overview of current concepts for both scanner output metrics and for patient dosimetry and will comment on their strengths and weaknesses. Controversial issues such as the appropriateness of the CT dose index (CTDI) are discussed in detail. A review of approaches to patient dose assessment presently in practice, of the dose levels encountered and options for further dose optimization are also given and discussed. Patient dose assessment remains a topic for further improvement and for international consensus. All approaches presently in use are based on Monte Carlo (MC) simulations. Estimates for effective dose are established, but they are crude and not patient-specific; organ dose estimates are rarely available. Patient- and organ-specific dose estimates can be provided with adequate accuracy and independent of CTDI phantom measurements by fast MC simulations. Such information, in particular on 3D dose distributions, is important and helpful in optimization efforts. Dose optimization has been performed very successfully in recent years and even resulted in applications with effective dose values of below 1 mSv. In general, a trend towards lower dose values based on technical innovations has to be acknowledged. Effective dose values are down to clearly below 10 mSv on average, and there are a number of applications such as cardiac and pediatric CT which are performed routinely below 1 mSv on modern equipment.
由于全球范围内CT检查数量不断增加，X射线计算机断层扫描（CT）中的辐射剂量已成为备受关注的话题。本综述旨在概述当前关于扫描仪输出指标和患者剂量测定的概念，并对其优缺点进行评论。详细讨论了诸如CT剂量指数（CTDI）的适用性等有争议的问题。还给出并讨论了目前实践中患者剂量评估的方法、所遇到的剂量水平以及进一步剂量优化的选项。患者剂量评估仍是一个有待进一步改进和达成国际共识的话题。目前所有使用的方法均基于蒙特卡罗（MC）模拟。有效剂量的估计值已经确定，但这些估计值粗略且并非针对特定患者；器官剂量估计值很少可得。通过快速MC模拟，可以以足够的精度提供特定患者和特定器官的剂量估计值，且独立于CTDI体模测量。此类信息，尤其是关于三维剂量分布的信息，在优化工作中非常重要且很有帮助。近年来剂量优化取得了非常成功的成果，甚至出现了有效剂量值低于1 mSv的应用。总体而言，必须承认基于技术创新的剂量值降低趋势。有效剂量值平均已降至明显低于10 mSv，并且有许多应用，如心脏CT和儿科CT，在现代设备上常规执行时剂量低于1 mSv。
