McNitt-Gray Michael F
Department of Radiology, David Geffen School of Medicine, University of California, Los Angeles, Box 951721, Los Angeles, CA 90095-1721, USA.
Radiographics. 2002 Nov-Dec;22(6):1541-53. doi: 10.1148/rg.226025128.
This article describes basic radiation dose concepts as well as those specifically developed to describe the radiation dose from computed tomography (CT). Basic concepts of radiation dose are reviewed, including exposure, absorbed dose, and effective dose. Radiation dose from CT demonstrates variations within the scan plane and along the z axis because of its unique geometry and usage. Several CT-specific dose descriptors have been developed: the Multiple Scan Average Dose descriptor, the Computed Tomography Dose Index (CTDI) and its variations (CTDI(100), CTDI(w), CTDI(vol)), and the dose-length product. Factors that affect radiation dose from CT include the beam energy, tube current-time product, pitch, collimation, patient size, and dose reduction options. Methods of reducing the radiation dose to a patient from CT include reducing the milliampere-seconds value, increasing the pitch, varying the milliampere-seconds value according to patient size, and reducing the beam energy. The effective dose from CT can be estimated by using Monte Carlo methods to simulate CT of a mathematical patient model, by estimating the energy imparted to the body region being scanned, or by using conversion factors for general anatomic regions. Issues related to radiation dose from CT are being addressed by the Society for Pediatric Radiology, the American Association of Physicists in Medicine, the American College of Radiology, and the Center for Devices and Radiological Health of the Food and Drug Administration.
本文介绍了基本的辐射剂量概念以及专门用于描述计算机断层扫描（CT）辐射剂量的概念。回顾了辐射剂量的基本概念，包括照射量、吸收剂量和有效剂量。由于CT独特的几何结构和用途，其辐射剂量在扫描平面内和沿z轴均表现出变化。已开发出几种特定于CT的剂量描述符：多次扫描平均剂量描述符、计算机断层扫描剂量指数（CTDI）及其变体（CTDI(100)、CTDI(w)、CTDI(vol)）以及剂量长度乘积。影响CT辐射剂量的因素包括束流能量、管电流-时间乘积、螺距、准直、患者体型以及剂量降低选项。降低患者CT辐射剂量的方法包括降低毫安秒值、增加螺距、根据患者体型改变毫安秒值以及降低束流能量。CT的有效剂量可通过使用蒙特卡罗方法模拟数学患者模型的CT、估计传递到被扫描身体区域的能量或使用一般解剖区域的转换因子来估算。儿科放射学会、美国医学物理学家协会、美国放射学会以及食品药品监督管理局的设备与放射健康中心正在解决与CT辐射剂量相关的问题。
