CT dosimetry: comparison of measurement techniques and devices
CT dosimetry: comparison of measurement techniques and devices
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DOI：
10.1148/rg.281075024
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发表时间：
2008-01-01
期刊：
影响因子：
5.5
通讯作者：
McCollough, Cynthia H.
中科院分区：
文献类型：
--
作者：
Bauhs, John A.;Vrieze, Thomas J.;McCollough, Cynthia H.
在X射线计算机断层扫描（CT）中，用于估计和最小化患者剂量的最常见参数是CT剂量指数（CTDI）。CTDI是一种体积平均测量值，用于检查床随试管旋转而增加的情况。CTDI的变体校正跨视场的平均值和相邻光束重叠或间隙。CTDI通常用一个椭圆形的电离室来测量，尽管已经开发了使用替代检测器的方法，包括光激发光探针和固态实时剂量计。由于CTDI代表均匀圆柱体模的平均剂量，因此测量值仅为患者剂量的近似值。此外，来自介入或灌注CT的剂量，其中床在多次扫描之间保持静止，最好通过用小探测器进行的点剂量测量来评估。螺旋CT表面剂量测量的CTDI值与点剂量值基本一致。然而，对于灌注CT的表面剂量测量，与点剂量值相比，CTDI值的剂量被高估了两倍或更多倍。CTDI和点剂量测量对于评估CT扫描仪输出和估计患者剂量都是有价值的。
In x-ray computed tomography (CT), the most common parameter used to estimate and minimize patient dose is the CT dose index (CTDI). The CTDI is a volume-averaged measure that is used in situations where the table is incremented in conjunction with the tube rotation. Variants of the CTDI correct for averaging across the field of view and for adjacent beam overlaps or gaps. CTDI is usually measured with a pencil-shaped ionization chamber, although methods have been developed that use alternative detectors, including an optically stimulated luminescence probe and a solid-state real-time dosimeter. Because the CTDI represents an averaged dose to a homogeneous cylindrical phantom, the measurements are only an approximation of the patient dose. Furthermore, dose from interventional or perfusion CT, in which the table remains stationary between multiple scans, is best evaluated with point dose measurements made with small detectors. CTDI and point dose values are nearly the same for measurement of surface dose from spiral CT. However, for measurement of surface dose from perfusion CT, the dose is overestimated by a factor of two or more with CTDI values in comparison with point dose values. Both CTDI and point dose measurement are valuable for evaluating CT scanner output and estimating patient dose.