From the Institute of Medical Physics, Friedrich-Alexander-University Erlangen-Nuremberg, Henkestrasse 91, Erlangen 91052, Germany (N.S., M.H., W.A.K.); and Gundersen Health System, La Crosse, Wis (M.E.J.).
Radiology. 2014 Oct;273(1):153-9. doi: 10.1148/radiol.14132903. Epub 2014 Jun 16.
To determine the dose-length product (DLP)-effective dose (ED) (DLP/ED) conversion coefficient (k) tables for the lower extremities that can be used for calculating ED.
Dose calculations were performed on standard phantoms using a validated Monte Carlo calculation tool. Calculations were performed to obtain ED values for tube voltages from 80 kV to 140 kV in steps of 20 kV for the following examinations: hip (femur), knee, ankle, and computed tomographic (CT) angiography of the lower extremities. Values of the DLP were calculated by multiplying measured CT dose index values by the scan length; k values resulted as the quotients of the ED and DLP values. DLP/ED coefficients averaged over the range of voltage values and their standard deviations were determined for the given lower-extremity CT examinations for all age groups and for both sexes.
Coefficients depend strongly on the phantom age and size, but little on the kilovolt value. In the case of the newborn, for example, k values were 0.0612, 0.0046, 0.0014, and 0.047 for hip, knee, ankle, and CT angiography, respectively, while in the case of the adult, these respective values were 0.0110, 0.0004, 0.0002, and 0.0062. A substantial difference up to 20% between coefficients in male and female phantoms was observed for CT angiographic examination.
DLP/ED conversion coefficients are provided for lower extremities and allow estimation of ED for commonly used clinical musculoskeletal CT and CT angiographic protocols.
确定可用于计算有效剂量（ED）的下肢剂量长度乘积（DLP）-ED（DLP/ED）转换系数（k）表。
使用经过验证的蒙特卡罗计算工具对标准体模进行剂量计算。针对以下检查，在 80kV 至 140kV 之间以 20kV 的步长进行管电压的 ED 值计算：髋关节（股骨）、膝关节、踝关节和下肢 CT 血管造影。通过将测量的 CT 剂量指数值乘以扫描长度来计算 DLP 值；ED 值除以 DLP 值得到 k 值。针对所有年龄段和性别，确定给定下肢 CT 检查的各年龄段和各性别中电压值范围内的 DLP/ED 系数的平均值及其标准差。
系数强烈依赖于体模的年龄和大小，但与千伏值关系不大。例如，对于新生儿，髋关节、膝关节、踝关节和 CT 血管造影的 k 值分别为 0.0612、0.0046、0.0014 和 0.047，而对于成年人，这些值分别为 0.0110、0.0004、0.0002 和 0.0062。对于 CT 血管造影检查，男女体模中的系数存在高达 20%的显著差异。
提供了下肢的 DLP/ED 转换系数，可用于估算常用的临床肌肉骨骼 CT 和 CT 血管造影协议的 ED。
