Khoramian Daryoush, Sistani Soroush
Independent Researcher, Tehran, Iran.
J Radiol Prot. 2017 Dec;37(4):826-836. doi: 10.1088/1361-6498/aa823f.
To estimate and compare the radiation dose associated with coronary computed tomography angiography (CCTA) examinations on two multi-detector CT scanners (MDCT), 64-MDCT and 128-MDCT, in daily practice.
Scan parameters of 90 patients undergoing retrospective electrocardiographic gating spiral CCTA exam were recorded during a period on a single-source 64-MDCT and a dual-source 128-MDCT, and average scan parameters were derived that were used for dosimetry. The computed tomography dose index (CTDI) with a pencil ionisation chamber and polymethyl methacrylate body phantom with diameter of 32 cm was measured on both scanners. The dose-length product (DLP) was calculated and the DLP to effective dose conversion factor (for chest scan at 120 kV of 0.014 mSv mGy cm) was used to estimate effective dose (ED).
Patients' heart rate, scan length, pitch factor, CTDIv, DLP and ED for 128-MDCT were 64 (5) (beats min), 161 (10) (mm), 0.26, 47 (12) (mGy), 769 (212) (mGy cm) and 10.3 (3.1) (mSv), respectively [mean (one standard deviation)]. Patients' heart rate, scan length, pitch factor, CTDIv, DLP and ED for 64-MDCT were 60 (7) (beats min), 172 (14) (mm), 0.2, 60 (6) (mGy), 1068 (98) (mGy cm) and 14.9 (1.4) (mSv), respectively.
Our results indicated that the CTDIv, DLP and the effective dose with 128-MDCT is significantly lower than with 64-MDCT (p < 0.05). As differences between the exposure parameter mAs on two CT scanners was not significant (p > 0.05) and the kV was constant for both scanners (120 kV), the differences resulted from a shorter scan length on the 128-MDCT and use of a higher pitch factor (0.26 and 0.2 in the 128-MDCT and 64-MDCT, respectively). Comparison with other published studies confirms the findings and indicates methods for reducing patient dose.
在日常实践中，估算并比较两台多排CT扫描仪（MDCT），即64排MDCT和128排MDCT，进行冠状动脉计算机断层扫描血管造影（CCTA）检查时的辐射剂量。
在同一时期，于单源64排MDCT和双源128排MDCT上记录90例接受回顾性心电图门控螺旋CCTA检查患者的扫描参数，并得出用于剂量测定的平均扫描参数。使用铅笔电离室和直径为32 cm的聚甲基丙烯酸甲酯体模在两台扫描仪上测量计算机断层扫描剂量指数（CTDI）。计算剂量长度乘积（DLP），并使用DLP至有效剂量转换系数（120 kV胸部扫描时为0.014 mSv mGy cm）估算有效剂量（ED）。
128排MDCT患者的心率、扫描长度、螺距因子、容积CT剂量指数（CTDIv）、DLP和ED分别为64（5）（次/分钟）、161（10）（mm）、0.26、47（12）（mGy）、769（212）（mGy cm）和10.3（3.1）（mSv）[均值（一个标准差）]。64排MDCT患者的心率、扫描长度、螺距因子、CTDIv、DLP和ED分别为60（7）（次/分钟）、172（14）（mm）、0.2、60（6）（mGy）、1068（98）（mGy cm）和14.9（1.4）（mSv）。
我们的结果表明，128排MDCT的CTDIv、DLP和有效剂量显著低于64排MDCT（p < 0.05）。由于两台CT扫描仪的曝光参数管电流时间积（mAs）差异不显著（p > 0.05）且两台扫描仪的管电压（kV）恒定（120 kV），差异源于128排MDCT扫描长度较短以及使用了更高的螺距因子（128排MDCT和64排MDCT的螺距因子分别为0.26和0.2）。与其他已发表研究的比较证实了这些发现，并指出了降低患者剂量的方法。
