Objective:To assess radiation dose and image quality of chest CT examinations in low weight (<20 kg) children acquired at ultra-low tube voltage (70 kVp) combined with iterative reconstruction technique.Methods: A total of 30 continuous pediatric patients (weight <20 kg) required non–contrast chest CT at 70 kVp from Dec 2014 to Mar 2015 and image was reconstructed by iflter back projection (FBP) and Sinogram Affrmed Iterative Reconstruction (SAFIRE, Siemens). The 30 matched patients for pediatric standard 80 kVp protocols with conventional spiral mode (control group) were selected from PACS. For each examination, the volume CT doseindex (CTDIvol) (mGy) and dose–length product (DLP) (mGy·cm), (effective dose) ED (mSv) were estimated. hTe image noise, signal to noise ratio (SNR) and overall subjective image quality.Results: For radiation dose, CTDIvol (mGy), DLP (mGy·cm) and ED (mSv) with ultra-low tube voltage group was significant lower than that with control group (decreased 18.7%, 21.6%, 20.2%,P<0.001). For ultra-low tube voltage group, the mean image noise of image obtained by SAFIRE decreased 35.1% (P<0.05) and mean SNR increased 16.0% compared to FBP and image obtained by SAFIRE had statistical lower image overall subjective image quality grades than image obtained by FBP. For the images obtained in ultra-low tube voltage group by FBP, the mean image noise increased 18.2% (P<0.05) and mean SNR decreased 3.8% (P>0.05) compared to control group. hTere were no signiifcant differences between the overall subjective image quality grades of FBP groups.Conclusion: Ultra-low tube voltage (70 kVp) combined with iterative reconstruction technique the of the chest can obtain image with the clinical acceptable image noise in low weight children, meanwhile reduce radiation does signiifcantly.%目的：研究超低管电压(70 kVp)与迭代重建联合应用对低体重(<20 kg)儿童胸部CT图像质量及辐射剂量的影响。方法：收集2014年12月1日至2015年3月31日进行胸部平扫的连续30例低体重(<20 kg)儿童患者，管电压降低为70 kVp，分别进行滤波反投影重建(filter back projection，FBP)及迭代重建(Sinogram Affirmed Iterative Reconstruction，SAFIRE，Siemens)获得图像，从PACS挑选30例体重及年龄匹配的低体重儿童(<20 kg)作为对照组，对CT容积辐射指数(the volume CT dose index，CTDIvol)(mGy)、剂量长度乘积(dose-length product，DLP)(mGy·cm)、有效辐射剂量(effective dose，ED)(mSv)、图像噪声、信噪比及总体主观图像质量、呼吸运动伪影进行对比评价。结果：超低管电压组较对照组CTDIvol(mGy)、DLP(mGy·cm)、ED(mSv)分别减少18.7%、21.6%、20.2%(P<0.001)。超低管电压组SAFIRE重建较FBP重建噪声减少35.1%，信噪比(signal to noise ratio，SNR)提高16%(P<0.05)，SAFIRE的图像的主观评分显著低于FBP。超低管电压组FBP重建较对照组，噪音增加18.2%(P<0.05)，SNR下降3.8%(P>0.05)，图像主观评分无统计学差异。结论：超低管电压(70 kVp)与迭代重建联合应用较传统螺旋扫描获得临床可以接受的图像质量，同时显著减少了辐射剂量。
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