多参数设置对低剂量胸部CT扫描图像质量及辐射剂量的影响

Impact of multiple parameters setting on image quality and radiation dose in low-dose chest CT scanning

目的探讨当iCT管电流设置为17mAs时,其他参数设置对低剂量胸部CT扫描图像质量及辐射剂量的影响。方法选取低剂量胸部CT筛查的200名志愿者,设定管电流为17mAs,根据管电压及自动曝光控制(DoseRight)设置分为4组:A组为120kV,DoseRight扫描;B组为100kV,DoseRight扫描;C组为120kV,固定管电流扫描;D组为100kV,固定管电流扫描。对所有扫描图像分别采用混合迭代重建(iDose^4)和全模型迭代重建(IMR)进行肺窗及纵隔窗算法重建。比较4组的有效剂量及图像质量。结果 4组肺窗、纵隔窗的iDose^4、IMR重建图像质量评分及有效剂量差异均有统计学意义;A、B组图像质量均较C组图像质量好(P均<0.05),与其余3组比较D组图像质量最差(P均<0.05);C组纵隔窗及D组肺窗、纵隔窗的iDose^4重建图像质量评分较低;A、B、C、D组SNR值依次降低(P均<0.01);A组有效剂量最高(P均<0.01),D组有效剂量最低(P均<0.01),B组和C组间有效剂量差异无统计学意义(P=0.055)。结论 iCT管电流为17mAs时,采用100kV管电压、DoseRight扫描及IMR重建方式可获得较满意的图像质量和较低的辐射剂量。

Objective To investigate the impact of parameters setting on image quality and radiation dose of low-dose chest CT scanning when iCT tube current was set as 17 mAs. Methods Two hundred volunteers who accepted low-dose chest CT screening with tube current was set as 17 mAs were randomly divided into four groups according to the tube voltage and automatic exposure control （DoseRight） settings （group A.. 120 kV, DoseRight; group B.. 100 kV, DoseRight; group C： 120 kV, fixed tube current; group D.. 100 kV, fixed tube current）. Then hybrid iterative reconstruction （HIR.. iDose4） and iterative model reconstruction （IMR） were performed on all scanned images of lung and mediastinal window algorithm, respectively. The effective dose and image quality of 4 groups were compared. Results There were significant differences of image quality score and effective dose among 4 groups. The image quality of group A and B were better than that of group C （P〈0.05）, and of group D was the worst compared with the other three groups （P〈0. 05）. Image quality scores of the mediastinal window of group C and D and the lung window of group D at iDose4 reconstruction were lower. SNR value of group A, B, C, D decreased in order （P〈0.01）. Group A had the highest effective dose （P〈0.01）, while the effective dose of group B and group C had no significant difference （P=0. 055）, and group D had the lowest effective dose （P〈0.01）. Conclusion When tube current was set as 17mAs at iCT, selecting 100 kV tube voltage, DoseRight and IMR reconstruction arithmetic can obtain satisfactory image quality and low radiation dose.