SAFIRE重建算法对胸部CT图像质量和辐射剂量的影响

目的 利用仿真胸部体模,比较原始数据域迭代重建(SAFIRE)算法与滤波反投影(FBP)算法对胸部CT图像质量和辐射剂量的影响。方法 在新双源CT(Somatom definition flash CT)设备上预设80、100、120 kV三组管电压值,采用自动毫安秒care dose 4D技术对仿真胸部体模进行扫描,分别用FBP及SAFIRE重建算法(等级1~5)重建图像,比较胸部不同组织结构的噪声及CT值,并由2名放射科医师独立评价图像质量。每组扫描结束后,记录CT剂量加权指数(CTDIvol)和剂量长度乘积(DLP),计算并比较有效剂量。结果 相同扫描参数检查时,SAFIRE重建算法较FBP算法图像噪声明显降低(P<0.05);不同扫描参数检查时,无论FBP算法或SAFIRE重建算法,图像噪声均随管电压增加而降低;胸部各组织结构的噪声会随重建算法和管电压改变而发生变化;100 kV/SAFIRE(等级3)的主观和客观图像质量指标均优于120 kV/FBP,且辐射剂量降低37.61%。结论 胸部CT扫描中,采用SAFIRE重建算法能有效提高图像质量,降低辐射剂量。

Impact of SAFIRE reconstruction algorithm on image quality and radiation dose of chest CT

Objective To investigate the differences of image quality and radiation dose of chest CT between sinogram affirmed iterative reconstruction (SAFIRE) algorithm and filtered back projection (FBP) algorithm. Methods Three sets of tube voltage values of 80, 100, 120 kV were defaulted. Using automatic mAs care dose 4D technology, a phantom was scanned with new dual-source CT (Somatom definition flash). Data sets were reconstructed with FBP and SAFIRE (level 1-5), and the noise and CT values of different structures of chest were compared. Two radiologists evaluated the image quality independently. After each scanning, the dose weighted index (CTDIvol) and dose-length product (DLP) were recorded, then effective dose was calculated and compared. Results With the same scan condition, image noise of SAFIRE of chest CT was significantly lower than that of FBP (P<0.05). Among different scan conditions, regardless of FBP algorithm or SAFIRE algorithm, image noise of chest CT went lower when tube voltage increased. Image noise of different structures of chest changed with different reconstruction algorithm and tube voltage. Both subjective and objective image quality indicators of 100 kV/SAFIRE (level 3) were better than those of 120 kV/FBP, and radiation dose reduced by 37.61%. Conclusion SAFIRE reconstruction algorithm can effectively improve image quality and reduce radiation dose in chest CT.