CT低剂量高分辨成像可行性研究体模实验

Technical Feasibility Proof for Low-Dose High-Resolution CT:A Phantom Study

目的探讨CT低剂量高分辨扫描成像的可行性,探寻低剂量下最佳的高分辨成像扫描参数组合。方法在Force CT和HD750 CT上通过改变管电流和管电压组合,并采用迭代(ADMIRE3/ASIR 50%)和滤波反投影(Filtered Back Projection,FBP)两种重建方式,对Catphan 600体模进行扫描,记录容积CT剂量指数(Volume CT Dose Index,CTDI_(vol)),分析不同重建算法对空间分辨力、密度分辨力和图像噪声的影响。按CTDI_(vol)值分为低剂量组(<2 mGy)和高剂量组(>8 mGy),分析辐射剂量与空间分辨力和密度分辨力的关系。结果与FBP相比,迭代重建图像噪声更低(P<0.05)。高、低剂量组中空间分辨力存在部分重叠。低剂量组中最佳的高分辨扫描参数组合:120 kV/25 mAs(60 mA)。结论管电压120 kV、管电流25 mAs(60 mA),结合迭代重建可实现低剂量高分辨成像,为临床胸部CT低剂量高分辨成像扫描提供了理论依据及扫描参数选择。

Objective To explore the feasibility of low-dose high-resolution CT scanning imaging and explore the optimal combination of high-resolution imaging scanning parameters at low dose.Methods The Catphan 600 was scanned on the Force CT and HD750 CT by varying the combination of current and voltage with both iterative reconstruction(ADMIRE3/ASIR 50%)and filtered back projection(FBP)reconstruction,and the volume CT dose index(CTDI_(vol))was recorded.The effects of iterative reconstruction and FBP reconstruction on spatial resolution,density resolution and image noise were analyzed.According to the value of CTDI_(vol),the patients were divided into a low-dose group(<2 mGy)and a high group(>8 mGy).The relationship between radiation dose and the subjective evaluation of spatial resolution and density resolution was analyzed to explore the optimal combination of scanning parameters of spatial resolution and density resolution under low-dose scanning.Results Compared with FBP reconstruction,the noise level of the iterative reconstruction image was lower(P<0.05).Partial overlap exists in spatial resolution in different radiation dose groups(low dose and high dose groups).In the low-dose group,the best scanning parameter combination of spatial resolution/density resolution was 120 kV/25 mAs(60 mA).Conclusion Low dose and high-resolution imaging can be realized with the low-dose scanning scheme of tube voltage 120 kV and tube current 25 mAs(60 mA)and the combined iterative reconstruction algorithm.It provides the theoretical basis and the selection of scanning parameters for clinical chest low-dose high-resolution CT.