能谱CT单能量成像去除体模对比剂硬化伪影的研究

Comparison of beam hardening artefact with spectral CT imaging mode versus conventional CT imaging

目的验证Revolution CT能谱单能量成像去除射线束硬化伪影的能力,寻求最佳单能量值的范围。方法采用Revolution CT对仿真对比剂体模进行常规和能谱CT扫描。能谱组重建40~140KeV单能量图,间隔10KeV,共获得11组单能量图,测量并比较常规组与能谱单能量组BHA。同时对图像质量进行主观评价。采用单因素方差分析,比较组间差异,P<0.05为差异有统计学意义。结果11组单能量图像平均噪声及BHA随着能量值的增大逐渐降低,主观评分先升高后降低。单能量值≥90KeV的图像平均噪声和BHA均较常规图像明显降低(P<0.05)。单能量值≥90KeV的6组图像两两之间的平均噪声及BHA差异均没有显著性(P>0.05)。主观评分结果显示单能量值为90KeV、100KeV的图像评分为常规图像组的2倍。结论RevolutionCT能谱单能量图像能明显改善常规扫描产生的射线束硬化伪影,在临床工作中应当选择单能量值范围为90~100KeV的图像,既能最小化射线束硬化伪影,又能保持较高的图像质量。

Objective The aim of study was to compare beam hardening artefact(BHA)in phantom experiment with conventional CT mode versus spectral CT imaging mode.Methods A polyethylene cylindrical phantom with nine tubes containing varying concentrations of iodine underwent both conventional CT imaging(120 kVp)and spectral CT imaging(80/140 kVp,pitch 0.992,rotation time 0.5 s)mode.Images were reconstructed with different virtual monochromatic energy levels ranging from 40 to 140 keV.BHA and subjective image quality was calculated.The differences between groups were assessed with one-way ANOVA.P<0.05 was considered statistically significant.Results The average noise and BHA of the 11 sets of monochromatic energy images gradually decreased with the increase of energy value,and the subjective score increased gradually,indicating that the average image noise and BHA with monochromatic energy≥90 KeV were significantly lower than those of conventional images(P<0.05).There were no significant differences in average noise and BHA among six groups with monochromatic energy≥90 KeV(P>0.05).The subjective scores of the monochromatic energy value 90 KeV,100 KeV image were 2 times of the conventional image group.Conclusion In comparison with conventional CT imaging mode,spectral CT mode with arrow high energy monochromatic image acquisition(90~100 KeV)revealed substantial reduction in beam hardening effects.