螺旋CT图像噪声的评价

Assessment of image noise in spiral CT

目的 :评价螺旋CT中内插方式、螺距以及重建间隔对噪声的影响。方法 :采用SomatomPlus 4螺旋CT机。在相同条件下扫描直径为 2 0cm的水模 ,测得水模图像中心 40cm2 兴趣区的CT值标准差作为评价噪声水平的指标。结果 :3 60°线性内插的噪声减少 (t =3 4.87,P <0 .0 0 1) ,180°线性内插的噪声增加 (t =18.78,P <0 .0 0 1)。螺距大于 1.0或小于 1.0与螺距为 1.0时噪声水平的差异无显著性意义 (P >0 .0 5 )。随着重建间隔改变 ,相应噪声水平的差异无显著性意义 (P >0 .0 5 )。结论 :与常规扫描相比 ,螺旋CT内插方式对噪声有一定影响 ,而螺距与重建间隔对噪声水平影响不明显。

Objective:To evaluate the effects on image noise level related to linear interpolation techniques,pitches and reconstruction intervals in spiral CT.Methods:All of measurements was carried out on a Somatom Plus4 scanner.The cylindrical water phantom to be scanned was 20cm in diameter.A 40cm 2 circular region on the image of the phantom was measured.The standard deviation of CT attenuation values was recorded as the index of image noise level.Results:Noise was reduced with 360°linear interpolation(t=34.87, P <0.001) and increased with 180° linear interpolation(t=18.78, P <0.001) when compared with the noise in conventional CT scanning.The differences in image noise level were not significant when pitches and reconstruction intervals changed ( P >0.05).Conclusion:In spiral CT,there is certain influence on image noise level with different linear interpolation techniques used,but there is no significant effect when pitches and reconstruction intervals are changed.