能谱CT对粪便掩盖背景下结肠息肉显示能力的体模研究

The efficacy of spectral CT colonography in detecting phantom polyps masked by bowel feces

目的：评价宝石能谱成像（GSI）单能量及质量控制（QC）图像对粪便掩盖背景下结肠小息肉的显示能力，确定显示结肠息肉最佳单能量图像。方法离体猪结肠结扎获得20个模拟息肉，向肠管中灌入碘水‐玉米糊混合物，使用宝石 CT 扫描，提取40-140keV 单能量及 QC 图像，在工作站获得多平面重建（MPR）图像、碘基图和水基图，比较不同图像噪声、对比噪声比（CNR）及息肉检出率。结果图像噪声在70keV 达相对低点，明显低于40、50、60、75、80、85keV 图像噪声（ F ＝443．946，P ＜0．05）。图像 CNR 在70keV 最高，明显高于除60keV 以外单能量图像（ F ＝15．138，P ＜0.05）。70keV（最佳 CNR 单能量图像）图像噪声低于 QC 图像噪声（ t ＝‐2．807，P ＜0．05），CNR 高于 QC 图像 CNR（ t＝2．619，P ＜0．05）。70、75、80、85、90keV 及 QC 图像息肉检出率为75％（15／20），高于其它单能量图像。结论 GSI 具有显示粪便掩盖背景下结肠小息肉的能力，GSI‐CT 显示粪便掩盖背景下结肠息肉的最佳单能量图像为70keV 图像。

Objective To evaluate the efficacy of monochromatic energy images and quality control （QC） images of Gem‐stone Spectral Imaging （GSI） in detecting small phantom colonic polyps masked by bowel feces ,and to choose the optimal monochromatic energy image .Methods A series of twenty phantom polyps sized from 1 mm to 10 mm were established by ligation on an isolated segment of porcine colon .Simulated iodine‐tagged fecal material was filled into the phantom . Volume data were acquired on a High Definition CT scanner ,monochromatic energy images at 40 - 140 keV and QC ima‐ges were reconstructed .Multiplanar reconstruction （MPR） ,iodine‐based images and water‐based images were reconstruc‐ted .The image noise levels ,the contrast to noise ratios （CNR） and the detection rate of phantom polyps were assessed by two radiologists blindly .Results The image noise of 70 keV achieved relatively low point which was significantly lower than 40 ,50 ,60 ,75 ,80 and 85 keV monochromatic energy images （ F = 443 .946 ,P 〈 0 .05） .The 70 keV monochromat‐ic energy images had the highest CNR ,and the CNR of 70 keV was significantly higher than other monochromatic energy images except 60 keV （ F = 15 .138 ,P 〈 0 .05） .The image noise of 70 keV monochromatic energy images were signifi‐cantly lower than QC images （ t = ‐2 .807 ,P 〈 0 .05） ,and the CNR of 70 keV monochromatic energy images were signifi‐cantly higher than QC images （ t = 2 .619 ,P 〈 0 .05） .The detection rates of colonic polyps were 75% （15/20） for 70 , 75 ,80 ,85 ,90 keV images and QC images ,which were higher than other monochromatic energy images .Conclusion GSI has the ability to detect small colonic polyps masked by bowel feces in phantom study .The optimal monochromatic energy images of GSI‐CT is 70 keV in detecting small phantom colonic polyps masked by bowel feces .