超低管电流三维自适应迭代剂量降低重建CT猪结肠成像质量与辐射剂量

Image quality and radiation dose of ultra-low current CT colonography with adaptive iterative dose reduction three-dimensional in pig model

目的探讨超低管电流三维自适应迭代剂量降低（AIDR3D）重建CT猪结肠成像的图像质量与辐射剂量。方法制作10段猪结肠息肉模型,每段猪结肠黏膜设有30枚直径1-15mm的结节样模拟息肉。对所有模型均采用640层CT机进行扫描,管电压120kVp,电流剂量分别为10、20、30、40、50mAs。并获得滤波反投影（FBP）和AIDR3D重建图像,不同管电流及重建方法组合10组数据：A组（10mA,FBP）、B组（10mAs,AIDR3D）、C组（20 mAs,FBP）、D组（20mAs,AIDR3D）、E组（30mAs,FBP）、F组（30mAs,AIDR3D）、G组（40mAs,FBP）、H组（40mAs,AIDR3D）、I组（50mAs,FBP）、J组（50mAs,AIDR3D）。测算图像的噪声、SNR及CNR作为定量指标,并对图像质量进行主观定性评分。以有效辐射剂量为指标比较各组图像的辐射剂量。结果相同管电流条件下,AIDR3D图像的噪声低于FBP图像,SNC及CNR均高于FBP图像（P均〈0.05）。D组与I组图像的噪声（P=0.052）、SNR（P=0.129）及CNR（P=0.053）差异均无统计学意义。B组图像的噪声（P=0.002）高于I组,SNR及CNR均低于I组（P均〈0.001）。相同管电流条件下,AIDR3D图像的质量评分高于FBP图像（P均〈0.05）。D组与I组的图像质量评分差异无统计学意义（P=0.121）。B组的图像质量评分低于I组（P〈0.001）。与I组（50 mAs,FBP）比较,D组（20 mAs,AIDR3D）的有效辐射剂量降低了59.90%,差异有统计学意义（P〈0.05）。结论超低管电流（20 mAs）扫描结合AIDR3D重建的猪结肠CT图像质量可媲美常规低管电流（50 mAs）扫描结合FBP重建的图像质量,并有效减低辐射剂量。

Objective To investigate image quality and radiation dose of ultra-low current CT colonography with adaptive iterative dose reduction three-dimensional（AIDR3D）in pig model.Methods Ten segments of porcine colon models were established,of which thirty pedunculated polyps with diameters ranging from 1mm to 15 mm were implanted.All colon models were scanned using 640-slice CT scanner with tube voltage of 120 kVp,and current of 10,20,30,40,50 mAs,respectively.CT colonography images were reconstructed using filtered back projection（FBP）and AIDR3 D.Ten groups data were obtained with 5current doses and 2reconstruction algorithms：Group A（10 mAs,FBP）,group B（10mAs,AIDR3D）,group C（20 mAs,FBP）,group D（20 mAs,AIDR3D）,group E（30 mAs,FBP）,group F（30 mAs,AIDR3D）,group G（40 mAs,FBP）,group H（40 mAs,AIDR3D）,group I（50 mAs,FBP）,group J（50 mAs,AIDR3D）.Quantitative image quality evaluation was preformed,included image noise,SNR,and contrast-to-noise ratio（CNR）.Qualitative image quality was also evaluated.Radiation dose was compared with the index of effective radiation dose.Results At the same level of current,image noise with AIDR3 D was lower than that with FBP,while SNR and CNR with AIDR3 Dwere higher than those with FBP（all P〈0.05）.There was no statistically significant difference in image noise（P=0.052）,SNR（P=0.129）and CNR（P=0.053）between groups D and I.Image noise of group B was higher than that of group I（P=0.002）,while SNR and CNR were all lower than group I（both P〈0.001）.Qualitative image quality scores with AIDR3 Dwere higher than that with FBP at the same level of current doses（all P〈0.05）.No significant difference of qualitative image quality scores between groups D and I was found（P=0.121）.Qualitative image quality score of group B was lower than that of group I（P〈0.001）.Compared with group I,effective radiation dose of group D decreased by 59.90%（P〈0.05）.Conclusion Image quality of ultra-low current of 20 mAs CT colonography with AIDR3 Dis comparable to currently standard low current dose of 50 mAs with FBP,and can decrease radiation dose effectively.