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低辐射剂量联合两种迭代重组方法对上腹部CT图像质量的影响研究 被引量:3

Effect of New Reconstruction Algorithms on the Upper Abdominal CT Image Quality using a Low Radiation Dose
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摘要 目的在低辐射剂量下,评估常规基于模型的迭代重组(MBIRc)和新一代基于模型的迭代重组(MBIRn)对上腹部CT图像质量的影响。方法将40例行上腹部CT增强扫描的患者随机分成两组:常规组20例[噪声指数(NI)=10],采用MBIRc进行图像重组;低辐射剂量组20例(NI=20),同时采用MBIRc和MBIRn进行图像重组。所有图像采用180 s延迟期进行重组,重组层厚为0.625 mm。测量肝脏、脾、肾脏、竖脊肌以及同层面脂肪的背景噪声(SD)值,并计算出相应的信噪比(SNR)和对比噪声比(CNR)。记录两组之间的CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP)和有效辐射剂量(ED)。采用5分盲法进行图像主观评分。三种重组方式各器官间的SD、SNR和CNR值采用单因素方差分析,两组间的辐射剂量采用独立样本t检验。两名医师之间主观评分的一致性采用Kappa检验。结果三组重组图像的主观评分(NI10 MBIRc、NI20 MBIRc、NI20 MBIRn)分别为(4.12±1.09)分、(3.48±0.98)分、(4.32±0.46)分,两名医师之间具有很好的一致性(Kappa值为0.82)。NI20 MBIRn重组图像的肝脏、脾、肾脏、竖脊肌的SD值分别为(11.17±2.12) HU、(11.01±1.31) HU、(13.98±4.27) HU和(14.05±2.96) HU,明显低于NI10 MBIRc和NI20 MBIRc(P<0.05)。NI20 MBIRn重组图像的各脏器的SNR值分别为7.75±1.60、7.49±1.12、10.73±2.65和4.26±1.39,明显高于NI10 MBIRc和NI20 MBIRc(P<0.05)。NI20MBIRn重组图像的各脏器的CNR值分别为12.04±4.13、11.88±4.11、16.46±6.09和9.65±3.14,明显高于NI10MBIRc(P<0.05)。结论当腹部CT辐射剂量降低75%时,相对于MBIRc重组算法,利用MBIRn重组的图像可以减少图像的噪声、提高图像质量。 Objective To evaluate the effect of the second generation model based iterative reconstruction(MBIRc)and the third generation model based iterative reconstruction(MBIRn)on a low radiation dose upper abdominal CT image quality.Methods 40 upper abdominal patients who underwent triple-phase scans with smart mA on a Discovery CT750 HD were randomly divided into two groups:Conventional dose group(Group A,n=20)used mA modulation for noise index(NI)of 10 HU,images were reconstructed at 0.625 mm thickness with MBIRc.Low radiation dose group(n=20)used mA modulation for 75%dose reduction at NI of 20 HU,images were reconstructed at 0.625 mm thickness with both MBIRc and MBIRn.Both groups use the delayed phase(180 s)images.The CT values and standard deviation(SD)of the liver,spleen,kidney and erector spinae at the same imaging level were measured with the fat SD value representing image noise to calculate signal to noise ratio(SNR=CTtissue/SDtissue)and contrast to noise ratio(CNR=(CTtissue-CT fat)/SDfat)for organs.Radiation doses were recorded.One-way ANOVA analysis was used to analyze the difference of SD,SNR and CNR.The subjective image scores of the three groups were assessed blindly by two experienced physicians using a 5-point system and the score consistency was compared by the Kappa test.Independent sample t-test was used to compare radiation doses.Results The subjective scores of the three groups(NI10 MBIRc,NI20 MBIRc and NI20 MBIRn)were 4.12±1.09,3.48±0.98 and 4.32±0.46,and there was good consistency between reviewers(Kappa=0.82).The SD values of the liver,spleen,kidney and erector spine with MBIRn were 11.17±2.12,11.01±1.31,13.98±4.27 and 14.05±2.96,statistically lower than those with MBIRc(NI=10 and NI=20,respectively)(P<0.05).With MBIRn,the SNR values of liver,spleen,kidney and erector spine were 7.75±1.60,7.49±1.12,10.73±2.65 and 4.26±1.39,were statistically higher than those of MBIRc(NI=10 and NI=20,respectively)(P<0.05).With MBIRn,the CNR values were 12.04±4.13,11.88±4.11,16.46±6.09 and 9.65±3.14,and they were statistically higher than MBIRc(NI=10)(P<0.05).Conclusion In the low radiation dose abdominal CT,MBIRn reconstruction reduces image noise and improves image quality when compared with MBIRc reconstruction.Using the third model based iterative reconstruction,can provide a basis for low dose scanning and high image quality.
作者 张喜荣 贾永军 马光明 冯璟 王恒伟 郭长义 ZHANG Xirong;JIA Yongjun;MA Guangming(Shaanxi University of Chinese Medicine,Technical College of Medical,Xianyang 712046,P.R.China)
出处 《临床放射学杂志》 CSCD 北大核心 2019年第6期1118-1122,共5页 Journal of Clinical Radiology
关键词 迭代重组 图像质量 体层摄影术 X线计算机 Iterative reconstruction Image quality Tomography,X-ray computed
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