低剂量条件下调制传递函数法与线对法的相关性分析
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摘要
通过在低剂量条件下对两种CT图像空间分辨率获得方法(调制传递函数法与线对法)的相关性分析,提供CT质量控制过程中空间分辨率评价的客观依据。研究使用GE Light Speed 16 CT对位于扫描正中线的Catphan 500体模中的CPT528及CPT486模块进行扫描。扫描条件:标准胸部扫描条件(120kV、200mA)以及低剂量扫描条件(电压:80kV、100kV、120kV、和140kV 4档;电流:10-60mA,10mA递增)。各扫描条件均使用CPT486模块测量噪声。调节窗宽窗位,观察不同扫描条件下可分辨的线对(为说明主观性对线对法的影响,随机选取部分CPT528扫描图像,由5名受试者进行读数,进行统计分析)。测量不同扫描图像中的点扩散函数(Point spread function,PSF),再对PSF进行二维傅里叶变换得到调制传递函数(Modulation transfer function,MTF),最后使用SAS8.2软件对10%MTF值与线对法目测值进行统计分析,寻找两种空间分辨率获得方法(MTF法与线对法)之间的相关性。结果表明,当MTF为10%时对应的空间分辨率与线对法目测值一致(t'=0.18、p=0.8556)。低剂量条件下部分MTF曲线受噪声影响导致MTF值增大。
The aim of this study is to analyze the correlation of two spatial resolution of CT image acquisition method(modulation transfer function method and line pair method) under low dose conditions,which to provide an objective basis for spatial resolution evaluation of CT quality control.This research scanned located mid-line CPT 528 and 486 module of Catphan 500 phantom by using GE Light Speed 16 CT under standard chest scanning conditions(120kV,200mA) and low dose conditions(80kV,100kV,120kV,and 140kV four gears; 10-60mA,10mA increased) separately,with CPT486 module measuring noise.Adjust the window wide and window level,observe distinguishable lines on the card under different scanning conditions(to illustrate the impact of subjectivity on the line pairs method,randomly selected parts of CPT528 scanned images were read by five testers and the results were statistically analyzed).The point spread function(PSF) on the different locations were measured via the program,and then on two-dimensional Fourier transformation of PSF to get modulation transfer function(MTF).Finally,we used SAS8.2 software statistical to analyze 10% MTF values and visual values in order to search the correlation between MTF method and line pairs method.The results show that when the MTF is 10% the corresponding spatial resolution and visual values obtained by lines pair method are consistent(t'=0.18,p=0.8556).Under low-dose conditions,part of MTF curves are influenced by noise,leading to increase of MTF value.
The aim of this study is to analyze the correlation of two spatial resolution of CT image acquisition method(modulation transfer function method and line pair method) under low dose conditions,which to provide an objective basis for spatial resolution evaluation of CT quality control.This research scanned located mid-line CPT 528 and 486 module of Catphan 500 phantom by using GE Light Speed 16 CT under standard chest scanning conditions(120kV,200mA) and low dose conditions(80kV,100kV,120kV,and 140kV four gears; 10-60mA,10mA increased) separately,with CPT486 module measuring noise.Adjust the window wide and window level,observe distinguishable lines on the card under different scanning conditions(to illustrate the impact of subjectivity on the line pairs method,randomly selected parts of CPT528 scanned images were read by five testers and the results were statistically analyzed).The point spread function(PSF) on the different locations were measured via the program,and then on two-dimensional Fourier transformation of PSF to get modulation transfer function(MTF).Finally,we used SAS8.2 software statistical to analyze 10% MTF values and visual values in order to search the correlation between MTF method and line pairs method.The results show that when the MTF is 10% the corresponding spatial resolution and visual values obtained by lines pair method are consistent(t'=0.18,p=0.8556).Under low-dose conditions,part of MTF curves are influenced by noise,leading to increase of MTF value.
引文
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16 Michael C S,Dick J D,Frank P.Computing the modulation transfer function of a magnetic resonance imager[J].Medical Physics,1994,21(3):483-489.
17 Mohapatra S M,Turley J D,Prince J R,et al.Transfer function measurement and analysis for a magnetic resonance imager[J].Medical Physics,1991,18(6):1141-1144.
18 石明国.医学影像设备学[M].北京:高等教育出版社,2008:269-361.SHI Mingguo.Medical Imaging Devices[M].Beijing:Higher Education Press,2008:269-361.
19 白玫.CT系统目测分辨率与系统调制传递函数相关性分析[J].中国医疗设备,2011,4:11-13.BAI Mei.Correlation analysis between visual resolution of CT system and modulation transfer function[J].China Medical Devices,2011,4:11-13.
2 葛虓俊.肺部低剂量CT的应用进展[J].中国医学影像学杂志,2009,8:225-227.GE Xiaojun.Application progress of low dose lung CT[J].Chinese Journal of Medical Imaging,2009,8:225-227.
3 张忠新,刘建功,刘红艳,等.低剂量电离辐射生物效应研究[J].辐射研究与辐射工艺学报,2013,31(5):050101.ZHANG Zhongxin,LIU Jiangong,LIU Hongyan,et al.Biological effects of low-dose ionizing radiation[J].Journal of Radiation Research and Radiation Processing,2013,31(5):050101.
4 陈伟,何颖,沈先蓉,等.低剂量辐射对小鼠血清蛋白差异表达的影响[J],辐射研究与辐射工艺学报,2014,32 (5):010203.CHEN Wei,HE Ying,SHEN Xianrong,et al.Effects of low radiation on differential expression of serum protein in mice[J].Journal of Radiation Research and Radiation Processing,2014,32(5):010203.
5 闵锐.低剂量/低剂量率电离辐射生物效应[J].辐射研究与辐射工艺学报,2014,32(6):060101.MIN Rui.Biological effects induced by low dose/low dose rate ionizing radiation[J].Journal of Radiation Research and Radiation Processing,2014,32(6):060101.
6 周平坤.低剂量辐射效应-辐射防护的基础[J].辐射防护通讯,2005,25(4):13-16.ZHOU Pingkun.Various biological effects of low dose ionizing radiation and challenge on radiological protection practice[J].Radiation Protection Bulletin,2005,25(4):13-16.
7 王济东,王俊杰.低剂量辐射生物效应的研究进展[J].国外医学·放射医学核医学分册,2005,29(4):186-189.WANG Jidong,WANG Junjie.Advances in study of biological effects with low-dose rate irradiation[J].Foreign Medical Science·Scection of Radiation Medicine and Nuclear Medicine,2005,29(4):186-189.
8 Karabulut N,Toru M.Gelebek V,et al.Comparison of low-dose and standard—dose helical CT in the evaluation of pulmonary nodules[J].European Radiology,2002,12(11):2764-2769.
9 Weng M J.Wu M T,Pan H B,et al.The feasibility of low-dose CT for pulmonary metastasis in patients with primary gyneco—logic malignancy[J].Clinical Imaging,2004,28(6):408-414.
10 Krabulut N,Toru M,Gelebek V,et al.Comparison of low-dose and standard—dose helical CT in the evaluation of pulmonary nodules[J].European Radiology,2002,12(11):2764-2769.
11 Weng M J,Wu M T,Pan H B,et al.The feasibility of low-dose CT for pulmonary metastasis in patients with primary gyneco—logic malignancy[J].Clinical Imaging,2004,28(6):408-414.
12 朱凯帮,黄照康.低剂量CT检查在肺癌筛查中的应用[J].当代医学,2014,20(10):29-30.ZHU Kaibang,HUANG Zhaokang.Application of low dose CT for lung cancer screening[J].Contemporary Medicine,2014,20(10):29-30.
13 李庚,高关心,夏慧琳.CT空间分辨率和低对比度分辨率的检测及其影响因素[J].中国医疗设备,2010,1:7-9.LI Geng,GAO Guanxin,XIA Huilin.Detection and influencing factor of CT spatial resolution and low-contrast resolution[J].China Medical Devices,2010,1:7-9.
14 康立丽,邓晓刚,陈阳,等.影像系统MTF算法实现级分析[J].北京生物医学工程,2002,21(3):179-183.KANG Lili,DENG Xiaogang,CHEN Yang,et al.The implementation and analysis of MTF algorithm of imaging system[J].Beijing Biomedical Engineering,2002,21(3):179-183.
15 Boone J M.Determination of the presampled MTF in computed tomography[J].Medical Physics,2001,28(3):356-360.
16 Michael C S,Dick J D,Frank P.Computing the modulation transfer function of a magnetic resonance imager[J].Medical Physics,1994,21(3):483-489.
17 Mohapatra S M,Turley J D,Prince J R,et al.Transfer function measurement and analysis for a magnetic resonance imager[J].Medical Physics,1991,18(6):1141-1144.
18 石明国.医学影像设备学[M].北京:高等教育出版社,2008:269-361.SHI Mingguo.Medical Imaging Devices[M].Beijing:Higher Education Press,2008:269-361.
19 白玫.CT系统目测分辨率与系统调制传递函数相关性分析[J].中国医疗设备,2011,4:11-13.BAI Mei.Correlation analysis between visual resolution of CT system and modulation transfer function[J].China Medical Devices,2011,4:11-13.