变速扫描心脏CT重建图像的研究
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摘要
近年来随着医用CT的广泛普及,心脏CT扫描重建技术已成为医学研究领域的热点。但当前的CT设备只能提供有限数目的可选择的固定扫描速度,由于个体心率的差异性,造成扫描与心脏运动不协调,重建图像特征表现出伪像。
为提高心脏CT图像的重建质量,本文研究了基于ECG心电信号的非周期情况下自适应变速心脏CT扫描,在对被测对象的心动周期进行准确预测和理想分段的条件下,重构逼真或者真实的心脏图像,减少伪影和噪声对图像的影响,提高图像的时间分辨率,有利于科研和临床的实际应用。本文主要的研究内容包括以下几个方面:
(1)研究心脏的运动特征,引入基于ECG心电数据的理想分段方法,归纳出满足理想分段的各项条件,对非理想分段下的图像重建进行分析与讨论。
(2)分析非周期情况下扫描速度与心率的关系,引入心率与扫描速度的关系模型,改进以扫描速度ν、心跳周期T_i和分段数目mbar为参数,k,m为控制变量的变速扫描算法公式,通过仿真实验分析论证改进后算法的可行性。
(3)研究心脏CT扫描重建图像质量的评价问题,引入多项性能指标以及主客观评价方法,归纳总结出适用于不同算法性能比较的评价标准。
(4)根据心脏CT图像特征,提出基于阈值和区域的改进分割算法,对重建图像进行分割处理。
In recent years, image reconstruction of cardiac CT became a hotspot due to the wide applications of CT in medical diagnosis. Currently, fixed scan velocity for cardiac CT is used and approximate projection can only be got due to the non-synchronism between the heartbeat and scan velocity, thus, that cause the images represent artifacts.
In order to improve the quality of cardiac CT image, in our method scan velocity can provide uniform projection with the same phases. The velocity varies with the heart beat, temporal resolution and control parameters to achieve a desirable temporal resolution in non-periodic heartbeat. The main contents of the paper are proposed as follows:
(1)Study the characters of the cardiac motion, and ideal segmentation method based on ECG signal was introduced. Conditions which meet with the ideal segments were concluded, and on non-ideal segments reconstruction was analyzed and discussed.
(2)A new scheme of variable velocity rotation is proposed for exact and approximate reconstructions in non-periodic case, the velocity v. varies with the heart beat T_i the number of sampling windows mbar and control parameters to achieve a desirable temporal resolution in non-periodic heartbeat.
(3)Introduce a number of parameters to evaluate the quality of the reconstructed images from subjective and objective views, get a conclusion to evaluate the performance of different algorithms.
(4)Based on the characters of cardiac CT imaging, improve several algorithms of image segment, the results proved the efficiently of the revised algorithms.
为提高心脏CT图像的重建质量,本文研究了基于ECG心电信号的非周期情况下自适应变速心脏CT扫描,在对被测对象的心动周期进行准确预测和理想分段的条件下,重构逼真或者真实的心脏图像,减少伪影和噪声对图像的影响,提高图像的时间分辨率,有利于科研和临床的实际应用。本文主要的研究内容包括以下几个方面:
(1)研究心脏的运动特征,引入基于ECG心电数据的理想分段方法,归纳出满足理想分段的各项条件,对非理想分段下的图像重建进行分析与讨论。
(2)分析非周期情况下扫描速度与心率的关系,引入心率与扫描速度的关系模型,改进以扫描速度ν、心跳周期T_i和分段数目mbar为参数,k,m为控制变量的变速扫描算法公式,通过仿真实验分析论证改进后算法的可行性。
(3)研究心脏CT扫描重建图像质量的评价问题,引入多项性能指标以及主客观评价方法,归纳总结出适用于不同算法性能比较的评价标准。
(4)根据心脏CT图像特征,提出基于阈值和区域的改进分割算法,对重建图像进行分割处理。
In recent years, image reconstruction of cardiac CT became a hotspot due to the wide applications of CT in medical diagnosis. Currently, fixed scan velocity for cardiac CT is used and approximate projection can only be got due to the non-synchronism between the heartbeat and scan velocity, thus, that cause the images represent artifacts.
In order to improve the quality of cardiac CT image, in our method scan velocity can provide uniform projection with the same phases. The velocity varies with the heart beat, temporal resolution and control parameters to achieve a desirable temporal resolution in non-periodic heartbeat. The main contents of the paper are proposed as follows:
(1)Study the characters of the cardiac motion, and ideal segmentation method based on ECG signal was introduced. Conditions which meet with the ideal segments were concluded, and on non-ideal segments reconstruction was analyzed and discussed.
(2)A new scheme of variable velocity rotation is proposed for exact and approximate reconstructions in non-periodic case, the velocity v. varies with the heart beat T_i the number of sampling windows mbar and control parameters to achieve a desirable temporal resolution in non-periodic heartbeat.
(3)Introduce a number of parameters to evaluate the quality of the reconstructed images from subjective and objective views, get a conclusion to evaluate the performance of different algorithms.
(4)Based on the characters of cardiac CT imaging, improve several algorithms of image segment, the results proved the efficiently of the revised algorithms.
引文
[1]C.H.Harris.CT:It's not just for diagnosis anymore.Medical Imaging.Jun 2001,16,(8):54-61.
[2]Ge Wang,An outlook on X-ray CT research and development.Medical physics.35(3):1051-1064,2008.
[3]夏顺仁,汪元美,吕维雪.心血管双投影下多目标优化截面重建方法.中国生物医学.工程学报,15(4)289-294,1996.
[4]孙伟,庄天戈.有限角投影重建图像的两种算法的比较.CT理论与应用研究.4:30-34,1991.
[5]吕维雪.医学图像技术的研究前沿.中国科学技术大学出版社,1-9,1993.
[6]Prince JL,Willsky AS.Convex set reconstruction using prior shape information.VGIP.53(5):413-427,1991.
[7]顾本立,陆季.极少投影的CT成像研究.CT的理论与应用研究.1994;3(2):14-17.
[8]康克军,毛希平,刘亚强.在二维和三维CT图像重建理论方法的研究工作及新进展.CT的理论与应用研究.6(2):48-51,1997.
[9]庄天戈.CT原理与算法[M],上海:上海交通大学出版社,1992.
[10]Feldkamp LA,et al Practical cone-beam Algorithm.J.Opt Soc Am A,1984,1-126.
[11]G.T.Herman,Imaging Reconstruction from Projections,Springer,1979.
[12]A.H.Andersen and A.C.Kak.Simultaneous algebraic reconstruction technique(SART):a superior implementation of the ART algorithm.Ultrasonic Imaging.6:81-94,1984.
[13]高欣,新型迭代图像重建算法的理论研究与实现.浙江大学博士学位论文.2004.5.
[14]杨晖,曲秀杰.图像分割方法综述.电脑开发与应用,2005,18(3):21-23.
[15]孟庆生.信息论[M].西安:西安交通大学出版社.1989:19-27.
[16]Xin Wang,Chen Guan Tui X-Ray Image Segmentation Based on Genetic Algorithm and Maximum Fuzzy Entropy.Proceedings of the 2004 IEEE.2004:991-995.
[17]Levine M D,Nazif A M.Dynamic measurement of computer generated image segmentation.IEEE-PAMI,1985,7:155-164.
[18]Lim,Jae S.Two-Dimensional Signal and Image Processing.Englewood Cliffs.NJ,Prentice Hall,1990:548.
[19]罗西平,田捷.用最大熵原则做多阈值选择的条件迭代算法.软件学报,2000,11(3):379-385.
[20]Mangin J F,Frouin V,Bloch I,Regis J,Lopez-Krahe J,From 3D Magnetic Resonance Images to Structural Representations of the Cortex Tomography Using Topology Preserving Deformations.Journal of Mathematical Imaging andVision,1995,5(3):297-318.
[21]Dzang L Pham,Jerry L Prince.An adaptive fuzzy C-means algorithm for image segmentation in the presence of intensity inhomogeneity[J].Pattern Recognition Letters,1999,(20):57-68.
[22]M.L.Bahner,J.M.Bose,H.Wallschlaeger,et al."Spiral CT of the heart with Retrospective ECG-Gating".Vol.67,No.2,pp.37-40,1999.
[23]A.F.Kopp,C.D.Claussen,M.Heuschmid,et al."New developments in cardiac imaging:the role of MDCT".Journal of clinical and basic cardiology.Vol.4,No.4,pp.253-256,2001.
[24]F.Noo,R.Clackdoyle,H.Kudo,"Image reconstruction from fan beam projection on less than a short scan".Physics in Medicine and Biology.Vol.47,No.7,pp.2525-2530.2002.
[25]T.Nielsen,R.Manzke,R.Proksa,et al."Cardiac cone-beam CT volume reconstruction using APT".Medical Physics;Vol.32,No.4,pp.851-852,2005.
[26]Liu Jie,Wang Chenglin,Liu Ying,Er Wei,Ge Wang,Selectable Source Rotational Velocity for Cardiac Computed Tomography".Journal of Computer Assisted Tomography.31(1):16-21,2007(SCI).
[27]Martin J,Image-guided motion adaption in radiotherapy.IEEE International Symposium on Biomedical Imaging.1-4244-0772-2,2008.
[28]S.Wicky,M.Rosol."Comparative study with a moving heart phantom of the impact of temporal resolution on image quality with two multi-detectors electro-cardiography-gated computed tomography units".Computer assist tomography.Vol.27,No.3,pp.392-393,2003.
[29]K.Taguchi,H.Anno."High temporal resolution for multi slice helical computed tomography".Medical Physics.Vol.27,No.5,pp.861-872,2000.
[30]Robert M.Cardiac cone-beam CT[J].Medical Physics.2005,32(10):3227-3229.
[31]Nielsen T,Manzke R,Proksa R.Cardiac cone-beam CT volume reconstruction using ART[J].Medical Physics.2005,32(4):851-854.
[32]Manzke R,Grass M,Nielson T.Adaptive temporal resolution optimization in helical cardiac cone beam CT reconstruction[J].Medical Physics,2003,30(12):3072-3080.
[33]孙丰荣,刘泽,李艳玲等.基于模型的CT三维医学图像重建仿真[J].系统仿真学报,2006.18(3):781-783.
[34]Wang G,Zhao S Y,Heuscher D.A knowledge-based cone-beam x-ray CT algorithm for dynamic volumetric cardiac imaging[J].Medical Physics,2002,29(8):807-810.Medical Physics.
[35]Hui H,Tinsu P,Yun S.Multi-slice helical CT:image temporal resolution.IEEE Transaction on Medical Imaging[J].2000,19(5):384-486.
[36]K.Taguchi,H.Anno."High temporal resolution for multi slice helical computed tomography".Medical Physics.Vol.27,No.5,pp.861-872,2000.
[37]高尚凯.医学成像系统[M].北京:清华大学出版社,2000.
[38]Liu Jie.Adaptive method of velocity control for cardiac CT.Chinese Journal of Electronincs.17(1):20-32,JAN,2008(SCI).
[39]李炳虎,宋元胜.基于变步长自适应滤波器在激光多普勒测量中的去噪研究[J].光学与光电技术,2006,14(1):62-64.
[40]G.Wang,S.Y.Zhao,D.Heuscher." A knowledge-based cone-beam x-ray CT algorithm for dynamic volumetric cardiac imaging".Medical Physics.Vol.29,No.8,pp.1807-1810,2002.
[41]M.Kachelrieβ,S.Ulzheimer,W.A.Kalender."ECG-Correlated imaging of the heart with subsecond multi-slice spiral CT".IEEE Transaction on medical imaging.Vol.19,No.9,pp.888-891,2000.
[42]M.Grass,R Manzke,T.Nielsen.et al."Helical cardiac cone beam reconstruction using retrospective ECG gating".Physics in Medicine and Biology.Vol.48,No.18,pp.3069-3071,2003.
[43]XydaesC,PetroviV.Objective image fusion Performance meabsure..Electronic Letter.Vol.36,Feb.2000,PP:308- 309.
[44]崔岩梅,倪国强.利用统计特性进行图像融合效果分析及评价.北京理工大学学报.Vol.20,No.1,Feb.Z000.
[45]夏明革.多传感器图像融合效果评价方法研究.电光与控制.vol.10,No.2,2003.
[46]李树涛.多传感器图像融合的客观评价与分析.仪器仪表学报.vol.23,No.6,Dee.2002.
[2]Ge Wang,An outlook on X-ray CT research and development.Medical physics.35(3):1051-1064,2008.
[3]夏顺仁,汪元美,吕维雪.心血管双投影下多目标优化截面重建方法.中国生物医学.工程学报,15(4)289-294,1996.
[4]孙伟,庄天戈.有限角投影重建图像的两种算法的比较.CT理论与应用研究.4:30-34,1991.
[5]吕维雪.医学图像技术的研究前沿.中国科学技术大学出版社,1-9,1993.
[6]Prince JL,Willsky AS.Convex set reconstruction using prior shape information.VGIP.53(5):413-427,1991.
[7]顾本立,陆季.极少投影的CT成像研究.CT的理论与应用研究.1994;3(2):14-17.
[8]康克军,毛希平,刘亚强.在二维和三维CT图像重建理论方法的研究工作及新进展.CT的理论与应用研究.6(2):48-51,1997.
[9]庄天戈.CT原理与算法[M],上海:上海交通大学出版社,1992.
[10]Feldkamp LA,et al Practical cone-beam Algorithm.J.Opt Soc Am A,1984,1-126.
[11]G.T.Herman,Imaging Reconstruction from Projections,Springer,1979.
[12]A.H.Andersen and A.C.Kak.Simultaneous algebraic reconstruction technique(SART):a superior implementation of the ART algorithm.Ultrasonic Imaging.6:81-94,1984.
[13]高欣,新型迭代图像重建算法的理论研究与实现.浙江大学博士学位论文.2004.5.
[14]杨晖,曲秀杰.图像分割方法综述.电脑开发与应用,2005,18(3):21-23.
[15]孟庆生.信息论[M].西安:西安交通大学出版社.1989:19-27.
[16]Xin Wang,Chen Guan Tui X-Ray Image Segmentation Based on Genetic Algorithm and Maximum Fuzzy Entropy.Proceedings of the 2004 IEEE.2004:991-995.
[17]Levine M D,Nazif A M.Dynamic measurement of computer generated image segmentation.IEEE-PAMI,1985,7:155-164.
[18]Lim,Jae S.Two-Dimensional Signal and Image Processing.Englewood Cliffs.NJ,Prentice Hall,1990:548.
[19]罗西平,田捷.用最大熵原则做多阈值选择的条件迭代算法.软件学报,2000,11(3):379-385.
[20]Mangin J F,Frouin V,Bloch I,Regis J,Lopez-Krahe J,From 3D Magnetic Resonance Images to Structural Representations of the Cortex Tomography Using Topology Preserving Deformations.Journal of Mathematical Imaging andVision,1995,5(3):297-318.
[21]Dzang L Pham,Jerry L Prince.An adaptive fuzzy C-means algorithm for image segmentation in the presence of intensity inhomogeneity[J].Pattern Recognition Letters,1999,(20):57-68.
[22]M.L.Bahner,J.M.Bose,H.Wallschlaeger,et al."Spiral CT of the heart with Retrospective ECG-Gating".Vol.67,No.2,pp.37-40,1999.
[23]A.F.Kopp,C.D.Claussen,M.Heuschmid,et al."New developments in cardiac imaging:the role of MDCT".Journal of clinical and basic cardiology.Vol.4,No.4,pp.253-256,2001.
[24]F.Noo,R.Clackdoyle,H.Kudo,"Image reconstruction from fan beam projection on less than a short scan".Physics in Medicine and Biology.Vol.47,No.7,pp.2525-2530.2002.
[25]T.Nielsen,R.Manzke,R.Proksa,et al."Cardiac cone-beam CT volume reconstruction using APT".Medical Physics;Vol.32,No.4,pp.851-852,2005.
[26]Liu Jie,Wang Chenglin,Liu Ying,Er Wei,Ge Wang,Selectable Source Rotational Velocity for Cardiac Computed Tomography".Journal of Computer Assisted Tomography.31(1):16-21,2007(SCI).
[27]Martin J,Image-guided motion adaption in radiotherapy.IEEE International Symposium on Biomedical Imaging.1-4244-0772-2,2008.
[28]S.Wicky,M.Rosol."Comparative study with a moving heart phantom of the impact of temporal resolution on image quality with two multi-detectors electro-cardiography-gated computed tomography units".Computer assist tomography.Vol.27,No.3,pp.392-393,2003.
[29]K.Taguchi,H.Anno."High temporal resolution for multi slice helical computed tomography".Medical Physics.Vol.27,No.5,pp.861-872,2000.
[30]Robert M.Cardiac cone-beam CT[J].Medical Physics.2005,32(10):3227-3229.
[31]Nielsen T,Manzke R,Proksa R.Cardiac cone-beam CT volume reconstruction using ART[J].Medical Physics.2005,32(4):851-854.
[32]Manzke R,Grass M,Nielson T.Adaptive temporal resolution optimization in helical cardiac cone beam CT reconstruction[J].Medical Physics,2003,30(12):3072-3080.
[33]孙丰荣,刘泽,李艳玲等.基于模型的CT三维医学图像重建仿真[J].系统仿真学报,2006.18(3):781-783.
[34]Wang G,Zhao S Y,Heuscher D.A knowledge-based cone-beam x-ray CT algorithm for dynamic volumetric cardiac imaging[J].Medical Physics,2002,29(8):807-810.Medical Physics.
[35]Hui H,Tinsu P,Yun S.Multi-slice helical CT:image temporal resolution.IEEE Transaction on Medical Imaging[J].2000,19(5):384-486.
[36]K.Taguchi,H.Anno."High temporal resolution for multi slice helical computed tomography".Medical Physics.Vol.27,No.5,pp.861-872,2000.
[37]高尚凯.医学成像系统[M].北京:清华大学出版社,2000.
[38]Liu Jie.Adaptive method of velocity control for cardiac CT.Chinese Journal of Electronincs.17(1):20-32,JAN,2008(SCI).
[39]李炳虎,宋元胜.基于变步长自适应滤波器在激光多普勒测量中的去噪研究[J].光学与光电技术,2006,14(1):62-64.
[40]G.Wang,S.Y.Zhao,D.Heuscher." A knowledge-based cone-beam x-ray CT algorithm for dynamic volumetric cardiac imaging".Medical Physics.Vol.29,No.8,pp.1807-1810,2002.
[41]M.Kachelrieβ,S.Ulzheimer,W.A.Kalender."ECG-Correlated imaging of the heart with subsecond multi-slice spiral CT".IEEE Transaction on medical imaging.Vol.19,No.9,pp.888-891,2000.
[42]M.Grass,R Manzke,T.Nielsen.et al."Helical cardiac cone beam reconstruction using retrospective ECG gating".Physics in Medicine and Biology.Vol.48,No.18,pp.3069-3071,2003.
[43]XydaesC,PetroviV.Objective image fusion Performance meabsure..Electronic Letter.Vol.36,Feb.2000,PP:308- 309.
[44]崔岩梅,倪国强.利用统计特性进行图像融合效果分析及评价.北京理工大学学报.Vol.20,No.1,Feb.Z000.
[45]夏明革.多传感器图像融合效果评价方法研究.电光与控制.vol.10,No.2,2003.
[46]李树涛.多传感器图像融合的客观评价与分析.仪器仪表学报.vol.23,No.6,Dee.2002.