医学超声穿刺导航的实时定位及软组织建模研究
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摘要
超声穿刺导航可以实时显示穿刺针在组织内的运动情况,为穿刺路径选择提供依据,是超声辅助治疗的重要手段,具有广阔的发展空间。然而,现有超声穿刺导航系统存在着操作复杂、定位不精确、穿刺角度固定麻烦等问题,所以穿刺手术对医生手法的依赖程度高,而且经常需要进行多次穿刺。针对上述情况,本文提出基于电磁定位方式的超声自由穿刺导航方法；并针对影响穿刺精度的关键因素——软组织变形,采用有限元方法进行详细的分析；最后基于便携式超声成像系统,提出自由穿刺导航的软硬件设计方案。具体研究内容如下：
1)超声穿刺导航算法研究。本文根据超声穿刺导航系统的临床应用,分析现有系统的不足和各种定位方式的优缺点,得出电磁定位系统具有定位准确、体积小、重量轻、受环境因素影响小等特性,适合用于超声穿刺系统实时定位的结论。故本文将电磁定位应用于现有的超声成像系统中,进而设计了基于电磁定位方式的实时导航算法——建立坐标变换的数学模型,研究将磁场坐标与声场坐标进行精确配准的手段,以便实时标示穿刺针相对于超声图像的位置,从而为提高穿刺准确性,缩短穿刺时间提供有效方法。
2)穿刺过程软组织形变的有限元仿真。软组织形变是影响穿刺精度最主要的因素,研究软组织变形对提高穿刺的准确性具有重要的临床意义。本文基于有限元方法,将软组织离散化为有限个单元,并对各个离散单元进行弹性力学分析,建立软组织的线性弹性模型。根据该理论模型,采用ANSYS有限元分析软件进行软组织变形仿真,根据软组织的材料属性、单元参数、应用边界条件和初值条件对网格化的模型施加载荷,仿真得出穿刺过程中软组织的形变数据。该形变模型可为穿刺导航系统实现穿刺前的路径规划和避障预警提供一种有效的手段。
3)软硬件方案设计。针对现有数字化便携式超声成像系统,本文设计了超声穿刺导航系统软硬件方案。硬件设计采用ARM+FPGA双核处理器外加电磁定位器的方案,系统中ARM除负责系统的实时控制,如按键响应、字符界面的显示、应用软件的选择、FPGA的信号控制等任务外,还进行定位系统位置信号的采集工作；而FPGA主要负责超声图像信息的采集和处理、探头控制、图像存储、定位信息的合成显示。系统软件体系结构的设计采用消息驱动的方式,以保证代码的运行效率。
The ultrasound guided puncture, in which the trajectory and the motion of biopsy needles is visualized in the ultrasound image in real-time, can provide the basis for the puncture path selection. Thus, it is a very important tool in the ultrasound-assisted treatment of diagnosis or therapy, and has a bright prospect. However, there are some shortcomings in the existing ultrasound guided puncture procedures, including the complexity of operation, difficulties in positing the needle precisely, and the inflexible of the puncture angle, etc., as a result, the success of ultrasound guided puncture are still largely depends on the physicians'experiences, punctures failure often happens and it often takes a long time to train new doctors. In response to these issues, a free path ultrasound puncture navigation methods based on electromagnetic positioning is proposed. The soft tissue deformation, which is the key factor of the puncture accuracy, is analyzed using the finite element method (FEM). And the free path puncture navigation method is implemented to a portable ultrasound imaging system. This thesis mainly focuses on:
1) Development of the ultrasound puncture navigation algorithm. According to the clinical applications of the ultrasound puncture navigation system, various positioning methods were compared. The electromagnetic positioning method was selected since its features of accuracy in positioning, compact in size, and light in weight. Base on the lab made portable medical ultrasound imaging device, a real-time navigation algorithm was developed, which composed of a mathematical model for different coordinates'transformation and a method for calibrating different coordinates, providing the puncture with information about the position and orientation of needle relative to the ultrasound image plane to improve puncture accurate and reduce the time of puncture.
2) Building the soft tissue deformation model using the finite element method (FEM). De-formation of the soft tissue is the most important factor of puncture accuracy, thus, it is very important to study the deformation of soft tissue during puncture. The soft tissue was discretized into a mesh of units using FEM. Then, the linear elastic model of each discrete unit was built based on the analysis of stress and strain in each unit. According to the theoretical model, ANSYS was used to simulate the soft tissue deformation by choosing a tissue geometry represented by a mesh of elements and nodes, selecting a function to describe the relationship between external forces applied to the nodes. It is found that the deformation model can provide reliable warning for puncture navigation systems.
3) Integral design of the free path ultrasound guided puncture system. Based on the lab made digital portable ultrasound imaging device, ARM-FPGA dual-core processors and electromagnetic positioning system are used as the hardware of the system. ARM is mainly responsible for the real-time control, such as key touch responding, application software selecting, and FPGA control, while the FPGA is mainly responsible for the information collection and the processing of ultra-sound images, probe control, image storage. The message-driven method is implemented in the design of the software architecture, which can ensure the operating efficiency of the code.
1)超声穿刺导航算法研究。本文根据超声穿刺导航系统的临床应用,分析现有系统的不足和各种定位方式的优缺点,得出电磁定位系统具有定位准确、体积小、重量轻、受环境因素影响小等特性,适合用于超声穿刺系统实时定位的结论。故本文将电磁定位应用于现有的超声成像系统中,进而设计了基于电磁定位方式的实时导航算法——建立坐标变换的数学模型,研究将磁场坐标与声场坐标进行精确配准的手段,以便实时标示穿刺针相对于超声图像的位置,从而为提高穿刺准确性,缩短穿刺时间提供有效方法。
2)穿刺过程软组织形变的有限元仿真。软组织形变是影响穿刺精度最主要的因素,研究软组织变形对提高穿刺的准确性具有重要的临床意义。本文基于有限元方法,将软组织离散化为有限个单元,并对各个离散单元进行弹性力学分析,建立软组织的线性弹性模型。根据该理论模型,采用ANSYS有限元分析软件进行软组织变形仿真,根据软组织的材料属性、单元参数、应用边界条件和初值条件对网格化的模型施加载荷,仿真得出穿刺过程中软组织的形变数据。该形变模型可为穿刺导航系统实现穿刺前的路径规划和避障预警提供一种有效的手段。
3)软硬件方案设计。针对现有数字化便携式超声成像系统,本文设计了超声穿刺导航系统软硬件方案。硬件设计采用ARM+FPGA双核处理器外加电磁定位器的方案,系统中ARM除负责系统的实时控制,如按键响应、字符界面的显示、应用软件的选择、FPGA的信号控制等任务外,还进行定位系统位置信号的采集工作；而FPGA主要负责超声图像信息的采集和处理、探头控制、图像存储、定位信息的合成显示。系统软件体系结构的设计采用消息驱动的方式,以保证代码的运行效率。
The ultrasound guided puncture, in which the trajectory and the motion of biopsy needles is visualized in the ultrasound image in real-time, can provide the basis for the puncture path selection. Thus, it is a very important tool in the ultrasound-assisted treatment of diagnosis or therapy, and has a bright prospect. However, there are some shortcomings in the existing ultrasound guided puncture procedures, including the complexity of operation, difficulties in positing the needle precisely, and the inflexible of the puncture angle, etc., as a result, the success of ultrasound guided puncture are still largely depends on the physicians'experiences, punctures failure often happens and it often takes a long time to train new doctors. In response to these issues, a free path ultrasound puncture navigation methods based on electromagnetic positioning is proposed. The soft tissue deformation, which is the key factor of the puncture accuracy, is analyzed using the finite element method (FEM). And the free path puncture navigation method is implemented to a portable ultrasound imaging system. This thesis mainly focuses on:
1) Development of the ultrasound puncture navigation algorithm. According to the clinical applications of the ultrasound puncture navigation system, various positioning methods were compared. The electromagnetic positioning method was selected since its features of accuracy in positioning, compact in size, and light in weight. Base on the lab made portable medical ultrasound imaging device, a real-time navigation algorithm was developed, which composed of a mathematical model for different coordinates'transformation and a method for calibrating different coordinates, providing the puncture with information about the position and orientation of needle relative to the ultrasound image plane to improve puncture accurate and reduce the time of puncture.
2) Building the soft tissue deformation model using the finite element method (FEM). De-formation of the soft tissue is the most important factor of puncture accuracy, thus, it is very important to study the deformation of soft tissue during puncture. The soft tissue was discretized into a mesh of units using FEM. Then, the linear elastic model of each discrete unit was built based on the analysis of stress and strain in each unit. According to the theoretical model, ANSYS was used to simulate the soft tissue deformation by choosing a tissue geometry represented by a mesh of elements and nodes, selecting a function to describe the relationship between external forces applied to the nodes. It is found that the deformation model can provide reliable warning for puncture navigation systems.
3) Integral design of the free path ultrasound guided puncture system. Based on the lab made digital portable ultrasound imaging device, ARM-FPGA dual-core processors and electromagnetic positioning system are used as the hardware of the system. ARM is mainly responsible for the real-time control, such as key touch responding, application software selecting, and FPGA control, while the FPGA is mainly responsible for the information collection and the processing of ultra-sound images, probe control, image storage. The message-driven method is implemented in the design of the software architecture, which can ensure the operating efficiency of the code.
引文
[1]钱林学,刘婧.介入性超声的研究现状及进展[J].中华临床医师杂志,2010,12(4).
[2]Berlyne GM. Ultrasonics in renal biopsy:An aid to determination of kidney position[J]. The Lancet,1961,(02).
[3]Ellis G, Goldberg D.M. Optimal conditions for the kinetic assay of serum glutamate dehydrogenase activity at 37℃. Clinical Chemistry,18,523-527.
[4]H.H. Holm, J. Kvist Kristensen, S. Norby Rasmussen, et al. Ultrasound as a guide in percutaneous puncture technique[J]. Ultrasonics.1972.
[5]Pedersen, J. F. Percutaneous puncture guided by ultrasonic multitransducer scanning [J]. Journal of Clinical Ultrasound,1977,5:175-177.
[6]Masahito Saitoh M.D., Hiroki Watanabe M.D., Hiroshi Ohe M.D., et al. Ultrasonic real-time guidance for percutaneous puncture[J]. Clinical Ultrasound.1979,7(4):269-272.
[7]Robert J. Isler, Joseph T. Ferrucci, Jr. et al. Tissue Core Biopsy of Abdominal Tumors with a 22 Gauge Cutting Needle[A]. American Roentgen Ray Society[C]. Las Vegas:Nev,1980, 725-728.
[8]Albrecht H, Stroszynski C, Felix R, et al. Real time 3D(4D) ultrasound guided percutaneous biopsy of solid tumours[J]. Ultras Chall in Med,2006,27(4):324-328.
[9]Chang CY, Wang HK, Chiou HJ, et al. Interventional procedures in superficial 1-esions:the value of 2D with additional coronal reformatted 4D ultrasonography guidance[J]. Korean Journal of Radiology,2006,7(1):28-34.
[10]郑若龙,高春恒.实时三维超声心动图指导心包穿刺抽液的临床应用[J].江苏医药,2009,35(7).
[11]飞利浦医疗保健事业部G4 Xmatrix iU22助力超声介入治疗学更快发展[J].中国介入影像与治疗学,2011,8(1).
[12]马志梅,梁笑坤,王桂香.经三维超声引导穿刺固化治疗卵巢单纯囊肿临床研究[J].Proceeding of Clinical Medicine,2010,19(10).
[13]陈占斌,刘金虎.三维超声引导下经皮肝胆管穿刺置管引流术的临床应用[J].西部医学.2010,22(5).
[14]刘吉斌.现代介入性超声诊断与治疗.北京：科学技术文献出版社,2004,19-20.
[15]Ursino M, Tasto JL, Nguyen BH, Cunningham R, Merril GL. Cathsim:an intravascular catheterization simulator on a PC[J]. Studies in Health Technology and Informat-ics,1999, 62:360-366.
[16]周玉清,张青萍.静态结构三维超声成像方法学进展[EB/OL].影像诊断与治疗,2010,http://www.cldal 20.com/NetTelecom/Content.jsp?id=5978.
[17]Mor A B, et al. Accuracy testing of electromagnetic tracking systems[J]. Journal of biomechanics,2006.
[18]Mor A B, et al. Accuracy testing of electromagnetic tracking systems[J]. Journal of biomechanics,2006.
[19]Birkfellner W, Watzinger F, Wanschitz F, et al. Systematic distortions in magnetic position digitizers[J]. Med Phys,1998,25:2242-2248.
[20]Schneider M, Stevens C. Development and Testing of a New Magnetic-Tracking Device for Image Guidance[C]. SPIE,2007.
[21]Hastenteufel M, et al. Effect of 3D Ultrasound Probes on the Accuracy Of Electromagnetic Tracking Systems[J]. Ultrasound in Medicine and Biology,2006,32(9):1359-1368.
[22]Schicho K.et al. Stability of Miniature Electromagnetic Tracking Systems[J]. Phys. Med. Biol,2005.50:2089-2098.
[23]Hummel J. Design and Application of an Assessment Protocol for Electromagnetic Tracking Systems[J]. Med Phys,2005.32(7):2371-9.
[24]陈新,林东,张庆辉等.磁场方式的内窥镜体内三维定位与追踪方法研究[J].中国生物医学工程学报,2002,21(5).
[25]黄立巍.医用电磁导航实验系统的研究[D].哈尔滨：哈尔滨工业大学电气工程系.2008.
[26]R.L. Pio. Euler angle transformation J]. IEEE Transactions on Automation and Control, 1966,11:707-715.
[27]Mei-Chan Chen, Ultrasound calibration[J]. Campar.in.tum.de,2005.
[28]R.W.Prager, et al. Rapid Calibration for 3-D freehand[J]. Ultrasound in Medicine&Biology, 1998,24(6).
[29]S.S. BHAVIKATTI. Finite Element Analysis[M]. New Delhi:New Age International(P) Ltd, 2005：1-9.
[30]张彤.有限元法在颅面复合体生物力学研究中的应用[J].口腔颌面修复学杂志,2000,1(2).
[31]罗建文,白净.超声弹性成像仿真的有限元分析[J].北京生物医学工,2003,22(2).
[32]Yan Chen, Qing-hong Zhu. Physically-based Animation of Volumetric Objects[J]. IEEE, 2000.
[33]Luciana Porcher Nedel, Dainel Thalmann. Real Time Muscle Deformations Using Mass-Spring Systems[J]. IEEE Conference 2000.
[34]Pras Pathmanathan et al. Predicting Tumour Location by Simulating Large Deformations of the Breast Using a 3D Finite Element Model and Nonlinear Elasticity[J]. MICCAI,2004.
[35]H. Zhong, MARK P. WACHOWIAK, TERRY M. PETERS. A real time finite element based tissue simulation method incorporating nonlinear elastic behavior [J]. Computer Methods in Biomechanics and Biomedical Engineering,2005,8(3):177-189.
[36]Wen Wu, Pheng Ann Heng. An Improved Scheme of an Interactive Finite Element Model for 3D Soft-Tissue Cutting and Deformation[J]. Visual Compute,2005.
[37]P. L. Gould. Introduction to Linear Elasticity [J]. Springer-Verlag.1994.
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[40]M. Bro-Nielsen. Finite Element Modeling in Surgery Simulation [J]. IEEE, 1998,86:490-503.
[41]M. Bro-Nielsen, Medical Image Registration and Surgery Simulation[D]. Technical University of Denmark,1997.
[42]C. Cuvelier, A. Segal, and A. van Steenhoven. Finite Element Methods and NavierStokes Equations[J]. D. Reidel Publishing Company,1986.
[43]陈琼.三维有限元建模方法的研究现状[J].口腔医学.2006.26(2).
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[48]章瑶瑛.全数字B型超声诊断仪的测量与报告模块设计[D].杭州：浙江大学生物医学工程与仪器科学学院,2006.
[49]樊燕红.全数字B型超声诊断仪系统结构的研究[D].杭州：浙江大学生物医学工程与仪器科学学院,2006.
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[2]Berlyne GM. Ultrasonics in renal biopsy:An aid to determination of kidney position[J]. The Lancet,1961,(02).
[3]Ellis G, Goldberg D.M. Optimal conditions for the kinetic assay of serum glutamate dehydrogenase activity at 37℃. Clinical Chemistry,18,523-527.
[4]H.H. Holm, J. Kvist Kristensen, S. Norby Rasmussen, et al. Ultrasound as a guide in percutaneous puncture technique[J]. Ultrasonics.1972.
[5]Pedersen, J. F. Percutaneous puncture guided by ultrasonic multitransducer scanning [J]. Journal of Clinical Ultrasound,1977,5:175-177.
[6]Masahito Saitoh M.D., Hiroki Watanabe M.D., Hiroshi Ohe M.D., et al. Ultrasonic real-time guidance for percutaneous puncture[J]. Clinical Ultrasound.1979,7(4):269-272.
[7]Robert J. Isler, Joseph T. Ferrucci, Jr. et al. Tissue Core Biopsy of Abdominal Tumors with a 22 Gauge Cutting Needle[A]. American Roentgen Ray Society[C]. Las Vegas:Nev,1980, 725-728.
[8]Albrecht H, Stroszynski C, Felix R, et al. Real time 3D(4D) ultrasound guided percutaneous biopsy of solid tumours[J]. Ultras Chall in Med,2006,27(4):324-328.
[9]Chang CY, Wang HK, Chiou HJ, et al. Interventional procedures in superficial 1-esions:the value of 2D with additional coronal reformatted 4D ultrasonography guidance[J]. Korean Journal of Radiology,2006,7(1):28-34.
[10]郑若龙,高春恒.实时三维超声心动图指导心包穿刺抽液的临床应用[J].江苏医药,2009,35(7).
[11]飞利浦医疗保健事业部G4 Xmatrix iU22助力超声介入治疗学更快发展[J].中国介入影像与治疗学,2011,8(1).
[12]马志梅,梁笑坤,王桂香.经三维超声引导穿刺固化治疗卵巢单纯囊肿临床研究[J].Proceeding of Clinical Medicine,2010,19(10).
[13]陈占斌,刘金虎.三维超声引导下经皮肝胆管穿刺置管引流术的临床应用[J].西部医学.2010,22(5).
[14]刘吉斌.现代介入性超声诊断与治疗.北京：科学技术文献出版社,2004,19-20.
[15]Ursino M, Tasto JL, Nguyen BH, Cunningham R, Merril GL. Cathsim:an intravascular catheterization simulator on a PC[J]. Studies in Health Technology and Informat-ics,1999, 62:360-366.
[16]周玉清,张青萍.静态结构三维超声成像方法学进展[EB/OL].影像诊断与治疗,2010,http://www.cldal 20.com/NetTelecom/Content.jsp?id=5978.
[17]Mor A B, et al. Accuracy testing of electromagnetic tracking systems[J]. Journal of biomechanics,2006.
[18]Mor A B, et al. Accuracy testing of electromagnetic tracking systems[J]. Journal of biomechanics,2006.
[19]Birkfellner W, Watzinger F, Wanschitz F, et al. Systematic distortions in magnetic position digitizers[J]. Med Phys,1998,25:2242-2248.
[20]Schneider M, Stevens C. Development and Testing of a New Magnetic-Tracking Device for Image Guidance[C]. SPIE,2007.
[21]Hastenteufel M, et al. Effect of 3D Ultrasound Probes on the Accuracy Of Electromagnetic Tracking Systems[J]. Ultrasound in Medicine and Biology,2006,32(9):1359-1368.
[22]Schicho K.et al. Stability of Miniature Electromagnetic Tracking Systems[J]. Phys. Med. Biol,2005.50:2089-2098.
[23]Hummel J. Design and Application of an Assessment Protocol for Electromagnetic Tracking Systems[J]. Med Phys,2005.32(7):2371-9.
[24]陈新,林东,张庆辉等.磁场方式的内窥镜体内三维定位与追踪方法研究[J].中国生物医学工程学报,2002,21(5).
[25]黄立巍.医用电磁导航实验系统的研究[D].哈尔滨：哈尔滨工业大学电气工程系.2008.
[26]R.L. Pio. Euler angle transformation J]. IEEE Transactions on Automation and Control, 1966,11:707-715.
[27]Mei-Chan Chen, Ultrasound calibration[J]. Campar.in.tum.de,2005.
[28]R.W.Prager, et al. Rapid Calibration for 3-D freehand[J]. Ultrasound in Medicine&Biology, 1998,24(6).
[29]S.S. BHAVIKATTI. Finite Element Analysis[M]. New Delhi:New Age International(P) Ltd, 2005：1-9.
[30]张彤.有限元法在颅面复合体生物力学研究中的应用[J].口腔颌面修复学杂志,2000,1(2).
[31]罗建文,白净.超声弹性成像仿真的有限元分析[J].北京生物医学工,2003,22(2).
[32]Yan Chen, Qing-hong Zhu. Physically-based Animation of Volumetric Objects[J]. IEEE, 2000.
[33]Luciana Porcher Nedel, Dainel Thalmann. Real Time Muscle Deformations Using Mass-Spring Systems[J]. IEEE Conference 2000.
[34]Pras Pathmanathan et al. Predicting Tumour Location by Simulating Large Deformations of the Breast Using a 3D Finite Element Model and Nonlinear Elasticity[J]. MICCAI,2004.
[35]H. Zhong, MARK P. WACHOWIAK, TERRY M. PETERS. A real time finite element based tissue simulation method incorporating nonlinear elastic behavior [J]. Computer Methods in Biomechanics and Biomedical Engineering,2005,8(3):177-189.
[36]Wen Wu, Pheng Ann Heng. An Improved Scheme of an Interactive Finite Element Model for 3D Soft-Tissue Cutting and Deformation[J]. Visual Compute,2005.
[37]P. L. Gould. Introduction to Linear Elasticity [J]. Springer-Verlag.1994.
[38]Y. C. Fung, A First Course in Continuum Mechanics[J]. Prentice Hall,1977.
[39]Y. Zhuang. Real-time Simulation of Physically Realistic Global Deformations [D]. Berkeley:University of California,2000.
[40]M. Bro-Nielsen. Finite Element Modeling in Surgery Simulation [J]. IEEE, 1998,86:490-503.
[41]M. Bro-Nielsen, Medical Image Registration and Surgery Simulation[D]. Technical University of Denmark,1997.
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