经颅磁刺激电磁场分析及线圈设计的研究
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摘要
经颅磁刺激技术通过将磁场施加于人脑来影响大脑的机能,从而达到诊断或治疗的目的。随着经颅磁刺激技术在各个领域内的广泛应用,研究经颅磁刺激中电磁场便显得尤为必要。针对经颅磁刺激特点,本文主要在经颅磁刺激电磁场环境仿真,线圈不同绕法和参数分析,线圈组电磁场研究三个方面进行了深入研究。
首先是模拟电磁场环境。这涉及到3个主要部分的建模问题:人的头部,线圈,电路。利用真人头部核磁共振图像作为原始数据,按照灰度阈值将不同人体组织轮廓提取出来构成真实头模型,再经过后期平滑处理和有限元网格剖分将其转化为头部有限元模型。提出一种螺旋线式建模方法对各种不同绕法线圈进行有限元建模。磁刺激仪电路也被转化为有限元模型,与由头部有限元模型和线圈有限元模型组成的电磁场一起进行电路电磁场耦合分析。
其次通过详细分析蚊香型,螺旋线型,混合式线圈,八字形线圈的电磁场表现,总结出它们的相同点和不同点,并得出混合式线圈性能最优且能替代八字形线圈的结论。然后对混合式线圈的各个参数在电磁场的作用进行总结,并以此为理论基础设计出经颅磁刺激电磁场分析系统,实现对经颅磁刺激电磁场的自动分析,并根据使用者的需求自动提供可用于实际制作的线圈参数。
最后通过分析线圈组的电磁场,发现线圈组在控制磁刺激范围,提高磁刺激深度方面要优于单线圈系统。119导脑部磁刺激仪的设计便充分利用了线圈组的优势。将119个小线圈按照刺激部位密布于头部周围,通过控制需要的线圈组工作,从而实现不同的功能。
线圈磁场检验试验表明:实际测量值与仿真分析值基本吻合,系统提供的线圈参数可靠,能够满足临床线圈设计的需要。
Transcranial magnetic stimulation(TMS) affects the working brain through the magnetic field, to achieve the goal of diagnosing or curing. With the wider application in the medical areas, it is meaningful to research the electromagnetic field under TMS. Basing on the characteristic, this paper focus on the following areas: simulate the electromagnetic environment; analyze different forms and parameters of the loop, and design the analyzing system; analyze the electromagnetic performance of the loop array
Firstly,simulate the electromagnetic environment under TMS. Thus 3 main parts should be modeled: the head, the coil, the circuit. Use MRI images as the original data, tisses are reconstructed to build up the real head model basing on the gray value. Then the head model is transferred to the finite element model after a series of post -operations. This paper proposed a new way to model the different forms of the loop.
The circuit is also transferred to the finite element model to do the circuit-the electromagnetic field coupling analysis with the models of the head and the coil. Secondly, through analyze the performance of the loops of the wenxiang type, the solenoid type, mixed type, and the 8-figure type, it’s known that the mixed type has the best performance and the 8-figure type can be replaced by the mixed type. Then summarize the action of the coil’s parameters in the electromagnetic field. Basing on the results, design the analyzing system to achieve the goal to analyze the electromagnetic field automatically and get the qualified parameters automatically.
Thirdly, through analyzing the performance of the coil array, we find out that the coil array acts better than the single coil in stimulating depth and controlling stimulating area. 119 channels magnetic stimulating instrument is advised to make use of the advantages of the coil array. The 119 small coils is put aroud the head, through controlling the opening of the different coils, we can achieve different functions.
The test of the coil’s magetic field shows that: the real value is similar to the value from the analyzing results; the coil’s paramenters from the system are reliable and can meet the needs of the clinical design of the coil.
首先是模拟电磁场环境。这涉及到3个主要部分的建模问题:人的头部,线圈,电路。利用真人头部核磁共振图像作为原始数据,按照灰度阈值将不同人体组织轮廓提取出来构成真实头模型,再经过后期平滑处理和有限元网格剖分将其转化为头部有限元模型。提出一种螺旋线式建模方法对各种不同绕法线圈进行有限元建模。磁刺激仪电路也被转化为有限元模型,与由头部有限元模型和线圈有限元模型组成的电磁场一起进行电路电磁场耦合分析。
其次通过详细分析蚊香型,螺旋线型,混合式线圈,八字形线圈的电磁场表现,总结出它们的相同点和不同点,并得出混合式线圈性能最优且能替代八字形线圈的结论。然后对混合式线圈的各个参数在电磁场的作用进行总结,并以此为理论基础设计出经颅磁刺激电磁场分析系统,实现对经颅磁刺激电磁场的自动分析,并根据使用者的需求自动提供可用于实际制作的线圈参数。
最后通过分析线圈组的电磁场,发现线圈组在控制磁刺激范围,提高磁刺激深度方面要优于单线圈系统。119导脑部磁刺激仪的设计便充分利用了线圈组的优势。将119个小线圈按照刺激部位密布于头部周围,通过控制需要的线圈组工作,从而实现不同的功能。
线圈磁场检验试验表明:实际测量值与仿真分析值基本吻合,系统提供的线圈参数可靠,能够满足临床线圈设计的需要。
Transcranial magnetic stimulation(TMS) affects the working brain through the magnetic field, to achieve the goal of diagnosing or curing. With the wider application in the medical areas, it is meaningful to research the electromagnetic field under TMS. Basing on the characteristic, this paper focus on the following areas: simulate the electromagnetic environment; analyze different forms and parameters of the loop, and design the analyzing system; analyze the electromagnetic performance of the loop array
Firstly,simulate the electromagnetic environment under TMS. Thus 3 main parts should be modeled: the head, the coil, the circuit. Use MRI images as the original data, tisses are reconstructed to build up the real head model basing on the gray value. Then the head model is transferred to the finite element model after a series of post -operations. This paper proposed a new way to model the different forms of the loop.
The circuit is also transferred to the finite element model to do the circuit-the electromagnetic field coupling analysis with the models of the head and the coil. Secondly, through analyze the performance of the loops of the wenxiang type, the solenoid type, mixed type, and the 8-figure type, it’s known that the mixed type has the best performance and the 8-figure type can be replaced by the mixed type. Then summarize the action of the coil’s parameters in the electromagnetic field. Basing on the results, design the analyzing system to achieve the goal to analyze the electromagnetic field automatically and get the qualified parameters automatically.
Thirdly, through analyzing the performance of the coil array, we find out that the coil array acts better than the single coil in stimulating depth and controlling stimulating area. 119 channels magnetic stimulating instrument is advised to make use of the advantages of the coil array. The 119 small coils is put aroud the head, through controlling the opening of the different coils, we can achieve different functions.
The test of the coil’s magetic field shows that: the real value is similar to the value from the analyzing results; the coil’s paramenters from the system are reliable and can meet the needs of the clinical design of the coil.
引文
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[9]Maeda F, Keenan JP, Tormos JM,et a1,Interindividual variability of the modulatory effects of repetitive transcranial magnetic stimulation on cortical excitability[J], Exp Brain Res,2000,133:425~430
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[11]Kosslyn SM, Pascual-Leone A, Felician O,The role of area 17 in visual imagery convergent evidence from PET and rTMS[J],Science,1999,284: 167~170
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[13]Mally J, Stone TW, Improvement in Parkinsonian symptoms after repetitive transcranial magnetic stimulation[J], J Neurol Sci, 1999, 162:179~184
[14]Siebner HR,Mentschel C,Auer C,et a1,Repetitive transcrania1 magnetic stimulation has a beneficial effect on bradykinesla in Parkinson's disease[J], Neuroreport,1999,10:589~594
[15]Lefaucheur JP, Transcranial magnetic stimulation in the management of pain[J], Suppl Clin Neurophysiol,2004,57:737~748
[16]郑旭媛,万柏坤,脑电逆问题的研究进展[J],国外医学生物医学工程分册,2001,24(4):179~183
[17]Ary JP, Localization of sources of EP:corrections for skull and scalp thicknesses [J], IEEE Trans BME,1981,28:447~452
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[19]Cuffin BN,Cohen D,Yunokuchi K,et al,Tests of EEG localization accuracy using implanted sources in the human brain[J]Ann Neuro,1991,29:132~138
[20]Haque HA,Musha T,Nakajima M,Three shelf head model constructed from scalp geometry for EEG dipote localizationl[J],Frontiers Med Biol Eng, 1999, 9 (4):295~304
[21]王云华,杨福生,马信山,脑电逆问题的建模与仿真[J],北京生物医学工程,1992,11(2):65~74
[22]贺士娟,杨雅妹,王霞等,脑电磁逆问题中头模型构造方法的研究[J],河北工业大学学报,2001,30(3):7~10
[23]冯远明,王明时,郭青,脑部磁刺激场的理论模型[J],生物物理学报,1993,9(1):95~99
[24]张迎春,邹凌,脑电正问题的模型与算法[J],生物医学工程学杂志,2004,21(2):337~339
[25]Tim A.Wagner,Markus Zahn,Three-Dimensional Head Model Stimulation Of Transcranial Magnetic Stimulation, IEEE Transactions On Biomedical Engineering, 2004,51(9):1586~1598
[26]郑建斌,霍小林,经颅磁刺激中大鼠真实头模型感应电场分布的研究[J],北京生物医学工程,2006,25(5):490~492
[27]冯远明,王明时,脑部磁刺激磁场和感应电场的初步研究[J],中国生物医学工程学报,1995,14(1):74~79
[28]冯远明,梁晓会,叶志生等,交变磁场在皮层内产生感应电场的理论计算[J],中国生物医学工程学报,1997,16(4):310~315
[29]王明时,冯远明,利用低频脉冲磁场诱导入眠的试验研究[J],中国生物医学工程学报,1997,16(1):13~27
[30]冯远明,王明时等,时变磁场促进睡眠的试验研究[J],中华物理医学杂志,1993,15(2):73~75
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[32]曾余庚,电磁场有限单元法,北京:科学出版社,1982,
[33]谢宏刚,徐亮,王汉,对MIMICS V10.0软件三种三维重建方法的研究[J],西部医学,2008,20(5):1089~1091
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