视觉诱发电位测量系统的研究
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摘要
视觉诱发电位是视网膜受到刺激后在大脑视皮质产生的生物电活动,它能探测视路中从视网膜到视皮质的功能性损伤。视觉诱发电位检查技术具有非损伤性、客观性、定性、定量、可重复性的特点,在眼科疾病的诊断和鉴别中具有重要作用。由于研究视觉诱发电位的需要,针对视觉诱发电位测量系统的研究和开发具有重要的意义。
视觉诱发电位属低频、微弱信号,测量过程中易受到强的背景噪声和干扰的影响,信号的放大成为了视觉诱发电位测量和分析中最为关键的环节。本文从介绍视觉诱发电位的特性出发,分析了用生物电极提取视觉诱发电位的等效电路模型,研究了来自系统内部噪声和外部干扰对视觉诱发电位测量的影响,探讨了高源阻抗微弱信号测量的影响因素,分析了元器件的分散性对电路性能的影响,利用保护、右腿驱动、隔离等技术设计了低噪声、高共模抑制比的视觉诱发电位放大电路系统,用ORCAD/PSpice软件对所设计的电路进行了仿真验证,以微控制器LPC2148作为控制单元设计了数据采集与控制系统,设计了VEP测量电路系统的印刷电路板,最后以图像翻转刺激方式对所设计的电路系统展开了实验,记录出了人体的图像翻转视觉诱发电位。
实验结果表明,VEP测量系统的增益范围:10 000~200 000,带宽:1~300Hz,短路等效输入噪声峰峰值范围:2~4μV ,共模抑制比:106.7dB,经过64次叠加平均,成功测试出了人体的视觉诱发电位。
Visual Evoked Potentials (VEPs) are produced by electrical activity of the visual cortex in response to light or pattern stimulation of the retina. It can detect functional loss in the visual pathway from retina to the visual cortex. VEP examination is a nondestructive, objective, qualitative, quantitative and repeatable measurement; it is the influential role to the visual disease diagnosis and distinction. For study of VEP, it is vital significance to research and develop VEP measurement system.
Vision evoked potentials are low frequency and weak signal, measurement for VEP are subject to strong background noise and interference. Amplification is the most critical step in measuring and analyzing VEP. This paper has presented the principle and characteristic of VEP, analyzed the equivalent circuit model of VEP with picked up by bioelectrode, researched the internal noise and external interference to influence on the outcome of VEP, discussed the influencing factor for high impedance weak signal measurement, analyzed the device's value deviation from normal to influence the circuit performance, designed a low noise and high CMRR amplification circuit with guarding, driven right led circuit, isolation etc, simulated the circuit system using ORCAD/PSpice simulation software, designed the data acquisition and control system with microcontroller LPC2148, and designed the printed circuit board of measurement system. Finally, performed the experiment by pattern reversal stimulation, and recorded the results of pattern reversal VEP.
The experimental results show that the VEP measurement system performance is that gain is 10 000~200 000, bandwidth is 1~300Hz, short-circuits equivalent input noise voltage peak-peak value is 2~4μV, CMRR is 106.7dB. It is undergoes 64 averaging be able to succeed recording VEP.
视觉诱发电位属低频、微弱信号,测量过程中易受到强的背景噪声和干扰的影响,信号的放大成为了视觉诱发电位测量和分析中最为关键的环节。本文从介绍视觉诱发电位的特性出发,分析了用生物电极提取视觉诱发电位的等效电路模型,研究了来自系统内部噪声和外部干扰对视觉诱发电位测量的影响,探讨了高源阻抗微弱信号测量的影响因素,分析了元器件的分散性对电路性能的影响,利用保护、右腿驱动、隔离等技术设计了低噪声、高共模抑制比的视觉诱发电位放大电路系统,用ORCAD/PSpice软件对所设计的电路进行了仿真验证,以微控制器LPC2148作为控制单元设计了数据采集与控制系统,设计了VEP测量电路系统的印刷电路板,最后以图像翻转刺激方式对所设计的电路系统展开了实验,记录出了人体的图像翻转视觉诱发电位。
实验结果表明,VEP测量系统的增益范围:10 000~200 000,带宽:1~300Hz,短路等效输入噪声峰峰值范围:2~4μV ,共模抑制比:106.7dB,经过64次叠加平均,成功测试出了人体的视觉诱发电位。
Visual Evoked Potentials (VEPs) are produced by electrical activity of the visual cortex in response to light or pattern stimulation of the retina. It can detect functional loss in the visual pathway from retina to the visual cortex. VEP examination is a nondestructive, objective, qualitative, quantitative and repeatable measurement; it is the influential role to the visual disease diagnosis and distinction. For study of VEP, it is vital significance to research and develop VEP measurement system.
Vision evoked potentials are low frequency and weak signal, measurement for VEP are subject to strong background noise and interference. Amplification is the most critical step in measuring and analyzing VEP. This paper has presented the principle and characteristic of VEP, analyzed the equivalent circuit model of VEP with picked up by bioelectrode, researched the internal noise and external interference to influence on the outcome of VEP, discussed the influencing factor for high impedance weak signal measurement, analyzed the device's value deviation from normal to influence the circuit performance, designed a low noise and high CMRR amplification circuit with guarding, driven right led circuit, isolation etc, simulated the circuit system using ORCAD/PSpice simulation software, designed the data acquisition and control system with microcontroller LPC2148, and designed the printed circuit board of measurement system. Finally, performed the experiment by pattern reversal stimulation, and recorded the results of pattern reversal VEP.
The experimental results show that the VEP measurement system performance is that gain is 10 000~200 000, bandwidth is 1~300Hz, short-circuits equivalent input noise voltage peak-peak value is 2~4μV, CMRR is 106.7dB. It is undergoes 64 averaging be able to succeed recording VEP.
引文
[1]李海生,潘家普.视觉电生理的原理与实践[M].上海:上海科学普及出版社,2002.
[2]吴德正.临床视觉电生理的进展[J].眼科,2001,10(1):9-12.
[3]周鑫,张玲莉,饶广勋.视觉诱发电位技术与视力客观评估[J].国际眼科杂志,2005,5(1):135-138.
[4]何庆华.基于视觉诱发电位的脑机接口实验研究[D].重庆:重庆大学,2003.
[5] J. Vernon Odom, Michael Bach, Colin Barber. Visual evoked potentials standard [S]. Doc Ophthalmol, 2004, 108: 115–123.
[6] UBA-4204 Universal Biomedical Amplifier [EB/OL].www.LKC.com.
[7] Specifications for biopotential measurement system, type ActiveTwo Mk2 with two-wire active electrodes [EB/OL]. http://www.biosemi.com/activetwo_full_specs.htm.
[8]余学飞.医学电子仪器原理与设计[M].广州:华南理工大学出版社,2007.
[9]黄群峰.脑电信号检测专用集成电路设计研究[D].广州:华侨大学,2007.
[10] Y.Q.Tan, F. Ibrahim, M. Moghavvemi, J. Ibrahim. Development of an EEG amplifier for Brain-Computer-Interface [J].Biomed 06, IFMBE Proceedings 15:378-382, 2007.
[11] Texas Instruments Inc. Medical applications guide [EB/OL]. www.ti.com/medical.
[12] G. B. Mukartihal, S. Radhakrishnan, M. Ramasubba Reddy, S.S.K.Ayyar. Design and development of visual evoked potentials recording system for diagnosis of optic nerve diseases [J].Instrum. Soc. India 36(4): 227-234.
[13]王立丽,李刚等.一种新型视觉诱发电位检测系统[J].电子产品世界,2005(19):94-95.
[14]孙友明,黄秉鍊,罗晓曙.新型脑电信号放大检测电路的设计[J].国外电子元器件,2006(9):58-62.
[15]魏彬,贾存良.脑电信号预处理电路的设计.中国仪器仪表学会医疗仪器分会2006年学术年会暨中国仪器仪表学会医疗仪器分会第三届第三次理事会论文汇编[C],2006.
[16] Anton F P Van Putten,张伦译.电子测量系统——理论与实践[M].北京:中国计量出版社,2000.
[17] C.D. Motchenbacher, F.C.Fitchen著,龙忠琪译.低噪声电子设计[M].北京:国防工业出版社,1977.
[18] Joshua Israelsohn.噪声与低噪声设计的探讨[OL].EDN China,2004.
[19]蔡建新,张唯真.生物医学电子学[M].北京:北京大学出版社,1997.
[20]远坂俊昭,彭军译.测量电子电路设计——模拟篇[M].北京:科学出版社,2006.
[21] Art Kay.运算放大器电路中固有噪声的分析与测量[EB/OL]. http://www.eetchina.com/,2007, 06.
[22] James M.Bryant. Operational Amplifier Noise [EB/OL]. Analog Device Inc. http://www.analog.com/static/imported-files/rarely_asked_questions/moreInfo_raq_opAmpNoise2.html.
[23]杨继深.共模干扰和差模干扰[J].安全与电磁兼容,2002(2):48-50.
[24]吴良斌,高玉良,李延辉.现代电子系统的电磁兼容型设计[M].北京:国防工业出版社,2004.
[25]孙伟国,邱扬,权修桥,田锦.共模与差模传导干扰分析及抑制技术研究[J].电子质量,2004(10):18-20.
[26]温世仁.微弱信号检测系统中的接地与屏蔽技术分析[J].宇航计测技术,2005(2):46-49.
[27] John Yeager, Mary Anne Hrusch Tupta著,催建平,汪铁华译.低电平测量手册[M].北京:美国Keithley仪器公司,2005.
[28] Walt Kester, Scott Wurcer, Chuck Kitchin. Sensor signal conditioning section 5: High impedance sensors [EB/OL]. http://www.analog.com/zh/rfif-components/rms-detectors/products/seminars-webcasts/resources/index.html, 1999.
[29] Glen Brisebois. Signal conditioning for high-impedance sensors [EB/OL]. http://www.edn.com/article/CA6305356.html, 2006.02.16.
[30] Enrique Mario Spinelli, Ramon Palls Areny, Miguel Angel Mayosky. AC-coupled front-end for biopotential measurements[J]. IEEE Trans Biomed Eng, 2003, 50(3):391-395.
[31] Clement Alphonse Berard. Guard circuit for high impedance signal circuits [P]. United States Patent, [19] 4 091 430. 3. 23. 1978.
[32] Ultralow noise BiFET Op Amp AD743 [Z]. REV. D. Analog Devices, Inc., 2002.
[33] John Ardizzoni. A practical guide to high-speed printed circuit board layout [EB/OL]. http://analog.com/library/analogdialogue/archives/39-09/layout.html, 2005.
[34]贾新章等.OrCAD/PSpice 9实用教程[M].西安:西安电子科技大学出本社,2001.
[35]王越,李刚,王立丽.几种新型的高性能生物电放大器[J].电子设计应用,2005,(6):126-128.
[36]姬军,俞梦孙.有效抑制50Hz干扰的生物电放大器[J].北京生物医学工程,2006,25(2):185-188.
[37]王三强,何为,石坚.新型脑电信号前置级放大电路设计[J].重庆大学学报,2006,29(6):51-53.
[38]张思杰,彭承琳,郭兴明等.用于多焦视觉电生理分析系统的生物信号放大器的设计[J].医疗卫生装备,2004,25(4),54.
[39] Charles Kitchin, Lew Counts. A designer’s guide to instrumentation amplifier [Z]. 3rd Edition, Analog Devices, Inc., 2006.
[40] Low cost, low power instrumentation amplifier AD620 [Z]. Rev. E. Analog Devices Inc., 1999.
[41] Precision instrumentation amplifier AD8221 [Z]. Rev. A. Analog Devices Inc., 2003.
[42] Precision, low power instrumentation amplifiers INA128 [Z]. Burr-Brown Inc., 1996.
[43] Thomas Kugelstadt. Getting the most out of your instrumentation amplifier design [J]. Analog Applications Journal. 2005(4):25-29.
[44] Winter BB , Webster JG. Driven right leg circuit design [J]. IEEE Trans Biomed Eng, 1983, 30(1):62–66.
[45] Charles Kitchin, Lew Counts, Moshe Gerstenhaber. Reducing RFI rectification errors in In-Amp circuits [J]. Analog Devices, Inc., 2003.
[46] Steven O. Smith.简单的CMRR微调改进AC和DC性能[J].电子产品世界,1997,(9),73.
[47] Miniature, 1W isolated unregulated DC/DC converters [Z]. Burr-Brown Inc., 2000.
[48] Precision lowest-cost isolation amplifier ISO124 [Z].SBOS074C, Texas Instruments Inc., 2005.
[49]杨素行.模拟电子技术简明教程[M].第二版.北京:高等教育出版社,1998.
[50] LF356 JFET Input operational amplifiers [Z]. National Semiconductor Corporation, 2001.
[51] High performance analog multiplexers ADG408 [Z]. Rev. A. Analog Devices Inc., 1998.
[2]吴德正.临床视觉电生理的进展[J].眼科,2001,10(1):9-12.
[3]周鑫,张玲莉,饶广勋.视觉诱发电位技术与视力客观评估[J].国际眼科杂志,2005,5(1):135-138.
[4]何庆华.基于视觉诱发电位的脑机接口实验研究[D].重庆:重庆大学,2003.
[5] J. Vernon Odom, Michael Bach, Colin Barber. Visual evoked potentials standard [S]. Doc Ophthalmol, 2004, 108: 115–123.
[6] UBA-4204 Universal Biomedical Amplifier [EB/OL].www.LKC.com.
[7] Specifications for biopotential measurement system, type ActiveTwo Mk2 with two-wire active electrodes [EB/OL]. http://www.biosemi.com/activetwo_full_specs.htm.
[8]余学飞.医学电子仪器原理与设计[M].广州:华南理工大学出版社,2007.
[9]黄群峰.脑电信号检测专用集成电路设计研究[D].广州:华侨大学,2007.
[10] Y.Q.Tan, F. Ibrahim, M. Moghavvemi, J. Ibrahim. Development of an EEG amplifier for Brain-Computer-Interface [J].Biomed 06, IFMBE Proceedings 15:378-382, 2007.
[11] Texas Instruments Inc. Medical applications guide [EB/OL]. www.ti.com/medical.
[12] G. B. Mukartihal, S. Radhakrishnan, M. Ramasubba Reddy, S.S.K.Ayyar. Design and development of visual evoked potentials recording system for diagnosis of optic nerve diseases [J].Instrum. Soc. India 36(4): 227-234.
[13]王立丽,李刚等.一种新型视觉诱发电位检测系统[J].电子产品世界,2005(19):94-95.
[14]孙友明,黄秉鍊,罗晓曙.新型脑电信号放大检测电路的设计[J].国外电子元器件,2006(9):58-62.
[15]魏彬,贾存良.脑电信号预处理电路的设计.中国仪器仪表学会医疗仪器分会2006年学术年会暨中国仪器仪表学会医疗仪器分会第三届第三次理事会论文汇编[C],2006.
[16] Anton F P Van Putten,张伦译.电子测量系统——理论与实践[M].北京:中国计量出版社,2000.
[17] C.D. Motchenbacher, F.C.Fitchen著,龙忠琪译.低噪声电子设计[M].北京:国防工业出版社,1977.
[18] Joshua Israelsohn.噪声与低噪声设计的探讨[OL].EDN China,2004.
[19]蔡建新,张唯真.生物医学电子学[M].北京:北京大学出版社,1997.
[20]远坂俊昭,彭军译.测量电子电路设计——模拟篇[M].北京:科学出版社,2006.
[21] Art Kay.运算放大器电路中固有噪声的分析与测量[EB/OL]. http://www.eetchina.com/,2007, 06.
[22] James M.Bryant. Operational Amplifier Noise [EB/OL]. Analog Device Inc. http://www.analog.com/static/imported-files/rarely_asked_questions/moreInfo_raq_opAmpNoise2.html.
[23]杨继深.共模干扰和差模干扰[J].安全与电磁兼容,2002(2):48-50.
[24]吴良斌,高玉良,李延辉.现代电子系统的电磁兼容型设计[M].北京:国防工业出版社,2004.
[25]孙伟国,邱扬,权修桥,田锦.共模与差模传导干扰分析及抑制技术研究[J].电子质量,2004(10):18-20.
[26]温世仁.微弱信号检测系统中的接地与屏蔽技术分析[J].宇航计测技术,2005(2):46-49.
[27] John Yeager, Mary Anne Hrusch Tupta著,催建平,汪铁华译.低电平测量手册[M].北京:美国Keithley仪器公司,2005.
[28] Walt Kester, Scott Wurcer, Chuck Kitchin. Sensor signal conditioning section 5: High impedance sensors [EB/OL]. http://www.analog.com/zh/rfif-components/rms-detectors/products/seminars-webcasts/resources/index.html, 1999.
[29] Glen Brisebois. Signal conditioning for high-impedance sensors [EB/OL]. http://www.edn.com/article/CA6305356.html, 2006.02.16.
[30] Enrique Mario Spinelli, Ramon Palls Areny, Miguel Angel Mayosky. AC-coupled front-end for biopotential measurements[J]. IEEE Trans Biomed Eng, 2003, 50(3):391-395.
[31] Clement Alphonse Berard. Guard circuit for high impedance signal circuits [P]. United States Patent, [19] 4 091 430. 3. 23. 1978.
[32] Ultralow noise BiFET Op Amp AD743 [Z]. REV. D. Analog Devices, Inc., 2002.
[33] John Ardizzoni. A practical guide to high-speed printed circuit board layout [EB/OL]. http://analog.com/library/analogdialogue/archives/39-09/layout.html, 2005.
[34]贾新章等.OrCAD/PSpice 9实用教程[M].西安:西安电子科技大学出本社,2001.
[35]王越,李刚,王立丽.几种新型的高性能生物电放大器[J].电子设计应用,2005,(6):126-128.
[36]姬军,俞梦孙.有效抑制50Hz干扰的生物电放大器[J].北京生物医学工程,2006,25(2):185-188.
[37]王三强,何为,石坚.新型脑电信号前置级放大电路设计[J].重庆大学学报,2006,29(6):51-53.
[38]张思杰,彭承琳,郭兴明等.用于多焦视觉电生理分析系统的生物信号放大器的设计[J].医疗卫生装备,2004,25(4),54.
[39] Charles Kitchin, Lew Counts. A designer’s guide to instrumentation amplifier [Z]. 3rd Edition, Analog Devices, Inc., 2006.
[40] Low cost, low power instrumentation amplifier AD620 [Z]. Rev. E. Analog Devices Inc., 1999.
[41] Precision instrumentation amplifier AD8221 [Z]. Rev. A. Analog Devices Inc., 2003.
[42] Precision, low power instrumentation amplifiers INA128 [Z]. Burr-Brown Inc., 1996.
[43] Thomas Kugelstadt. Getting the most out of your instrumentation amplifier design [J]. Analog Applications Journal. 2005(4):25-29.
[44] Winter BB , Webster JG. Driven right leg circuit design [J]. IEEE Trans Biomed Eng, 1983, 30(1):62–66.
[45] Charles Kitchin, Lew Counts, Moshe Gerstenhaber. Reducing RFI rectification errors in In-Amp circuits [J]. Analog Devices, Inc., 2003.
[46] Steven O. Smith.简单的CMRR微调改进AC和DC性能[J].电子产品世界,1997,(9),73.
[47] Miniature, 1W isolated unregulated DC/DC converters [Z]. Burr-Brown Inc., 2000.
[48] Precision lowest-cost isolation amplifier ISO124 [Z].SBOS074C, Texas Instruments Inc., 2005.
[49]杨素行.模拟电子技术简明教程[M].第二版.北京:高等教育出版社,1998.
[50] LF356 JFET Input operational amplifiers [Z]. National Semiconductor Corporation, 2001.
[51] High performance analog multiplexers ADG408 [Z]. Rev. A. Analog Devices Inc., 1998.