基于闭环控制的神经电刺激器设计
摘要
电刺激在神经系统基础研究以及癫痫等大脑疾病治疗过程中都得到越来越广泛的应用,但是,能够基于大脑的电活动状态发出刺激信号的闭环式电刺激器产品却不多。因此,本文设计的闭环式刺激器对于各种电刺激实验和临床治疗仪器的开发具有重要的意义。
本文利用美国国家仪器公司生产的数据采集卡和普通PC机的声卡,基于LabVIEW开发环境,针对大鼠脑部海马区场电位信号的特性,设计了一种闭环控制的电刺激器,主要设计工作包括如下3个部分：(1)设计场电位信号的θ节律检测及相位预测方法,能够根据需要,使电刺激发生于θ节律的波峰或者波谷。(2)设计癫痫棘波的检测方法,能够按照预先的设置,在痫样波出现后的不同延迟时间上发出电刺激,可用于大脑深部电刺激治疗癫痫的实验研究。(3)设计基于普通PC机声卡的简易癫痫脑电信号监测器,并具有声音提示功能,有利于相关仪器功能的家用普及。
本文的主要研究结果如下：
(1)所设计的电刺激器能够根据需要输出脉冲波、正弦波、三角波和锯齿波等刺激波形,
并能设置脉宽、刺激间隔、刺激个数等；最小脉宽可以达到50μs,能够满足大脑神经系统电刺激实验的要求。
(2)大鼠海马脑区场电位信号的检测结果表明,该电刺激器预测θ节律波峰位置和波谷位置的平均误差分别为波形周期的10%和15%左右,两者的预测正确率都在92%以上。
(3)癫痫信号识别实验的结果表明,癫痫棘波检测的正确率都能达到99%,能较好的区别正常脑电信号,并不受50 Hz工频噪声的干扰。
(4)PC机声卡频率响应特性的测试结果表明,声卡的频响能够满足癫痫脑电的监测要求,其检测准确率可达到97%以上。
总之,本文开发的闭环式电刺激器,能够自动预测脑电信号中的θ波等节律的相位,检测癫痫棘波；并根据用户的设置,在所需时刻发出各种波形的电刺激,为大脑神经系统工作机理和电刺激作用机制的深入研究提供了有用的工具。同时,本文利用PC机声卡实现的简易癫痫棘波监测器,检测准确率较高,可以用于家庭远程医疗等领域。
Since the electrical stimulation has been widely used both in theoretic neurophysiologic research and therapeutic research of brain diseases such as epilepsy, the development of the electrical stimulators has made great progress. But the stimulators that able to generate stimulus according to the electrical activity recorded from the target area, i.e. brain, also called closed-loop stimulator, is very limited. Therefore, it is significant to design such a closed-loop control electrical stimulator either for physiologic research in laboratory or therapeutic treatments in clinical.
In this thesis, we designed a LabVIEW-based closed-loop electrical stimulator, which mainly aimed at the rat's hippocampal field potential signals. The key hardware of this stimulator is composed from a data acquisition card (NI, USA) and an ordinary PC sound card. The main work and analyzing methods involved in the design of this stimulator were listed as followings:
(1) Developed an algorithm to detect and predict the 9 rhythm among the field potentials of hippocampus. With this algorithm the stimulator can deliver stimulus right at the moment of the peak or trough point of 9 wave on the demand. (2) Designed a spike detection algorithm of epilepsy. This algorithm could help the stimulator generate stimulus after the emergence of epileptic spike with a pre-set delay. This function might be used in deep brain stimulation research. (3) Developed a simple epileptic EEG monitor with sound alarm. By taking advantage of a PC sound card Such vocal EEG monitor is cheap and easy to imitate.
The main results of this thesis were summarized as followings:
(1)The electrical stimulator can generate diverse stimulus waves selection, e.g., pulse, sine, triangle, sawtooth. It also supports alteration of stimulation settings, such as pulse width, stimulus interval, stimulus number, etc. The minimum pulse width is 50μs, meeting the need of most neurophysiological experiments.
(2) The test results of the algorithms showed that average error between prediction ofθwave's peak and actual peak is 10% of period, while the average error of trough is 15%. The correct rates of peak and trough both are above 92%.
(3) The results of epileptic spikes detection experiment showed that the epileptic detection algorithm could avoid the influence of normal EEG or noise signal and the accuracy of the detection of epileptic spikes could almost reach 100%.
(4) The frequency response test of PC sound card showed that most of the sound card can meet the need of epilepsy EEG detection and the accuracy of the detection is around 97%.
In a word, this paper designed a neural stimulator with closed-loop control, which can automatically predict the phase of 0 wave rhythm and detect epileptic spikes. It can also provide a variety of stimulus waves by users' set. Such stimulator can be used for the study of the mechanisms of nervous system or brain stimulation. At the same time, the simple epileptic EEG monitor by sound card has a high detection accuracy rate, which can be used in the field of telemedicine.
本文利用美国国家仪器公司生产的数据采集卡和普通PC机的声卡,基于LabVIEW开发环境,针对大鼠脑部海马区场电位信号的特性,设计了一种闭环控制的电刺激器,主要设计工作包括如下3个部分：(1)设计场电位信号的θ节律检测及相位预测方法,能够根据需要,使电刺激发生于θ节律的波峰或者波谷。(2)设计癫痫棘波的检测方法,能够按照预先的设置,在痫样波出现后的不同延迟时间上发出电刺激,可用于大脑深部电刺激治疗癫痫的实验研究。(3)设计基于普通PC机声卡的简易癫痫脑电信号监测器,并具有声音提示功能,有利于相关仪器功能的家用普及。
本文的主要研究结果如下：
(1)所设计的电刺激器能够根据需要输出脉冲波、正弦波、三角波和锯齿波等刺激波形,
并能设置脉宽、刺激间隔、刺激个数等；最小脉宽可以达到50μs,能够满足大脑神经系统电刺激实验的要求。
(2)大鼠海马脑区场电位信号的检测结果表明,该电刺激器预测θ节律波峰位置和波谷位置的平均误差分别为波形周期的10%和15%左右,两者的预测正确率都在92%以上。
(3)癫痫信号识别实验的结果表明,癫痫棘波检测的正确率都能达到99%,能较好的区别正常脑电信号,并不受50 Hz工频噪声的干扰。
(4)PC机声卡频率响应特性的测试结果表明,声卡的频响能够满足癫痫脑电的监测要求,其检测准确率可达到97%以上。
总之,本文开发的闭环式电刺激器,能够自动预测脑电信号中的θ波等节律的相位,检测癫痫棘波；并根据用户的设置,在所需时刻发出各种波形的电刺激,为大脑神经系统工作机理和电刺激作用机制的深入研究提供了有用的工具。同时,本文利用PC机声卡实现的简易癫痫棘波监测器,检测准确率较高,可以用于家庭远程医疗等领域。
Since the electrical stimulation has been widely used both in theoretic neurophysiologic research and therapeutic research of brain diseases such as epilepsy, the development of the electrical stimulators has made great progress. But the stimulators that able to generate stimulus according to the electrical activity recorded from the target area, i.e. brain, also called closed-loop stimulator, is very limited. Therefore, it is significant to design such a closed-loop control electrical stimulator either for physiologic research in laboratory or therapeutic treatments in clinical.
In this thesis, we designed a LabVIEW-based closed-loop electrical stimulator, which mainly aimed at the rat's hippocampal field potential signals. The key hardware of this stimulator is composed from a data acquisition card (NI, USA) and an ordinary PC sound card. The main work and analyzing methods involved in the design of this stimulator were listed as followings:
(1) Developed an algorithm to detect and predict the 9 rhythm among the field potentials of hippocampus. With this algorithm the stimulator can deliver stimulus right at the moment of the peak or trough point of 9 wave on the demand. (2) Designed a spike detection algorithm of epilepsy. This algorithm could help the stimulator generate stimulus after the emergence of epileptic spike with a pre-set delay. This function might be used in deep brain stimulation research. (3) Developed a simple epileptic EEG monitor with sound alarm. By taking advantage of a PC sound card Such vocal EEG monitor is cheap and easy to imitate.
The main results of this thesis were summarized as followings:
(1)The electrical stimulator can generate diverse stimulus waves selection, e.g., pulse, sine, triangle, sawtooth. It also supports alteration of stimulation settings, such as pulse width, stimulus interval, stimulus number, etc. The minimum pulse width is 50μs, meeting the need of most neurophysiological experiments.
(2) The test results of the algorithms showed that average error between prediction ofθwave's peak and actual peak is 10% of period, while the average error of trough is 15%. The correct rates of peak and trough both are above 92%.
(3) The results of epileptic spikes detection experiment showed that the epileptic detection algorithm could avoid the influence of normal EEG or noise signal and the accuracy of the detection of epileptic spikes could almost reach 100%.
(4) The frequency response test of PC sound card showed that most of the sound card can meet the need of epilepsy EEG detection and the accuracy of the detection is around 97%.
In a word, this paper designed a neural stimulator with closed-loop control, which can automatically predict the phase of 0 wave rhythm and detect epileptic spikes. It can also provide a variety of stimulus waves by users' set. Such stimulator can be used for the study of the mechanisms of nervous system or brain stimulation. At the same time, the simple epileptic EEG monitor by sound card has a high detection accuracy rate, which can be used in the field of telemedicine.
引文
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[2]Halpern CH, Samadani U, Litt B, et al. Deep brain stimulation for epilepsy[J]. Neurotherapeutics,2008,5(1):59-67.
[3]Feng ZY and Durand DM. Low-Calcium Epileptiform activity in the hippocampus in vivo[J]. Journal of Neurophysiology,2003,90 (4):2253-2260.
[4]粱华为,沈岳良,陈志雄等.低频刺激后海马CA1区场兴奋性突触后电位与群体锋电位的变化[J].生理学报,2002,54(5)：431-434.
[5]Roger ML and Peter MF. A portable device for the electrical extraction of scorpion venom[J]. Toxicon,2011,57:244-247.
[6]王卫,黄英,张德昌.生物电与电刺激及其在医学中的应用[J].医疗卫生装备,2003,24(4)：28-29.
[7]Jarvis JC and Salmons S. A family of neuromuscular stimulators with optical transcutaneous control[J]. Journal of Medical Engineering & Technology,1991,3,15(2):53-57.
[8]周平,李胜利,黄耀熊.基于虚拟仪器技术的时序功能电刺激系统[J].中国医学物理学杂志,2009,5,26(3)：1220-1223.
[9]牛川森,胡春华等.可编程式经皮神经肌肉电刺激系统的设计及初步实验研究[J].航天医学与医学工程,2009,22(3)：211-215.
[10]王娅,周鹏,张爽等.基于ERD/ERS脑电信号的智能化功能电刺激系统的设计[J].生物医学工程学杂志,2007,24(5)：1157-1160.
[11]王卫东,刘洪运,吕昊.多通道可植入神经刺激器的设计和实现[J].医疗卫生装备,2008,29(7)：1-3.
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