生理信号时问序列周期性和平稳性对近似熵和样本熵算法的影响分析

目的提高近似熵和样本熵算法在评价生理信号时间序列非线性复杂度应用中的精度。方法首先生成生理信号时间序列数据库,通过对周期序列和叠加有周期成分的非线性序列的分析,研究序列周期性对熵测度算法的影响,并通过对心率变异性（hear trat evariability,HRV）序列在去除非平稳趋势前后的对比分析,研究序列平稳性对熵测度算法的影响。结果在序列长度范围内,不同重复频率的周期序列熵测度不同,不同比重的周期成分叠加到非线性序列中引起序列熵测度的变化也不同。生理信号时间序列中大都存在非平稳成分,而非平稳成分会降低序列的复杂度,因此进行熵测度计算前首先要去除非平稳成分。结论周期性和非平稳成分显著影响生理信号时间序列的熵测度算法。     

神经放电脉冲间隔的自回归分析

本文提出对神经放电脉冲间隔(Interspike interval,简记ISI)序列进行自回归(Autoregressire,简记AR)分析的方法。利用AR模型及格林函数和功率谱密度函数对猫的大脑体感皮层一区(First Somatosensory area of corfex,简记SI区)的神经细胞在不同条件下的ISI序列进行处理分析,从而提取ISI序列的AR阶数及参数、记忆指标、相依性和周期性等特征。     

基于经验模式分解与样本熵的癫痫预测方法

本研究提出一种基于经验模式分解（empirical mode decomposition，EMD）与样本熵的癫痫预测方法；该方法首先对原始信号进行了经验模态分解，将其分解为多个平稳的固有模态函数（intrinsic mode function，IMF）之和，再选取若干个包含主要癫痫预报信息的IMF分量，将其求和后，计算其样本熵（sample entropy，SampEn）。结果表明，癫痫发作前期样本熵呈减小趋势，基于EMD的样本熵其减小幅度显著增加，同时抑制了伪差对实验结果的影响。基于经验模式分解与样本熵的癫痫预测方法能够很好的对癫痫进行预测。     

基于样本熵的生物医学信号复杂度分析方法及其优化算法

介绍了样本熵的严格定义,阐述了样本熵的性质及在生物医学信号处理方面的意义。基于样本熵的定义,通过引入二值距离阵,将两向量距离的比较转化成了一系列的逻辑判断,对样本熵的算法进行了优化,提出了一种较为快速实用的样本熵计算方法。该算法减少了计算冗余度,加快了计算速度。最后,对样本熵信号复杂度分析方法在中医推拿量化研究领域的应用前景进行了讨论。     

基于局部场电位样本熵分析的麻醉深度监测

背景：目前的麻醉深度监测多以大脑皮质脑电信号分析为主,然而,大脑皮质脑电信号不能反映皮质下组织的功能状况、不包含高频信息并且易受外界环境干扰,从而导致基于大脑皮质脑电信号分析的麻醉深度监测在稳定性、精确性等方面有固有缺陷。 目的：分析局部场电位信号样本熵在麻醉深度监测中的效果,实现麻醉深度的实时监测。 方法：以大鼠为模型动物进行实验,对整个麻醉过程中的大鼠初级视觉皮质局部场电位信号进行快速样本熵计算,并对样本熵曲线动态变化进行分析,判定麻醉状态;然后将样本熵分别与大鼠尾部受热刺激时的甩尾延迟时间、局部场电位信号的中心频率和边缘频率做统计分析,验证基于局部场电位快速样本熵分析的麻醉状态判定方法。 结果与结论：局部场电位信号的样本熵可以快速、准确、稳定地反映大鼠的麻醉深度,用于麻醉深度实时监测。     

磁刺激神门穴脑电信号的样本熵分析与诱发电位的研究

研究用经颅磁刺激仪在不同频率下刺激肢体神门穴,在安静、磁刺激、假刺激、假穴4种不同状态下脑电信号的样本熵值以及脑电信号诱发电位的特征。对8名被试者进行实验,实验分为4组即安静、磁刺激、假刺激、假穴,测量3种不同频率(0.5、1、3 Hz)刺激下的脑电信号并计算样本熵值,对刺激后的脑电信号诱发电位进行了分析。结果显示,1 Hz与0.5 Hz磁刺激脑电信号样本熵没有明显变化(P0.05);3 Hz时4种状态下的脑电信号样本熵变化较明显(P0.05),磁刺激组和假穴组明显高于安静组和假刺激组,且磁刺激组略低于假穴组;3 Hz磁刺激无诱发电位;而假穴组产生明显体感诱发电位等其他诱发电位。实验表明,对人体神门穴进行磁刺激对脑电信号有明显抑制,与进行针刺或电刺激同样具有调节神经机能的作用。     

醉酒者和正常人脑电的样本熵研究

为了探索应用非线性动力学理论研究醉酒者脑电信号的新方法,采用非线性动力学指标:样本熵对醉酒者和正常人的脑电信号进行分析和比较。试验随机选取了相同数目的醉酒者和正常人,运用样本熵算法对他们的脑电数据进行计算,得到样本熵值,然后对这些熵值进行分析。结果显示:醉酒者的样本熵普遍都大于正常人的样本熵,表明大脑在醉酒状态下复杂度会比正常状态要高。样本熵能够有效地区分醉酒者和正常人的脑电状态。     

二进制序列在心率变异性分析中的应用及推广

目的：探究二进制序列在心率变异性分析中的应用。方法：提出了一种将RR间期序列转化成二进制序列的方法一阈值法,并利用这种方法分别将年轻组和老年组各20名健康受试者RR间期的原始序列转化成为二进制序列,计算了这两组健康受试者RR间期的原始序列和转化成二进制序列的近似熵与样本熵。结果：通过计算,得到转化后两组二进制序列的近似熵分别为0．5923±0．1071、0．3270±0．2057,样本熵分别为0．5315±0．1528、0．2238±0．1993。对这两个指标分别进行t检验表明：年轻组的近似熵与样本熵均明显大于老年组（P〈0．001,P〈0．001）,经与原始序列的t检验结果对照发现,二进制序列的t检验效果更好．结论：经过讨论,本文介绍的经阈值法转化为二进制序列在心率变异性分析中有较明显的优点。     

缺血性脑卒中患者脑电信号的样本熵特征分析

目的：探究不同病程缺血性脑卒中患者脑电图（EEG）非线性复杂度特征。方法对20例不同病程的缺血性脑卒中患者及10例健康人各频段EEG信号进行样本熵特征提取及统计学分析。结果脑卒中患者全频段EEG信号样本熵在大部分导联处显著小于健康人;不同病程卒中患者α频段样本熵在额叶、颞叶及枕叶差异具有统计学意义（P<0.05）,部分导联处α频段样本熵与卒中后时间显著线性负相关。结论缺血性脑卒中患者存在异常神经元放电活动,利用样本熵探究脑卒中患者EEG复杂度异常改变初步可行,值得深入研究。     

Conduction of trains of impulses in uniform myelinated fibers: Computed dependence on stimulus frequency

The conduction of trains of action potentials in myelinated fibers was studied using computer simulations based on a modification of the Hodgkin-Huxley equations. Stimulation at short but regular interstimulus intervals caused some stimuli to fail to elicit propagated action potentials.Propagated impulse trains observed close to the stimulation site, elicited by high frequency stimulus trains, took the form of ‘clusters’ of impulses, e.g. doublets or triplets. When these impulse trains were observed at distances farther from the stimulation site, interspike intervals were more uniform. For interstimulus intervals of less than 10 ms, distant intervals between impulses were relatively insensitive to the temporal patterning of impulses at the initiation zone and tended toward regular intervals corresponding to the average interstimulus intervals for propagated stimuli. This tendency toward uniform intervals between impulses was also observed for lower average frequency stimulus trains with irregular interstimulus intervals. Moreover, for the first two stimuli in a train, there was a very strong tendency toward impulse entrainment.These results indicate that intervals between impulses along unbranched myelinated axons are not fixed, but vary according to the site along the conduction pathway where they are observed. The tendency toward entrainment, and regularization of intervals, may represent a factor limiting the frequency with which interval-coded impulses are initiated.     

Effects of rate of tone-pip stimulation on the evoked K-Complex

SUMMARY  The effects of rate of presentation on the evoked K-Complex were examined. In different conditions, brief duration tone pips were presented every 5, 10 or 30 s. Trials were sorted into those on which a K-Complex was or was not elicited and averaged separately. The evoked K-Complex consisted of two different negative components peaking at approximately 350 and 550 ms (respectively), followed by a positive component peaking at approximately 900 ms. K-Complexes were elicited more often in Stage 2 early and 2 late than in slow-wave sleep although the differences were not significant. K-Complexes were elicited more often in the Long ISI compared to the Short and Medium ISI conditions. When a K-Complex was evoked, the amplitude of N350 and N550 was greater for the Long ISI than for the Short or Medium ISI conditions. P900 amplitude remained invariant regardless of the ISI. A micro-analysis was carried out whenever 3 consecutive occurring K-Complexes were elicited. During the Short and Medium ISI conditions, N350 and N550 following the second and third occurrence of the K-Complex were significantly attenuated compared to the first occurrence. There was no difference in N350 and N550 amplitudes among the 3 consecutive occurrences during the Long ISI condition. The decay in amplitude over consecutive occurrences of the K-Complex might be a reflection of either habituation or refractory processes.     

Comparative study of approximate entropy and sample entropy robustness to spikes

Objective

There is an ongoing research effort devoted to characterize the signal regularity metrics approximate entropy (ApEn) and sample entropy (SampEn) in order to better interpret their results in the context of biomedical signal analysis. Along with this line, this paper addresses the influence of abnormal spikes (impulses) on ApEn and SampEn measurements.

Methods

A set of test signals consisting of generic synthetic signals, simulated biomedical signals, and real RR records was created. These test signals were corrupted by randomly generated spikes. ApEn and SampEn were computed for all the signals under different spike probabilities and for 100 realizations.

Results

The effect of the presence of spikes on ApEn and SampEn is different for test signals with narrowband line spectra and test signals that are better modeled as broadband random processes. In the first case, the presence of extrinsic spikes in the signal results in an ApEn and SampEn increase. In the second case, it results in an entropy decrease. For real RR records, the presence of spikes, often due to QRS detection errors, also results in an entropy decrease.

Conclusions

Our findings demonstrate that both ApEn and SampEn are very sensitive to the presence of spikes. Abnormal spikes should be removed, if possible, from signals before computing ApEn or SampEn. Otherwise, the results can lead to misunderstandings or misclassification of the signal regularity.     

Dynamics of assessments of time intervals by patients with heroin addiction

The perception of 12-sec time intervals time by patients with heroin addiction was assessed in 10 trials with precision of up to 0.1 sec. A total of 82 patients with heroin addiction were studied in the withdrawal and post-withdrawal periods. The results obtained in patients were comparable to measurements obtained in 52 healthy subjects. The time interval estimated by patients as an overall group was shorter than that in healthy subjects during the first two days of in-patient treatment (during development of withdrawal syndrome); the 12-sec period was reproduced accurately at 5–6 days, after which the period was exceeded; perception of time again became accurate on days 15–16 (the post-withdrawal period). Changes in the subjective perception of time were found to depend on the duration of addiction and the individual characteristics of interhemisphere brain asymmetry.Translated from Zhurnal Nevrologii i Psikhiatrii imeni S. S. Korsakova, Vol. 104, No. 3, pp. 21– 24, March, 2004.     

基于Labview大鼠心电信号采集及实时RR间期检测

目的 大鼠心电信号采集目前依赖于生理信号采集系统,其采样频率低,且无法进行软件算法的内部改造,不利于实验使用.本文设计了高精度大鼠心电信号采集系统以实现RR间期实时检测.方法 采用AD620设计心电信号采集电路,信号经USB-6008进行A/D转换后送入PC机,通过Labview编程完成滤波、预处理及显示.然后,通过Labview与Matlab混合编程,采用模板匹配方法实现RR间期实时检测.最后,随机选取10只大鼠心电数据进行离线分析,以阈值法作为对照检验RR间期实时检测的准确性.结果 阈值法检出率96.62%,模板匹配法检出率99.16%.结论 通过硬件与软件结合的方法能够获得高精度的大鼠心电信号.通过Labview与Matlab混合编程,采用模板匹配法能够实现RR间期实时检测,且检测准确性较高,为进一步的实验研究提供了基础.     

基于样本熵和个体化阈值的表面膈肌肌电信号起点检测

膈肌是人体最主要的呼吸肌,表面膈肌肌电(sEMGdi)信号的动作区间起点检测可用于呼吸康复训练,但心电(ECG)信号的存在增加了其检测难度,故本文对此提出了基于样本熵(SampEn)和个体化阈值的起点检测方法,简称样本熵法。该方法涉及样本熵特征的提取,样本熵特征参数w和r0的优化,个体化阈值的选取以及判断条件的设立。同时还选用其他三种常用方法与本文所提的样本熵法进行起点检测方面的比较,即利用小波变换(WT)去噪后再分别使用均方根(RMS)和能量算子(TKE)的起点检测方法,以及不做小波变换而直接使用TKE的起点检测方法。本文共采集12名健康受试者在2种呼吸状态下的sEMGdi信号,用于信号合成和算法检测。最后以误差的绝对值累加和作为评价起点检测精度的指标。最终结果表明,样本熵法在稳定性和精度两方面皆优于其他三种方法,是一种能适应个体间差异,无需提前对sEMGdi信号进行ECG信号去噪便可获得较高精度的起点检测方法,为基于sEMGdi信号的呼吸康复训练和实时交互提供了依据。     

基于统计学的生理期语音特征分析

目的：建立快速准确且安全无创的生理期语音监测模式。方法：采用中医闻声诊技术对育龄期女性进行生理期语音特征分析,分别以排卵期、月经期、痛经程度作为判别依据,筛选出可反映上述指征的差异性语音频率特征,拟建立相关回归模型。结果：在242项语音指标中分析得出排卵期与非排卵期、月经期与非月经期、4种痛经程度中,分别有14、11、4项语音特征指标差异具有统计学意义,其中与排卵期相关的语音特征指标为语音第五共振峰高度和最持续帧最大能量频率占时比,与月经期呈负相关的语音特征指标为最高能频段序号,与痛经程度呈正相关的语音特征指标为音阶。结论：育龄期女性在生理期语音呈现特征性变化,对排卵期、月经期具有一定的预测能力,对痛经程度的量化具有一定的参考价值。     

基于脑电信号样本熵的急性脑梗死患者溶栓效果评价

目的:通过研究急性脑梗死患者溶栓治疗前后的脑电信号特征,探讨样本熵算法在急性脑梗死溶栓治疗监测中的应用。方法:采用频谱和样本熵分析76例急性脑梗死患者在溶栓前和溶栓治疗后24 h的EEG数据。分析溶栓治疗前后的变化规律。结果:溶栓治疗有效的患者,Delta与Alpha频段的能量在溶栓治疗前后差异具有统计学意义（P<0.05）;同时,溶栓前后,溶栓有效患者的Delta频段的样本熵在溶栓治疗前后的差异有统计学意义（P<0.001）。结论:Delta频段和Alpha频段的能量,以及样本熵可用于急性脑梗死溶栓治疗效果的监测评估。 【关键词】急性脑梗死;血栓溶解疗法;脑电图;频谱;样本熵     

Fuzzy entropy based interactive enhancement of radiographic images

In certain radiographic images, fuzziness exists due to the vague nature of image characteristics and limitations of visual perception. Accordingly, a gap exists between the information content of an image and the information that can be retrieved. In this paper, a new fuzzy logic based intensification operator has been proposed for enhancement of images. For applying the operator effectively, selection of crossover point is critical. In this paper, the concept of fuzzy entropy has been proposed for objective selection of crossover point. Owing to semantic nature of information content, the methodology has a provision to change levels of enhancement interactively, to help in retrieving the information as required. The effectiveness of the methodology has been demonstrated. Comparison of the results with the Zadeh's INT operator and conventional histogram equalization techniques has established its superiority.