Non-stationary interference or intrinsic low frequency fluctuation of dynamic system--the correlation between non-stationarity and short-term analysis of heart rate variability / 生物医学工程学杂志

The non-stationary interference with the analysis parameters of short-term heart rate variability (HRV) has been studied. The results show that although all considered parameters fluctuate with the lapse of time, only HFnorm and sample entropy (SE) correlate significantly with non-stationary interference. Therefore, the low frequency fluctuations of HRV contain not only the non-stationary interference, but also the intrinsic cardiac dynamic characteristics. Specially, the results of the base-scale entropy (BE) analysis of three groups of people, and of three kinds of noises are contrasted. It is shown that, at the expense of outstanding anti-nonstationarity, BE fails to depict the long range correlation of HRV.

Mosaicing for medical microscopic images based on estimation and compensation / 生物医学工程学杂志

Image mosaicing can solve the problem that only very limited field of view is available when highly magnifying lens is used in microscope imaging. This paper puts forward an equation of the system's influence to the grayscale distribution of the medical microscopic images, based on the analysis of the influence. Then, by the system equation and the accurate registration equation, the least-squares optimization error function can be formulated. By these equations, a set of transcendental equations is formed. We can estimate the system's influence on the gray-level of the images by singular-value decomposition (SVD), based on the equations set, and compensating for it. This permits image mosaicing seamlessly, without lowering the speed.

Singularity spectra analysis of the ST segments of 12-lead electrocardiogram / 生物医学工程学杂志

By analysing the f(a) singularity spectra of the ST segments of the synchronous 12-lead ECG, we have found that the singularity spectrum is close to monofractality and its area is only half the area of the synchronous 12-lead ECG f(alpha) singularity spectrum. The ST segments of the synchronous 12-lead ECG signal also has f(alpha) singularity spectra distribution and it also has a reasonable varying scope. We have also found that the lead number of the ST segment f (alpha) singularity spectra for adults having coronary heart disease overstep the reasonable scope tends to increase over that of the ECG f(alpha) singularity spectra. These findings show that using the ST segments f(alpha) singularity spectra distribution of the synchronous 12-lead ECG is more effective than using the synchronous 12-lead ECG on the clinical analysis.

Multiscale entropy analysis of electrocardiogram / 生物医学工程学杂志

Using the algorithm proposed by Costa M, et al., we studied the multiscale entropy (MSE) of electrocardiogram. The sample entropy (SampEn) of the healthy subjects was found to be higher than that of the subjects with coronary heart disease or myocardial infarction. The healthy subjects' complexity was found to be the highest. The SampEn of the subjects with coronary heart disease was noted to be only slightly higher than that of the subjects with myocardial infarction. These findings show that the complexity of the subjects with coronary heart disease or myocardial infarction is distinctly lower than the complexity of the healthy ones, and the subjects suffereing from coronary heart disease are liable to the onset of myocardial infarction.

Nonlinear dynamical complexity analysis of short-term heartbeat series using joint entropy / 生物医学工程学杂志

In this paper is reported a method using joint entropy to analyze the nonlinear dynamical complexity of short-term heart rate variability(HRV) signal. This method can effectively pick up dynamical information from the short-term heartbeat time series, reflect the dynamical complexity of heart rate variability, and so improve the quality of being covenient in clinical application. At first, the joint entropy method is demonstrated by applying it to the low-dimensional nonlinear deterministic systems such as logistic map and henon map. Then, the proposition is applied to the short-term heartbeat time series. The result shows that the method could robustly discriminate the patterns generated from healthy and pathologic states, as well as aging. Furthermore, the authors point out that decreased nonlinear dynamical complexity in the heartbeat time series with physiological aging and pathologic states is probably due to self-adjusting ability depression with aging and disease. At last, using the joint entropy method,the authors uncover nonrandom patterns in the ventricular response to atrial fibrillation.

Influence of heart and brain disease on multifractal singularity spectrum of synchronous 12-lead ECG signals / 生物医学工程学杂志

We analyzed the multifractal singularity spectrum of synchronous 12-lead ECG (electrocardiogram) signals from heart and brain disease patients, and found that multifractal curves of different leads do not overlap each other. After calculating the scope of the singularity strength, we noticed that the averages of scope are not the same in different subjects,and the dispersing degree is also different in someone's different leads. Both the deltaalpha, the average of the deltaalpha, and the dispersing degree deltaalpha (be defined as standard deviation) of the deltaalpha of every one's 12-lead ECG were computed. Then, a comparison was made between the spectrum of the healthy subjects and the heart disease patients. The results showed that their deltaalpha are close, but their deltaalpha are markedly different. Also the healthy subjects and brain disease patients were compared, we found that their deltaalpha are close, but their deltaalpha are markedly different. These indicate that the character of multifractal spectrum is controlled by both the neurosystem of body and the self-syntonic property of cardiac structures. Furthermore, the deltaalpha is related with the neuroautonomic control of people's body on the ECG, and the deltaalpha is related with the anisotropy of the heterogeneous tissue and the electric signal propagation in heart.

Research on the application of neural network to diagnosis of cardiopathy / 生物医学工程学杂志

Neural networks can fit any nonlinear function. After drawing out several characteristic parameters from the three-dimension spectrum for high frequency QRS waves, we input them into the network and trained the network. In this way, we can get a m-dimension curved surface in the m-dimension space which is constructed by those parameters, and this curved surface divides the space into two parts: the unhealthiness and the health. Now, the network can automatically distinguish between the healthiness and the unhealthiness according to their three-dimension spectrum for high frequency QRS waves.

Dynamical analysis of the nonlinearity in the model of acute myocardial ischemia / 生物医学工程学杂志

By analyzing the electrocardiosignals, many scholars have found remarkable and outstanding dynamic characteristics in both normal hearts and sick hearts. Based on those findings, a model of acute myocardial ischemia of six rabbits is designed by us and is presented here. The electrocardiogram (ECG) signals of different time series are calculated, and the figures of correlation dimensions-time and the maximum Lyapunov exponents-time are given. The results show that the existence of myocardial ischemia will bring the decline of the value of maximum Lyapunov exponents and correlation dimensions, after the figures being analyzed with electrophysiological and anatomical knowledge. The maximum Lyapunov exponents of ECG demonstrate the chaotic quality of the system and the correlation dimension of ECG demonstrates the complexity of the system, and there is no explicit relation between them. Correlation dimensions of ECG signals might be more influenced by partial heart system, compared with the maximum Lyapunov exponents of ECG signals.

A primary investigation on the dynamic changes of correlation dimension of animal's ECG signals / 生物医学工程学杂志

The dynamic changes of synchronous 12-lead ECG signal's correlation dimension (D2) of an anesthetized rabbit were investigated primarily under three different pathologic conditions. The results showed that the D2 derived from different lead signals was not a constant whether the rabbit was in normal state or in emergent myocardial infarction condition, it demonstrated distribution characteristic. Compared with the same lead signal, D2 of limb lead almost kept constant, D2 of chest lead got higher when the sphere of emergent ischemia extended larger. D2 showed the potential application in the diagnosis of coronary heart disease.