基于ECG频带特征的身份识别

目的：心电图作为活体的生理信号,可以方便的从手指中提取,具备易采集、难复制的特点。因此,本文提出了基于单导联ECG频带特征的身份识别方法。方法：文中首先对单周期ECG进行小波包变换,提取各子带的波形与能量,并将子带能量、ECG波形、子带波形作为分类特征;然后,引入DTW算法确定待测数据与模板之间的ECG波形、子带波形的最优匹配距离,同时提取待测数据与模板之间的子带能量比值与差值,为上述参数设置合适阈值并进行身份识别。结果：当测试数据与模板取自同一样本时,同频带的子带能量、ECG波形、子带波形差异较小,所以同一子带能量之比接近于1,同一子带的能量之差与波形的匹配距离接近于0。反之,上述参数差异较大,这为ECG提供了良好的分类特征。结论：将ECG用于身份识别,识别装置的硬件成本低,并且用于识别的信号难以窃取,是一种比较安全的身份识别手段。实验结果表明,相较传统算法,本文提出的方法具有较高识别率,这为ECG身份识别提供了一种新的方法。     

Modeling the pharyngeal anatomical effects on breathing resistance and aerodynamically generated sound

The objective of this study was to systematically assess the effects of pharyngeal anatomical details on breathing resistance and acoustic characteristics by means of computational modeling. A physiologically realistic nose-throat airway was reconstructed from medical images. Individual airway anatomy such as the uvula, pharynx, and larynx was then isolated for examination by gradually simplifying this image-based model geometry. Large eddy simulations with the FW-H acoustics model were used to simulate airflows and acoustic sound generation with constant flow inhalations in rigid-walled airway geometries. Results showed that pharyngeal anatomical details exerted a significant impact on breathing resistance and energy distribution of acoustic sound. The uvula constriction induced considerably increased levels of pressure drop and acoustic power in the pharynx, which could start and worsen snoring symptoms. Each source anatomy was observed to generate a unique spectrum with signature peak frequencies and energy distribution. Moreover, severe pharyngeal airway narrowing led to an upward shift of sound energy in the high-frequency range. Results indicated that computational aeroacoustic modeling appeared to be a practical tool to study breathing-related disorders. Specifically, high-frequency acoustic signals might disclose additional clues to the mechanism of apneic snoring and should be included in future acoustic studies.     

Proposed use of a digital signal processor in an experimental tactile hearing aid for the profoundly deaf: preliminary communication

An experimental system for a tactile hearing aid using a digital signal processor (DSP) is being developed. This system can be used to test and evaluate not only the familiar techniques for a tactile hearing aid, such as energy level display, filterbank analysis, etc., but also novel techniques. The system is being developed especially to try out new recognition strategies, because the currently available strategies are not satisfactory. A portable tactile hearing aid that can recognize certain environmental sounds (alarm sounds) and certain features from the speech signal (such as pitch, voiced/voiceless, or even complete phonemes), being a good support for lipreading, should be the final result of the experiments.     

Proposed use of a digital signal processor in an experimental tactile hearing aid for the profoundly deaf: preliminary communication

An experimental system for a tactile hearing aid using a digital signal processor (DSP) is being developed. This system can be used to test and evaluate not only the familiar techniques for a tactile hearing aid, such as energy level display, filterbank analysis, etc., but also novel techniques. The system is being developed especially to try out new recognition strategies, because the currently available strategies are not satisfactory. A portable tactile hearing aid that can recognize certain environmental sounds (alarm sounds) and certain features from the speech signal (such as pitch, voiced/voiceless, or even complete phonemes), being a good support for lipreading, should be the final result of the experiments.     

Measurement of upper airway movement by acoustic reflection

The acoustie reflection method provides a noninvasive way to determine the airway geometry. Based on a discrete upper airway model, an inverse scheme is developed to infer the upper airway area as a function of distance. We incorporate this scheme into a system that can generate multiple acoustic pulses to sample the upper airway geometry at a maximum frequency of 30 Hz, making possible determination of the airway area-distance relation as a function of time. Therefore, we can monitor the dynamic behavior of the upper airway during breathing. To validate the approach, we visualized vocal cord movements in three normal subjects via laryngoscopy; simultaneously acoustic measurements were made at 10 Hz. Video images of vocal cord movement were recorded and digitized. We compared the laryngeal area from analysis of the video images with the acoustic assessment at the level of the glottis. Linear regression analysis shows that the correlation coefficients are between 0.85 and 0.9 for all three subjects. We conclude that the acoustic reflection method is a useful tool for measuring vocal cord movement without the use of laryngoscopy, and the approach promises to be a useful one to measure the movement of the whole upper airway. This paper also discusses the limitations inherent in the algorithm and some useful procedures to ensure accurate and reliable area computation during implemention.     

Evaluation of protective shielding thickness for diagnostic radiology rooms: theory and computer simulation

This work presents the development and evaluation using modern techniques to calculate radiation protection barriers in clinical radiographic facilities. Our methodology uses realistic primary and scattered spectra. The primary spectra were computer simulated using a waveform generalization and a semiempirical model (the Tucker-Barnes-Chakraborty model). The scattered spectra were obtained from published data. An analytical function was used to produce attenuation curves from polychromatic radiation for specified kVp, waveform, and filtration. The results of this analytical function are given in ambient dose equivalent units. The attenuation curves were obtained by application of Archer's model to computer simulation data. The parameters for the best fit to the model using primary and secondary radiation data from different radiographic procedures were determined. They resulted in an optimized model for shielding calculation for any radiographic room. The shielding costs were about 50% lower than those calculated using the traditional method based on Report No. 49 of the National Council on Radiation Protection and Measurements.     

Van den Ende-Gupta syndrome: laryngeal abnormalities in two siblings

In 1992, van den Ende et al. first reported an autosomal recessive multiple congenital anomaly syndrome characterized by blepharophimosis, arachnodactyly, and congenital contractures in a Brazilian girl born to consanguineous parents. Since then, nine total patients have been reported with van den Ende-Gupta syndrome (VDEGS), and the syndrome's phenotype has been found to also include additional dysmorphic facial features, palatal abnormalities, and slender skeletal features. We present two African-American sisters born to nonconsanguineous parents who have been diagnosed with VDEGS. Both sisters developed stridor and were found to have an unusual malformation characterized by large, globular cuneiform cartilages, shortened aryepiglottic folds, a tightly coiled epiglottis, and laryngomalacia. Both patients underwent supraglottoplasty with a successful outcome. A review of the literature reveals that airway problems have been reported in a previous patient. However, no specific airway anomaly has been reported. We suggest that all patients with VDEGS and stridor undergo direct laryngoscopy with consideration for surgical correction.     

Computer methods for analysing the high-frequency electrocardiogram

The high-frequency electrocardiogram (e.c.g.) is similar to the clinical e.c.g. commonly interpreted by clinicians except that a wider recording bandwidth is used. This extended signal bandwidth permits more information about the cardiac electrical activity to be perceived than can be seen in a clinical e.c.g. The high-frequency data appear as waveform features called notches and slurs. The notches have been correlated with coronary heart disease by several investigators. Most of the work in high-frequency electrocardiography has been done by manual techniques with minimal automation of the signal analysis. The purpose of this project was to develop computer algorithms for the automatic recognition and characterisation of notch parameters. Investigations in this study were conducted in both the time and frequency domains using digital filtering and fast Fourier transform techniques. Methods for notch recognition and quantification by computers were evaluated.     

Classification of foetal heart rate sequences based on fractal features

Visual inspection of foetal heart rate (FHR) sequences is an important means of foetal well-being evaluation. The application of fractal features for classifying physiologically relevant FHR sequence patterns is reported. The use of fractal features is motivated by the difficulties exhibited by traditional classification schemes to discriminate some classes of FHR sequence and by the recognition that this type of signal exhibits features on different scales of observation, just as fractal signals do. To characterise the signals by fractal features, two approaches are taken. The first models the FHR sequences as temporal fractals. The second uses techniques from the chaos-theory field and aims to model the attractor based on FHR sequences. The fractal features determined by both approaches are used to design a Bayesian classification scheme. Classification results for three classes are presented; they are quite satisfactory and illustrate the importance of this type of methodology.     

Measurement of the micro-electroretinogram and component analysis

The authors propose a new technique for detecting micro-electroretinograms (μERG) which uses light-emitting diode (LED) stimulation and frequency analysis. The advantage of this method is the applicability of linear system analysis to a μERG obtained by partial stimulation of a computer-controlled waveform. The paper discusses two basic techniques for detecting the μERG. One is Fourier analysis of a synchronised ERG obtained by sine-wave stimulus, and the other is correlation analysis using a random stimulus. The results of the two methods are compared, and the usefulness of the proposed method is indicated; the μERG is analysed by means of a model consisting of five components of a second-order transfer function with delay. Functions of the central and peripheral areas of the retina could be analysed in more detail by this technique.     

用自适应AR模型提高血氧饱和度测量中脉搏波信号的检出率

血氧饱和度是人体一项重要的生理参数，它的准确测量对于生理研究及医学应用都具有很重要的意义。对血氧饱和度的无创伤检验通常采用双波长法，在该方法中，血氧饱和度的计算是以识别脉搏波并提取其特征值为基础进行的。由于采用双波长法得到的脉搏波信噪比较低，且脉搏波又不具有明显的特征（例如心电信号中有ＱＲＳ波群），因此常用的脉搏波波形识别方法正确检出率不高，经常出现漏检或误检。本文提出利用时间序列建模的方法，建立     

数字助听器中若干主要算法的发展和现状

首先简要介绍了数字助听器的概念 ,随后分别针对数字助听器中信号处理的几个主要部分 :多通道频响补偿、噪声去除和反馈消除 ,分析和比较了它们的常用算法。文章最后介绍了一些助听器信号处理的新思路。     

Knee acoustic emission: a potential biomarker for quantitative assessment of joint ageing and degeneration

Based on a single time-point study of 34 healthy and 19 osteoarthritic knees in three different age groups (early, middle and late adulthood), this paper reports the potential of knee acoustic emission as a biomarker to monitor joint ageing and degeneration. Measurements were made of short transient high frequency acoustic emission signals generated by knee joints under stress during repeated sit-stand-sit movements along with joint angle. A statistically significant feature profile was established using a four-phase model of sit-stand-sit movements and two waveform features. The four-phase movement model is derived from joint angle measurement during repeated sit-stand-sit movements, and it consists of the ascending-acceleration and ascending-deceleration phases in the sit-to-stand movement, followed by the descending-acceleration and descending-deceleration phases in the stand-to-sit movement. The two statistically significant waveform features are extracted from AE measurement during repeated sit-stand-sit movements, and they consist of the peak magnitude value and average signal level of each AE burst. In addition to the use of bilateral plots, statistical distributions and 2D colour histograms to visualise the differences and similarities among participants, use of principal component analysis showed not only distinct data clusters corresponding to participating groups, but also an age- and disease-related trajectory progressing from the early adulthood healthy group to the late adulthood healthy group followed by the middle adulthood osteoarthritic group to the late adulthood osteoarthritic group. Furthermore, this trajectory shows increasing areas for each data cluster, with a highly compact cluster for the early adulthood healthy group at one end and a widely spread cluster for the late adulthood osteoarthritic group at the other end. From these results, a strong basis is formed for further development of knee acoustic emission as a convenient and non-invasive biomarker for quantitative assessment of joint ageing and degeneration.     

Extracellular matrix remodeling by dynamic strain in a three-dimensional tissue-engineered human airway wall model

Airway wall remodeling is a hallmark of asthma, characterized by subepithelial thickening and extracellular matrix (ECM) remodeling. Mechanical stress due to hyperresponsive smooth muscle cells may contribute to this remodeling, but its relevance in a three-dimensional environment (where the ECM plays an important role in modulating stresses felt by cells) is unclear. To characterize the effects of dynamic compression in ECM remodeling in a physiologically relevant three-dimensional environment, a tissue-engineered human airway wall model with differentiated bronchial epithelial cells atop a collagen gel containing lung fibroblasts was used. Lateral compressive strain of 10 or 30% at 1 or 60 cycles per hour was applied using a novel straining device. ECM remodeling was assessed by immunohistochemistry and zymography. Dynamic strain, particularly at the lower magnitude, induced airway wall remodeling, as indicated by increased deposition of types III and IV collagen and increased secretion of matrix metalloproteinase-2 and -9. These changes paralleled increased myofibroblast differentiation and were fibroblast-dependent. Furthermore, the spatial pattern of type III collagen deposition correlated with that of myofibroblasts; both were concentrated near the epithelium and decreased diffusely away from the surface, indicating some epithelial control of the remodeling response. Thus, in a physiologically relevant three-dimensional model of the bronchial wall, dynamic compressive strain induced tissue remodeling that mimics many features of remodeling seen in asthma, in the absence of inflammation and dependent on epithelial-fibroblast signaling.     

Optimal Pressure Waveforms for Pressure-Limited Ventilation

In this paper, we find the pressure waveform that minimizesthe work of distending the alveoli in the lungs while achievingthe desired mean airway pressure and alveolar tidal volume.The model used takes into account the compliance of the airway.The main result is a formula for the pressure waveform at themouth as a function of time and lung parameters.     

Waveform simulation based on 3D dose distribution for acoustic wave generated by proton beam irradiation

A pulsed proton beam is capable of generating an acoustic wave when it is absorbed by a medium. This phenomenon suggests that the acoustic waveform produced may well include information on the three-dimensional (3D) dose distribution of the proton beam. We simulated acoustic waveforms by using a transmission model based on the Green function and the 3D dose distribution. There was reasonable agreement between the calculated and measured results. The results obtained confirm that the acoustic waveform includes information on the dose distribution.     

Distribution and size of mucous glands in the ferret tracheobronchial tree

A transgenic ferret model of cystic fibrosis has recently been generated. It is probable that malfunction of airway mucous glands contributes significantly to the airway pathology of this disease. The usefulness of the ferret model may therefore depend in part on how closely the airway glands of ferrets resemble those of humans. Here, we show that in the ferret trachea glands are commonest in its most ventral aspect and disappear about half way up the lateral walls; they are virtually absent from the dorsal membranous portion. Further, the aggregate volume of glands per unit mucosal surface declines progressively by about 60% between the larynx and the carina. The average frequency of glands openings for the ferret trachea as a whole is only about one‐fifth that in humans (where gland openings are found at approximately the same frequency throughout the trachea). Glands in the ferret trachea are on average about one‐third the size of those in the human. Therefore, the aggregate volume of tracheal glands (per unit mucosal surface area) in the ferret is only about 6% that in humans. As in other mammalian species, airway glands in the ferret disappear at an airway internal diameter of ～1 mm, corresponding approximately in this species to airway generation 6. Anat Rec, 296:1768–1774, 2013. © 2013 Wiley Periodicals, Inc.     

Optimal pressure waveforms for pressure-limited ventilation

In this paper, we find the pressure waveform that minimizes the work of distending the alveoli in the lungs while achieving the desired mean airway pressure and alveolar tidal volume. The model used takes into account the compliance of the airway. The main result is a formula for the pressure waveform at the mouth as a function of time and lung parameters.     

Auditory brainstem response classification: a hybrid model using time and frequency features

OBJECTIVE: The auditory brainstem response (ABR) is an evoked response obtained from brain electrical activity when an auditory stimulus is applied to the ear. An audiologist can determine the threshold level of hearing by applying stimuli at reducing levels of intensity, and can also diagnose various otological, audiological, and neurological abnormalities by examining the morphology of the waveform and the latencies of the individual waves. This is a subjective process requiring considerable expertise. The aim of this research was to develop software classification models to assist the audiologist with an automated detection of the ABR waveform and also to provide objectivity and consistency in this detection. MATERIALS AND METHODS: The dataset used in this study consisted of 550 waveforms derived from tests using a range of stimulus levels applied to 85 subjects ranging in hearing ability. Each waveform had been classified by a human expert as 'response=Yes' or 'response=No'. Individual software classification models were generated using time, frequency and cross-correlation measures. Classification employed both artificial neural networks (NNs) and the C5.0 decision tree algorithm. Accuracies were validated using six-fold cross-validation, and by randomising training, validation and test datasets. RESULTS: The result was a two stage classification process whereby strong responses were classified to an accuracy of 95.6% in the first stage. This used a ratio of post-stimulus to pre-stimulus power in the time domain, with power measures at 200, 500 and 900Hz in the frequency domain. In the second stage, outputs from time, frequency and cross-correlation classifiers were combined using the Dempster-Shafer method to produce a hybrid model with an accuracy of 85% (126 repeat waveforms). CONCLUSION: By combining the different approaches a hybrid system has been created that emulates the approach used by an audiologist in analysing an ABR waveform. Interpretation did not rely on one particular feature but brought together power and frequency analysis as well as consistency of subaverages. This provided a system that enhanced robustness to artefacts while maintaining classification accuracy.     

Development of a computational biomechanical model of the human upper‐airway soft‐tissues toward simulating obstructive sleep apnea

Numerous challenges are faced in investigations aimed at developing a better understanding of the pathophysiology of obstructive sleep apnea (OSA). The anatomy of the tongue and other upper‐airway tissues, and the ability to model their behavior, are central to such investigations. We present details of the construction and development of a soft‐tissue model of the human upper airway, with the ultimate goal of simulating obstructive sleep apnea. The steps taken to produce a representative anatomical geometry, of which the associated muscle histology is also captured, are documented. An overview of the mathematical models used to describe tissue behavior, both at a macro‐ and microscopic level, is given. A neurological model, which mimics the proprioceptive capabilities of the body, is described as it is applies to control of the active dynamics of the tongue. A simplified scenario, which allows for the manipulation of several environmental influences, is presented. It is demonstrated that the response of the genioglossus is qualitatively similar to that determined through experimental techniques. Furthermore, insights into the stress distribution developed within the tongue are discussed. It is shown that changes in almost any aspect of the breathing or physiological conditions invoke a significant change in the response of the airway dilators. The results of this study provide further evidence of the importance of modeling and simulation techniques as an aid in understanding the complex behavior of the human body. Clin. Anat. 27:182–200, 2014. © 2013 Wiley Periodicals, Inc.