WAP-based telemedicine applications.
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Computer Systems↗
Biomedical subjects
Y T Zhang
Publications and source records attributed to Y T Zhang.
Bionic wavelet transform: a new time-frequency method based on an auditory model.
In this paper, a new adaptive wavelet transform, named bionic wavelet transform (BWT), is developed based on a model of the active auditory system. The most distinguishing characteristic of BWT is that its resolution in the time-frequency domain can be adaptively adjusted not only by the signal frequency but also by the signal instantaneous amplitude and its first-order differential. The automatically adjusted resolution, even in a fixed frequency along the time-axis, is achieved by introducing the active control of the auditory system into the wavelet transform (WT). Other properties of BWT include that: 1) BWT is a nonlinear transform that has high sensitivity and frequency selectivity; 2) BWT represents the signal with a concentrated energy distribution; and 3) the inverse BWT can reconstruct the original signal from its time-frequency representation. In order to compare these three properties between BWT and WT, experiments were conducted on both constructed signals and real speech signals. The results show that BWT performs better than WT in these three aspects, and that BWT is appropriate for speech signal processing, especially for cochlear implants.
Algorithms↗
A new method for experimental simulation of EMG using multi-channel independent stimulation of small groups of motor units.
The experimental simulation method was based upon the separate activation of up to 10 small groups of motor units (MU) in an acute nerve-muscle preparation. The investigator was able to precisely control and systematically alter the features of MU pool activation strategies. No implicit assumptions were made regarding MU properties. The purpose of this study was to evaluate the validity of this method. Three criteria were formulated and found to be satisfied: First, in the time domain, visual and audio displays of simulated EMG were indistinguishable from physiological EMG. Secondly, in the frequency domain, power spectra of simulated EMG revealed the typical features of EMG recorded during voluntary activation in the cat. Thirdly, the well-known monotonic relationship between EMG magnitude and force was readily reproduced, although strictly linear relations were not found. In addition, the relationship between the pool's ensemble activation rate and EMG magnitude showed distinct gain compression, mostly attributable to signal cancellation.
Animals↗
Fuzzy EMG classification for prosthesis control.
This paper proposes a fuzzy approach to classify single-site electromyograph (EMG) signals for multifunctional prosthesis control. While the classification problem is the focus of this paper, the ultimate goal is to improve myoelectric system control performance, and classification is an essential step in the control. Time segmented features are fed to a fuzzy system for training and classification. In order to obtain acceptable training speed and realistic fuzzy system structure, these features are clustered without supervision using the Basic Isodata algorithm at the beginning of the training phase, and the clustering results are used in initializing the fuzzy system parameters. Afterwards, fuzzy rules in the system are trained with the back-propagation algorithm. The fuzzy approach was compared with an artificial neural network (ANN) method on four subjects, and very similar classification results were obtained. It is superior to the latter in at least three points: slightly higher recognition rate; insensitivity to overtraining; and consistent outputs demonstrating higher reliability. Some potential advantages of the fuzzy approach over the ANN approach are also discussed.
Algorithms↗
Theoretical analysis of a rectifying gap junction model.
Based on the experimental observations, an electrical circuitry model for a rectifying gap junction was developed in previous work. In order to show the physiological function for each element in the model, a theoretical analysis is carried out in this report. The results indicate that the gap junctional capacitance Cj newly introduced into the model plays a major role in determining the duration increase, the peak attenuation, and the peak delay on the postmembrane action potential. Also, a comparison between the newly proposed model and the widely accepted kinetic model by Giaume is made. The results show that the electrical circuitry model can not only describe the characteristics of Giaume's model but also allow the interpretation of some experimental phenomena that were not reflected in other gap junctional models.
Animals↗
A fast recursive-least-squares adaptive notch filter and its applications to biomedical signals.
A fast recursive-least-squares (FRLS) adaptive notch filter (ANF) for cancellation of sinusoidal interference from recorded biomedical signals is investigated. The FRLS ANF is derived by making an approximation to the conventional recursive-least-squares (RLS) ANF for computation economy. It outperforms the commonly adopted least-mean-squares (LMS) ANF, demonstrating a rapid and bandwidth-insensitive initial convergence. A novel application of the FRLS ANF is for the elimination of the tonal artefact in distortion product otoacoustic emission (DPOAE) signals.
Electronics, Medical↗
Synthesis and decomposition of transient-evoked otoacoustic emissions based on an active auditory model.
In this paper, transient-evoked otoacoustic emissions (TEOAE's) are synthesized by an active auditory model, and decomposed by continuous wavelet transform (CWT) to study the frequency-latency relationship and the generation of TEOAE signals. The controlled voltage sources that relate to the mobile mechanism of the outer hair cells (OHC's) are proposed to serve as the generation sources of TEOAE signals. The state-variable method is adopted to calculate the auditory model. The mother wavelet used in CWT is selected on basis of the model. The results of this study show that the simulated TEOAE signal is similar to the clinically detected ones not only in the time-domain waveform, but also in the frequency-latency relationship. It seems to be clear that the generation of TEOAE signals is related to the same active mechanism as the cochlear sharp frequency selectivity.
Adult↗
Estimation of distortion product otoacoustic emissions.
Distortion product otoacoustic emissions (DPOAE's) are acoustic signals generated from the cochlea when stimulated by dual tone stimulus. The measurement of the DPOAE's is useful in objectively assessing the hearing functionality of humans. The parameter estimation of the DPOAE's has been based on the fast Fourier transform (FFT) technique, which may not guarantee optimum performance in general. In this paper, we investigate the optimal maximum-likelihood estimator (MLE) for the DPOAE's. Experiments showed that the performance of the MLE is superior to those of the conventional FFT estimators. Furthermore, it is proven that the unwindowed FFT estimator is essentially the MLE when the stimulus tones are constrained to exhibit complete cycle within the data frame.
Acoustic Stimulation↗
The latex allergen Hev b 5 transcript is widely distributed after subcutaneous injection in BALB/c mice of its DNA vaccine.
BACKGROUND: DNA vaccines reduce IgE responses to selected allergens, but severe reactions to the expressed antigen may limit the usefulness of the technique in allergen immunotherapy. OBJECTIVE: We sought to determine the extent of spread of an injected DNA vaccine in mice. METHODS: We placed the gene encoding the potent Hevea latex allergen Hev b 5 in a mammalian expression vector and injected this DNA vaccine subcutaneously into BALB/c mice. At several times after injection, the presence of Hev b 5 transcript was determined in multiple tissues by RT-PCR. The identity of the amplification product was confirmed by Southern hybridization and restriction analyses. RESULTS: Hev b 5 RNA appeared at the injection site and in the lymph nodes, spleen, and lungs within 1 day after injection and persisted for at least 14 days. Hev b 5 RNA was also identified in the blood and tongue 14 days after injection. Antibody and cell-mediated responses to Hev b 5 were also noted in the immunized animals at later time points. As expected, animals injected with the identical plasmid containing the Hev b 5 DNA in the antisense orientation mounted no immune response to Hev b 5. CONCLUSIONS: The rapid and widespread appearance of the Hev b 5 transcript in the injected mice confirms that DNA is translocated from the injection site, transcribed, and expressed in immune and nonimmune tissues after injection. Controlling the extent and degree of expression in specific target tissues may allow therapeutic DNA vaccination with plasmids that encode potentially toxic allergens.
Allergens↗
EMG-force relation in dynamically contracting cat plantaris muscle.
The purpose of this study was to revisit the electromyographical (EMG)-force relationship of dynamically contracting muscles using direct measurements of EMG and force in cat hindlimb muscles during locomotion. EMG signals were recorded from the plantaris muscle using bipolar indwelling wire electrodes, and the corresponding forces were measured using a tendon force transducer. Force-time histories of cat plantaris muscle were predicted by estimating selected force parameters from EMG and timing parameters, and then constructing two smoothly fitting quintic spline functions from the estimated force parameters. The force predictions did not contain information on force-length or force-velocity properties of the cat plantaris and did not use instantaneous contractile conditions as input. It was found that two smoothly fitting quintic spline functions provided the required properties to approximate plantaris force-time histories accurately, and approximations of the force-time histories using EMG and timing parameters as input for the quintic splines were good. The root mean square errors (RMS) of the predicted compared to the actual plantaris forces were smaller than corresponding results reported in the literature, even though the prediction model did not require the force-length-velocity properties or the instantaneous contractile conditions of the target muscles as input. From the results obtained in this study, it appears that force-time histories of the cat plantaris muscle during locomotion can be predicted adequately from information obtained using EMG and video records, without information on either the force-length and force-velocity properties, or the instantaneous contractile conditions of the muscle.
Algorithms↗
[Multivariate analysis on prognostic factors of non-Hodgkin's lymphoma].
OBJECTIVE: To predict the prognostic factors and to improve the response and survival in intermediate-grade and high-grade non-Hodgkin lymphoma (NHL). METHODS: 200 patients with intermediate-grade and high-grade NHL were treated with chemotherapy. A multivariate Cox model was used to analyse the prognostic factors that significantly affect the treatment outcome. The variables examined included: sex, age, clinic stage of disease, B symptoms, extranodal sites, bone marrow involvement, tumor bulk, performance status (ECOG) and malignancy grades. RESULTS: Multivariate analysis showed that performance status, the number of extranodal sites, pathologic malignancy grade and tumor bulk were significantly independent prognostic factors. These factors were put together to construct a prognostic index formula. The index partitioned the patients into low risk group (PI -2.43(-)-1.30), intermediate risk group (PI -1.29-1.0) and high risk group (PI > 1.0) giving 5-year survival rates of 76.0%, 21.6% and 7.4%, respectively. CONCLUSION: The prognostic index formula and subgroups could serve as a reference to distinguish patients requiring more intensive chemotherapy and autologous stem cell transplantation from those who should be treated with standard regimens in order to improve the prognosis.
Adolescent↗
Movements of vertebrae during manipulative thrusts to unembalmed human cadavers.
OBJECTIVE: The purpose of this study was to measure the relative movements of vertebrae during manipulative thrusts to unembalmed post-rigor mortis human cadavers. SETTING: The investigation was conducted in the gross anatomy laboratory at the University of Calgary. SUBJECTS: Two 77-yr-old, unembalmed, post-rigor mortis, male cadavers were used. INTERVENTIONS: The movements of vertebrae were investigated by using high-speed cinematography to record the movements of bone pins threaded into T10, T11 and T12 during spinal manipulative therapy to unembalmed post-rigor human cadavers. A single clinician delivered a series of posterior-to-anterior (p-to-a) thrusts to the right transverse process of either T10, T11 or T12, using a reinforced hypothenar contact. Relative p-to-a and lateral translations, as well as axial and sagittal rotations, in T10-T11 and T11-T12 were calculated. Corresponding p-to-a forces exerted by the clinician onto the cadaver were recorded using a pressure pad. MAIN RESULTS: Significant relative movements were measured primarily between the targeted and immediately adjacent vertebrae during the thrusts. Vertebral pairs remained slightly 'hyper-extended' after the rapid thrusts to T11, when the p-to-a forces returned to preload levels. CONCLUSIONS: These findings may be useful for the understanding of the deformation behavior of the vertebral column during therapeutic manipulation. A fully three-dimensional analysis of all six degrees of freedom, using a larger number of unembalmed cadavers, would be useful in clarifying the relationship between the externally applied forces and the observed relative movement patterns of the vertebrae.
Aged↗
Vibromyography as a quantitative measure of muscle force production.
This study was undertaken to investigate the use of vibromyography (VMG) as a tool for quantifying skeletal muscle force production. Fourteen healthy volunteers were pretested using a Cybex isokinetic dynamometer to determine their isometric quadricep maximum voluntary contraction (MVC) values. On the basis of these results, the subjects were separated into two groups: high-force ("HF" MVC mean = 289 ft.lb., range 254-330) and low-force ("LF" MVC mean = 154 ft.lb., range 101-198). A vibromyographic piezoelectric accelerometer (Dytran 3115A) and electromyographic (EMG) surface electrodes were affixed to the rectus femoris muscle and recordings were obtained at 20, 40, 60, 80, and 100% MVC. Root mean squares, median and mean values were computed from digitized data in the time domain while peak values were calculated from a fast Fourier transform for both the VMG and EMG data. A two-way repeated measures MANOVA using relative values and a linear regression model using absolute values were studied using BMDP and MiniTab software. Linear correlations were found between quadricept force and all EMG variables (R2 range 0.71-0.90) except peak (R2 = 0.39). The relationship between VMG and force was less linear (R2 range 0.19-0.69) because VMG values reach a plateau or even drop at 80% and 100% MVC. The HF-LF group differences were significant (p < 0.05), for all VMG values with the exception of root mean squares, but were not significant (p > 0.05) for all four EMG values. This study shows that, while EMG can discriminate force production within a given subject, VMG is a better discriminator of absolute muscle force values between subjects, particularly up to 60% MVC.
Adult↗
Mechanism of electrically elicited muscle vibrations in the in situ cat soleus muscle.
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Animals↗
Screening of vibroarthrographic signals via adaptive segmentation and linear prediation modeling.
This paper proposes a noninvasive method to diagnose chondromalacia patella at its early stages by recording knee vibration signals (also known as vibroarthrographic or VAG signals) over the mid-patella during normal movement. An adaptive segmentation method was developed to segment the nonstationary VAG signals. The least squares modeling method was used to reduce the number of data samples to a few model parameters. Model parameters along with a few clinical parameters and a signal variability parameter were then used as discriminant features for screening VAG signals by applying logistic and discriminant algorithms. The system was trained using ten normal and eight abnormal signals. It correctly screened a separate test set of ten normal and eight abnormal signals except for one normal signal. The proposed method should find use as an alternative technique for diagnosis of knee joint pathology or as a test before arthroscopy or major knee surgery.
Algorithms↗
The behavior of rectus femoris and vastus lateralis during fatigue and recovery: an electromyographic and vibromyographic study.
Eleven subjects performed isometric knee extensor contractions at maximum voluntary contraction (MVC), and at 70% of MVC preceding and following a fatigue test. The fatigue test consisted of a continuous isometric knee extensor contraction at 70% of MVC. The purpose of this study was to describe and compare the behavior of electromyographic (EMG) and vibromyographic (VMG) signals of rectus femoris (RF) and vastus lateralis (VL) muscles during a fatigue-recovery protocol by analyzing the median frequency (MDF) and the root mean square (RMS) values obtained from these signals. EMG and VMG signals of RF and VL muscles were recorded using bipolar surface electrodes and miniature accelerometers, respectively. The MDF of EMG and VMG signals of the two muscles decreased during muscle fatigue and returned to the pre-fatigue values during the fifteen minute recovery period. Assuming a relation between the decrease of the MDF of the EMG signals and a decrease in the conduction velocity of the action potentials in the muscle fibers with fatigue, the subsequent restoration of the MDF indicates that muscle fiber conduction velocity returned to a pre-fatigue state within a short time. The decrease in the MDF of the VMG signals seems to be associated with low-frequency tremor that typically occurs towards the end of exhausting isometric contractions. The RMS of the EMG increased in both RF and VL throughout fatigue and recovery, and may be attributed to increased muscle activation. The RMS values of the VMG do not appear to change in a systematic way during the fatigue and recovery periods.
Adult↗
Relationships of the vibromyogram to the surface electromyogram of the human rectus femoris muscle during voluntary isometric contraction.
The relationship between vibromyographic (VMG) and electromyographic (EMG) signals during isometric contraction of the human rectus femoris muscles was studied. The method of least squares was used to obtain the best-fitting linear regression model to the root mean squared (RMS) values of the VMG and the EMG. It is shown that for the rectus femoris of four subjects, a linear VMG versus EMG relationship exists during 20-80% of the maximum voluntary contraction (MVC) at 30 degrees, 60 degrees, and 90 degrees of knee joint flexion angles. The relation between the VMG and the EMG may be explained by the order recruitment of motor units and by the "onion-skin" phenomenon of the firing rates of recruited motor units in the regulation of muscle force production as reported in electro-neurophysiologic studies.
Adult↗
Localization of knee joint cartilage pathology by multichannel vibroarthrography.
This paper proposes non-invasive techniques to localize sound or vibroarthrographic (VAG) signal sources in human knee joints. VAG signals from normal subjects, patients who subsequently underwent arthroscopy, and cadavers with arthroscopically-created lesions, obtained by stimulation with a finger tap over the mid-patella and swinging movement of the leg, were analyzed for time delays using cross-correlation functions for source localization. Correct results were obtained for 13 of the 14 subjects tested by finger stimulation, and for 11 of the 12 subjects whose VAG signals during swinging movement were analyzed. The techniques could be valuable in the diagnosis and treatment of knee pathology before and after joint surgery or drug therapy.
Arthroscopy↗