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Biomedical subjects

H Nazeran

Publications and source records attributed to H Nazeran.

11 recordsLinked to original sources
PubMed2004

A device for investigating neuromuscular control in the human masticatory system.

A new apparatus has been developed to study the control of mastication in humans. The subject places his/her teeth on fixed upper and mobile lower bite plates; the device then enables opening and closing movements of the lower jaw against a controlled resistance. It is also possible to vary the number of teeth in contact with the device during an experiment from the entire dental arcade to a single tooth. The specially designed lower bite plate is dynamic and allows for both rotation and translation of the lower jaw during movement, thus, permitting the natural curvilinear trajectory of the jaw. The lower bite plate can follow chewing initiated by the subject without resisting the movement ('no force' mode) via a dedicated microprocessor controlled compensation mechanism. Another function of the device is to inject a constant predetermined load onto the lower bite plate so that the subject 'chews' against a fixed resistance simulating rapidly yielding food bolus ('fixed force' mode). The device can be programmed to increase or decrease the force during the closing or opening phase of chewing by feeding the position information into the force compensation system so both position and force change in parallel, hence, simulating a bite onto a non-yielding, or sticky, food bolus ('normal chewing' mode). By use of a jaw position compensation mechanism, the device can actively move the lower jaw, following any imposed position pattern ('position controlled' mode). The chewing simulator also has a mode that holds the position at a fixed level and allows the force to change ('position hold' mode). Furthermore, the device can inject additional rapid or slow forces or displacements onto the lower bite plate in order to elicit reflexes so that the response of jaw muscles to such stimuli can be examined at various jaw positions, force levels, phases of motion and velocities. The different modes of the apparatus can be used to study the operation and feedback control of human mastication; in particular whether modulations in jaw muscle activity and reflexes are due to changes in force, velocity, position, chewing cycle phase or a combination of these factors.

Afferent Pathways↗
PubMed2004

Reducing power line interference in digitised electromyogram recordings by spectrum interpolation.

Interference from power lines (50 or 60 Hz) is the largest source of extraneous noise in many bio-electric signals and is within the bandwidth of many such signals. In this study, two different methods were compared for their efficacy in removing 50 Hz noise added to surface electromyogram (EMG) signals free of power line interference. The first was a simple second-order recursive digital notch filter. The second was an approach called spectrum interpolation, in which it is assumed that the magnitude of the original 50 Hz component of the EMG signal can be approximated by interpolation of the amplitude spectrum of the signal. When the spectrum was based on records containing an integer number of cycles of 50 Hz interference, and the frequency resolution was finer than 1 Hz, spectrum interpolation performed similarly to, or significantly better than, the notch filter (p < 0.01). It was also possible to make spectrum interpolation more robust than the notch filter. The Pearson squared correlation coefficient r2 between clean signals and signals processed using the notch filter was reduced from 0.98 to 0.65 when the interference frequency was increased by 0.5 Hz, but r2 for spectrum interpolation at 0.2 Hz resolution was only reduced from 0.99 to 0.85 if spectral values between approximately 49.5 and 50.5 Hz were modified by interpolation.

Artifacts↗
PubMed2004

Compensation of limb weight on interfaced raw torque signals from a KIN-COM dynamometer to an AMLAB workstation.

The effect of gravity should be considered when using isokinetic devices to measure human movement performance. In most isokinetic dynamometers gravity compensation is controlled by software through a gravity correction option. However in some complex research protocols the dynamometer signal acquisition and processing capability is not adequate to effectively synchronize or process a wide range of captured signals. Therefore when the force/torque signals from a commonly used dynamometer such as KIN-COM are interfaced into a signal processing workstation such as AMLAB, it is necessary to further process the received raw signals for gravity correction. The aim of this study was to evaluate the effectiveness of an AMLAB-based instrument designed for gravity compensation of raw torque signals acquired from a KIN-COM dynamometer. To check the accuracy of weight compensation within the AMLAB, environment, torque signals produced by a known weight during a 180-degree range of KIN-COM lever arm movement were compared with and without weight compensation. The results indicated that this technique is an accurate means for weight compensation when raw torque signals from a KIN-COM dynamometer are interfaced to an AMLAB workstation.

Biomechanical Phenomena↗
PubMed2003

An integrated AMLAB-based system for acquisition, processing and analysis of evoked EMG and mechanical responses of upper limb muscles.

An integrated multi-channel AMLAB-based data acquisition, processing and analysis system has been developed to simultaneously display, quantify and correlate electromyographic (EMG) activity, resistive torque, range of motion, and pain responses evoked by passive elbow extension in humans. The system was designed around the AMLAB analog modules and software objects called ICAMs. Each channel consisted of a time and frequency domain block, a torque and angle measurement block, an experiment number counter block and a data storage and retrieval block. The captured data in each channel was used to display and quantify: raw EMG, rectified EMG, smoothed rectified EMG, root-mean-squared EMG, fast Fourier transformed (FFT) EMG, and normalized power spectrum density (NPSD) of EMG. Torque and angle signals representing elbow extension measured by a KIN-COM dynamometer during neural tension testing, as well as signals from an electronic pain threshold marker were interfaced to AMLAB and presented in one integrated display. Although this system has been designed to specifically study the patterns and nature of evoked motor responses during clinical investigation of carpal tunnel syndrome (CTS) patients, it could equally well be modified to allow acquisition, processing and analysis of EMG signals in other studies and applications. In this paper, we present for the first time the steps involved in the design, implementation and testing of an integrated AMLAB-based system to study and analyse the mechanically evoked electromyographic, torque and ROM signals and correlate various levels of pain to these signals. We also present samples of resistive torque ROM, and raw and processed EMG recordings during passive elbow extension.

Adult↗
PubMed1998

ECG compression: evaluation of FFT, DCT, and WT performance.

This work investigates a set of ECG data compression schemes to compare their performances in compressing and preparing ECG signals for automatic cardiac arrhythmia classification. These schemes are based on transform methods such as fast Fourier transform (FFT), discrete cosine transform (DCT), wavelet transform (WT), and their combinations. Each specific transform is applied to a pre-selected data segment from the MIT-BIH database and then compression is performed in the new domain. These transformation methods are known as an important class of ECG compression techniques. The WT has been shown as the most efficient method for further improvement. A compression ratio of 7.98 to 1 has been achieved with a percent of root mean square difference (PRD) of 0.25%, indicating that the wavelet compression technique offers the best performance over the other evaluated methods.

Algorithms↗
PubMed1997

Power spectrum analysis of human femoral rotations during gait.

Femoral rotational waveforms sampled at 15 Hz for a duration 20 s satisfy the sampling rate and frequency resolution requirements of such waveforms during walking. Spectral analysis provides a unique signature of the frequency composition of such signals. This identity may prove useful in characterising human gait and could be of value in future studies of walking in health and disease.

Biomedical Engineering↗
PubMed1996

The enteric neural network and three dimensional computer modelling of intestinal peristalsis.

A computer model of the enteric nervous system has been developed using MATLAB in order to determine the extent to which the nature of intestinal activity can be explained by our current understanding of the projections and connectivity of enteric neurons. The model is based on repeated, identical overlapping modules, each of which contains the same number of neurones and circular muscle. The connections between modules were derived from microanatomical data. This simple model explains some characteristic features of the generation of an intestinal motor pattern.

Animals↗
PubMed1995

Biomedical image processing in pathology: a review.

Pathologists make a diagnostic decision by viewing a specimen and measuring various diagnostically important attributes of an isolated object such as size, shape, darkness, colour and texture. This is a complex process. In recent years, computer-aided image processing and analysis systems have played a significant role in quantitative pathology. This paper summarises basic image processing and analysis techniques and reviews related work in pathology and cytology based on computational image processing since 1987. Firstly, we present a general introduction to image enhancement, segmentation, morphometry and visualisation for those medical colleagues who may not have the necessary background in this area. (The mathematical treatment is kept to minimum and appropriate references are cited to satisfy the more mathematically oriented readers. Selected examples are provided to demonstrate the effects of various basic image processing algorithms on a MRI scan. It should be emphasised that the reviewed techniques are generally used as preprocessing steps in analysing microscopic images and powerful algorithms are more sophisticated and problem-specific.) Secondly, we review image cytometric and histometric methods, standards, calibration and applications. Finally, we touch upon three dimensional confocal image processing and analysis, applications of artificial neural networks, and optical disk database management for recording and retrieving a large number of digitised high resolution images. The development of integrated optical microscope and computer, systems is also briefly described.

Artificial Intelligence↗
PubMed1995

Development of a low cost microP-based blood gas monitor.

A low cost microprocessor-based system for continuous in-vivo measurement of blood pH and pCO2 using a biosensor is being developed. The biosensor is a pH Ti2O3 ISFET (Ion Sensitive Field Effect Transistor) with a sensitivity of -56 mV/pH and a linear response over physiologically meaningful blood pH range of 6.5 to 8.0. The ISFET chip is bonded onto a printed circuit board substrate to enable reliable and robust connections to three wires. The small sensor tip sized of 0.95 mm facilitates its incorporation into a catheter tip and its placement into a rat's artery. A microcontroller supervises preusage calibration, data logging, display of alphanumeric information on a LCD (liquid crystal display) unit, and resettable visual & audio alarm indicators. Preliminary clinical testing are underway to perfect the system and use it on a routine basis to monitor the physiological state of laboratory animals during neurophysiological experiments.

Animals↗
PubMed1992

Exposure to free radicals alters ionic calcium transients in isolated adult rat cardiac myocytes.

Oxygen-derived free radical production has been documented to occur on reperfusion of the ischemic myocardium. Intracellular ionic calcium ([Ca++]i) levels in isolated adult rat cardiac myocytes exposed to free radicals were evaluated using fura-2. The effect of different time periods of free radical exposure on altering [Ca++]i was examined. Myocytes were either exposed to the free radical generating system continuously or exposed for 5 or 10 minutes and then returned to the HEPES buffer. Myocytes maintained in HEPES buffer or the HEPES buffer containing purine and iron-loaded transferrin continued to stimulate, exhibited relatively uniform 340/380 nm ratios and maintained a rod shape. Continuous exposure to free radicals resulted in a significant increase in [Ca++]i. Myocytes became unresponsive to stimulation at 31 +/- 7 (SE) minutes and eventually exhibited contracture. Exposure to the free radical generating system for 10 minutes resulted in a response similar to continuous exposure. Myocytes exposed to the generating system for 5 minutes exhibited regular calcium transients for 55 +/- 5 minutes. Thus, even a brief period of free radical exposure alters calcium flux and may induce subsequent myocardial damage.

Animals↗