Simulation Techniques in Electromyography (original) (raw)
Related papers
Simulation of concentric needle EMG motor unit action potentials
Muscle & Nerve, 1988
~ ~~ Computer simulations of motor unit action potentials (MUAPs) as measured by a concentric needle (CN) electromyography (EMG) electrode in normal motor units (MUs) indicated that the MUAP amplitude is determined mainly by the proximity of the electrode to the closest muscle fiber. The area and duration of the simulated MUAPs were affected by all muscle fibers in front of the active recording surface but mainly by those that were less than 2 and 2.5 mm, respectively, from the active recording surface. The MUAP area was also affected by the proximity of the electrode to the closest muscle fiber. The number of phases of the simulated MUAPs increased when the dispersion of the arrival times of individual muscle fiber APs at the electrode was increased. Increased temporal dispersion of APs decreased the MUAP amplitude and area slightly but did not affect the MUAP duration. It is inferred that different features of the CN MUAP are determined by the distribution of muscle fibers within different portions of the MU territory and thus provide complementary information about the MU architecture.
Simulation of the normal concentric needle electromyogram by using a muscle model
Clinical Neurophysiology, 2001
Objectives: To study the correlation between anatomical parameters and EMG signals by means of simulations. Methods: A mathematical model of the electrical activity from muscle ®bres and motor units has been developed. The electrical ®elds around the muscle ®bres are simulated using a line source model. The model permits the simulation of single muscle ®bre action potentials obtained by SFEMG, concentric and Macro EMG electrodes. By using appropriate anatomical parameters EMG recordings with these electrodes can be simulated. The model is¯exible and permits a number of anatomical parameters to be changed such as; number of muscle ®bres in a motor unit, ®bre diameter distribution, and motor end-plate geometry. Some physiological parameters can be optionally varied; ®ring rate, threshold for recruitment, jitter. Results: In this study, simulations of CNEMG are performed and the in¯uence of a number of parameters on the CNEMG signal is studied. It is shown that the model produces motor unit potentials reasonably well resembling those from live recordings. More important is however the relative change in MUP parameters when certain conditions are changed; number of muscle ®bres in a motor unit, recording position, muscle ®bre diameters and some special effects of the recording conditions. Conclusions: The simulated muscle and corresponding EMG recording can be used both as a research tool and for teaching.
Analysis of amplitude and area of concentric needle EMG motor unit action potentials* 1
Electroencephalography …, 1988
Computer simulations indicate that measurements of the area of motor unit action potentials (MUAPs) recorded with a concentric needle electrode could be useful in differentiating between neuropathy and myopathy. However, MUAP area varies markedly when the position of the recording electrode is changed only slightly within the motor unit territory, mainly because of the changes in the MUAP amplitude produced by only slight electrode movements. The ratio of MUAP area to amplitude is much less affected by changes in electrode position and measures the 'thickness' of the MUAP wave form. We found that the MUAP area:amplitude ratio was reduced in myopathy even when the MUAP amplitude was normal or increased. In patients with neuropathy, the MUAP amplitude and area both tend to be increased while their ratio is normal or increased. The diagnostic yield obtained from MUAP area, amplitude and their ratio in combination was similar to that obtained using measurements of MUAP duration. Unlike the MUAP duration, the MUAP area, amplitude and area : amplitude ratio are robust features of the MUAP in that they are less sensitive to the signal-to-noise ratio and inter-operator differences in signal selection.
Analysis of amplitude and area of concentric needle EMG motor unit action potentials
Electroencephalography and Clinical Neurophysiology, 1988
Computer simulations indicate that measurements of the area of motor unit action potentials (MUAPs) recorded with a concentric needle electrode could be useful in differentiating between neuropathy and myopathy. However, MUAP area varies markedly when the position of the recording electrode is changed only slightly within the motor unit territory, mainly because of the changes in the MUAP amplitude produced by only slight electrode movements. The ratio of MUAP area to amplitude is much less affected by changes in electrode position and measures the 'thickness' of the MUAP wave form. We found that the MUAP area:amplitude ratio was reduced in myopathy even when the MUAP amplitude was normal or increased. In patients with neuropathy, the MUAP amplitude and area both tend to be increased while their ratio is normal or increased. The diagnostic yield obtained from MUAP area, amplitude and their ratio in combination was similar to that obtained using measurements of MUAP duration. Unlike the MUAP duration, the MUAP area, amplitude and area : amplitude ratio are robust features of the MUAP in that they are less sensitive to the signal-to-noise ratio and inter-operator differences in signal selection.
Principal component analysis of the features of concentric needle EMG motor unit action potentials
Muscle & Nerve, 1989
Motor unit action potentials (MUAPs) were recorded from the biceps muscle of normal subjects and of patients with nerve or muscle diseases. Principal component analysis of the MUAP amplitude, area, area/amplitude ratio, duration, and the number of turns and phases produced three components that among them contained 90% of the variance of the data set. Thus the dimensionality of data was reduced from six to three. The first component reflected changes in the size of the MU, whereas the second reflected variations in the arrival time at the recording electrode of the action potentials of muscle fibers in the motor unit. The third factor reflected local loss of muscle fibers within the MU territory. Patterns of variations in the three components were different in patients with neuropathy and myopathy.
IEEE Transactions on Biomedical Engineering
Multi-channel intramuscular EMG (iEMG) provides information on motor neuron behavior, muscle fiber (MF) innervation geometry and, recently, has been proposed as a means to establish a human-machine interface. Objective: to provide a reliable benchmark for computational methods applied to such recordings, we propose a simulation model for iEMG signals acquired by intramuscular multi-channel electrodes. Methods: we propose several modifications to the existing motor unit action potentials (MUAPs) simulation methods, such as farthest point sampling (FPS) for the distribution of motor unit territory centers in the muscle cross-section, accurate fiber-neuron assignment algorithm, modeling of motor neuron action potential propagation delay, and a model of multi-channel scanning electrode. Results: we provide representative applications of this model to the estimation of motor unit territories and the iEMG decomposition evaluation. Also, we extend it to a full multichannel iEMG simulator using classic linear EMG modeling. Conclusions: altogether, the proposed models provide accurate MUAPs across the entire motor unit territories and for various electrode configurations. Significance: they can be used for the development and evaluation of mathematical methods for multichannel iEMG processing and analysis.
Simulation of electromyographic signals
Journal of Electromyography and Kinesiology, 1993
A technique for simulating electromyographic (EMG) signals is reported. The four step method is physiologically based and begins with the modelling of a cross-section of a muscle. Within this cross-section motor unit territories of various sizes are randomly distributed and within a detection area at the centre of the cross-section individual muscle fibres are modelled and randomly assigned to appropriate motor units. For the motor units with fibres in the detection area, recruitment and firing time behaviours, as a function of an assumed level of contraction, are then simulated. For each active motor unit with fibres in the detection area, motor unit action potentials (MUAPs) are created using a line source volume conductor model. MUAPs can be created for various types of detecting electrodes including concentric and monopolar needle electrodes. Finally, the individual motor unit firing time behaviours and MUAPs are combined to create a complete EMG signal. The routines are interfaced through a series of user-friendly menus and forms, are implemented in C and can be run on any IBM compatible machine. Exemplary data are presented along with results from attempts to evaluate the model. Suggested uses of the simulation package, especially with respect to EMG signal decomposition, are discussed.
Annals of Biomedical Engineering, 1993
From regular one-channel registrations of single muscle fiber action potential no measures on the recording configuration can be derived. When multichannel recordings are made, experimental parameters such as the distance between muscle fiber and needle electrode can be estimated. With the help of a volume conductor model, the single fiber activity at each of the electrodes can be predicted as a function of the recording conditions. Within known physical and physiological constraints such a model approach can be inverted (the inverse model) and used to estimate basic experimental conditions. From eight simultaneous single fiber action potential recordings we estimated (a) the distance between fiber and needle, (b) the axial position of the needle with respect to the muscle fiber, (c) a factor related to the muscle tissue anisotropy, and (d) a factor combining the muscle fiber diameter and the effective muscle tissue conductivity. With the help of a model describing the influence of the needle shaft it is made plausible that the needle inhomogeneity influences the results of the proposed procedure.
Macro electromyography, an update
Muscle & Nerve, 2011
The macro electromyography method was developed in the 1980s. 1 Since then, technical modifications have been made, and a number of conditions have been explored. 2,3 This study is a methodological introduction and an update of findings in some nerve-muscle disorders. The spike component of a motor unit potential (MUP) recorded by a concentric or monopolar needle electromyography (EMG) electrode is generated primarily by fibers within 1-2 mm of the needle recording area. Given that a MUP's typical anatomical reach is 5-15 mm in diameter, it follows that conventional EMG is unable to record activity from the entire motor unit. Such information could promote understanding of muscle in health and disease. Macro EMG, with its large recording area, appears to provide this information by recording the activity from most of the fibers in a given motor unit. The value of combining macro EMG with single-fiber EMG and conventional EMG recordings is discussed.