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Determination of peak-ratio by digital turns-amplitude analysis on line
R Liguori1, K Dahl, S Vingtoft
1Department of Clinical Neurophysiology, Hvidovre Hospital, University of Copenhagen, Denmark.
Abstract:
In a previous study the peak-ratio of turns to mean amplitude of the EMG interference pattern obtained from tape recordings identified 80% of patients with myopathy. In order to obtain the peak-ratio during the examination using the mean amplitude as an indication of force a digital turns-amplitude computer with a TMS 320/10 digital signal processor was developed. The EMG was analysed with a 12 bit resolution and a sampling rate of 100 kHz. In 492 samples from the brachial biceps muscle of controls, patients with myopathy and neuropathy, the digital method gave about the same turns-amplitude values as the analogue analyser. Control material for on line analysis of the peak-ratio was obtained in the brachial biceps, the abductor pollicis brevis, the medial vastus and the anterior tibial muscles of 20 subjects.