[Methodologic studies in dynamic EMG mapping based on the Hilbert transformation].

Abstract

On the basis of Discrete Hilbert Transformation spectral parameters for dynamic EMG analysis can be introduced. Within analysis intervals which are used in the same manner as in spectral analysis, the momentary power of EMG frequency bands can be computed as time series of the same interval duration. A close connection exists between momentary power and the current phenomenology of power spectral analysis because the momentary power of a defined frequency band can be seen as the exact dynamic equivalent of the corresponding mean power value deduced from the power spectrum. A multichannel EMG recording (greater than or equal to 16 channels) makes the representation of the topographical distribution of the spectral parameter by a coloured map possible. Additionally, the momentary power can be used to calculate map sequences. In this way, changes of EMG activity can be quantified by map sequences of an arbitrary time resolution. By calculation of momentary frequency via DHT an artefact detection scheme for ECG interference can be suggested. A completion of this methodology can be carried out by applications of adaptive filtration procedures. Using this concept of EMG processing, a new and common methodical basis of EMG power spectral analysis can be introduced.