METHOD AND SYSTEM FOR SIGNAL ANALYSIS

摘要

An image of a human, animal or machine subject, is analysed to detect regions which include strong periodic intensity variations, such as a photoplethysmogram (PPG) signal in a human or animal, or some periodic vibration in a machine. The image is divided into plural regions of fixed order is fitted to a representative intensity signal for that region. The poles of the fitted autoregressive model are thresholded by magnitude to select only the pole or poles with a magnitude greater than the threshold. The pole magnitude therefore acts as a signal quality index. The dominant pole is representative of the strongest periodic information and the frequency of that spectral component can be derived from the phase angle of the pole. The image may be redisplayed with image attributes, e.g. colour-coding, according to the pole magnitude in each region of interest and/or the dominant pole phase angle in each region of interest. In the case of a PPG image signal this can give maps of heart rate and breathing rate.

主权项

1. A method of analyzing an image of a subject to identify spatial areas which contain periodic intensity variations representing valid temporal information about the subject, comprising the steps of:
dividing said image into a plurality of spatial areas and obtaining respective signals representative of an image intensity for each spatial area; spectrally analyzing the intensity variations of each representative signal by fitting respective autoregressive models to the representative signals, each of the fitted autoregressive models comprising a plurality of poles representing spectral components of the intensity variations of each representative signal, each pole having a magnitude dependent upon the strength of the spectral component and a phase angle dependent upon the frequency of the spectral component; selecting those spatial areas whose fitted autoregressive model has a dominant pole whose magnitude is greater than a predetermined threshold and identifying those spatial areas as containing periodic intensity variations representing said valid temporal information.