Method and apparatus for measuring and displaying a haemodynamic parameter
First Claim
1. A method of measuring and displaying a haemodynamic parameter comprising the steps of:
- acquiring a video image of a region of interest on the skin of a subject;
processing the video image to obtain a first remote reflectance photoplethysmogram signal for the region of interest;
performing signal averaging on the first remote reflectance photoplethysmogram signal for the region of interest to obtain a reference average pulse waveform;
splitting the region of interest into plural subsidiary regions of interest and processing the video signal to obtain a subsidiary remote reflectance photoplethysmogram signal for each subsidiary region of interest, performing signal averaging on each subsidiary remote reflectance photoplethysmogram signal to obtain a subsidiary average pulse waveform for each subsidiary region of interest;
determining the phase difference between each subsidiary average pulse waveform and the reference average pulse waveform; and
displaying as said haemodynamic parameter the phase difference for each subsidiary region of interest.
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Accused Products
Abstract
Haemodynamic parameters such as the amplitude and phase of a pulse wave passing through a region of interest can be obtained from a video image of the exposed skin of a patient by processing of the reflectance photoplethysmographic signal using signal averaging. The region of interest is defined and a reflectance photoplethysmographic signal obtained by finding the mean pixel intensity across the region of interest for each video frame. Signal averaging is performed on the resulting pulsatile waveform by detecting peaks in the waveform, selecting those parts of the waveform which lie within a window centered on the peaks, and summing the selected parts of the waveform to find an average pulse waveform. The region of interest is then divided into sub-regions and an average pulse waveform for the video sequence is found for each of the sub-regions in the same way. The amplitudes of the average pulse waveforms for the sub-regions can be measured and displayed, for example as a spatial map across the region of interest. The phase of the average pulse waveforms in the sub-regions in the sub-regions relative to the average pulse waveform for the whole region of interest can be measured and displayed, again as a spatial map. The phase and amplitude maps give an indication of the quality of perfusion across the region of interest.
10 Citations
13 Claims
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1. A method of measuring and displaying a haemodynamic parameter comprising the steps of:
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acquiring a video image of a region of interest on the skin of a subject; processing the video image to obtain a first remote reflectance photoplethysmogram signal for the region of interest; performing signal averaging on the first remote reflectance photoplethysmogram signal for the region of interest to obtain a reference average pulse waveform; splitting the region of interest into plural subsidiary regions of interest and processing the video signal to obtain a subsidiary remote reflectance photoplethysmogram signal for each subsidiary region of interest, performing signal averaging on each subsidiary remote reflectance photoplethysmogram signal to obtain a subsidiary average pulse waveform for each subsidiary region of interest; determining the phase difference between each subsidiary average pulse waveform and the reference average pulse waveform; and displaying as said haemodynamic parameter the phase difference for each subsidiary region of interest. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification