Methods and apparatus for estimating a physiological parameter using transforms
First Claim
1. A method for use in a system for determining a physiological parameter, the system having a sensor for transmitting electromagnetic energy of first and second wavelengths toward a tissue sample and detecting the electromagnetic energy after scattering of the electromagnetic energy by the tissue sample, thereby generating a first signal corresponding to the first wavelength and a second signal corresponding to the second wavelength, the method comprising:
- transforming the first and second signals into a frequency domain, thereby generating third and fourth signals;
generating a ratio signal using the third and fourth signals;
applying more than two variable weights to various parts of the ratio signal, the variable weights being derived with reference to at least one of the third and fourth signals;
for each of a plurality of ratio values in the ratio signal, generating an associated weighted sum corresponding to each time the ratio signal coincides with the ratio value associated with the sum; and
selecting a best ratio value from the plurality of ratio values based on the sums associated therewith.
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Abstract
A method for use in a system for determining a physiological parameter is described. The system has a sensor for transmitting electromagnetic energy of first and second wavelengths toward a tissue sample and detecting the electromagnetic energy after scattering of the electromagnetic energy by the tissue sample, thereby generating a first signal corresponding to the first wavelength and a second signal corresponding to the second wavelength. The first and second signals are transformed into the frequency domain, thereby generating third and fourth signals. A ratio signal is generated using the third and fourth signals. For each of a plurality of ratio values an associated sum is generated corresponding to the number of times the ratio signal coincides with the ratio value associated with the sum. Contributions to each sum are weighted in accordance with the third signal. A best ratio value is selected from the plurality of ratio values based on the sums associated therewith.
426 Citations
32 Claims
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1. A method for use in a system for determining a physiological parameter, the system having a sensor for transmitting electromagnetic energy of first and second wavelengths toward a tissue sample and detecting the electromagnetic energy after scattering of the electromagnetic energy by the tissue sample, thereby generating a first signal corresponding to the first wavelength and a second signal corresponding to the second wavelength, the method comprising:
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transforming the first and second signals into a frequency domain, thereby generating third and fourth signals; generating a ratio signal using the third and fourth signals; applying more than two variable weights to various parts of the ratio signal, the variable weights being derived with reference to at least one of the third and fourth signals; for each of a plurality of ratio values in the ratio signal, generating an associated weighted sum corresponding to each time the ratio signal coincides with the ratio value associated with the sum; and selecting a best ratio value from the plurality of ratio values based on the sums associated therewith. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. An apparatus for determining a physiological parameter, comprising:
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a sensor for transmitting electromagnetic energy of first and second wavelengths toward a tissue sample and detecting the electromagnetic energy after scattering of the electromagnetic energy by the tissue sample, the sensor generating a first signal corresponding to the first wavelength and a second signal corresponding to the second wavelength; and a signal processor for calculating an estimate of the physiological parameter using the first and second signals, the signal processor having a central processing unit which is operable to transform the first and second signals into a frequency domain, and thereby generate third and fourth signals; generate a ratio signal using the third and fourth signals; apply more than two variable weights to various parts of the ratio signal, the variable weights being derived with reference to at least one of the third and fourth signals; for each of a plurality of ratio values in the ratio signal, generate an associated weighted sum corresponding to each time the ratio signal coincides with the ratio value associated with the sum; and select a best ratio value from the plurality of ratio values based on the sums associated therewith.
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25. A method of estimating a physiological variable of living tissue, comprising:
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detecting at least first and second time domain signals corresponding to at least two light wavelengths scattered by living tissue; transforming the time domain signals into another domain and associated other domain signals; using the other domain signals to calculate a plurality of values representative of the physiological variable at a like plurality of different other domain signals; applying more than two variable weights to various ones of the values to form weighted values, the variable weights being derived with reference to at least one of the other domain signals; and compiling the weighted values to estimate the physiological variable. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32)
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Specification