METHOD OF ANALYZING PHOTON DENSITY WAVES IN A MEDICAL MONITOR
First Claim
1. A medical monitoring system, comprising:
- an emitter;
a modulator configured to control the emitter with a drive signal that provides modulation frequencies in a frequency range suitable to produce photon density waves;
a detector configured to detect the photon density waves to generate a photon density wave signal;
a memory storing instructions to;
apply a fixed or adaptive filter to the photon density wave signal to generate a conditioned photon density wave signal;
determine a photon path length or phase delay based on the conditioned photon density wave signal; and
calculate a physiological parameter based at least in part on the mean photon path length; and
a processor configured to execute the instructions.
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Accused Products
Abstract
A monitoring system may include an emission feature capable of emitting light into tissue, a modulator capable of modulating the emitter at a modulation frequency, e.g., in a range of about 10 MHz to 3.0 GHz, to generate resolvable photon density waves, a detection feature capable of detecting photons of the photon density waves after passage through the tissue, and a processor capable of using phase and amplitude differences of the photon density wave signal relative to a reference to determine one or more physiological parameters. The phase and amplitude differences may be much lower frequency that the modulation rate. Accordingly, these differences may be masked by signal artifacts. Provided herein are signal conditioning techniques that may improve the signal to noise ratio of photon density wave signals and yield a more robust phase and amplitude signal.
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Citations
25 Claims
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1. A medical monitoring system, comprising:
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an emitter; a modulator configured to control the emitter with a drive signal that provides modulation frequencies in a frequency range suitable to produce photon density waves; a detector configured to detect the photon density waves to generate a photon density wave signal; a memory storing instructions to; apply a fixed or adaptive filter to the photon density wave signal to generate a conditioned photon density wave signal; determine a photon path length or phase delay based on the conditioned photon density wave signal; and calculate a physiological parameter based at least in part on the mean photon path length; and a processor configured to execute the instructions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of analyzing tissue, comprising:
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receiving from the tissue a signal representative of detected photon density waves; comparing an amplitude and phase of the signal to a reference signal to determine an amplitude difference and a phase difference over time; evaluating a reliability of the phase difference using metrics; and determining a physiological parameter based on the phase difference and the amplitude difference when the metrics indicate the phase difference is reliable. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A pulse oximeter, comprising:
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a modulator configured to modulate a first light source and a second light source at modulation frequencies in a frequency range suitable to produce photon density waves of at least two frequencies of light; a detector configured to detect the photon density waves from the first light source and the second light source after the photon density waves have passed through tissue and output a multiplexed analog photon density wave signal that is indicative of a number of photons detected over a time period from the first light source and the second light source; an analog to digital converter configured to digitize a multiplexed signal representative of the detected photon density waves from the first light source and the second light source; and analysis circuitry configured to receive the digitized multiplexed photon density wave signal, demodulate the multiplexed signal into component parts representative of the photon density wave signal from the first light source and the second light source, and determine a physiological parameter based on a phase component and an amplitude component of the photon density wave signal from the first light source and the second light source. - View Dependent Claims (24, 25)
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Specification