Pathlength corrected oximeter and the like
First Claim
1. A spectrophotometer for tissue examination utilizing a measured average pathlength of migrating photons, comprising:
- an oscillator adapted to generate a carrier waveform of a selected frequency comparable to an average migration time of photons scattered in tissue on paths from an optical input port to an optical detection port;
a light source, operatively connected to said oscillator, adapted to generate light of a selected wavelength that is intensity modulated at said frequency, said light being introduced to a subject at said input port;
a photodiode detector adapted to detect, at said detection port, light of said wavelength that has migrated in said tissue of the subject between said input and detection ports;
a phase detector, operatively connected to receive signals from said oscillator and said diode detector, adapted to measure a phase shift between said introduced and said detected light;
a processor adapted to determine said pathlength based on said phase shift; and
said processor further adapted to determine a physiological property of the examined tissue based on said pathlength.
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Abstract
A pathlength corrected spectrophotometer for tissue examination includes an oscillator for generating a carrier waveform of a selected frequency, an LED light source for generating light of a selected wavelength that is intensity modulated at the selected frequency introduced to a subject, and a photodiode detector for detecting light that has migrated in the tissue of the subject. The spectrophotometer also includes a phase detector for measuring a phase shift between the introduced and detected light, a magnitude detector for determination of light attenuation in the examined tissue, and a processor adapted to calculate the photon migration pathlength and determine a physiological property of the examined tissue based on the pathlength and on the attenuation data.
210 Citations
21 Claims
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1. A spectrophotometer for tissue examination utilizing a measured average pathlength of migrating photons, comprising:
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an oscillator adapted to generate a carrier waveform of a selected frequency comparable to an average migration time of photons scattered in tissue on paths from an optical input port to an optical detection port;
a light source, operatively connected to said oscillator, adapted to generate light of a selected wavelength that is intensity modulated at said frequency, said light being introduced to a subject at said input port;
a photodiode detector adapted to detect, at said detection port, light of said wavelength that has migrated in said tissue of the subject between said input and detection ports;
a phase detector, operatively connected to receive signals from said oscillator and said diode detector, adapted to measure a phase shift between said introduced and said detected light;
a processor adapted to determine said pathlength based on said phase shift; and
said processor further adapted to determine a physiological property of the examined tissue based on said pathlength. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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2. A spectrophotometer for tissue examination utilizing a measured average pathlength of migrating photons, comprising:
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an oscillator adapted to generate a carrier waveform of a selected frequency comparable to an average migration time of photons scattered in tissue on paths from an optical input port to an optical detection port;
a light source, operatively connected to said oscillator, adapted to generate light of a selected wavelength that is intensity modulated at said frequency, said light being introduced to a subject at said input port;
a photodiode detector adapted to detect, at said detection port, light of said wavelength that has migrated in said tissue of the subject between said input and detection ports;
a phase splitter adapted to produce, based on said carrier waveform, first and second reference phase signals of predefined substantially different phase;
first and second double balanced mixers adapted to correlate said reference phase signals and signals of said detected radiation to produce therefrom a real output signal and an imaginary output signal, respectively;
a processor adapted to determine, on the basis of said real output signal and said imaginary output signal, a phase shift between said introduced light and said detected light; and
said processor further adapted to determine a physiological property of the examined tissue based on said phase shift.
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3. A spectrophotometer for tissue examination utilizing a measured average pathlength of migrating photons, comprising:
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a first oscillator adapted to generate a carrier waveform of a first selected frequency comparable to an average migration time of photons scattered in tissue on paths from an optical input port to an optical detection port;
a light source, operatively connected to said oscillator, adapted to generate light of a selected wavelength that is intensity modulated at said first frequency, said light being introduced to a subject at said input port;
a photodiode detector adapted to detect, at said detection port, light of said wavelength that has migrated in said tissue of the subject between said input and detection ports, said detector producing a detection signal at said first frequency corresponding to said detected light;
a second oscillator adapted to generate a carrier waveform of a second frequency that is offset on the order of 104 Hz from said first frequency;
a reference mixer, connected to said first and second oscillators, adapted to generate a reference signal of a frequency approximately equal to the difference between said first and second frequencies;
a mixer connected to receive signals from said second oscillator and said detection signal and adapted to convert said detection signal to said difference frequency;
a phase detector, operatively connected to receive signals from said reference mixer and said converted detection signal, adapted to measure a phase shift between said introduced light and said detected light, a processor adapted to determine said pathlength based on said phase shift; and
said processor further adapted to determine a physiological property of the examined tissue based on said pathlength.
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Specification