Phase modulation spectroscopic system
AssigneeNIM Incorporated
InventorsBritton Chance, Jian Weng
Life of this patent
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Abstract
A phase modulated spectroscopy (PMS) system for detecting a pathophysiological condition in a subject includes two laser diodes emitting radiation at wavelengths of about 754-760 nm and 816-840 nm. These two laser diodes are modulated sinusoidally at about 220 MHz. The signals from each laser diode are brought to the subject by a bifurcated plastic optical fiber of 1 mm diameter. After transmission through the subject, the signals are detected by a Hamamatsu R928 photomultiplier (PMT), which generates two experimental signals. The experimental signals are compared to a reference signal in a phase detector. The respective phase shifts experienced by the signals are combined to form sum and difference signals, which are correlated to a pathophysiological condition.
Claims37
A spectroscopic method for detecting at least one pathophysiological change in a subject, comprising the steps:
- (a) introducing into the subject, at an input port, first and second electromagnetic signals of wavelengths sensitive to hemoglobin oxygenation, said signals being modulated by a carrier waveform of frequency on the order of 10.sup.8 hz;
- (b) measuring the phase shift of said first and second electromagnetic signals that have migrated in the subject from said input to a detection port and
- (c) determining, on the basis of said relative phase shifts of said signal that have migrated in the subject said pathophysiological change in the subject.
A spectroscopic method for analyzing a scattering medium comprising at least one absorptive constituent, comprising:
- (a) generating a first carrier waveform at a first frequency of at least 200 MHz;
- (b) generating a second carrier waveform at a second frequency, said second frequency being offset on the order of 25 KHz from said first frequency;
- (c) generating two electromagnetic signals modulated by said first carrier waveform, said two electromagnetic signals having different selected wavelengths;
- (d) coupling said two electromagnetic signals of said selected wavelengths to the scattering medium;
- (e) detecting two altered phase-shifted waveforms corresponding to said two electromagnetic signals, said altered signals having been phase-shifted during migration in the scattering medium;
- (f) generating a reference signal having a frequency approximately equal to the difference between said first and second frequencies;
- (g) generating, at each said wavelength, a difference signal indicative of the phase-shift that is characteristic of said medium;
- and
- (h) determining, on the basis of said phase-shifts, selected property of the subject.
A phase modulation spectroscopic system for detecting at least one pathophysiological change in a subject, comprising:
- (a) means for introducing into the subject, at an input port, first and second electromagnetic signal of wavelengths sensitive to hemoglobin oxygenation, said signals being modulated by a carrier waveform of frequency on the order of at least 10.sup.8 Hz;
- (b) means for measuring the phase shift of said first and second electromagnetic signals that have migrated in the subject;
- and
- (c) means for determining, on the basis of said relative phase shifts of said signals that have migrated in the subject, said pathophysiological change in the subject.
A phase modulation spectroscopic system for analyzing a scattering medium comprising at least one absorptive constituent, comprising:
- (a) first oscillator means for generating a first carrier waveform at a first frequency of at least 200 MHz;
- (b) second oscillator means for generating a second carrier waveform at a second frequency offset on the order of 25 KHz from said first frequency;
- (c) light source means coupled to said first oscillator means, for generating two electromagnetic signals modulated by said first carrier waveform, said two electromagnetic signals having different selected wavelengths;
- (d) means for coupling said two electromagnetic signals of said selected wavelengths to the scattering medium;
- (e) detector means for detecting two altered phase-shifted waveforms corresponding to said two electromagnetic signals, said altered signals having been phase-shifted during migration in the scattering medium;
- (f) mixer means, coupled to said first and second oscillator means, for generating a reference signal having a frequency approximately equal to the difference between said first and second frequencies;
- (g) phase detector means for alternatively generating, at each wavelength, a difference signal indicative of of the phase shift that is characteristic of said medium;
- and
- (h) means for determining, on the basis of said phase-shifts, selected property of the subject.
A spectroscopic method of examination of a subject, the subject lying between an optical input port and an optical detection port of a spectroscopic system, the optical pathlength of photons migrating between said ports being determined by the scattering and absorptive properties of the particular subject, the method comprising the steps of:
- (a) introducing into the subject at the input port at least one electromagnetic signal of selected wavelength, the signal having been modulated by a carrier waveform of frequency that enables determination of said pathlength;
- (b) detecting the signal at the detection port that has migrated in the path in the subject;
- (c) comparing the detected signal with the introduced signal and determining therefrom the phase shift of said detected signal from said introduced signal, said phase shift being indicative of said scattering and absorptive properties of the subject;
- and
- (d) examining said subject by employing said phase shift.
Dependencies are inferred from the claim text.