Thermal measuring and testing – Temperature measurement – Nonelectrical – nonmagnetic – or nonmechanical temperature...
Patent
1997-06-30
1999-03-02
Dougherty, Elizabeth L.
Thermal measuring and testing
Temperature measurement
Nonelectrical, nonmagnetic, or nonmechanical temperature...
374121, 356 43, G01K 1100, G01J 500
Patent
active
058761217
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/CA 95/00466 filed Aug. 3, 1995.
TECHNICAL FIELD
This invention relates to determination of a parameter of a medium which scatters infrared radiation; in particular, it is concerned with a method and apparatus for determining the temperature of such a medium.
The invention has particular application to the determination of the temperature of biological tissue, but also has application to other media which contain water and which scatter infrared radiation, for example, substrates in paper, cement and clay product manufacture.
The invention is more especially concerned with a method and apparatus for quantitative, non-invasive bioenergetic measurement. Towards this end, a method and apparatus for determining tissue temperature is provided.
BACKGROUND ART
Tissue temperature is critical to cellular bioenergetics and can be useful clinically to locate blood perfused regions in diseased or inflamed tissue. Clinical use of tissue temperature or thermography has been limited by uncertainties in temperature measurement. The most common method for temperature measurement is to use invasive micro-electrodes or thermocouples. However, these probes have several disadvantages, including: tissue damage, alterations of tissue temperature and single point detection. Measurement of tissue temperature using emitted light in the infrared or microwave region has overcome many of the disadvantages of electrode measurements. Assuming the tissue is a blackbody radiator, noninvasive images of tissue are possible using infrared emission. However, the extremely high extinction coefficients for the infrared wavelengths in wet tissue result in light penetration of a few hundred microns or less. For wet tissue such as the lung or gut, this penetration depth is not sufficient. Likewise, infrared light is not easily coupled into fiber optic systems for endoscopic or bronchoscopic measurements.
U.S. Pat. No. 5,262,644, J. F. Maguire describes a method and apparatus for providing spectroscopic information remotely using incident radiation, a detector and fiber optic coupling; it is indicated that the temperature of a sample may be deduced from the intensity difference between the Stokes and anti-Stokes lines by application of the Boltzmann relationship to the intensity difference.
DISCLOSURE OF THE INVENTION
The present invention employs measurements of the reflectance infrared spectra from a specimen, especially the near-infrared spectra. Temperature dependent changes in the hydrogen bonding of water within the specimen, for example tissue, results in change of the reflectance spectra. Using sets of specimen measurements with known temperature, a calibration equation is determined by statistical analysis of the data. Computer simulations and infrared, especially near-infrared, measurements of known phantoms are used to evaluate the sensitivity of the method for studies of specimens with different scattering properties. The system provides a new tool to study local specimen temperature thereby providing a means for rapid, non-invasive measurement of parameters, for example, parameters critical to bioenergetics in tissue for research and clinical use.
Thus in accordance with the invention there is provided a method of determining the temperature of an infrared radiation scattering medium comprising: exposing an infrared scattering medium containing a liquid which contains different hydrogen bonding at different temperatures to infrared radiation, measuring reflected infrared radiation scattered by the medium, comparing the reflected radiation with calibrated values of reflected radiation and temperature, and evaluating the temperature of the medium from the comparison.
In particular the radiation has a near-infrared wavelength between 700 nm and 2500 nm.
In particular reflected infrared radiation at different wavelengths is measured. In particular, the different wavelengths comprise wavelengths for water between 1100 and 1300 nm including a wavelength for free OH groups and a wavelength for hydrogen
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Burns David H
Series Frederic
Amrozowicz Paul D.
Dougherty Elizabeth L.
McGill University
Universite Laval
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