Patent ID: 6442411
Filing Date: 2002-08-27
Classification: A61B

Abstract:
A method of improving accuracy in non-invasive, in vivo concentration measurements of a substance of interest in blood comprising the steps of:providing an illumination source which is adapted to generate illumination radiation to a measurement site, said illumination source providing illumination radiation across a portion of the spectrum which contains absorbance bands of said substance of interest; illuminating said measurement site with said illumination radiation; detecting radiation transmitted, transflected, or reflected from said measurement site with a detector array, said detector array having a plurality of detectors each having broadband spectral response characteristics with broadband spectral response characteristics with distinct maximum spectral response characteristics within different regions of said portion of the spectrum used for illuminating; each of said detectors in said detector array being selected and located such that said detector collects radiation only from a limited solid angle, said detector array providing an output signal indicative of the amount of radiation it receives in a selected time period; determining a differential value of said output signals for periods of arterial pulsations of the blood in said measurement site, said differential values being a comparison of values obtained during a systolic portion of said pulsations and values obtained during a diastolic portion of said pulsations; and generating a response which comprises a comparison of said differential value of said output signals to a simultaneous water-specific measurement, said water specific measurement being related to the amount of water in said blood during the measurement cycle, said water specific measurement being generated using at least a portion of said detector array; whereby said response provides a means for improving the accuracy of said concentration measurements.