CONSTRUCTION OF A 200-MHZ PHASE MODULATION SYSTEM

CONTINUOUS NEAR-RED LIGHT SPECTROSCOPY FOR EARLY WARNING OF HYPOXIC/ISCHEMIC STRESS HAS THE GREAT ADVANTAGE OF SIMPLICITY AND EFFICACY AS A TREND INDICATOR, ON THE ONE HAND, AND TIME-RESOLVED SPECTROSCOPIC TECHNIQUES IN THE PICOSECOND/NANOSECOND REGIONS GIVE THE EXACT PATHLENGTH TRAVELED BY THE PHOTONS, ON THE OTHER. BY TIME SHARING LIGHT WITH THE APPROPRIATE CHOICE OF WAVELENGTHS, THE ABSOLUTE HEMOGLOBIN CONCENTRATION CAN BE DETERMINED IN THE ARTERIOLAR-VENULAR CAPILLARY BED. AT THE SAME TIME, CHANGES IN DEOXYHEMOGLOBIN DUE TO HYPOXIC STRESS CAN BE QUANTIFIED. MOST IMPORTANT, SIMULTANEOUS USE OF CONTINUOUS LIGHT AND TIME-RESOLVED SPECTROSCOPY AT THE SAME POINT IN THE TISSUE AFFORDS A CALIBRATION OF THE EFFECTIVE OPTICAL PATH OF THE CONTINUOUS LIGHT METHOD, THEREBY GREATLYINCREASING THE UTILITY OF THE LATTER. A SIMPLE, DUAL-WAVELENGTH PHASE MODULATION SPECTROPHOTOMETERACHIEVES THESE GOALS IN A COMPACT, ECONOMIC, EFFICIENT, AND READILY MARKETABLE DEVICE.