The Characterization of a Two Wavelength Time-resolved System for the Determination of Hemoglobin Saturation through Comparison with Continuous Wave and Frequency Domain Systems

The absorption coefficient of hemoglobin is dependent upon its oxygenation status and on the wavelength of interest. The known absorption differences can be used to monitor noninvasively hemoglobin saturation, which is indicative of the oxygenation state of the tissue volume being probed. Time-resolved measurements combined with diffusion theory provide a means of quantifying the optical properties of a turbid medium, like tissue. To characterize the ability of our time domain system to measure optical properties, its performance was compared to a continuous wave and a frequency domain system in our laboratory. The response to changes in either optical property was determined. Following these investigations, preliminary in vivo measurements were performed. The time domain system proved sensitive enough to detect induced oxygenation changes in the hand of a volunteer.