Application of time gating in the measurement of glucose level in a three-layer biotissue model by using ultrashort laser pulses

The efficiency of using the time-of-flight (TOF) method at a wavelength of 820 nm for detecting the changes in the optical properties of multilayer light scattering medium in connection with the problem of the glucose level detection in the human tissue is discussed. Pulses scattered from a three-layer biotissue phantom consisting of two skin layers and a blood layer between them, are calculated with the help of a program code based on the Monte Carlo algorithm for different glucose concentrations. Relative changes in the recorded signals caused by variations in the glucose content are analysed for different source — detector separations. It is shown that the maximum relative change in the total pulse energy is 7.2% and 4.8% for the anisotropy factor of the layer mimicking skin g = 0.9 and 0.7, respectively, and the change in the glucose concentration from 0 up to 500 mg dL^-1. The use of time gating leads to the increase in these values up to 12% and 8.5%, respectively. The sensitivity maps are obtained which can be used to determine the optimal duration and the time delay of the time gate relative to the probe pulse for five values of the source — detector separations.