Measurements of glucose content in scattering media with time-of-flight technique; comparison with Monte Carlo simulations

摘要

Scattering effect of the media can be seen as a pulse broadening and time delay of the pulse maximum relatively to the initial pulse. The purpose of this paper is to study the applicability of the time-of-flight measurement technique for glucose detection in 2% Intralipid~(TM) solutions in vitro. Glucose samples with concentrations of 100, 200, 300, 500, 1000, 2000, 4000, and 8000 mg/dl are studied. Laser pulses with λ = 906 nm and FWHM = 30 ps are used in the experiments to investigate scattering properties of Intralipid~(TM). 1 - 5% Intralipid~(TM) suspensions are used to simulate scattering properties of different skin layers in the NIR spectrum region. Measurements are conducted with a slab cuvette, with 300-μm step index type fibers, and with 100-μm gradient index type fibers. Light propagation in the aqueous solutions is also studied by the Monte Carlo simulation. The simulations and the measurement results seem to correlate quite well for Intralipid suspensions. A clear correlation of pulse parameters as a function of Intralipid~(TM) concentration was found. Slight changes of time delays of pulse maxima and the pulse broadening as a function of glucose concentration were revealed. Gradient index type fibers are found to be better choice for sensing glucose than the step index type fibers.