Optimization of low coherence interferometry for quantitative analysis of tissue optical properties

Noninvasive monitoring of analytes can be performed with optical coherence tomography (OCT) technique. This technique may allow measurement of optical properties of tissue (attenuation, scattering, optical thickness, etc.) that may be dependent on analyte concentration. Accurate monitoring of analyte concentration requires measurement of the optical properties with high accuracy. The accuracy of measurements depends on OCT technical characteristics and the level of speckle noise. In this paper, we report the results of the calibration of OCT system sensitivity for absolute and relative measurements of the backscattering and total attenuation coefficients in scattering standard, tissue phantoms (suspensions of polystyrene microspheres in water solutions of glucose), and human skin. We measured the OCT sensitivity as a function of depth and used this dependence for correction of signals. The amplitude and spatial period of backscattered signal modulation resulted from speckle noise were measured for the scattering standard and human skin. The dependence of speckle and electronic noise on the range of spatial and temporal averaging of OCT signals was determined. Our studies show that the accuracy of measurement of changes in optical properties of tissue with OCT technique can be significantly improved by reducing of speckle noise and by using the signal correction algorithm.