Characterization of 2D surface imaging of tissue optical properties using a sub-millimeter fiber optic probe

摘要

Broad-band light reflectance spectroscopy (LRS) of tissue with sub-millimeter fiber optic probes in the visible and near-infrared range has shown its utility in differentiation of tissue types, identification of cancer, and measurement of stimulus-induced physiological responses. So far, single point measurement set-up has been widely employed to determine local optical properties of tissue. However, it may often be of interest to obtain a 2D map of a surface area of a tissue under investigation, rather than a single point reading, as in case of cancer margin detection or intraoperative perfusion measurement. It is thus imperative to expand the LRS technique to multipoint measurement covering a larger surface area. Here we describe the two methods that we use to quantify the hemoglobin derivatives and scattering of tissue under investigation, and then utilize two bifurcated fiber optic probes with different fiber diameters and different source-detector separations, to demonstrate the 2D imaging capability of LRS technique. In this study, we constructed a tissue phantom, simulating tissue and blood vessel, and used 2D scanning to determine the spatial resolution and depth resolution using two different probe geometries. Our results suggest that the depth sensitivity of these probes was limited to sub-millimeter for hemoglobin derivatives, whereas scattering changes could be observed up to 2mm deep. It was also found that the lateral resolution was affected, and the scattering signal became more diffuse, as a function of depth.