Abstract
Experimental data on the dependence of the average refractive index of rat tail tendon (RTT) on water content are reported. Using optical coherence tomography, the average group refractive index (at a wavelength of 930 nm) and cross-section area of rat tail tendon fascicle specimens during their air-drying and rehydration were monitored. The dependence of the average group refractive index of RTT ( n g ) on the volume fraction of water ( C w ) has been found to be nonlinear and to be well approximated by the quadratic polynomial n g = 1.5713 – 0.1969 C w – 0.0328( C w ) 2 . The reported data are shown to be in good agreement with previously published data for bovine cornea.
Highlights
One of the optical parameters that can be directly measured for biological tissues is the average refractive index of the tissue [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
In this paper we present experimental estimates for the average tissue refractive index as a function of water content for tendon, a collagenous tissue with the highest normal collagen content—tendons contain typically 24–38 wt % collagen and 55–72 wt % water [18,19,20]
In order to determine the average refractive index of rat tail tendon (RTT) fascicles as a function of water content, we monitored, using optical coherence tomography (OCT), the cross-section area and average refractive index of RTT fascicle specimens during their air-drying from the native state to the air-dry state and in the process of rehydration of dried specimens in normal saline solution (NSS: aqueous solution of 0.9 wt % NaCl)
Summary
One of the optical parameters that can be directly measured for biological tissues is the average refractive index of the tissue [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. Fascicles, whose diameter typically lies within the range from 250 to 500 μm, are tens times thicker than dermal and scleral collagen fibers, which makes them quite convenient for experimentation Due to their relatively simple structure, ease of extraction and manipulation, and ready availability, RTT fascicles are a very popular model object for studying physical and physiological properties of collagen fibers and collagenous tissues. They are used in studying the effect of immersion agents, which are employed in the immersion optical clearing technique [23], on collagen bundles (see, e.g., [24]). These data can be used for evaluating the duration of the solely dehydration stage of the immersion agent – biotissue interaction
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