Quantitative analysis of dehydration in porcine skin for assessing mechanism of optical clearing

Abstract

Abstract. Dehydration induced by optical clearing agents (OCAs) can improve tissue optical transmittance; however, current studies merely gave some qualitative descriptions. We develop a model to quantitatively evaluate water content with partial least-squares method based on the measurements of near-infrared reflectance spectroscopy and weight of porcine skin. Furthermore, a commercial spectrometer with an integrating sphere is used to measure the transmittance and reflectance of skin after treatment with different OCAs, and then the water content and optical properties of sample are calculated, respectively. The results show that both the reduced scattering coefficient and dehydration of skin decrease with prolongation of action of OCAs, but the relative change in former is larger than that in latter after a 60-min treatment. The absorption coefficient at 1450 nm decreases completely coincident with dehydration of skin. Further analysis illustrates that the correlation coefficient between the relative changes in the reduced scattering coefficient and dehydration is ∼1 during the 60-min treatment of agents, but there is an extremely significant difference between the two parameters for some OCAs with more hydroxyl groups, especially, glycerol or D-sorbitol, which means that the dehydration is a main mechanism of skin optical clearing, but not the only mechanism. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Optical clearing mechanisms characterization in muscle

“…Quantitative characterization of the OC mechanisms has been tried by measuring optical transmittance and re°ectance from porcine skin samples. 29 Similar studies have demonstrated that di®erent OCA di®usion enhancers (alcohols) provide signi¯-cant transmittance increase in porcine skin samples. 33 Sample thickness was also measured in these studies before and after the treatment, showing a small global variation.…”

“…The dehydration mechanism in particular, has been widely investigated using di®erent techniques that involves mechanical and temperature variation methods to remove water from tissue area under study. 11,[28][29][30][31] These studies reported that the water loss provides a greater tissue transparency through the combination of the smaller sample thickness and the better ordering of scatterers.…”

Development of an Optical Tissue Clearing Laser Probe System

“…3 demonstrates that decreasing the tissue temperature resulted in decreasing the µ's and, therefore, increasing the PI and TI which means enhancement of photon density in the dermis. As described in previous studies, such results may be caused by the modification of collagen fiber structure, degradation of cellular components, and change of the refractive index of intercellular fluid [15][16][17][18][19][20].…”

“…Skin dehydration and collagen dissociation may cause the reduction of light scattering by minimizing refractive index mismatching [15][16][17]. Recently, Yu et al [19] reported that the dehydration induced by an optical clearing agent is a prominent mechanism for improving tissue optical transmittance. Direct injection of glycerol may have a clinical advantage of an immediate OTC effect in local treatment.…”

“…Rylander et al [18] and Yu et al [19] that skin dehydration is the prominent mechanism of OTC and Yeh et al [20] suggested that the reversible change of both collagen structure and size can affect OTC. In recent in-vivo studies, Ghosn et al monitored and quantified the permeability rate of glucose solutions in in-vivo monkey skin by using OCT [21], and Wen et al reported that the thickness decrease of dermis and regular arrangement of tissue fibers were prominent OTC mechanisms [22].…”