Background and Objective: A method to increase light transport deeply into target areas of tissue would enhance both therapeutic and diagnostic laser applications. The effects of a hyperosmotic agent on the scattering properties of rat and hamster skin were investigated. Study Design/Materials and Methods: A hyperosmotic agent, glycerol, was applied in vitro and in vivo to rat and hamster skin to assess the changes in tissue optical properties. Changes in the reduced scattering coefficient after application of the agent in vitro to rat skin and after the skin has been rehydrated were assessed to evaluate the effect of the agent on tissue. Results: Experimental results showed a transient change in the optical properties of in vitro rat skin. A 50% increase in transmittance and decrease in diffuse reflectance occurred within 5‐10 min after the introduction of anhydrous glycerol. In addition, reduction of light scattering with this technique increased depth of visibility with optical coherence tomography. Injection of glycerol under the skin allowed in vivo visualization of blood vessels. Conclusions: The application of the agent reduces the amount of refractive mismatch found in the tissue and markedly reduces random scattering, thereby making the skin less turbid for visible wavelengths for a controlled period of time. Lasers Surg. Med. 24:133‐141, 1999. © 1999 Wiley-Liss, Inc.

Use of an agent to reduce scattering in skin

Theoretical and computer modeling approaches, such as Mie theory, radiative transfer theory, diffusion wave
correlation spectroscopy, and Monte Carlo simulation were used to analyze tissue optics during a process of
optical clearing due to refractive index matching. Continuous wave transmittance and forward scattering
measurements as well as intensity correlation experiments were used to monitor tissue structural and optical properties. As a control, tissue samples of the human sclera were taken. Osmotically active solutions, such as Trazograph, glucose, and polyethylene glycol, were used as chemicals. A characteristic time response of human scleral optical clearing the range 3 to 10 min was determined. The diffusion coefficients describing the permeability of the scleral samples to Trazograph were experimentally estimated; the average value was DT'(0.960.5)31025 cm2/s. The results are general and can be used to describe many other fibrous tissues.

https://www.spiedigitallibrary.org/journals/Journal-of-Biomedical-Optics/volume-2/issue-04/0000/Light-propagation-in-tissues-with-controlled-optical-properties/10.1117/12.281502.pdf

Light propagation in tissues with controlled optical properties.

Tissue optical clearing technique provides a prospective solution for the application of advanced optical methods in life sciences. This paper gives a review of recent developments in tissue optical clearing techniques. The physical, molecular and physiological mechanisms of tissue optical clearing are overviewed and discussed. Various methods for enhancing penetration of optical-clearing agents into tissue, such as physical methods, chemical-penetration enhancers and combination of physical and chemical methods are introduced. Combining the tissue optical clearing technique with advanced microscopy image or labeling technique, applications for 3D microstructure of whole tissues such as brain and central nervous system with unprecedented resolution are demonstrated. Moreover, the difference in diffusion and/or clearing ability of selected agents in healthy versus pathological tissues can provide a highly sensitive indicator of the tissue health/pathology condition. Finally, recent advances in optical clearing of soft or hard tissue for in vivo imaging and phototherapy are introduced.

/pdf/recent-progress-in-tissue-optical-clearing-jqy4eb1xzd.pdf

Recent progress in tissue optical clearing

We have proposed a tested in tissue phantoms and in vivo a novel sensor based on optical coherence tomography (OCT) for noninvasive and continuous monitoring of blood glucose concentration. OCT images were obtained from pig and rabbit skin before and after glucose administration. Slopes of OCT signals decreased substantially (∼40% in tissues in vivo) and linearly with the increase of blood glucose concentration from 4 to 30  mM, typical for normal and diabetic subjects. Phantom studies demonstrated 1% accuracy of scattering-coefficient measurement. Our theoretical and experimental studies suggest that glucose concentration can potentially be measured noninvasively with high sensitivity and accuracy with OCT systems.

Noninvasive monitoring of glucose concentration with optical coherence tomography

http://www.qbic.riken.jp/syn-bio/publications/Cell%20Chemical%20Biology%20(2016).pdf

Whole-body and Whole-Organ Clearing and Imaging Techniques with Single-Cell Resolution: Toward Organism-Level Systems Biology in Mammals

Theoretical and computer modeling approaches, such as Mie theory, radiative transfer theory, diffusion wave correlation spectroscopy, Monte Carlo simulation method were applied for tissue optics analysis in a process of its clearance. CW collimated transmittance and forward scattering measurements as well as intensity correlation experiments were used for tissue structure and optical properties monitoring. Conrolled tissue samples of the human sclera were taken. A chemical applicator-conrollers Trazograph, glucose and polyethileneglycol solutions were used. On the base of sclera samples clearance investigation the general principles of tissue optical and structural parameters controlling were established.

Light propagation in tissues with controlled optical properties

Theoretical and computer modeling approaches, such as Mie theory, radiative transfer theory, Monte Carlo simulation method were applied for tissue optics analysis in a process of its optical clearing due to refractive indices matching. CW transmittance and forward and backward scattering measurements were used for tissue structural and optical properties monitoring. As a controlled tissue samples of the human sclera were taken. As a chemical applicator-controller osmotically active trazograph solution was used. The scleral absorption and scattering spectra as well as diffusion coefficient describing the samples of the human sclera permeability to trazograph wer experimentally estimated. Presented results are general and can be applicable for description of many other fibrous tissues.

Albert Kh. Mavlutov

Papers

Light propagation in tissues with controlled optical properties

Scleral tissue light scattering and matter diffusion