Abstract
Tissue clearing has gained attention as a pioneering research tool for imaging of large tissue samples. This technique improves light transmission by reducing light scattering within tissues, either by removing lipids or by replacing water with a high refractive index solution. Although various clearing techniques have been developed, quantitative assessments on clearing efficacy depending on tissue properties are rare. In this study, we developed the quantitative mapping of regional clearing efficacy using mean free path in optical coherence tomography (OCT) and proton density in magnetic resonance imaging (MRI), and demonstrated its feasibility in the brain sample with four representative clearing techniques (benzyl alcohol and benzyl benzoate [BABB], ClearT, Scale, and passive CLARITY technique [PACT]). BABB (solvent-based clearing), involving both refractive index matching and lipid removal, exhibited best optical clearing performance with the highest proton density reduction both in gray and white matter. Lipid-removing techniques such as Scale (aqueous hyperhydration) and PACT (hydrogel embedding) showed higher clearing efficiency in white matter than gray matter in accordance with larger proton density increase in white matter. For ClearT (aqueous-based simple immersion), we observed lowest clearing efficiency in the white matter as well as poor lipid removal reflected in low proton density reduction. Our results showed the feasibility of the regional mapping of clearing efficacy and correlating optical transparency and proton density changes using OCT and MRI from existing tissue clearing techniques. This novel quantitative mapping of clearing efficacy depending on tissue types and clearing methods may be helpful in the development of optimized clearing methods for different biological samples.
Highlights
Light microscopy is one of the most prominent tool in neuroscience as it allows the study of the structure and function of the brain
Using optical coherence tomography (OCT) and magnetic resonance imaging (MRI)-based analyses, we compared the effect of different tissue clearing methods, in terms of proton density and mean free path (MFP) changes
The changes in proton density observed in the cortical regions after the application of passive CLARITY (PACT) and Scale were similar, correlating with the similar changes observed in the corresponding MFPs
Summary
Light microscopy is one of the most prominent tool in neuroscience as it allows the study of the structure and function of the brain. Tissue clearing techniques usually reduce inhomogeneity in optical properties in the tissue by (1) removing lipids, a main source of light scattering in the turbid tissue, and/or (2) replacing water in the sample with the clearing solution having a high refractive index. “Hydrogel embedding” techniques such as PACT7 enable more severe detergent treatment to remove lipids and immerse the cleared sample in a refractive index matching solution Performance of these clearing techniques might vary depending on the constitution of the biological tissue. The attenuation coefficients were quantified and the efficiencies of three different clearing techniques, including BABB and passive CLARITY (PACT), were compared[21] These studies demonstrated that OCT is suitable for the quantitative monitoring of optical attenuation in biological tissues during clearing. The quantitative comparison of proton densities with respect to optical transparency would facilitate the evaluation and understanding of clearing efficacies of the various clearing methods in relation to tissue characteristics
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
