Using an oblique incident laser beam to measure the optical properties of stomach mucosa/submucosa tissue

<p>Abstract</p> <p>Background</p> <p>The purpose of the study is to determine the optical properties and their differences for normal human stomach mucosa/submucosa tissue in the cardiac orifice <it>in vitro </it>at 635, 730, 808, 890 and 980 nm wavelengths of laser.</p> <p>Methods</p> <p>The measurements were performed using a CCD detector, and the optical properties were assessed from the measurements using the spatially resolved reflectance, and nonlinear fitting of diffusion equation.</p> <p>Results</p> <p>The results of measurement showed that the absorption coefficients, the reduced scattering coefficients, the optical penetration depths, the diffusion coefficients, the diffuse reflectance and the shifts of diffuse reflectance of tissue samples at five different wavelengths vary with a change of wavelength. The maximum absorption coefficient for tissue samples is 0.265 mm^-1at 980 nm, and the minimum absorption coefficient is 0.0332 mm^-1at 730 nm, and the maximum difference in the absorption coefficients is 698% between 730 and 980 nm, and the minimum difference is 1.61% between 635 and 808 nm. The maximum reduced scattering coefficient for tissue samples is 1.19 mm^-1at 635 nm, and the minimum reduced scattering coefficient is 0.521 mm^-1at 980 nm, and the maximum difference in the reduced scattering coefficients is 128% between 635 and 980 nm, and the minimum difference is 1.15% between 890 and 980 nm. The maximum optical penetration depth for tissue samples is 3.57 mm at 808 nm, and the minimum optical penetration depth is 1.43 mm at 980 nm. The maximum diffusion constant for tissue samples is 0.608 mm at 890 nm, and the minimum diffusion constant is 0.278 mm at 635 nm. The maximum diffuse reflectance is 3.57 mm^-1at 808 nm, and the minimum diffuse reflectance is 1.43 mm^-1at 980 nm. The maximum shift Δx of diffuse reflectance is 1.11 mm^-1at 890 nm, and the minimum shift Δx of diffuse reflectance is 0.507 mm^-1at 635 nm.</p> <p>Conclusion</p> <p>The absorption coefficients, the reduced scattering coefficients, the optical penetration depths, the diffusion coefficients, the diffuse reflectance and the shifts of diffuse reflectance of tissue samples at 635, 730, 808, 890 and 980 nm wavelengths vary with a change of wavelength. There were significant differences in the optical properties for tissue samples at five different wavelengths (<it>P </it>< 0.01).</p

Tissue optical clearing mechanisms

The high scattering and absorption of opaque tissues limit the penetration of light into deep tissues, limiting the imaging depth of various optical imaging techniques. The proposed tissue optical clearing technique provides an innovative way to perform deep-tissue imaging. Recently, various optical clearing methods have been developed. They result in tissue clearing with similar physical principles but different chemical approaches. This chapter will introduce the mechanisms of the current tissue optical clearing methods, ranging from fundamental physical to chemical perspectives, including the main physical principle, refractive index matching; and chemical approaches such as dissociation of collagen, dehydration, delipidation, decalcification, and hyperhydration to reduce scattering, as well as the use of decolorization to reduce absorption.T.Y. and D.Z. were supported by the National Key Research and Development Program of China grant number 2017YFA0700501, and NSFC grant number 81171736. E.A.G, A.N.B., and V.V.T were supported by RFBR grant number 18-52-16025. L. O. was supported by the Portuguese Science Foundation grant number FCT-UIDB/04730/2020. The authors are thankful to the staff of the Portuguese Oncology Institute of Porto (IPO-Porto), Portugal, for providing the human colorectal specimens used in the research presented in this chapter. The authors also appreciate the histological photograph of the human colorectal wall, which was supplied by Dr Sónia Carvalho from IPO-Porto.info:eu-repo/semantics/publishedVersio