Optical Properties of Tissues

Mobley J,Vo-DinhT. Optical properties of tissue. In Vo-DinhT,ed. Biomedical Photonics Handbook. New York CRC Press, 2003 2.1-2.77. 

J. Mobley, T. Vo-Dinh, Optical properties of tissue, in T. Vo-Dinh (ed.) Biomedical Photonics Handbook, CRC Press, 53-1 to 53-48 (2003)... 

The author of this book has had considerable experience with the ATR technique and finds it particularly useful for work with biological specimens. The optical properties of tissues are such that they must be very thinly sectioned to obtain transmission spectra, whereas the ATR method does not depend on sample thickness. Useful spectra have been recorded from normal and diseased human arterial tissue (Fig. 3.25) and heart tissue (chicken, rat, calf) (Parker and Ans, 1967). Examinations... 

Vargas G, Chan KF, Thomsen SL, Welch AJ. Use of osmotically active agents to alter optical properties of tissue effects on the detected fluorescence signal measured through skin. Lasers Surg Med 2001 29(3) 213-220. 

X. The reflectance depends on optical properties of tissue or blood, i.e. the absorption (// ) and scattering (// ) coefficients, or total attenuation... 

This overview shows that optical immersion technology allows one to control effectively optical properties of tissues and blood. Such control leads to essential reduction of scattering and therefore causes much higher transmittance (optical clearing), appearance of a big amount of least scattered (shake) and ballistic photons allowing for successful application of coherent-domain and polarisation imaging techniques. 

G. Vargas, K.F. Chan, S.L. Thomsen, and A.J. Welch, Use of OsmoticaUy Active Agents to Alter Optical Properties of Tissue Effects on the Detected Fluorescence Signal Measured through Skin, Lasers Surg. Med., vol. 29,2001, pp. 213-220. 

A limiting factor in noninvasive optical technology is variations in the optical properties of samples under investigation that result in spectral distortions44 8 and sampling volume (effective optical path length) variability 49-54 These variations will impact a noninvasive optical technique not only in interpretation of spectral features, but also in the construction and application of a multivariate calibration model if such variations are not accounted for. As a result, correction methods need to be developed and applied before further quantitative analysis. For Raman spectroscopy, relatively few correction methods appear in the literature, and most of them are not readily applicable to biological tissue.55-59... 

CNTs and other nano-sized carbon structures are promising materials for bioapplications, which was predicted even previous to their discovery. These nanoparticles have been applied in bioimaging and drag delivery, as implant materials and scaffolds for tissue growth, to modulate neuronal development and for lipid bilayer membranes. Considerable research has been done in the field of biosensors. Novel optical properties of CNTs have made them potential quantum dot sensors, as well as light emitters. Electrical conductance of CNTs has been exploited for field transistor based biosensors. CNTs and other nano-sized carbon structures are considered third generation amperometric biosensors, where direct electron transfer between the enzyme active center and the transducer takes place. Nanoparticle functionalization is required to achieve their full potential in many fields, including bio-applications. 

The optical properties of liver tissue and liver metastases were examined by NIR in a paper by Germer et al. [115]. Since laser-induced thermotherapy is becoming popular, the team wanted to describe the light scattering effects of both types of tissue. 

C. T. Germer, A. Roggan, J. P. Ritz, C. Isbert, D. Albrecht, G. Muller, and H. J. Buhr, Optical Properties of Native and Coagulated Human Liver Tissue and Liver Metastases in the Near-Infrared Range, Lasers Surg. Med., 23(4), 194-203 (1998). 

The semiquantitative and quantitative methods discussed in this section are based on the optical properties of melanins in both the transmission and reflection mode, and they may require solubilization and/or partial degradation of the samples (305). The melanin content in tissues has been determined visually (306) following treatment with Fe and potassium ferricyanide (307) and by reflectance (308) and remittance (143) methods. For fluorimetric determination of melanins (melanoma cells), the sample is solubilized with alkaline hydrogen peroxide (pH 7.8, 100°C, 30 min) the excitation wavelength is 410 nm, emission 500 nm (148). Fairly good chemical stability of melanins has been determined in gravimetric determinations after separation from all other constituents of melanosomes with acid digestion (6 N HCl, 100°C, 72 hr) (110). 

The in vitro experiments, combined with the pharmacokinetic data available from the literature the absorption characteristics of the drugs and the optical properties of the tissues, resulted in an estimate of the capability of each compound to act as an in vivo photosensitizer. A thorough discussion of the photoreactivity of the... 

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