Abstract
The broadband absorption coefficient spectrum of the rabbit lung presents some particular characteristics that allow the identification of the chromophores in this tissue. By performing a weighted combination of the absorption spectra of water, hemoglobin, DNA, proteins and the pigments melanin and lipofuscin, it was possible to obtain a good match to the experimental absorption spectrum of the lung. Such reconstruction provided reasonable information about the contents of the tissue components in the lung tissue, and allowed to identify a similar accumulation of melanin and lipofuscin. The broadband absorption coefficient spectrum of the rabbit lung was reconstructed from the absorption spectra of tissue components. The similar accumulation of melanin and lipofuscin was retrieved from the broadband baseline in the absorption coefficient spectrum, and the calculation of the absorption fold ratios for proteins, DNA and hemoglobin provided good results. The method used is innovative and can be improved to allow the quantification of tissue components concentrations directly. image

Abstract
The evaluation of the diffusion properties of different molecules in tissues is a subject of great interest in various fields, such as dermatology/cosmetology, clinical medicine, implantology and food preservation. In this review, a discussion of recent studies that used kinetic spectroscopy measurements to evaluate such diffusion properties in various tissues is made. By immersing ex vivo tissues in agents or by topical application of those agents in vivo, their diffusion properties can be evaluated by kinetic collimated transmittance or diffuse reflectance spectroscopy. Using this method, recent studies were able to discriminate the diffusion properties of agents between healthy and diseased tissues, especially in the cases of cancer and diabetes mellitus. In the case of cancer, it was also possible to evaluate an increase of 5% in the mobile water content from the healthy to the cancerous colorectal and kidney tissues. Considering the application of some agents to living organisms or food products to protect them from deterioration during low temperature preservation (cryopreservation), and knowing that such agent inclusion may be reversed, some studies in these fields are also discussed. Considering the broadband application of the optical spectroscopy evaluation of the diffusion properties of agents in tissues and the physiological diagnostic data that such method can acquire, further studies concerning the optimization of fruit sweetness or evaluation of poison diffusion in tissues or antidote application for treatment optimization purposes are indicated as future perspectives.

Abstract
With the objective of developing new methods to acquire diagnostic information, the reconstruction of the broadband absorption coefficient spectra (mu a[lambda]) of healthy and chromophobe renal cell carcinoma kidney tissues was performed. By performing a weighted sum of the absorption spectra of proteins, DNA, oxygenated, and deoxygenated hemoglobin, lipids, water, melanin, and lipofuscin, it was possible to obtain a good match of the experimental mu a(lambda) of both kidney conditions. The weights used in those reconstructions were estimated using the least squares method, and assuming a total water content of 77% in both kidney tissues, it was possible to calculate the concentrations of the other tissue components. It has been shown that with the development of cancer, the concentrations of proteins, DNA, oxygenated hemoglobin, lipids, and lipofuscin increase, and the concentration of melanin decreases. Future studies based on minimally invasive spectral measurements will allow cancer diagnosis using the proposed approach.

Abstract
[No abstract available]

Abstract
The optical immersion clearing is an effective method to reduce light scattering in tissues, but to optimize each treatment, it is necessary to understand the mechanisms involved. Since these treatments are intended to be temporary, it is also important to know if the mechanisms involved are reversible. Various studies have been made to evaluate and characterize the mechanisms of optical clearing. In all cases studied, two major mechanisms were observed—the tissue dehydration and the refractive index matching mechanisms. Some particular studies have reported that the agents used in treatments also dissolve proteins and suggested that protein dissolution is also a clearing mechanism. All these mechanisms have been reported as reversible, both on ex vivo or on in vivo studies. We make an analysis on these studies and present a method based on ex vivo collimated transmittance and thickness measurements to characterize the major clearing mechanisms—tissue dehydration and refractive index matching. Although this method can only be made with ex vivo tissues, alternative measurements are suggested for in vivo characterization of the clearing mechanisms. © 2019, The Author(s), under exclusive license to Springer Nature Switzerland AG.

Abstract
After making an overview on the most recent progresses regarding the optical immersion treatment technique, we use this chapter to look to the future and perspectives of the following developments and benefits that can be achieved. The increasing number of publications on OC in the last 30 years, which we present in Sect. 9.1, indicates that this is a promising method to aid in the application of optical techniques in clinical practice for diagnosis or treatment purposes. Since several spectroscopy, fluorescence, or imaging methods have recently been used to test and validate the OC effects in various human and animal tissues, a collection of OCAs and OC protocols have been developed. Section 9.2 shows that to get even better results in tissue OC, the discovery of new agents and establishment of new protocols is a work in progress. Section 9.3 indicates the future perspectives for tissue spectroscopy during OC treatment and that the potential of the refractive index matching mechanism can also be evaluated in the ultraviolet range. Section 9.4 discusses the future perspectives of tissue imaging and OC. The establishment of new and faster OC protocols for tissue imaging is suggested, and indication for the necessary efforts to adapt the light-sheet technique to image in vivo is also made. Finally, Sect. 9.5 presents other applications of tissue OC and suggests the cooperation between research fields to increase knowledge in the use of OCAs and their benefits for each field. © 2019, The Author(s), under exclusive license to Springer Nature Switzerland AG.