ISEP – CIETI – Comunicações em eventos científicos
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Browsing ISEP – CIETI – Comunicações em eventos científicos by Subject "Absorption coefficient"
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- Measurement of optical properties of normal and pathological human liver tissue from deep-UV to NIRPublication . Carneiro, Isa; Carvalho, Sónia; Henrique, Rui; Oliveira, Luís; Tuchin, Valery V.The interest of using light in clinical practice is increasing strongly and many applications work at various wavelengths from the ultraviolet to the infrared. Due to this great range of applications, the determination of the optical properties of biological tissues in a wide spectral range becomes of interest. The liver is an important organ, since it has a major role in the human body and various pathologies are known to develop within it. For these reasons, this study concerns the estimation of the optical properties of human normal and pathological (metastatic carcinoma) liver tissues between 200 and 1000 nm. The obtained optical properties present the expected wavelength dependencies for both tissues – the refractive index, the absorption and the scattering coefficients decrease with the wavelength and the anisotropy and light penetration depth increase with the wavelength. Although similar behavior was observed for the various properties between the normal and pathological tissues, evidence of smaller blood content in the pathological tissues was found. A possible explanation is that the cancer cells destroy liver’s vasculature and internal architecture, providing though a reduction in the blood content. For low wavelengths, it was observed a matching between the scattering and the reduced scattering coefficients, which implies a nearly zero anisotropy in that range. The scattering coefficient decreases from nearly 140 cm-1 (at 200 nm) to 80 cm-1 (at 1000 nm) for the normal liver and from nearly 140 cm-1 (at 200 nm) to 95 cm-1 (at 1000 nm) for the pathological tissue.
- Optical properties of colorectal muscle in visible/NIR rangePublication . Carneiro, Isa; Carvalho, Sónia; Henrique, Rui; Oliveira, Luís; Tuchin, ValeryKnowledge of the optical properties of tissues is necessary, since they change from tissue to tissue and can differ between normal and pathological conditions. These properties are used in light transport models with various areas of application. In general, tissues have significantly high scattering coefficient when compared to the absorption coeficiente and such difference usually increases with decreasing wavelength. The study of the wavelength dependence of the optical properties has been already made for several animal and human tissues, but extensive research is still needed in this field. Considering that most of the Biophotonics techniques used in research and clinical practice use visible to NIR light, we have estimated the optical properties of colorectal muscle (muscularis propria) between 400 and 1000 nm. The samples used were collected from patients undergoing resection surgery for colorectal carcinoma. The estimated scattering coefficient for colorectal muscle decreases exponentially with wavelength from 122 cm-1 at 400 nm to 95 cm-1 at 650 nm and to 91 cm-1 at 1000 nm. The absorption coefficient shows a wavelength dependence according to the behavior seen for other tissues, since it decreases from 8 cm-1 at 400 nm to 2.6 cm-1 at 650 nm and to 1.3 cm-1 at 1000 nm. The estimated optical properties differ from the ones that we have previously obtained for normal and pathological colorectal mucosa. The data obtained in this study covers an extended spectral range and it can be used for planning optical clearing treatments for some wavelengths of interest.