Thermal coagulation-induced changes of the optical properties of normal and adenomatous human colon tissuesin vitroin the spectral range 400–1100 nm

Abstract

The absorption coefficients, the reduced scattering coefficients and the optical penetration depths for native and coagulated human normal and adenomatous colon tissues in vitro were determined over the range of 400-1,100 nm using a spectrophotometer with an internal integrating sphere system, and the inverse adding-doubling method was applied to calculate the tissue optical properties from diffuse reflectance and total transmittance measurements. The experimental results showed that in the range of 400-1,100 nm there were larger absorption coefficients (P < 0.01) and smaller reduced scattering coefficients (P < 0.01) for adenomatous colon tissues than for normal colon tissues, and there were smaller optical penetration depths for adenomatous colon tissues than for normal colon tissues, especially in the near-infrared wavelength. Thermal coagulation induced significant increase of the absorption coefficients and reduced scattering coefficients for the normal and adenomatous colon tissues, and significantly reduced decrease of the optical penetration depths for the normal and adenomatous colon tissues. The smaller optical penetration depth for coagulated adenomatous colon tissues is a disadvantage for laser-induced thermotherapy (LITT) and photodynamic therapy (PDT). It is necessary to adjust the application parameters of lasers to achieve optimal therapy.

Oblique incidence reflectometry: optical models and measurements using a side-viewing gradient index lens-based endoscopic imaging system

“…The measured effective attenuation coefficient varied between visually normal and adenomatous tissue, and was increased in adenoma, in agreement with previously reported studies. [39][40][41][42][43] Further improvements in endoscope design and the method of extracting tissue optical properties (μ a and μ 0 s ) will enable additional future functionality.…”

“…Light propagated through the system and illuminated a semi-infinite tissue model with refractive index, n ¼ 1.4, and cylindrical surface in contact with the endoscope envelope. A range of tissue absorption and reduced scattering properties spanning those reported in the literature for colon [39][40][41][42][43] were used: μ a , between 0.125 and 1 mm −1 and μ 0 s between 0.25 and 2.5 mm −1 , with g constant at 0.9. Diffuse light remitted from the tissue, imaged back through the distal optics, and collected within the NA of the fiber bundle was studied at an analysis surface whose square dimension was the same diameter as the clear aperture of the fiber bundle, CA ¼ 0.72 mm, and whose bin size was equal to the core size of a single fiber element within the bundle (Fig.…”

Laser surgery planning in gastrointestinal neoplasms by means of predictive modeling

“…Para modelar adecuadamente el proceso de distribución óptica es necesario conocer las propiedades ópticas de los tejidos del colon en diferentes estados a la longitud de onda de interés. En total se consideraron cinco tipos diferentes de tejidos tanto sanos como patológicos, cada uno de ellos con sus propiedades ópticas características [10][11][12][13]. Los modelos tisulares empleados fueron: modelo de tejido sano compuesto de cuatro capas (mucosa, submucosa, muscular y serosa); modelo de tejido sano coagulado con una estructura similar al anterior pero en este caso con la capa superficial (mucosa y submucosa) habiéndose sometido a un tratamiento previo de coagulación de parte del tejido (1 cm de profundidad); modelo tumoral superficial cuya primera capa está afectada por un tumor superficial de 0.1 cm de grosor que no afecta al resto del tejido; modelo tumoral no superficial en el que el tejido maligno no aparece en una zona superficial sino a una profundidad intermedia de 0.06 cm en el interior de la capa mucosa/submucosa; modelo tumoral coagulado que al igual que en el modelo de tejido sano coagulado, se asume que ha sido sometido a un tratamiento de coagulación previo que ha coagulado la zona superficial del tumor con el objetivo de conocer su influencia en la eliminación tumoral.…”

Trimodal color-fluorescence-polarization endoscopy aided by a tumor selective molecular probe accurately detects flat lesions in colitis-associated cancer

“…In order to simulate the differential optical parameters arising from tumor versus unhealthy tissue, differences in nuclear radii, density of nuclei, index of refraction of nuclei, and absorption coefficient were considered and obtained from the literature. [27][28][29][30] Perelman has successfully extracted valuable information about the density and size distribution of mucosal cells and used them as indicators of disease state (neoplastic precancerous changes in biological tissue). Increases in size and density of the nucleus is associated with a later diseased state in these studies.…”