Monte Carlo model to describe depth selective fluorescence spectra of epithelial tissue: applications for diagnosis of oral precancer

Abstract

We present a Monte Carlo model to predict fluorescence spectra of the oral mucosa obtained with a depth-selective fiber optic probe as a function of tissue optical properties. A model sensitivity analysis determines how variations in optical parameters associated with neoplastic development influence the intensity and shape of spectra, and elucidates the biological basis for differences in spectra from normal and premalignant oral sites. Predictions indicate that spectra of oral mucosa collected with a depth-selective probe are affected by variations in epithelial optical properties, and to a lesser extent, by changes in superficial stromal parameters, but not by changes in the optical properties of deeper stroma. The depth selective probe offers enhanced detection of epithelial fluorescence, with 90% of the detected signal originating from the epithelium and superficial stroma. Predicted depth-selective spectra are in good agreement with measured average spectra from normal and dysplastic oral sites. Changes in parameters associated with dysplastic progression lead to a decreased fluorescence intensity and a shift of the spectra to longer emission wavelengths. Decreased fluorescence is due to a drop in detected stromal photons, whereas the shift of spectral shape is attributed to an increased fraction of detected photons arising in the epithelium.

Dual‐wavelength excitation for fluorescence‐based quantification of zinc protoporphyrin IX and protoporphyrin IX in whole blood

“…Among the main tissue fluorophores are collagen and elastin crosslinks [43], whose fluorescence intensities are expected to exceed the ZnPP fluorescence signal remitted from tissue surfaces by two orders of magnitude. Therefore, methods for efficient suppression of background fluorescence are required for successful non-invasive ZnPP/heme ratio quantification.…”

Fluorescence spectroscopy for the detection of potentially malignant disorders and squamous cell carcinoma of the oral cavity

“…This finding is particularly visible in the excitation at 406 nm. Epithelial fluorophores such as NADH also play a role in the features of the spectra of shallow depths and stromal fluorophores, such as collagen, contribute to the measured signal from deeper regions [8,18,19].…”

“…In non-keratinized tissue diagnostic performance was achieved using only optical spectra short and medium depths. The discrimination spectra normal and abnormal sites is better when used excitations smaller ranges, which is heavily skewed to the epithelial layer and minimizes the effects of the absorption of hemoglobin [19,35]. Our optical system do not have discrimination of the information from distinct tissue layers, the final response is the contribution of the total volume.…”

“…The fluorescence spectroscopy has become an important tool in detecting potentially malignant and malignant lesions in the oral mucosa [17,18]. The biochemical composition and tissue architecture can be assessed by the emitted fluorescence spectrum, which will be modified in the presence of tissue alterations [19]. Mathematical algorithms can then be developed and optimized to classify the respective tissues in histological categories based on their spectral characteristics [20][21][22][23].…”

Multipurpose Monte Carlo simulator for photon transport in turbid media

“…This work deals with photon transport simulation in a complex setup in which multiple light sources illuminates the sample and several detectors are placed around the object. The goal is to develope a flexible code capable of simulating diagnostic [2,3] and therapeutic [4] particular emphasis on optical tomography, either diffuse (DFOT) [5,6], or projective [7]. Fluorescence optical tomography (FOT), is a particular case of DFOT, where the aim is to retrieve the localization of fluorochrome-labeled agents.…”