Diagnosis of vulvar lesions by non-invasive optical analysis: a pilot study

A procedure that could allow an early in vivo and non-invasive detection of vulvar lesions would be extremely useful. We tested an innovative optical method (Optiprobe), which uses a harmless, visible light source for the in vivo, on-line detection of minimal alterations in the structure of vulvar epithelium. A group of 3 female volunteers without gynecological symptoms were first screened to evaluate optical properties of normal vulvar tissue. Next, a group of 16 patients undergoing gynecological examination for vulvar lesions was evaluated by the Optiprobe at suspected sites before these sites were biopsied for histological analysis. Adjacent, non-involved sites were also measured to provide internal controls. Histological analysis of the biopsies identified one case that did not show obvious alterations, 4 cases of high-grade vulvar intraepithelial neoplasia (VIN), 5 cases of vulvitis, and 6 cases of lichen sclerosis (LS)

Optical spectral probing for epithelial tissue characterisation

In this thesis, a new method has been developed, which determines the optical coefficients spectra (absorption and scattering) of small volumes of tissue (1 mm3) by the measurement of spatially resolved reflectance between 480 and 950 nm. Firstly, an algorithm has been developed to determine the optical coefficients form reflectance measurements: It is based on the optical propagation model introduced by Bevilacqua [Bevilacqua 99 JOSA]. This model takes the first two moments of the phase function into account through the γ parameter, allowing to accurately simulate the propagation of photons close to the source by the Monte Carlo method. These simulations are then fitted to the reflectance to obtain the optical coefficients. To obtain any value of absorption, scattering or γ parameter, the simulations are interpolated by 3D B-splines. A complete robustness to noise study of the algorithm has been presented. A theoretical study of the γ parameter in tissue over broad wavelengths has been reported. Tissue was simulated with Mie theory for a fractal distribution of sphere diameters. For such a distribution, the γ spectrum is almost flat, instead of being wavy like in the case of mono-disperse sphere diameter. The correlation of the mean value of γ with the fractal power (or dimension) of the distribution was made and showed an analytical form of hyperbolic tangent. It allowed deepening the interpretation of the γ parameter as being an indicator of the relative number of small scatterers (much smaller than the wavelength, e.g. of Rayleigh type) in comparison of bigger ones (their size being comparable to the wavelength). The assessment of the set-up and the algorithm was made by measuring the reflectance of a solution containing 5 different diameters of polystyrene spheres simulating the scattering and Nigrosin colorant as absorber. It showed a good agreement between measurements and prediction. In order to built a better comprehension of absorption and scattering at the tissue scale, a first part of in vivo investigations has been made on an animal model. The skin of the mouse back was altered with Freund's adjuvant and TPA and the optical coefficients were measured on treated and control sites. The effect of alteration (epidermis and dermis thickening, oil vesicle appearing, inflammatory cells infiltration, etc.) was clearly correlated with optical coefficients variations. The scattering spectrum always showed the better contrast. The absorption spectrum, especially in the haemoglobin peak region (between 550 and 600 nm) also showed significant information, in terms of oxy and deoxy-haemoglobin concentration and saturation. Sensitivity and specificity of the "diagnosis" was evaluated. The study of stomach epithelium in vivo on 29 human subjects was made using a small optical fibre probe (<2mm in diameter) through the working channel of an endoscope used in routine gastroscopic examination. An optical contrast in scattering and absorption was found between the antral (lower) part of the stomach and the fundus (upper part). In the antrum, gastritis cases were studied and showed a good optical contrast (100% sensitivity and 78.8% of specificity). Indications on sub-types of gastritis are likely to be deduced from optical properties, but further measurements should be made to confirm this tendency. Because of its high sensitivity, the optical set-up and algorithm presented in this work has been found to give valuable indications to physicians to localise the interesting biopsy sites and may give on-time indications on the tissue pathology

In vivo endoscopic tissue diagnostics based on spectroscopic absorption, scattering, and phase function properties

A fast spectroscopic system for superficial and local determination of the absorption and scattering properties of tissue (480 to 950 nm) is described. The probe can be used in the working channel of an endoscope. The scattering properties include the reduced scattering coefficient and a parameter of the phase function called gamma, which depends on its first two moments. The inverse problem algorithm is based on the fit of absolute reflectance measurements to cubic B-spline functions derived from the interpolation of a set of Monte Carlo simulations. The algorithm's robustness was tested with simulations altered with various amounts of noise. The method was also assessed on tissue phantoms of known optical properties. Finally, clinical measurements performed endoscopically in vivo in the stomach of human subjects are presented. The absorption and scattering properties were found to be significantly different in the antrum and in the fundus and are correlated with histopathologic observations. The method and the instrument show promise for noninvasive tissue diagnostics of various epithelia. (c) 2003 Society of Photo-Optical Instrumentation Engineers