Proc. SPIE. 11640, Optical Interactions with Tissue and Cells XXXII
KEYWORDS: Photodetectors, Diffuse reflectance spectroscopy, Tissues, Scattering, Skin, Monte Carlo methods, In vivo imaging, Tissue optics, Spectroscopes, Inverse optics
In the context of cutaneous carcinoma in vivo diagnosis, Diffuse Relectance (DR) acquired using Spatially Resolved (SR) optical biopsy, can be analysed to discard healthy from pathological areas. Indeed, carcinogenesis induces local morphological and metabolic changes affecting the skin optical answer to white light excitation. The present contribution aims at studying the epidermis thickness impact on the path and propagation depth distribution of DR photons in skin in the perspective of analyzing how these photons contribute to the corresponding acquired spectra carrying local physiological information from the visited layers. Modified CudaMCML-based simulations were performed on a five-layer human skin optical model using (i) wavelength-resolved scattering and absorption properties and (ii) the geometrical configuration of a multi-optical fiber probe implemented on a SR-DR spectroscopic device currently used in clinics. Through maps of scattering events and histograms of maximum probed depth, we provide numerical evidences linking the characteristic penetration depth of the detected photons to their wavelengths and four source-sensor distances for thin, intermediate and wide skin thicknesses model. The study provides qualitative and quantitative tools that can be useful during the design of an optical SR-DR spectroscopy biopsy device.
In the context of cutaneous carcinoma in vivo diagnosis, Diffuse Relectance (DR) and skin endogenous fluores- cence (AF) spectra, acquired using Spatially Resolved (SR) multimodal optical biopsy, can be analysed to discard healthy from pathological areas. Indeed, carcinogenesis induces morphological and metabolic changes affecting endogenous fluorophores such as for instance elastosis and enzymatic degradation of collagen fluorescence in the dermis or decreased NADH fluorescence in the epidermis. The present contribution aims at studying the path and propagation depth distribution of DR and AF photons in skin in the perspective of analyzing how these photons contribute to the corresponding acquired spectra carrying local physiological information. Modified CudaMCML-based simulations were performed on a five-layer human skin optical model with (i) wavelength resolved scattering, absorption and endogenous fluorescence properties and (ii) multiple fiber optic probe ge- ometrical configuration of a SR-DR and -AF spectroscopic device. The simulation results provided numerical evidences of the behaviour of detected photons in the tissue. In particular, we succeeded in linking the character- istic penetration depth of the detected photons to their wavelengths and the source-sensor distance. In addition, we managed to identify the region where the fluorescence events associated with the AF spectrum photon take place. The study provides qualitative and quantitative tools that can be useful during the design of an optical multimodal biopsy device.
A 5-ALA-induced fluorescence-based imaging device for guidance during surgery of malignant and non-malignant preliminary photosensitized tumors is presented. The setup fits existing clinical optical rigid and flexible endoscopes and operation microscopes. It consists of three light sources including white light, red light fluorescence excitation and blue light fluorescence excitation sources. The light from any combination of the latter sources is delivered to tissue using specially designed fiber optic light guide. Two cameras are used to acquire fluorescence and back reflected white light images: a gray-level camera for fluorescence in the far red range and a color camera for white light images. A dichroic mirror is implemented to spectrally split the light coming from tissue. Images from both cameras are processed into a computer with specially developed software where it can be displayed in different modes including overlaying or been used for image mosaicing which allows for increasing the intrinsic reduced field of view of endoscopes by providing highly resolved extended cartography. Experiments were carried out on phantoms and on patients in clinical conditions during surgery of brain and other tissues. Blue light excitation was more sensitive for thin tumors but red light excitation was more beneficial for solid tumors and for navigation in presence of slight bleeding.
This contribution presents a fast global adjustment scheme exploiting SURF descriptor locations for constructing large skin mosaics. Precision in pairwise image registration is well-preserved while significantly reducing the global mosaicing error.
Cystoscopy is the standard procedure for clinical diagnosis of bladder cancer diagnosis. Bladder carcinoma in situ are often multifocal and spread over large areas. In vivo, localization and follow-up of these tumors and their nearby sites is necessary. But, due to the small field of view (FOV) of the cystoscopic video images, urologists cannot easily interpret the scene. Bladder mosaicing using image registration facilitates this interpretation through the visualization of entire lesions with respect to anatomical landmarks. The reference white light (WL) modality is affected by a strong variability in terms of texture, illumination conditions and motion blur. Moreover, in the complementary fluorescence light (FL) modality, the texture is visually different from that of the WL. Existing algorithms were developed for a particular modality and scene conditions. This paper proposes a more general on fly image registration approach for dealing with these variability issues in cystoscopy. To do so, we present a novel, robust and accurate image registration scheme by redefining the data-term of the classical total variational (TV) approach. Quantitative results on realistic bladder phantom images are used for verifying accuracy and robustness of the proposed model. This method is also qualitatively assessed with patient data mosaicing for both WL and FL modalities.
Determining the optical properties of biological tissues in vivo from spectral intensity measurements performed at their surface is still a challenge. Based on spectroscopic data acquired, the aim is to solve an inverse problem, where the optical parameter values of a forward model are to be estimated through optimization procedure of some cost function. In many cases it is an ill-posed problem because of small numbers of measures, errors on experimental data, nature of a forward model output data, which may be affected by statistical noise in the case of Monte Carlo (MC) simulation or approximated values for short inter-fibre distances (for Diffusion Equation Approximation (DEA)). In case of optical biopsy, spatially resolved diffuse reflectance spectroscopy is one simple technique that uses various excitation-toemission fibre distances to probe tissue in depths. The aim of the present contribution is to study the characteristics of some classically used cost function, optimization methods (Levenberg-Marquardt algorithm) and how it is reaching global minimum when using MC and/or DEA approaches. Several methods of smoothing filters and fitting were tested on the reflectance curves, I(r), gathered from MC simulations. It was obtained that smoothing the initial data with local regression weighted second degree polynomial and then fitting the data with double exponential decay function decreases the probability of the inverse algorithm to converge to local minima close to the initial point of first guess.
Bladder cancer is widely spread in the world. Many adequate diagnosis techniques exist. Video-endoscopy
remains the standard clinical procedure for visual exploration of the bladder internal surface. However, video-endoscopy
presents the limit that the imaged area for each image is about nearly 1 cm2. And, lesions are,
typically, spread over several images. The aim of this contribution is to assess the performance of two mosaicing
algorithms leading to the construction of panoramic maps (one unique image) of bladder walls. The quantitative
comparison study is performed on a set of real endoscopic exam data and on simulated data relative to bladder
phantom.
Bladder cancer is widely spread. Moreover, carcinoma in situ can be difficult to diagnose as it may be difficult to see,
and become invasive in 50 % of case. Non invasive diagnosis methods like photodynamic or autofluorescence
endoscopy allow enhancing sensitivity and specificity. Besides, bladder tumors can be multifocal. Multifocality
increases the probability of recurrence and infiltration into bladder muscle. Analysis of spatial distribution of tumors
could be used to improve diagnosis. We explore the feasibility to combine fluorescence and spatial information on
phantoms. We developed a system allowing the acquisition of consecutive images under white light or UV excitation
alternatively and automatically along the video sequence. We also developed an automatic image processing algorithm
to build a partial panoramic image from a cystoscopic sequence of images. Fluorescence information is extracted from
wavelength bandpass filtered images and superimposed over the cartography. Then, spatial distribution measures of
fluorescent spots can be computed. This cartography can be positioned on a 3D generic shape of bladder by selecting
some reference points. Our first results on phantoms show that it is possible to obtain cartography with fluorescent spots
and extract quantitative information of their spatial distribution on a "wide" field of view basis.
The contribution aims at describing a computer-based structured light imaging system to be applied to automated recovery of quantitative 3D information on sculptured surfaces, in order to take in charge (industrial) inspection/3D reconstruction tasks. Recovery is based on evaluation of images of the light pattern induced by projection into the scene of a specifically deviced parallel grid. The system has been designed for direct use in industrial environments, e.g. for integration into on-line quality control systems. Consequently, particular emphasis has been put on efforts for fulfilling requirements usually implied by this type of application, such as simplicity of set-up, application real-time, high accuracy, and low cost. This paper gives a discription of the system realized, including the algorithms specifically designed and implemented for calibration, nonambiguous labeling of the imaged fringes, and subpixel evaluation of their locations. The integration of the system into an on-line inspection system for 100% control of manufactured parts illustrates its application. Inspection is based on comparison of extracted features gained from a CAD model of the part and including tolerance information. Currently, a measurement accuracy of the order of 25 micrometers can be routinely achieved.
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