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International audience; In the context of cutaneous carcinoma diagnosis based on in vivo optical biopsy, Diffuse Reflectance (DR) spectra, acquired using a Spatially Resolved (SR) sensor configuration, can be analyzed to distinguish healthy from pathological tissues. The present contribution aims at studying the depth distribution of SR-DR-detected photons in skin from the perspective of analyzing how these photons contribute to acquired spectra carrying local physiological and morphological information. Simulations based on modified Cuda Monte Carlo Modeling of Light transport were performed on a five-layer human skin optical model with epidermal thickness, phototype and dermal blood content as variable parameters using (i) wavelength-resolved scattering and absorption properties and (ii) the geometrical configuration of a multi-optical fiber probe implemented on an SR-DR spectroscopic device currently used in clinics. Through histograms of the maximum probed depth and their exploitation, we provide numerical evidence linking the characteristic penetration depth of the detected photons to their wavelengths and four source–sensor distances, which made it possible to propose a decomposition of the DR signals related to skin layer contributions.

International audience; A spatially resolved multimodal spectroscopic device was used on a two-layered “hybrid” model made of ex vivo skin and fluorescent gel to investigate the effect of skin optical clearing on the depth sensitivity of optical spectroscopy. Time kinetics of fluorescence and diffuse reflectance spectra were acquired in four experimental conditions: with optical clearing agent (OCA) 1 made of polyethylene glycol 400 (PEG-400), propylene glycol and sucrose; with OCA 2 made of PEG-400 and dimethyl sulfoxide (DMSO); with saline solution as control and a “dry” condition. An increase in the gel fluorescence back reflected intensity was measured after optical clearing. Effect of OCA 2 turned out to be stronger than that of OCA 1, possibly due to DMSO impact on the stratum corneum keratin conformation. Complementary experimental results showed increased light transmittance through the skin and confirmed that the improvement in the depth sensitivity of the multimodal spectroscopic approach is related not only to the dehydration and refractive indices matching due to optical clearing, but also to the mechanical compression of tissues caused by the application of the spectroscopic probe.

International audience; In this paper, a novel optical encryption algorithm for multiple images based on chaos and DNA-blend in gyrator transform domain is proposed. Firstly, the multispectral image is divided into eight parts regularly. Subsequently the pixel positions of the blocked images are scrambled according to the pixel values of the chaotic sequences generated by 4D Lorenz system. Furthermore, eight kinds of deoxyribonucleic acid (DNA) matrices in binary form are also considered and utilized among the eight blocked fragments. Finally, the scrambled images are encoded and transformed in optical gyrator transform light field and the ciphertext is scrambled by Arnold transform to enhance the security. The proposed cryptosystem can be implemented by an electro-optical hybrid setup. Some parameters of the chaos system and gyrator transform serves as the extra keys of the encryption scheme. Some numerical simulations are implemented to testify the validity and robustness of the proposed cryptosystem for multiple images.

Published in SPIE Proceedings Volume 11640, Optical Interactions with Tissue and Cells XXXII, 116400H (2021); International audience; 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.

A novel chaotic cryptosystem for hyperspectral image, in this paper, is proposed by using a 4D hyperchaotic system in gyrator transform domains. In encryption process, a random spiral phase function (RSPF) is designed to generate variable spiral phase mask, which can be used for phase encoding with the hyperspectral image. Subsequently, the 4D hyperchaotic system is utilized to generate the chaotic sequences and these chaotic data is employed in designing RSPF, scrambling the hyperspectral image and synthesizing complex ciphertext, respectively. Finally, an improved spiral phase transform (SPT) in gyrator domains is implemented to obtain the ciphertext. To enhance the security of the encryption scheme, the ciphertext is reorganized according to the hyperchaotic attractor. Theoretical simulation analysis is given to demonstrate the validity and robustness of the proposed cryptosystem.

International audience; In this study, the changes in Spatially Resolved Diffuse Reflectance and AutoFluorescence spectra acquired on ex vivo human skin during optical clearing process (topical application) are investigated and their impact on skin optical properties (absorption, scattering and fluorescence) analyzed using inverse problem solving and multidimensional data processing approaches.

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.

International audience; Background: The study proposes to improve bladder cancer diagnosis by (i) photodynamic diagnosis (PDD) using red-light excitation (632.8 nm) of 5-ALA induced-protoporphyrin IX in 9 patients’ bladder associated to the analysis of two types of signals to improve the diagnostic accuracy, and (ii) numerical modeling of scattering coefficient for providing biological explanations of the results obtained.Methods: Two modalities of the bladder cancer spectral diagnosis are presented: conventional PDD and intensity assessment of the diffusely reflected laser light by fiber-optic spectroscopy. Experiments are done in clinical conditions and as a series of numerical simulations.Results: High-grade cancerous bladder tissues display twice a higher relative fluorescence intensity (mean value 1, n = 9) than healthy (0.39, n = 9), dysplastic (0.44, n = 5) tissues and CIS (0.39, n = 2). The laser back-scattering signal allows to discriminate most effectively high-grade cancerous and dysplastic tissues from normal. Numerical modeling of diffuse reflectance spectra reveals that spectral behavior of the back-scattered light depends on both, nuclear size and nuclear density of tumoral cells.Conclusions: Unlike the fluorescence signal, where its value is higher in the case of pathological tissues, the tendency of the laser signal to, both, decrease or increase in comparison with the signal from normal urothelium, should be perceived as a sign towards the neoplasm. Numerical simulation reveals that such a double-analysis at a multiwavelength mode potentially may be used to provide diagnostic accuracy.

We present a comprehensive analysis of the submissions to the first edition of the Endoscopy Artefact Detection challenge (EAD). Using crowd-sourcing, this initiative is a step towards understanding the limitations of existing state-of-the-art computer vision methods applied to endoscopy and promoting the development of new approaches suitable for clinical translation. Endoscopy is a routine imaging technique for the detection, diagnosis and treatment of diseases in hollow-organs; the esophagus, stomach, colon, uterus and the bladder. However the nature of these organs prevent imaged tissues to be free of imaging artefacts such as bubbles, pixel saturation, organ specularity and debris, all of which pose substantial challenges for any quantitative analysis. Consequently, the potential for improved clinical outcomes through quantitative assessment of abnormal mucosal surface observed in endoscopy videos is presently not realized accurately. The EAD challenge promotes awareness of and addresses this key bottleneck problem by investigating methods that can accurately classify, localize and segment artefacts in endoscopy frames as critical prerequisite tasks. Using a diverse curated multi-institutional, multi-modality, multi-organ dataset of video frames, the accuracy and performance of 23 algorithms were objectively ranked for artefact detection and segmentation. The ability of methods to generalize to unseen datasets was also evaluated. The best performing methods (top 15%) propose deep learning strategies to reconcile variabilities in artefact appearance with respect to size, modality, occurrence and organ type. However, no single method outperformed across all tasks. Detailed analyses reveal the shortcomings of current training strategies and highlight the need for developing new optimal metrics to accurately quantify the clinical applicability of methods.

International audience; We propose a method to generate beams according to transmission limitation condition by using the multi-distance phase retrieval algorithm. Propagation properties of hollow beams were determined by several intensity patterns along the travel axis. Predicted beams were obtained using a two-step phase filtering from a Gaussian beam with fundamental mode. An iterative phase retrieval method was employed for calculating the phase distribution in the filtering mask. This beam generation approach matched special propagation characteristics of the beams in practical applications.

International audience; An enhanced optical single-channel asymmetric cryptosystem for color image is proposed by using hyperchaotic system and random modulus decomposition (RMD) in gyrator domains. For increasing the security of the encryption scheme, a novel 4D four-winged hyperchaotic system is utilized to generate several hyperchaotic phases in the encryption approach. Subsequently, the RMD is implemented to obtain the effective trapdoor one-way function in the asymmetric process. Finally, a scrambling encoding algorithm is designed to combine and randomize the intermediate and hyperchaotic data, and the result can be regarded as the ciphertext and private key of the cryptosystem. In the decryption approach, the ciphertext and private key are imported into the input plane of gyrator transform. In fact, the proposed cryptosystem is also applicable in information authentication since the hyperchaotic data is prerequisite both in encryption and decryption approaches. Various numerical simulations are made to demonstrate the validity and capability of the proposed cryptosystem.

International audience; The current clinical study is aimed at evaluating the clinical relevance of an innovative device (called CyPaM2 device) that for the first time provides urologists with (i) a panoramic image of the bladder inner wall within the surgery time, and with (ii) a simultaneous (bimodal) display of fluorescence and white-light video streams during the fluorescence assisted–transurethral resection of bladder cancers procedure. The clinical relevance of this CyPaM2 device was evaluated on 10 patients according to three criteria (image quality, fluorescent lesions detection relevance, and ergonomics) compared with a reference medical device. Innovative features displayed by the CyPaM2 device were evaluated without any possible comparison: (i) simultaneous bimodal display of white-light and fluorescence video streams, (ii) remote light control, and (iii) time delay for the panoramic image building. The results highlight the progress to achieve in order to obtain a fully mature device ready for commercialization and the relevance of the innovative features proposed by the CyPaM2 device confirming their interest.

International audience; Spatially resolved multiply excited autofluorescence spectroscopy is a valuableoptical biopsy technique to investigate skin UV-visible optical properties in vivo in clinics.However, it provides bulk fluorescence signals from which the individual endogenous fluorophorecontributions need to be disentangled. Skin optical clearing allows for increasing tissuetransparency, thus providing access to more accurate in-depth information. The aim of thepresent contribution was to study the time changes in skin spatially resolved and multiplyexcited autofluorescence spectra during skin optical clearing. The latter spectra were acquiredon an ex vivo human skin strip lying on a fluorescent gel substrate during 37 minutes of theoptical clearing process of a topically applied sucrose-based solution. A Non Negative MatrixFactorization-based blind source separation approach was proposed to unmix skin tissue intrinsicfluorophore contributions and to analyze the time evolution of this mixing throughout the opticalclearing process. This spectral unmixing exploited the multidimensionality of the acquired data,i.e., spectra resolved in five excitation wavelengths, four source-to-detector separations, and eightmeasurement times. Best fitting results between experimental and estimated spectra were obtainedfor optimal numbers of 3 and 4 sources. These estimated spectral sources exhibited commonidentifiable shapes of fluorescence emission spectra related to the fluorescent gel substrate and toknown skin intrinsic fluorophores matching namely dermis collagen/elastin and epidermis flavins.The time analysis of the fluorophore contributions allowed us to highlight how the clearingprocess towards the deepest skin layers impacts skin autofluorescence through time, namely witha strongest contribution to the bulk autofluorescence signal of dermis collagen (respectivelyepidermis flavins) fluorescence at shortest (respectively longest) excitation wavelengths andlongest (respectively shortest) source-to-detector separations.

International audience; A single channel optical asymmetric cryptosystem for color image in fractional Fourier transform (FrFT) domain is presented. Instead of commonly used RGB channels encryption system, the color image is encoded into grayscale format and encrypted in a single optical channel system. For the design of asymmetric approach, the effective trapdoor one-way function is calculated by employing equal modulus decomposition (EMD). To enhance the security of the proposed cryptosystem, the Ushiki chaotic system is performed to generate the random phase mask in FrFT and a random sequence for scrambling the private key. The sensitive initial values and chaotic data can be regarded as the additional keys and public key. Various numerical experiments are given to verify the validity and capability of the proposed color cryptosystem.

International audience; This paper introduces a robust image mosaicing method. A variational optical flow (OF) method is first proposed to deal with scenes exhibiting strong specular reflections and few texture information. Then, a general form of descriptors invariant to complex illumination variations is given from which a novel descriptor is obtained. Non-linear transformations computed with the OF fields between the images are used to construct the mosaics. Experimental results demonstrate that the proposed method leads to coherent mosaics, even for complex gastroscopic image sequences. Furthermore, it can be potentially used to build mosaics for non-medical scenes.

Article issued from an Invited Internet Lecture. Published in Proceedings of SPIE, Volume 11065, Saratov Fall Meeting 2018: Optical and Nano-Technologies for Biology and Medicine; International audience; Optical clearing of the human skin under the action of hyaluronic acid (HA) as an enhancer for optical clearing by polyethylene glycol (PEG-300) was studied in vivo by optical coherent tomography (OCT) method on the wavelength 930±5 nm. The results have showed an increase in the transparency of the epidermis at the optical depth of 50±5 μm by 44±9% within 15 min with the use of a solution of HA in combination with sonophoresis before application of PEG-300 to the skin surface. At the same time, when using PEG-300 without preliminary treatment of the skin with the HA, an increase in the transparency of the epidermis at the same depth was 21±8% within 25 min. In dermis at the depth of 500 μm the OCT signal in the experimental group increased more than 1.6 fold what indicates an increasing of optical probing depth.

International audience; The abilities of the optical probe for fluorescence-guided stereotactic biopsy were investigated by means of a multifiber probe under 532 or632.8 nm excitation. The set of multilayered phantoms representing a border between normal brain-tissue and a tumor with photosensitizerand gold nanoparticles (spheres or stars) in different concentrations were made to investigate the macroscopic parameters observed during theneurosurgical biopsy sample collection by means of the optical probe. These investigantions will allow to define the border of a brain tumor andcontrol the type of tissue being collected by a stereotactic cannula during surgery. The impact of gold nanospheres and gold nanostars addedin different concentrations to the bottom-layer of phantom was analyzed by fluorescence quenching or enhancement due to energy transferbetween nanoparticles and fluorescent molecules. The results allow determining the tumor border and to make the biopsy uptake more efficientby observing the character of signal change while penetrating a tumor and while going out of it.

International audience; This work investigates the modifications of (i) spatially resolved diffuse reflectance and autofluorescence spectra and (ii) estimated optical properties of skin tissue resulting from optical clearing agent application.

International audience; A novel image encryption method is proposed by using the expanded fractional Fourier transform, which is implemented with a pair of lenses. Here the centers of two lenses are separated at the cross section of axis in optical system. The encryption system is addressed with Fresnel diffraction and phase modulation for the calculation of information transmission. The iterative process with the transform unit is utilized for hiding secret image. The structure parameters of a battery of lenses can be used for additional keys. The performance of encryption method is analyzed theoretically and digitally. The results show that the security of this algorithm is enhanced markedly by the added keys.

International audience; 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 dichroicmirror 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.

International audience; In this paper, a new technique for optical color image encryption by using Fresnel diffraction and a phase modulation in an extended fractional Fourier transform domain is proposed. Different from the RGB component separation based method, the color image is converted into one component by improved Chirikov mapping. The encryption system is addressed with Fresnel diffraction and phase modulation. A pair of lenses is placed into the fractional Fourier transform system for the modulation of beam propagation. The structure parameters of the optical system and parameters in Chirikov mapping serve as extra keys. Some numerical simulations are given to test the validity of the proposed cryptosystem.

International audience; After a general overview on the various types of features extracted and on the main selection and classification methods implemented in the frame of tissue fibered spectroscopy studies, the present contribution will focus on the implementation of multi-class classification schemes and the original combination of decision fusion approaches based on AutoFluorescence (AF) and Diffuse Reflectance (DR) modalities and spatial resolution through multiple Collecting-Excitation Fiber Distances (CEFS). Results confirm the interest to couple AF and DR spectroscopy measurements and show that this innovative solution based on spatial resolution data fusion leads to optimized discrimination between histological classes and reduced confusion between the closest histological classes.

This paper introduces a generalized descriptor formulation facilitating the design of illumination invariant data-terms in variational optical flow. This contribution also proposes a criterion to check whether a patch-based descriptor is illumination invariant or not. To do so, a local model is used to simulate complex illumination changes between images. As an example, it is shown how a novel patch-based descriptor can be derived from the generalized form. The performances of this descriptor are compared to those of reference descriptors in the literature using data sets with and without strong illumination changes. The accuracy and robustness of the proposed descriptor is also demonstrated through tests on gastroscopic image sequences including complex illumination changes.

Published in SPIE Proceeding, volume 10056, Design and Quality for Biomedical Technologies X, Ramesh Raghavachari, Rongguang Liang, T. Joshua Pfefer (eds), San Francisco, California, United States, January 28, 2017; International audience; Aging population as well as growing incidence of type 2 diabetes induce a growing incidence of chronic skin disorders. In the meantime, chronic shortage of dermatologists leaves some areas underserved. Remote triage and assistance to homecare nurses (known as “teledermatology”) appear to be promising solutions to provide dermatological valuation in a decent time to patients wherever they live. Nowadays, teledermatology is often based on consumer devices (digital tablets, smartphones, webcams) whose photobiological and electrical safety levels do not match with medical devices’ levels. The American Telemedicine Association (ATA) has published recommendations on quality standards for teledermatology. This “quick guide” does not address the issue of image quality which is critical in domestic environments where lighting is rarely reproducible. Standardized approaches of image quality would allow clinical trial comparison, calibration, manufacturing quality control and quality insurance during clinical use. Therefore, we defined several critical metrics using calibration charts (color and resolution charts) in order to assess image quality such as resolution, lighting uniformity, color repeatability and discrimination of key couples of colors. Using such metrics, we compared quality of images produced by several medical devices (handheld and video-dermoscopes) as well as by consumer devices (digital tablet and cameras) widely spread among dermatologists practice. Since diagnosis accuracy may be impaired by “low quality-images”, this study highlights that, from an optical point of view, teledermatology should only be performed using medical devices. Furthermore, a dedicated medical device should probably be developed for the time follow-up of skin lesions often managed in teledermatology such as chronic wounds that require i) noncontact imaging of ii) large areas of skin surfaces, both criteria that cannot be matched using dermoscopes.

Published in Proc. SPIE 10063, Dynamics and Fluctuations in Biomedical Photonics XIV, 100630Y; International audience; Diffuse reflectance spectroscopy (DRS) has been acknowledged as a valuable optical biopsy tool for in vivo characterizing pathological modifications in epithelial tissues such as cancer. In spatially resolved DRS, accurate and robust estimation of the optical parameters (OP) of biological tissues is a major challenge due to the complexity of the physical models. Solving this inverse problem requires to consider 3 components: the forward model, the cost function, and the optimization algorithm. This paper presents a comparative numerical study of the performances in estimating OP depending on the choice made for each of the latter components. Mono- and bi-layer tissue models are considered. Monowavelength (scalar) absorption and scattering coefficients are estimated. As a forward model, diffusion approximation analytical solutions with and without noise are implemented. Several cost functions are evaluated possibly including normalized data terms. Two local optimization methods, Levenberg-Marquardt and TrustRegion-Reflective, are considered. Because they may be sensitive to the initial setting, a global optimization approach is proposed to improve the estimation accuracy. This algorithm is based on repeated calls to the above-mentioned local methods, with initial parameters randomly sampled. Two global optimization methods, Genetic Algorithm (GA) and Particle Swarm Optimization (PSO), are also implemented. Estimation performances are evaluated in terms of relative errors between the ground truth and the estimated values for each set of unknown OP. The combination between the number of variables to be estimated, the nature of the forward model, the cost function to be minimized and the optimization method are discussed.

Published in Clinical and Preclinical Optical Diagnostics, J. Quincy Brown, ed., SPIE Proceedings , Vol. 10411, paper 104110O, 2017; International audience; 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.

International audience; This paper presents a framework for mosaicing high resolution skin video sequences in the context of teledermatology. While considering different stages of the mosaicing pipeline, including stitching and blending, several feature- and intensity-based image registration approaches are compared. Their performances in terms of quantitative and qualitative results are discussed so as to move towards the selection of the most suited approach. Although the intensity based approach proved to be more precise over short displacements, the feature based approach is advantageous in terms of computation time apart from being more reliable over large displacements, thus permitting a faster mosaic construction by skipping over some frames in the sequence.

Optical flow approach robust towards illumination changes and texture variability.Accurate multiscale TV-l1 approach for both small and large displacements.Accurate results for very different scenes with constant algorithm parameters.High performance was obtained on the Middlebury, KITTI and MPI Sintel databases.The algorithm enabled mosaicing of endoscopic images under different modalities. Total variational (TV) methods using l1-norm are efficient approaches for optical flow determination. This contribution presents a multi-resolution TV-l1 approach using a data-term based on neighborhood descriptors and a weighted non-local regularizer. The proposed algorithm is robust to illumination changes. The benchmarking of the proposed algorithm is done with three reference databases (Middlebury, KITTI and MPI Sintel). On these databases, the proposed approach exhibits an optimal compromise between robustness, accuracy and computation speed. Numerous tests performed both on complicated data of the reference databases and on challenging endoscopic images acquired under three different modalities demonstrate the robustness and accuracy of the method against the presence of large or small displacements, weak texture information, varying illumination conditions and modality changes.

Image mosaicing is a technique widely used for extending the field of view of industrial, medical, outdoor or indoor scenes. However, image registration can be very challenging, e.g. due to large texture variability, illumination changes, image blur and camera perspective changes. In this paper, a total variational optical flow approach is investigated to estimate dense point correspondences between image pairs. An edge preserving Riesz wavelet scale-space combined with a novel TV-regularizer is proposed for preserving motion discontinuities along the edges of weak textures and for handling strong in-plane rotations present in image sequences. An anisotropic weighted median filtering is implemented for minimizing outliers. Quantitative evaluation of the method on the Middlebury image database and simulated sequences with known ground truth demonstrates high accuracy of the proposed method in comparison with other state-of-the-art methods, including a robust graph-cut method and a patch matching approach. Qualitative results on video-sequences of difficult real scenes demonstrate the robustness of the proposed method. HighlightsMosaicing of images with strong texture and illumination variability.Fast, robust and accurate optical flow computation.TV-L1 method on a second order Riesz wavelet basis for preserving texture discontinuities.Novel anisotropic TV-regularizer.Accurate results for both the Middlebury data set and various complicated scenes.

International audience; Fluorescence endomicroscopy with spectroscopic analysis capability was used during bronchoscopy, at 488nm excitation, to record, simultaneously, autofluorescence (AF) images and associated emission spectra of the alveoli of healthy smoking volunteers (HS) and amiodarone treated non-smoker patients (ATNS). Alveolar fluorescent cellular infiltration was observed in both groups. Our objective was to assess the potential of spectroscopy in differentiating these two groups. Each normalized spectrum was modeled as a linear combination of several components: cellular flavins (FAD) and another cellular component, namely lipopigments, modelled by a Voigt profile, extracellular matrix (ECM) elastin and tobacco tar; HbO2 absorption was also taken into account. Besides the FAD and elastin contributions, the addition of a tobacco tar component is necessary to account for HS group spectral shape. The ATNS patients autofluorescence spectra result from the contribution of elastin, FAD and lipopigments, the tobacco tar component being found to zero. In conclusion, spectral analysis is able to differentiate between similar cellular infiltrated images from healthy smokers and ATNS patients.

Diagnosis improvement by means of metal nanoparticles possibilities is studied. Set of experiments to reveal their presence in deeper layers of multilayered biological tissue on optical properties is performed. Spectra in the optical range were collected on several distances, from several thicknesses of the first layer. Results are being discussed.

Published in Proc. SPIE 9537 Clinical and Biomedical Spectroscopy and Imaging IV, 95370F; International audience; This paper proposes a new approach to process spatially resolved bimodal spectroscopic data applied to mouse skin precancerous stages non-invasive diagnosis. In this field, the development of efficient methods of extraction of discriminant features followed by supervised classification step is of a crucial importance.Our idea is to exploit the spatial resolution dimensions (3 in the present study) to take advantage from the fact that each collecting fiber provides a complementary piece of information for the discrimination. The purpose of acquiring data at three different source-to-detector distances is to combine complementary spatially resolved information i.e. data from three sources on one single skin spot. Such spatial resolution allows to probe skin at three different mean depths in order to get knowledge from the various layers of skin dermis and epidermis.The first step of our method proposed here consists in applying (i) 2D discrete cosine transform to extract discriminant spectral features from autofluorescence excitation emission matrices and (ii) mutual information to select relevant features from diffuse reflectance spectra. In thesecond step, these feature sets, which capture information from each collecting fiber (among 3) per modality, is independently classified by one versus all decomposition involving support vector machines, creating a multiclassifier system. In the last step, classification results are fused using the first combination rule of belief function theory to produce one final classification. The proposed method improves overall classification accuracy over independent classifiers. The best recognition rate obtained is 86.1%.

International audience; 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.

International audience; Mosaicing of biological tissue surfaces is challenging due to the weak image textures. This contribution presents a mosaicing algorithm based on a robust and accurate variational optical flow scheme. A Riesz pyramid based multi-scale approach aims at overcoming the “flattening-out” problem at coarser levels. Moreover, the structure information present in images of epithelial surfaces is incorporated into the data-term to improve the algorithm robustness. The algorithm accuracy is first assessed with simulated sequences and then used for mosaicing standard clinical endoscopic data.

International audience; Robustness and accuracy of the existing optical flow algorithms can still be improved for noisy, low textured and poorly contrasted images. Most methods are based on the variational approach given by the Horn-Schunck model which can suffer from over-smoothing problems. In this paper, wepropose to take into account the significant structural information of the images during optical flow computation. This will allow for discontinuities across the structure boundaries. In the data-term, our optical flow model uses a classical brightness constancy assumption complemented by a modified Hessian constancy assumption based on shape structure. A constraint is added along with the regularization term, for handling the oversmoothing problems. Results on the Middlebury benchmark show the competitiveness of this algorithm. Quantitative optical flow results are given for different noise levels. Finally, application to registration of a complicated bladder cystoscopic data gives a qualitative analysis for robustness of this method.

The current study deals with new perspectives to perform more efficient classification of mouse skin precancerous stages by exploiting the spatial resolution of multimodal spectroscopic data in a decision fusion scheme based on belief functions. Keywords— optical spectroscopy, diffuse reflectance; autofluorescence; spatial resolution; data fusion; classification; skin cancer

For the estimation of in vivo tissue optical parameters based on spatially-resolved diffuse reflectance spectroscopy measures, a non-derivative Particle Swarm Optimisation approach was successfully applied as part of the inverse problem solving associated to forward Monte Carlo simulations to avoid trapping in local minima. Keywords—spectroscopy, inverse problem, particle swarm optimisation, Monte Carlo simulation

International audience; This paper describes an experimental study combining spatially resolved AutoFluorescence (AF) and Diffuse Reflectance (DR) fibred spectroscopies to discriminate in vivo between healthy and pathological tissues in a preclinical model of bladder cancer. Then, a detailed step-by-step analysis scheme is presented for the extraction and the selection of discriminative spectral features (correlation, Linear Discriminant and Logistic Regression Analysis), and for the spectroscopic data final classification algorithms (Regularized Discriminant Analysis and Support Vector Machines). Significant differences between healthy, inflammatory and tumoral tissues were obtained by selecting a reasonable number of discriminant spectral features from AF, DR and Intrinsic Fluorescence spectra, leading to improved sensitivity (87%) and specificity (77%) compared to monomodality (AF or DR alone).

International audience; Gap-Fluorescence Recovery After Photobleaching (gap-FRAP) is a technique used to estimate functionality of intercellular connections in biology. Such a technique could potentially be involved in the diagnostic of normal/cancer cells. Discrimination of cell types may be performed directly, by comparing plots of fluorescence kinetics or indirectly by statistical testing applied to model parameters. This paper focuses on the latter model-based approach. Up to now, more than ninety percent of the models used to fit gap-FRAP responses have been derived from diffusion equations (partial differential equation). We propose to simplify the modeling procedure by using behavioral models derived from system identification techniques used in control engineering. To assess in practice the relevance of this concurrent method, two human head and neck carcinoma cell lines (KB and FaDu) were used. The former (KB) expresses connexin proteins (positive line) while the latter (FaDu) does not (negative line). Moreover, each cell line was tested on spheroid (3-D) and monolayer (2-D) slices and in vitro assays were repeated six times. System identification algorithms of the CONTSID Matlab toolbox were used to estimate the model parameters from the in vitro data sets. Results have particularly emphasized there is no need to use complex models to fit the observed gap-FRAP responses. We show that the static gain of the estimated transfer functions is able to discriminate cell types used in this study, which corroborates the relevance of system identification techniques for diagnostic applications based on gap-FRAP analysis.

International audience; Structured-light systems (SLSs) are widely used in active stereo vision to perform 3D modelling of a surface of interest. We propose a flexible method to calibrate SLSs projecting point patterns. The method is flexible in two respects. First, the calibration is independent of the number of points and their spatial distribution inside the pattern. Second, no positioning device is required since the projector geometry is determined in the camera coordinate system based on unknown positions of the calibration board. The projector optical center is estimated together with the 3D rays originating from the projector using a numerical optimization procedure. We study the 3D point reconstruction accuracy for two SLSs involving a laser based projector and a pico-projector, respectively, and for three point patterns. We finally illustrate the potential of our active vision system for a medical endoscopy application where a 3D cartography of the inspected organ (a large field of view surface also including image textures) can be reconstructed from a video acquisition using the laser based SLS.

Fibered confocal fluorescence microscopy (FCFM) with spectroscopic analysis capability was used during bronchoscopy, at 488nm excitation, to record autofluorescence images and associated emission spectra of the alveoli of 5 healthy smoking volunteers and 7 non-smoking amiodarone-induced pneumonitis (AIP) patients. Alveolar fluorescent cellular infiltration was observed in both groups. Our objective was to assess the potential of spectroscopy in differentiating these two groups. Methods: We previously demonstrated that in healthy smokers alveolar elastin backbone and tobacco tar contained in macrophages contribute to the observed signal. Each normalized spectrum was modeled as a linear combination of 3 components: S exp (λ) = C e .S e (λ)+C t .S t (λ)+C G .S G (λ), C e , C t and C G are amplitude coefficients. S e (λ) and S t (λ) are respectively the normalized elastin and tobacco tar emission spectra measured experimentally and S G (λ) a gaussian spectrum with tunable width and central wavelength. Levenbergt-Marquardt algorithm determined the optimal set of coefficients. Results: AIP patient autofluorescence spectra can be uniquely modelized by the linear combination of the elastin spectrum (C e = 0.61) and of a gaussian spectrum (center wavelength 550nm, width 40nm); the tobacco tar spectrum coefficient C t is found to be zero. For healthy smoking volunteers, only two spectral components were considered: the tobacco tar component (C t = 1,03) and the elastin component (C e = 0). Conclusion: Spectral analysis is able to distinguish cellular infiltrated images from AIP patients and healthy smoking volunteers. It appears as a powerful complementary tool for FCFM.

Objective: The objective of this study was two folds: firstly, we would like to investigate the efficiency of bimodal spectroscopic technique in characterization of hypertrophic scarring tissue deliberately created on a preclinical model (rabbit's ear); on the other hand, we evaluate the inhibition effect of an anti-inflammatory medication (tacrolimus) on hypertrophic formation in scar by using our bimodal spectroscopic system. Study design: This study was conducted on 20 New Zealand Rabbits receiving hypertrophic scarring treatment on their ears. Fluorescence and Diffuse Reflectance spectra were collected from each scar, amongst which some had received tacrolimus treatment. Features were extracted from corrected spectral data and analyzed to classify the scarring tissues into hypertrophic or non-hypertrophic. Diagnostic algorithms were developed with the use of k-NN classifier and validated by comparing to histological classification result with Leave-one- out cross validation. Results and discussion: The accuracy of our bimodal spectroscopy method for detecting hypertrophic scarring scar tissue was good (sensibility: 90.84%, specificity: 94.44%). The features used for classification were mainly extracted from the spectra exited at 360, 410 and 420 nm. This indicates that the difference between the spectra acquired from hypertrophic and non-hypertrophic tissue may be due to the different intensity distribution of several fluorophores (collagen,elastin and NADH) excited in this range, or to the change in proportion of tissue layers (epidermis and dermis) explored by the CEFS in use.

Nombre de pages : 4; International audience; Video-endoscopy is the standard clinical procedure for visual exploration of internal walls of hollow organs. For the bladder, the lesion diagnosis is complex because the endoscopic images are bi-dimensional and cover only small bladder areas. 3D endoscopes, based on stereoscopic active vision principles, were recently proposed and validated. This paper presents a 3D reconstruction algorithm using 2D texture images and a few 3D points located on the internal wall surfaces provided by such endoscopes. The algorithm constructs a 3D panoramic surface using the 3D reconstruction method guided by 2D image registration. We show on realistic bladder phantoms that the algorithm is able to reconstruct 3D points and surfaces with a sub-millimetre accuracy.

International audience; This contribution deals with the calibration of active stereoscopic systems consisting of a camera and a structured light projector. Usually, expensive equipments like precise calibration pieces or dedicated positioning devices are used for the projector calibration. We developed a flexible calibration method using only a planar target as calibration board without other equipment. The method requires only two image acquisitions from which the projector parameters are estimated using an optimization method. A quantitative evaluation demonstrates the accuracy and flexibility of the proposed calibration method.

International audience; Spatially-resolved bimodal spectroscopy (multiple AutoFluorescence AF excitation and Diffuse Reflectance DR), was used in vivo to discriminate various healthy and precancerous skin stages in a pre-clinical model (UV-irradiated mouse): Compensatory Hyperplasia CH, Atypical Hyperplasia AH and Dysplasia D. A specific data preprocessing scheme was applied to intensity spectra (filtering, spectral correction and intensity normalization), and several sets of spectral characteristics were automatically extracted and selected based on their discrimination power, statistically tested for every pair-wise comparison of histological classes. Data reduction with Principal Components Analysis (PCA) was performed and 3 classification methods were implemented (k-NN, LDA and SVM), in order to compare diagnostic performance of each method. Diagnostic performance was studied and assessed in terms of Sensibility (Se) and Specificity (Sp) as a function of the selected features, of the combinations of 3 different inter-fibres distances and of the numbers of principal components, such that: Se and Sp [approximate] 100% when discriminating CH vs. others; Sp [approximate] 100% and Se > 95% when discriminating Healthy vs. AH or D; Sp [approximate] 74% and Se [approximate] 63% for AH vs. D.

This paper deals with the development and application of in vivo spatially-resolved bimodal spectroscopy (AutoFluorescence AF and Diffuse Reflectance DR), to discriminate various stages of skin precancer in a preclinical model (UV-irradiated mouse): Compensatory Hyperplasia CH, Atypical Hyperplasia AH and Dysplasia D. A programmable instrumentation was developed for acquiring AF emission spectra using 7 excitation wavelengths: 360, 368, 390, 400, 410, 420 and 430 nm, and DR spectra in the 390–720 nm wavelength range. After various steps of intensity spectra preprocessing (filtering, spectral correction and intensity normalization), several sets of spectral characteristics were extracted and selected based on their discrimination power statistically tested for every pair-wise comparison of histological classes. Data reduction with Principal Components Analysis (PCA) was performed and 3 classification methods were implemented (k-NN, LDA and SVM), in order to compare diagnostic performance of each method. Diagnostic performance was studied and assessed in terms of sensitivity (Se) and specificity (Sp) as a function of the selected features, of the combinations of 3 different inter-fibers distances and of the numbers of principal components, such that: Se and Sp ≈ 100% when discriminating CH vs. others; Sp ≈ 100% and Se > 95% when discriminating Healthy vs. AH or D; Sp ≈ 74% and Se ≈ 63% for AH vs. D.

International audience; Histopathological analysis and in vivo optical spectroscopy were used to discriminate several histological stages of UV-irradiated mouse skin. At different times throughout the 30-week irradiation, autofluorescence (AF) and diffuse reflectance (DR) spectra were acquired in a bimodal approach. Then skin was sampled and processed to be classified, according to morphological criteria, into four histological categories: normal, and three types of hyperplasia (compensatory, atypical, and dysplastic). After extracting spectral characteristics, principal component analysis (data reduction) and the k-nearest neighbor classifying method were applied to compare diagnostic performances of monoexcitation AF (based on each of the seven excitation wavelengths: 360, 368, 390, 400, 410, 420, and 430 nm), multiexcitation AF (combining the seven excitation wavelengths), DR, and bimodal spectroscopies. Visible wavelengths are the most sensitive ones to discriminate compensatory from precancerous (atypical and dysplastic) states. Multiexcitation AF provides an average 6-percentage-point increased sensitivity compared to the best scores obtained with monoexcitation AF for all pairs of tissue categories. Bimodality results in a 4-percentage-point increase of specificity when discriminating the three types of hyperplasia. Thus, bimodal spectroscopy appears to be a promising tool to discriminate benign from precancerous stages; clinical investigations should be carried out to confirm these results.

International audience; Combining autofluorescence (AF) and Diffuse Reflectance (DR) spectroscopies is supposed to improve diagnosispsila accuracy of early stages of cancer (as well as precancerous stages) which is of great clinical importance. For the present study, we developed a bimodal instrumentation combining spatially resolved AF and DR spectroscopies, and evaluated its ability to distinguish between healthy, inflammatory and early stages of cancers in vivo. In order to get such tissue types, we used 2 animal models: a rat bladder orthotopic cancer model and a mice UV-irradiated skin model. The first study shows that combining AF and DR improves both sensitivity and specificity of the diagnosis compared to one modality used alone: Se = 67% (DR alone), 72% (AF alone) increases up to 78% when combining the two modalities. Preliminary results of the second study reveal that some spectroscopic criteria may help quantitative histological analysis in making the difference between acute and precancerous hyperplasia.

http://www.biotechniques.com/default.asp?page=article_archive&subsection=article_display&year=2008&issue=7/1/2008&id=112810; The role of gap junctional intercellular communication (GJIC) in regulation of normal growth and differentiation is becoming increasingly recognized as a major cellular function. GJIC consists of intercellular exchange of low molecular weight molecules, and is the only means for direct contact between cytoplasms of adjacent animal cells. Disturbances of GJIC have been associated with many pathological conditions, such as carcinogenesis or hereditary illness. Reliable and accurate methods for the determination of GJIC are therefore important in cell biology studies. There are several methods used successfully in numerous laboratories to measure GJIC both in vitro and in vivo. This review comments on techniques currently used to study cell-to-cell communication, either by measuring dye transfer, as in methods like microinjection, scrape loading, gap-fluorescence recovery after photobleaching (gap-FRAP), the preloading assay, and local activation of a molecular fluorescent probe (LAMP), or by measuring electrical conductance and metabolic cooperation. As we will discuss in this review, these techniques are not equivalent but instead provide complementary information. We will focus on their main advantages and limitations. Although biological applications guide the choice of techniques we describe, we also review points that must be taken into consideration before using a methodology, such as the number of cells to analyze.

This work describes an algorithm for the automatic construction of 2-D panoramas from sequences of images taken from a cystoscopic exam. During a cystoscopy, the existent distance between the cystoscope and the bladder walls allows the clinician to observe only a reduced region of the zone of interest. A panoramic representation of this zone could represent a better visual support to the clinician in the localization of eventual lesions and in the application of further exams. We also explore the application of this algorithm to endoscopic fluorescence imaging, one of the main procedures used in the detection of epithelial cancers.