Source separation approach for the analysis of spatially resolved multiply excited autofluorescence spectra during optical clearing of ex vivo skin

Spatially resolved multiply excited autofluorescence spectroscopy is a valuable optical biopsy technique to investigate skin UV-visible optical properties in vivo in clinics. However, it provides bulk fluorescence signals from which the individual endogenous fluorophore contributions need to be disentangled. Skin optical clearing allows for increasing tissue transparency, thus providing access to more accurate in-depth information. The aim of the present contribution was to study the time changes in skin spatially resolved and multiply excited autofluorescence spectra during skin optical clearing. The latter spectra were acquired on an ex vivo human skin strip lying on a fluorescent gel substrate during 37 minutes of the optical clearing process of a topically applied sucrose-based solution. A Non Negative Matrix Factorization-based blind source separation approach was proposed to unmix skin tissue intrinsic fluorophore contributions and to analyze the time evolution of this mixing throughout the optical clearing 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 eight measurement times. Best fitting results between experimental and estimated spectra were obtained for optimal numbers of 3 and 4 sources. These estimated spectral sources exhibited common identifiable shapes of fluorescence emission spectra related to the fluorescent gel substrate and to known skin intrinsic fluorophores matching namely dermis collagen/elastin and epidermis flavins. The time analysis of the fluorophore contributions allowed us to highlight how the clearing process towards the deepest skin layers impacts skin autofluorescence through time, namely with a strongest contribution to the bulk autofluorescence signal of dermis collagen (respectively epidermis flavins) fluorescence at shortest (respectively longest) excitation wavelengths and longest (respectively shortest) source-to-detector separations

Traitement primaire des fentes labio-maxillo-palatines unilatérales (résultats à long terme sur la croissance faciale de l'uranoplastie par greffe de périoste tibial (Nancy) en comparaison avec le protocole de traitement classique (Strasbourg) (période 1982-1986).)

STRASBOURG-Medecine (674822101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Spatially resolved diffuse reflectance and autofluorescence photon depth distribution in human skin spectroscopy: a modeling study

Published in Proceeding SPIE 11553, Optics in Health Care and Biomedical Optics X, 115531A (10 October 2020)International audienceIn the context of cutaneous carcinoma diagnosis, diffuse reflectance and skin endogenous fluorescence spectra can be analysed to spatially discard a healthy from a pathological area. Indeed, carcinogenesis is at the origin of morphological changes such as elastosis in the upper part of the dermis, or the decrease of NADH fluorescence in the basal layer of the epidermis. To ensure that the photons that contribute to the diffuse reflectance and autofluorescence spectra are likely to carry the information related to these local phenomena, we conducted an in Silico study of photon penetration into the skin. The simulation results provided numerical evidences of the behaviour of detected photons in the tissue. In particular, we succeeded in linking the characteristic penetration depth of the detected photons to their wavelengths and the source-sensor distance

Proposal for a Skin Layer-Wise Decomposition Model of Spatially-Resolved Diffuse Reflectance Spectra Based on Maximum Depth Photon Distributions: A Numerical Study

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

Impact de la pression exercée par la sonde optique sur les spectres optiques acquis sur peau humaine ex vivo et in vivo

International audienceThis work investigates the impact of several levels of optical probe pressure on human skin autofluorescence (AF) and diffuse reflectance (DR) spectra acquired using spatially-resolved optical spectroscopy in vivo and on ex vivo, i.e. exsanguinated, skin samples

Optical spectroscopy as an effective tool for skin cancer features analysis: applicability investigation

Skin Carcinoma is one of the most frequent and spreaded type of skin cancers. Its diagnosis and the resulting surgical treatment are complicated due to the lack of precise surgical margin delineation approaches. Optical methods are very promising and effective tools for bringing a clinically compatible solution to this problem because of their non-invasive principles and high informativity. Spatially Resolved Multi-Modal Spectroscopy (SRMMS) provide in vivo information with depth resolution about cancer specific features with high precision by analyzing skin Diffuse Reflectance and and Autofluorescence spectra at specific locations on tissue. Due to multiple light scattering, absorption and reflectance of the photons in the biological tissue it results in very poor photons penetration into the deeper areas and, consecutively, low depth sensitivity. Potential solution of this problem is optical clearing technology. In this work, we analyzed the time kinetics of DR and multiply excited AF spectra collected on an ex vivo skin strip on top of ex vivo skin/gel hybrid model following topical application of OCA at 4 different acquisition distances and 5 different excitation wavelengths. We then investigated the possible impact of probe pressure as well as drying of the skin sample on the spectroscopic signals, besides the optical clearing effect. The results obtained showed that the studied OCA solutions reduced autofluorescence of the skin and improved the depth sensitivity of the spectroscopy applied to the skin. Another notable effect is the strong increasing of collected exogenous fluorescence of a bottom layer in a “dry” conditions

Spatially-Resolved Multiply-Excited Autofluorescence and Diffuse Reflectance Spectroscopy: SpectroLive Medical Device for Skin In Vivo Optical Biopsy

This contribution presents the development of an optical spectroscopy device, called SpectroLive, that allows spatially-resolved multiply-excited autofluorescence and diffuse reflectance measurements. Besides describing the device, this study aims at presenting the metrological and safety regulation validations performed towards its aimed application to skin carcinoma in vivo diagnosis. This device is made of six light sources and four spectrometers for detection of the back-scattered intensity spectra collected through an optical probe (made of several optical fibers) featuring four source-to-detector separations (from 400 to 1000 µm). In order to be allowed by the French authorities to be evaluated in clinics, the SpectroLive device was successfully checked for electromagnetic compatibility and electrical and photobiological safety. In order to process spectra, spectral correction and metrological calibration were implemented in the post-processing software. Finally, we characterized the device’s sensitivity to autofluorescence detection: excitation light irradiance at the optical probe tip in contact with skin surface ranges from 2 to 11 W/m², depending on the light source. Such irradiances combined to sensitive detectors allow the device to acquire a full spectroscopic sequence within 6 s which is a short enough duration to be compatible with optical-guided surgery. All these results about sensitivity and safety make the SpectroLive device mature enough to be evaluated through a clinical trial that aims at evaluating its diagnostic accuracy for skin carcinoma diagnosis

Caractérisation par spectroscopie optique des classes tissulaires rencontrées lors de résection chirurgicale des carcinomes cutanés

National audienceLes cancers cutanés non mélanocytaires (appelés carcinomes cutanés) sont les cancers les plusfréquents, et leur prévalence est en augmentation dans l’hémisphère Nord : 20 % des plus de 60 ans sontporteurs de lésions précancéreuses [1]. La chirurgie est le traitement de référence dans la prise en chargethérapeutique de ces cancers et le plus souvent, la résection chirurgicale se fait en « fuseau » (Fig. 1). Cefuseau contient 3 types de tissu cutané dont la nature est évaluée visuellement par le chirurgien (avantdiagnostic définitif par anatomo-pathologie) : lésionnel (« L », partie visible du carcinome cutané), périlésionnel(« PL », marge de sécurité) et non-lésionnel (« NL », extrémités du fuseau).L’essai clinique SpectroLive mené actuellement au CHR Metz-Thionville propose d’évaluer lacapacité de la spectroscopie optique résolue spatialement à caractériser la nature histologique et photobiologiquede ces 3 types de tissus. Le dispositif SpectroLive [2] permet l’acquisition de spectres d’autofluorescence(pics d’excitation entre 365 et 415 nm) et de réflectance diffuse recueillis à 4 distances interfibres: de 0,4 à 1 mm. Le but est d’aider le chirurgien dans son orientation diagnostique visuelle pourdiscriminer plusieurs classes tissulaires d’intérêt clinique : (i) sain, (ii) cancer, (iii) kératose actinique àhaut potentiel évolutif et (iv) kératose à faible potentiel évolutif. Afin d’augmenter le rapport signal àbruit, 3 spectres sont acquis consécutivement sur un même site, pour chacun des 3 types de tissusrencontrés au sein du fuseau chirurgical (L, PL et NL). Les résultats préliminaires montrent unediminution globale du signal entre cancer (site de mesure « L ») et tissu sain (site de mesure « NL »), enRD à toutes les distances inter-fibres (Fig. 1b) comme en auto-fluorescence

Impact of standardization of autofluorescence and diffuse reflectance spectra on diagnosis accuracy of optical spectroscopy used for skin carcinomas diagnosis

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Analysis of skin intrinsic fluorophore contributions during optical clearing: source separation technique applied to spatially resolved multiply excited autofluorescence spectra

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