Quick and specific non-linear microscopy using shaped pulses with durations down to 10fs

Nonlinear optical microscopy is ideally suited for in vivo imaging: it provides label-free contrast revealing intrinsic structural and chemical properties of the sample in a non-invasive way. Successful nonlinear microscopy relies on the use of pulsed lasers to obtain high signal levels at moderate average laser power. In particular, broadband excitation increases the nonlinear generation efficiency as well as the spectral coverage. However, lower photodamage thresholds and less straightforward signal interpretation have prevented its application to sensitive samples. In this thesis, a pulse shaper is used to tailor ultrashort pulses for optimal imaging. This work concentrates on Coherent Anti-Stokes Raman Scattering (CARS) because it provides an access to highly specific vibrational spectra. The main concept is to encode molecule-specific information directly in the excitation. This is realized either by direct tailoring in a shaperassisted variant of a Multiplex CARS setup or by phase shaping of a single ultrashort pulse (<10fs). The photon load reduction and the optimization of the pulse profile achieved by shaping are demonstrated with the imaging of polymer samples and sensitive biological tissue. The flexibility of the setup allows switching between spectrally resolved acquisition for precise chemical mapping and single channel detection for rapid imaging. Further nonlinear effects can likewise be controlled by pulse shaping. In this work, the systematic modification of the relative intensities of Second Harmonic Generation (SHG), Two-Photon Excited Fluorescence (TPEF) and CARS is investigated as well as selective excitation of fluorophores and molecular vibrations. Multimodal imaging with shaped ultrashort pulses proves to be particularly efficient for biological samples as illustrated by the imaging of plant cells and skin biopsies

Complementary analysis of Mueller-matrix images of optically anisotropic highly scattering biological tissues

Background: Using optical techniques for tissue diagnostics (so-called ‘optical biopsy’) has been a subject of extensive research for many years. Various groups have been exploring different spectral and/or imaging modalities (e.g. diffuse reflectance spectroscopy, autofluorescence, Raman spectroscopy, optical coherence tomography (OCT), polarized light microscopy, etc.) for biomedical applications. In this paper, we report on using multi-wavelength imaging Mueller polarimetry combined with an appropriated image post-processing for the detection of tissue malignancy. Methods: We investigate a possibility of complementary analysis of Mueller matrix images obtained for turbid tissue-like scattering phantoms and excised human normal and cancerous colorectal tissue samples embedded in paraffin. Combined application of correlation, fractal and statistical analysis was employed to assess quantitatively the polarization-inhomogeneous scattered fields observed at the surface of tissue samples. Results: The combined analysis of the polarimetric images of paraffin-embedded tissue blocks has proved to be an efficient tool for the unambiguous detection of tissue malignant transformation. A fractal structure was clearly observed at spatial distributions of depolarization of light scattered in healthy tissues in a visible range of spectrum, while corresponding distributions for cancerous tissues did not show such dependence. We demonstrate that paraffin does not destroy a fractal structure of spatial distribution of depolarization. Thus, the loss of fractality in spatial distributions of depolarization for cancerous tissue is related to the structural changes in the tissue sample induced by cancer itself and, therefore, may serve as a marker of the disease. Conclusion: The obtained results emphasize that a combined use of statistical, correlation and fractal analysis for the Mueller-matrix image post-processing is an effective approach for an assessment of variations of optical properties in turbid tissue-like scattering media and biological tissues, with a high potential to be transferred to clinical practice for screening cancerous tissue samples

Berner Kommentar, Der Arbeitsvertrag, Art. 319-362 OR, Einleitung und Kommentar zu Art. 319-330b, Band VI, 2. Abteilung, 2. Teilband, 1. Abschnitt

Seit dem Erscheinen der von Manfred Rehbinder verfassten Vorauflage (1985) ist die Entwicklung im Einzelarbeitsvertragsrecht vor allem durch eine wesentlich dichtere Rechtsprechung geprägt. Vermehrt sind auch die Urteile kantonaler Gerichte verfügbar gemacht worden. Dadurch erhöhte sich die Rechtssicherheit deutlich. Ferner sind vermehrt normative Bestimmungen von Gesamtarbeitsverträgen als weitere wichtige Rechtsquelle exemplarisch in den Kommentar eingearbeitet worden

Mueller Polarimetric Imaging for Cervical Intraepithelial Neoplasia Detection

International audienc

Depolarization imaging for fast and non-invasive monitoring of cervical microstructure remodeling in vivo during pregnancy

Abstract The cervix plays a crucial role in conception, maintenance of pregnancy, and childbirth. The mechanical properties of a pregnant woman's cervix change dramatically during gestation due to a remodeling of its microstructure, necessary for delivery. However, external factors can accelerate this process and lead to prematurity, the primary cause of perinatal mortality worldwide, due to the inefficiency of existing diagnostic methods. This study shows that polarized light is a powerful tool to probe the cervical microstructure during pregnancy. A wide-field multispectral polarimetric imaging system was fabricated to explore in vivo the cervix of full-term pregnant women. The polarimetric properties of the cervix change significantly with pregnancy progression. In particular, a set of several depolarization parameters (intrinsic and extrinsic) showed a strong linear correlation with gestational age in the red part of the visible spectral range. This trend can be attributed, among other things, to a decrease in collagen density and an increase in hydration of cervical connective tissue. Wide field depolarization imaging is a very promising tool for rapid and non-invasive analysis of cervical tissue in vivo to monitor the steady progression of pregnancy, providing the practitioner with useful information to improve the detection of preterm birth

Monitoring subcutaneous tumors using Mueller polarimetry: study on two types of tumors

A better understanding of tumor development is crucial for treating cancer. Polarimetric imaging is an interesting alternative for monitoring subcutaneous tumors as it is non-invasive. In this study, a Mueller spectro-polarimeter is used to monitor tumor development on mice injected with non-pigmented breast cancer cells or with pigmented murine melanoma cells. Three stages of non-pigmented tumor development are revealed with three polarimetric parameters. These stages also appear for pigmented tumors, although less clearly. A halo of high depolarization surrounding the non-pigmented tumor in the first stage allows the outlining of the tumor. Considering polarimetric parameters, a biological interpretation is proposed