Parmi les approches d'imagerie préclinique, les techniques optiques sur petit animal fournissent une information fonctionnelle sur un phénomène biologique ainsi que sur sa localisation. De récents développements permettent d'exploiter ces méthodes dans le cadre de l'imagerie sur animal vigile. Les conditions physiologiques se rapprochent alors de celles du fonctionnement normal de l'organisme. Les travaux de cette thèse ont porté sur l'utilisation optimale de cette modalité via des méthodes originales d'analyse et de traitement.Les problèmes soulevés par la fusion des flux cinématiques et de données de bioluminescence nous ont amené à proposer des approches complémentaires d’estimationde mouvement de l’animal. La représentation sous forme implicite des informations issuesde la vidéo de l’animal permettent de construire un critère robuste à minimiser. L’ajout d’uncritère global mesurant la compacité du signal optique permet de considérer dans sa totalité les données multicanaux acquises pour augmenter la précision du recalage. Finalement ces deux modélisations offrent des résultats pertinents et validés expérimentalement.Dans le but de s'affranchir des contraintes de l'observation planaire de nos données nous avons conçu une méthode d’estimation du mouvement 3D de l’animal à partir d’un modèle pré-calculé. Grâce à un système d'acquisition multi-vues et simultanée de la scène, il est possible d’ajouter une contrainte sur l'estimation de la position de la source pour rendre robuste le suivi des poses issues de la vidéo. Les résultats expérimentaux montrent le potentiel de cette méthode pour fournir des mesures 3D précises sur l'animal vigile. / Optical imaging techniques, have taken, since many years, a great part in the preclinicalstudies. The luminescence signal could be now recorded with a short time resolution whichenables studies with freely moving animals. This is an improvement because several studieshighlighted the impact of anesthetics agent and animal handling to perform studies inphysiological conditions. In this thesis, we define the tools, based on computer visionmethods, which offer the possibility to express the potential of this modality.In some cases, animal movement and low signal produce weak localization of the signal.Therefore we propose to improve localization of the optical data for a freely moving animal byusing motion field obtained from the multi-channel data. First, we introduce silhouetteconstraints and landmarks on the mouse skin within a variation framework. To take intoaccount all data in the registration framework, we combine the previously defined criteria,with global ones which measure compactness of signal distribution. Fusion is formulated as adiscrete population framework which produces strong experimental results in comparison topairwise method.In the last part, we propose an original approach to enable 3D optical imaging in case offreely moving animal. Therefore, we present a novel model-based method to animal trackingfrom monocular video which allows the 3D measurement of the signal. The 3D animal poseand the illumination are dynamically estimated through minimization of an objective functionwith constraints on the signal position. Experimental results demonstrate the potential of ourapproach for 3D accurate measurement with freely moving animal.

New methods to measure and quantify tissue molecular composition and metabolism are a major driver of discovery in basic and clinical research. Optical methods are well suited for this task based on the non-invasive nature of many imaging and spectroscopy techniques, the variety of exogenous fluorescent probes available, and the ability to utilize label-free endogenous absorption signatures of tissue chromophores including oxy- and deoxy-hemoglobin, water, lipid, collagen, and glucose. Despite significant advances in biomedical imaging, there remain challenges in probing tissue information in a fast, wide-field, and non-invasive manner. Moreover, quantitative in vivo mapping of endogenous biomarkers such as water and lipids remain relatively less explored by the biomedical optics community due to their characteristic extinction spectra, which have distinct spectral features in the shortwave infrared, a wavelength band that has been traditionally more challenging to measure. The work presented in this dissertation was focused on developing instrumentation and algorithms for non-invasive quantification of tissue optical properties, fluorophore concentrations, and chromophore concentrations in a wide-field imaging format. All of the imaging methods and algorithms developed in this thesis extend the capability of the emerging technique called Spatial Frequency Domain Imaging (SFDI). First, a new imaging technique based on SFDI is presented that can quantify the quantum yield of exogenous fluorophores in tissue. This technique can potentially provide a new non-invasive means for in vivo mapping of local tissue environment such as temperature and pH. Next, an angle correction algorithm was developed for SFDI for more accurate estimation of tissue optical properties as well as chromophore concentrations in highly curved tissue, including small animal tumor models. Next, a wide-field label-free optical imaging system was developed to simultaneously measure water and lipids using the shortwave infrared (SWIR) wavelength region. Last, to break the bottleneck of processing speed in optical property inversion, new deep learning based models were developed to provide over 300× processing speed improvement. Together, these projects substantially extend the available contrasts and throughput of SFDI, providing opportunities for new preclinical and clinical applications. / 2020-10-22T00:00:00Z

<p><br></p> <p>Magnetic resonance imaging (MRI) plays an important role in providing structural information, aiding in disease diagnosis, probing neuron activities, and etc. Sampling k-space, which is the Fourier transform of the image, is a necessary step in MRI scans. The most widely used k-space sampling strategy is the Cartesian trajectories. However, novel non-Cartesian trajectories are flexible and efficient in k-space sampling, permit shorter echo time, and are insensitive to motion artifacts. The non-Cartesian k-space patterns include radial, spiral, concentric rings, rosette, and etc. Some protons restricted by the chemical environment, or other nuclei because of their nature, have short transverse relaxation times (T₂). Ultra-short echo time (UTE) and zero echo time (ZTE) modalities are the promising techniques to capture the rapid decaying signals directly. The common k-space pattern for UTE and ZTE applications is the three-dimensional radial acquisition, which allows a center-out trajectory. Rosette k-space trajectory, which also allows center-out sampling, is a potential candidate for UTE purposes. In addition, it acquires more samples in the peripheral k-space for better spatial resolution, and is more incoherent to stand image quality upon undersampling than radial. However, the rosette trajectories have not yet been applied in UTE.</p> <p> </p> <p>In this study, a 3D rosette k-space trajectory designed for UTE acquisition is developed. In addition, a rosette-based magnetic resonance spectroscopic imaging (MRSI) is also developed to measure metabolites with short echo time. A comparison between 3D rosette and 3D radial UTE sequences, based on both phantom and <em>in vivo</em> scans, was performed to test the performance of the novel sequence. In addition, the 3D rosette UTE sequence was also applied in 1) myelin bilayer imaging, 2) brain iron content mapping, 3) cartilage image by sodium MRI, and 4) phosphorus MRSI. In summary, the 3D rosette k-space trajectory performs better than radial, in terms of point spread function (PSF), signal-to-noise ratio (SNR), and ability to provide structural details. Furthermore, the applications have demonstrated that 3D rosette UTE sequence is able to capture fast decaying signals.</p>

<p> This thesis presents solutions to several inverse problems m electromagnetism and microwave engineering. In general, these inverse problems belong to two applications: breast cancer diagnosis using microwave imaging and defect characterization in metallic structures using magnetic flux leakage (MFL). </p> <p> Our contribution in microwave imaging for breast tumor detection can be divided into three parts. First, we propose a novel ultra-wide band (UWB) antenna that can operate in direct contact with the breast without the need for coupling liquids. This antenna is designed such that more than 90% of the radiated power is directed toward the tissue from its front aperture over the UWB. The performance of the antenna is investigated via simulation and measurement of the following parameters: return loss, near-field directivity, efficiency, fidelity, and group velocity. Overall, the results show that the antenna is a good candidate for frequency and time-domain imaging techniques. </p> <p> Second, we have proposed an aperture raster scanning setup that benefits from the features of our novel antenna. In this scanning setup, the breast tissue is compressed between two rectangular plates (apertures) while two antennas perform two-dimensional (2-D) scan by moving together on both sides of the compressed tissue. For each scanning step, the transmission S-parameter between the two antennas is recorded at several frequencies within UWB. Then, the modulus of the calibrated transmission S-parameter is plotted at each frequency to provide a 2-D image of the interior of the breast. The images are enhanced using a de-blurring technique based on blind de-convolution. This setup provides real time images of strong scatterers inside the normal tissue. </p> <p> Third, we propose 2-D and three-dimensional (3-D) holography algorithms to further improve the quality of the images obtained from the proposed planar scanning setup. These techniques are based on the Fourier transforms of the collected data to provide an image of a 2-D target (when collecting data at a single frequency) or a 3-D target (when collecting wide-band data). These techniques are fast and very robust to noise. The capability of the 2D and 3-D holographic imaging techniques is examined via simulation results. </p> <p> For defect characterization in metallic structures using MFL technique, we propose fast and reliable methodologies to invert the measured MFL response to the defect's shape parameters. First, we present a procedure to estimate the shape parameters of rectangular cracks which are the most common type of defects in the metallic structures. The procedure consists of estimating orientation, length, and depth of the cracks, consecutively. We validate this procedure via estimating the shape parameters of pre-known cracks from the simulated and measured MFL responses. Then, we present a methodology based on space mapping (SM) optimization for defect characterization. We examme the efficiency of this methodology for two types of defects: rectangular cracks and cylindrical pits. </p> / Thesis / Doctor of Philosophy (PhD)

No description available.

<p dir="ltr">Murine, or small rodent, models can provide valuable and translatable insights into human pathophysiology. Specifically, we are looking to combine murine models and high-frequency ultrasound to non-invasively investigate microrobot drug delivery systems, cardiac effects of lactation on the mother during postpartum, and cardiac remodeling due to the combination of pregnancy and hypertension.</p><p dir="ltr">Currently, we are looking at the applications of microrobots within the colon to provide targeted treatment for patients suffering from inflammatory bowel disease (IBD). IBD is an overarching term encompassing chronic inflammation of the digestive tract tissue. The standard treatment of IBD includes oral and injectable treatments depending on disease severity. The drawbacks of these therapeutics are the associated systemic toxicity, non-specific treatment allocation, and degradation of the treatment in proximal portions of the gastrointestinal (GI) system. The goal of this research is to use an external magnetic torque to cause the microrobots to tumble to targeted areas of inflammation and release a drug payload. Retroactive locomotion of these microrobots can avoid degradation in the proximal GI tract. Therefore, these microrobots need a smaller drug payload to provide the same efficacy as traditional treatments.</p><p dir="ltr">The cardiovascular system adapts to meet the growing physiological demands of pregnancy. Although this change has been greatly studied, it is unclear if this change in shape and function returns to prepregnant values during postpartum. Previous research has also shown that lactation affects the mother’s hemodynamics during postpartum, but its impact on cardiac morphology is still not completely understood. To study this further, we longitudinally tracked cardiovascular changes using ultrasound and blood pressure measurements in C57BL6/J mice during pregnancy and postpartum that were either lactating or not.</p><p dir="ltr">Chronic hypertension affects approximately 1 in 20 pregnancies and its prevalence in pregnancies continues to increase. The maternal cardiovascular system goes through dynamic changes during pregnancy to meet the demands of perfusing the gestation, especially during the exponential growth seen later in pregnancy. Studies with female C57BL6/J mice demonstrate comparable cardiovascular changes during pregnancy to those observed in humans. Additionally, a study using rats showed the cardioprotective properties of pregnancy against angiotensin II-induced fibrosis. The objective of this study is to characterize non-invasive cardiac remodeling in a small animal model of hypertensive disorders in pregnancy. We used a combination of ultrasound imaging and noninvasive blood pressure measurements to longitudinally monitor the physiological adaptations that occur during pregnancy with superimposed hypertension.</p>

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-05-17T18:27:28Z No. of bitstreams: 1 Tese - Elisa Magno Nunes de Oliveira.pdf: 7318970 bytes, checksum: a50f399a4afea119cd760c93cd71ff72 (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-05-23T14:59:14Z (GMT) No. of bitstreams: 1 Tese - Elisa Magno Nunes de Oliveira.pdf: 7318970 bytes, checksum: a50f399a4afea119cd760c93cd71ff72 (MD5) / Made available in DSpace on 2018-05-23T15:10:26Z (GMT). No. of bitstreams: 1 Tese - Elisa Magno Nunes de Oliveira.pdf: 7318970 bytes, checksum: a50f399a4afea119cd760c93cd71ff72 (MD5) Previous issue date: 2018-03-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / The present study focuses on the development of nanoparticles with an iron oxide magnetic core, with different biocompatible coatings, and on a comparative study of their toxicities. Uncoated and dextran-, chitosan-, polyethylene glycol- and silica-coated nanoparticles were synthesized. The addition of optical markers of the benzo-thiazoles class was also accomplished. The physico-chemical properties of the nano-particles were characterized, including their magnetic, optical and contrast properties in nuclear magnetic resonance imaging (relaxivities). In the particular case of nanopar-ticles functionalized with 6-OH-BTA-1 molecules, the affinity to the beta-amyloid pep-tide was also investigated. A second step was to evaluate the toxicological effects of these nanoparticles in vitro (using in VERO cells), and in vivo with zebrafish as an animal model. The size of the nanoparticles with the coatings ranged from 13 to 30 nm. Their crystalline structure was consistent with the ferrite spinel. The nanoparticles, independent of the coating, did not present residual magnetization and hysteresis, in-dicating superparamagnetic behaviour. For most nanoparticles, the r2 transverse re-laxivity values ranged from 76-64 mM-1.s-1, exceptfor uncoated and chitosan-coated nanoparticles, which present higher values, possibly due to the aggregation. The val-ues of r1 were similar for all nanoparticles (12.6 to 18 mM-1.s-1), with the exception of silica-coated nanoparticles (r1=2.1 mM-1.s-1). The r2/r1 ratios were between 4 and 17, typical of commercially available negative contrast-agents. The nanoparticles function-alized with benzothiazoles showed fluorescence with a Stokes shift of the emission peak of ~ 197 nm. The interaction of the beta-amyloid peptide with the 6-OH-BTA-1 molecule analyzed by fluorescence suppression is characterized by a static mecha-nism and Stern-Volmer constants of 1.53x104 mM-1 for the monomeric form, 1.40x104 mM -1 for oligomers) and 1.33x104 mM -1 for amyloid plaques.The in vitro toxicity assays indicated acceptable values of cell viability for iron concentration up to 2 mmol.L-1. The nanoparticles with the carboxysilane and polyethylene glycol showed higher biocom-patibility and silica-coated nanoparticles had the highest cytotoxicity. The in vivo as-says did not show significant changes in survival and hatchability rates, except for doses greater than 2 mmol.L-1 in the case of the chitosan-coated nanoparticles. The percentages of animals with anatomical alterations were similar between the treated and control groups. In the locomotion and exploration tests, only chitosan- and silica-coated nanoparticles induced significant changes. / O presente trabalho aborda o desenvolvimento de nanopart?culas compostas por um n?cleo magn?tico de ?xido de ferro com diferentes revestimentos biocompat?-veis e estudo comparativo de suas toxicidades. Foram sintetizadas nanopart?culas de ?xido de ferro sem revestimento e com revestimentos de dextrana, quitosana, polieti-lenoglicol e s?lica, e com a adi??o de marcadores ?pticos da classe dos benzotiaz?is. As propriedades f?sico-qu?micas das nanopart?culas foram caracterizadas, incluindo as suas propriedades magn?ticas, ?pticas e de contraste em imagens por resson?ncia magn?tica nuclear (relaxividades), bem como a afinidade ao pept?deo beta-amiloide, no caso particular de funcionaliza??o com a mol?cula 6-OH-BTA-1. Em uma segunda etapa, foram avaliados os efeitos toxicol?gicos dessas nanopart?culas em ensaios bi-ol?gicos in vitro em c?lulas VERO, e in vivo tendo como animal modelo o peixe zebra. O tamanho das nanopart?culas com revestimentos variou entre 13 a 30 nm, e estrutura cristalina coerente com o espin?lio de ferrita. As nanopart?culas n?o apresentaram magnetiza??o residual e histerese, indicando superparamagnetismo, independente do revestimento. Para a maioria das nanopart?culas, os valores de relaxividade transver-sal r2 variaram de 76-64 mM-1.s-1, com exce??o das nanopart?culas sem revestimento e de quitosana, os quais foram mais elevados, possivelmente devido ao efeito de agrega??o. Os valores de r1 foram semelhantes para todas as nanopart?culas (12,6 a 18 mM-1.s-1), com exce??o das nanopart?culas de s?lica (r1 = 2,1 mM-1.s-1). As raz?es r2/r1 foram entre 4 e 17, valores t?picos de agentes de contraste negativos comercial-mente dispon?veis. As nanopart?culas funcionalizadas com os benzotiaz?is mantive-ram sua fluoresc?ncia com deslocamentos de Stokes na ordem de 197 nm para o pico de emiss?o. As an?lises da intera??o do pept?deo beta-amiloide com a mol?cula 6-OH-BTA-1, mostraram valores de constante de Stern-Volmer para supress?o de fluo-resc?ncia de 1,53x104 mM-1 (mon?mero), 1,40x104 mM-1 (olig?mero) e 1,33x104 mM-1 (placa), indicando quenching por um mecanismo est?tico. O pept?deo na forma mo-nom?rica demonstrou maior facilidade de acesso ?s mol?culas de 6-OH-BTA-1. Os resultados dos ensaios in vitro indicaram valores aceit?veis de viabilidade celular para concentra??o de ferro inferior a 2 mmol.L-1. As nanopart?culas com o carboxisilano e polietilenoglicol demostraram maior biocompatibilidade e as nanopart?culas de s?lica tiveram a maior citotoxicidade. Os resultados dos ensaios in vivo n?o mostraram alte-ra??es significativas na taxa de sobreviv?ncia e de eclos?o do corium, exceto para as doses maiores que 2 mmol.L-1 das nanopart?culas revestidas com quitosana. Os per-centuais de animais com altera??es anat?micas foram similares entre os grupos tra-tados e de controle. Nos ensaios de locomo??o e explora??o, apenas as nanopart?cu-las de quitosana e de s?lica induziram altera??es adversas significativas.

Cartilage tissue engineering has been emerging as a promising therapeutic approach, where engineered constructs or scaffolds are used as temporary supports to promote regeneration of functional cartilage tissue. Hybrid constructs fabricated from cells, hydrogels, and solid polymeric materials show the most potential for their enhanced biological and mechanical properties. However, fabrication of customized hybrid constructs with impregnated cells is still in its infancy and many issues related to their structural integrity and the cell functions need to be addressed by research. Meanwhile, it is noticed that nowadays monitoring the success of tissue engineered constructs must rely on animal models, which have to be sacrificed for subsequent examination based on histological techniques. This becomes a critical issue as tissue engineering advances from animal to human studies, thus raising a great need for non-invasive assessments of engineered constructs in situ. To address the aforementioned issues, this research is aimed to (1) develop novel fabrication processes to fabricate hybrid constructs incorporating living cells (hereafter referred as “construct biofabrication”) for cartilage tissue regeneration and (2) develop non-invasive monitoring methods based on synchrotron X-ray imaging techniques for examining cartilage tissue constructs in situ. Based on three-dimensional (3D) printing techniques, novel biofabrication processes were developed to create constructs from synthetic polycaprolactone (PCL) polymer framework and cell-impregnated alginate hydrogel, so as to provide both structural and biological properties as desired in cartilage tissue engineering. To ensure the structural integrity of the constructs, the influence of both PCL polymer and alginate was examined, thus forming a basis to prepare materials for subsequent construct biofabrication. To ensure the biological properties, three types of cells, i.e., two primary cell populations from embryonic chick sternum and an established chondrocyte cell line of ATDC5 were chosen to be incorporated in the construct biofabrication. The biological performance of the cells in the construct were examined along with the influence of the polymer melting temperature on them. The promising results of cell viability and proliferation as well as cartilage matrix production demonstrate that the developed processes are appropriate for fabricating hybrid constructs for cartilage tissue engineering. To develop non-invasive in situ assessment methods for cartilage and other soft tissue engineering applications, synchrotron phase-based X-ray imaging techniques of diffraction enhanced imaging (DEI), analyzer based imaging (ABI), and inline phase contrast imaging (PCI) were investigated, respectively, with samples prepared from pig knees implanted with low density scaffolds. The results from the computed-tomography (CT)-DEI, CT-ABI, and extended-distance CT-PCI showed the scaffold implanted in pig knee cartilage in situ with structural properties more clearly than conventional PCI and clinical MRI, thus providing information and means for tracking the success of scaffolds in tissue repair and remodeling. To optimize the methods for live animal and eventually for human patients, strategies with the aim to reduce the radiation dose during the imaging process were developed by reducing the number of CT projections, region of imaging, and imaging resolution. The results of the developed strategies illustrate that effective dose for CT-DEI, CT-ABI, and extended-distance CT-PCI could be reduced to 0.3-10 mSv, comparable to the dose for clinical X-ray scans, without compromising the image quality. Taken together, synchrotron X-ray imaging techniques were illustrated promising for developing non-invasive monitoring methods for examining cartilage tissue constructs in live animals and eventually in human patients.

Les nanocristaux à structure non-centrosymétrique présentent des propriétés optiques non linéaires prometteuses pour une utilisation en tant que marqueurs optiques en imagerie biomédicale, avec un intérêt significatif en termes de suivi sur de longues durées et de profondeur de pénétration dans les tissus biologiques. Le développement de ces marqueurs nécessite la détermination de leurs efficacités optiques non linéaires afin de pouvoir sélectionner les nanocristaux les plus prometteurs. Pour cela, la technique de diffusion Hyper-Rayleigh a été adaptée à la caractérisation de suspensions de nanoparticules (BaTiO3, KNbO3, KTP, LiNbO3 et ZnO, BiFeO3) pour lesquelles l’influence de paramètres comme la taille, la concentration ou l’état d’agrégation a été analysée et discutée. Les nanocristaux de BiFeO3 possèdent une efficacité optique non linéaire largement supérieure aux autres particules, démontrant leur potentiel pour la réalisation de nano-sondes optiques particulièrement performantes. Des mesures résolues en polarisation ont également été mises en œuvre pour déterminer les coefficients optiques non linéaires indépendants des particules étudiées. Dans ce cadre, une étude a permis de mettre en évidence l’influence de la forme des nanocristaux sur cette réponse. / Non-centrosymetric nanocrystals show promising nonlinear optical properties for being used as optical labels in bio-imaging applications, with significant interest for observations of long duration and for penetration depth into biological tissues. The development of such biomarkers requires the determination of their nonlinear optical properties to select the best potential markers. In this thesis, Hyper-Rayleigh Scattering (HRS) technique is used to determine nonlinear efficiencies of several nanocystals (BaTiO3, KNbO3, KTP, LiNbO3, ZnO and BiFeO3). These ensemble measurements have been performed on nanocrystals suspensions, for which the influence of parameters such as size, concentration and aggregation state was discussed. BiFeO3nanocrystals offer the best nonlinear optical efficiency compared to other particles, showing their potential as efficient optical biomarkers. Polarisation-resolved measurements have also been performed to retrieve individual coefficients of the nonlinear tensor of the investigated materials and influent parameters such as nanocrystals shape have been identified.

L’imagerie de filtrage en polarisation est une technique populaire largement utilisée en optique pour le biomédical pour le sondage des tissus superficiels, pour le sondage de volumes plus profonds, mais aussi pour l’examen sélectif de volumes sub-surfaciques. Du fait de l’effet de ’mémoire de polarisation’ de la lumière polarisée, l’imagerie de filtrage en polarisation elliptique est sensible á des épaisseurs de tissus différentes, depuis la surface, accessible avec la polarisation linéaire, jusqu’á une épaisseur critique accessible par la polarisation circulaire. Nous nous concentrons sur des méthodes utilisant des combinaisons de polarisations elliptiques afin de sélectionner la portion de lumière ayant maintenu son état de polarisation et éliminer le fond pour un meilleur contraste avec de plus une information sur la profondeur. Avec ce type de filtrage, il est possible d’accéder á des profondeurs de tissus biologiques bien définies selon l’ellipticité de polarisation. De plus, ces travaux ont permis d’étendre la méthode á la spectroscopie pour quantifier la concentration en chromophores á une profondeur spécifique. Les méthodes développées ont été validées in vivo á l’aide d’expériences réalisées sur des anomalies de la peau et aussi sur le cortex exposé d’un rat anesthésié. Enfin, une étude préliminaire a été réalisée pour examiner la possibilité d’étendre la méthode á l’imagerie de 'speckle'. Des tests préliminaires réalises sur fantômes montrent l’influence de l’ellipticité de polarisation sur la formation et le comportement du speckle, ce qui offre la possibilité d’accéder á des informations sur le flux sanguin á des profondeurs spécifiques dans les tissus. / Polarization gating imaging is a popular and widely used imaging technique in biomedical optics to sense tissues, deeper volumes, and also selectively probe sub-superficial volumes. Due to the ‘polarization memory’ effect of polarized light, elliptical polarization gating allows access to tissue layers between those of accessible by linear or circular polarizations. As opposed to the conventional linearly polarized illumination, we focus on polarization gating methods that combine the use of elliptically polarized light to select polarization-maintaining photons and eliminate the background while providing superior contrast and depth information. With gating, it has also become possible to access user-defined depths (dependent on optical properties) in biological tissues with the use of images at different ellipticities. Furthermore, this investigation allowed the application of polarization gating in spectroscopy to selectively quantify the concentration of tissue chromophores at user-desired depths. Polarization gating methods have been validated and demonstrated with in vivo experiments on abnormalities of human skin (nevus, burn scar) and also on the exposed cortex of an anaesthetized rat. Finally, as a first step towards the use of coherent illumination, adding the concept of polarimetry to laser-speckle imaging was demonstrated. Preliminary tests on phantoms (solid and liquid) suggested evidence of the influence of polarization ellipticity on the formation and behaviour of speckles, which could pave the way for more insight in the study of blood flow in tissues.