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Deruelle, Tristan. "Magnetic Resonance Elastography : towards prostate cancer imaging and slow compression wave imaging in softtissues". Electronic Thesis or Diss., Lyon, 2022. http://www.theses.fr/2022LYSE1068.
Pełny tekst źródłaProstate cancer is the second most prevalent cancer in men worldwide. It is suspected when the PSA density is high or/and the superficial prostate feels hard during digital rectal examination. Multiparametric MRI is now recommended prior biopsy when detecting for cancer. However, image interpretation is challenging, even for specialists, and brings many false-positive. Elastography is a technique to assess tissue stiffness by inducing small vibrations. It could provide a 3D map of the stiffness of the prostate. We believe that MR elastography could complement the current multiparametric MRI. Given prostate location and consitution, wave propagation is difficult though. The current work presents the design of a non-invasive wave generation device for the prostate. Then, a new field separation algorithm is presented. This algorithm provides a better estimation of the stiffness, and the correction of artefact generated by common vibrators. Finally, this algorithm can have applications in porous media. Indeed, in poro-elastic materials, a slow compression wave propagates. We observe such a wave in an agar gel, in a foam phantom, and in vivo in human kidney graft. In addition to the classic shear wave velocity estimation, it is now possible to estimate the compression wave velocity. This is an additional piece of information that the operator can use in its diagnostic. In the future, more porous parameters could be derived
Tardieu, Marion. "Élastographie par résonance magnétique et onde de pression guidée". Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01059105.
Pełny tekst źródłaJulea, Felicia. "Conditions de validité de l'Élastographie par Résonance Magnétique". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS053/document.
Pełny tekst źródłaMagnetic Resonance Elastography (MRE) is a imaging technique, recognized as a pertinent method for the mechanical characterization of human tissue in vivo. It offersa particular interest in clinical diagnosis because the development of a pathological process is often accompanied by modifications of the mechanical properties of diseased tissues. MRE consists of recording, along the three spatial dimensions, the displacement field induced by the propagation of a shear wave generated by excitation of the investigated tissue. Mechanical parameters such as shear wave velocity, v, and shear moduli, G' and G'', can then be mapped. The quantification of the mechanical parameters depends on the frequency of the mechanical excitation, fexc, the spatial resolution, a, the amplitude of the induced displacement field, A and the amplitude of the curl field displacement, q, with associated measurement errors, ΔA and Δq, (related to the signal-to-noise ratio, SNR) and finally the reconstruction method. All these parameters were considered to determine the precision and the accuracy of the estimated mechanical moduli and to establish the conditions of validity of MRE following the inversion of the differential equations of the displacement field. In this work, first A and A/ΔA were considered to define a validity threshold for MRE. The influence of A and A/ΔA was studied on a heterogeneous phantom acquired using a 1.5 T MRI with two different types of coils. In a first study, the displacement fields were acquired as a function of A using motion-sensitized spin-echo (REF) and gradient-echo (FFE) sequences for an isotropic spatial resolution of 1 mm. In a second study, the displacement field was acquired as a function of A using RFE for three different spatial resolutions. These studies revealed the existence of a threshold in A/ΔA beyond which the extracted parameters (G', G'') reach a plateau and the MRE is reliable. Then the number of voxels per wavelength, λ/a was considered as a parameter determining the conditions of validity of MRE. This parameter was studied according to the quality of the acquired data characterized by the ratio q//Δq. Simulations were carried in a homogeneous and isotropic elastic medium with a SNR between 5 and 30. The accuracy and the precision of the measurements were found optimal for 6 to 9 voxels per wavelength. The simulation conditions were experimentally reproduced at 2 kHz on a home-made polyvinyl alcohol phantom. The displacement fields were acquired at 11.7 T using a motion-sensitized RFE sequence with spatial resolutions ranging from 150 μm to 300 μm in order to obtain a λ/a ratio ranging from 1 to 20. The experimental results fully confirm the predictions of the simulation. The shear wave velocity decreases with λ/a. It tends towards the expected reference value when the acquisition is performed in the optimal condition, namely here when a is less than or equal to 200 μm. In addition, the standard deviation of the shear wave velocity is reduced for the optimal conditions. Therefore, accurate estimation of mechanical parameters could be deduced. This thesis first demonstrates that the precision and accuracy of MRE are optimal when the acquisitions are performed or processed for a certain wavelength sampling range determined by the SNR. We also showed that for fair comparison of the results, MRE must be carried out in a similar range of q/Δq. Taking into account the conditions of validity of MRE, determined by the ratios λ/a and q/Δq, leads to an effective quantitative measurement of the mechanical parameters making it possible to establish a relevant clinical diagnosis within the same organ, the same subject, between subjects or over time
Kurtz, Samuel. "Caractérisation et limitation des biais de mesure de l’élastographie par résonance magnétique". Electronic Thesis or Diss., Université de Montpellier (2022-....), 2023. http://www.theses.fr/2023UMONS023.
Pełny tekst źródłaMagnetic Resonance Elastography (MRE) is an adapted technique of MRI for non-invasive and in vivo characterization of mechanical properties of living tissues. MRE typically involves identifying properties associated with a displacement field induced by the propagation of shear waves in the tissue medium. The fundamental interest of MRE relies in the strong contrast of the mechanical properties of soft tissues, which are relevant biomarkers for the detection and staging of pathological processes. Since its introduction in the late 1990s, MRE has established itself as a versatile medical imaging modality providing quantitative maps of the soft tissues viscoelasticity. The field of applications of MRE is vast, and the gradual growth of this technique in a clinical setting testifies to its significant interest.However, the high degree of interdisciplinarity of MRE, and the resulting interactions between actors from different communities, represent a barrier to its development. The absence of rigorous methods for integrating measurement biases is an illustrative example of this problem. This thesis work is built around addressing this bias problem.The first axis is motivated by the need to characterize biases related to MRI measurements. To do this, an optical slicing tomography device and a digital volume correlation procedure are adapted to provide three-dimensional harmonic kinematic field measurements. The validation of the device is tested by analyzing the fields obtained on different phantom materials. The consideration of different sources of measurement errors and the diversity of measurable fields make this device a metrological tool for measuring such kinematic fields in an MRI environment.The second axis focuses on limiting the impact of measurement errors in the identification model. To achieve this, a coupled formulation of the direct adjoint problem that underlies MRE is implemented in a subzone decomposition-based identification algorithm for a nearly-incompressible, isotropic, viscoelastic model. This specific formulation relies on the presence of a complementary field to avoid the indirect influence of measurement errors through their application as Dirichlet-type boundary conditions which are particularly abundant considering the subzone decomposition of the problem. It is thus demonstrated that the non-consideration of the boundary conditions contributes significantly to the quality of identifications.The developments presented in this work are compared to several studies on reconstructions of mechanical properties of in silico data, phantoms, and in vivo human brain. These applications provide a detailed evaluation of the stability gains of the algorithm and establish new standards for driving the spatial resolution of identifications in MRE. These developments are particularly useful for validating preclinical MRE studies
Madelin, Guillaume. "Développements méthodologiques de l'IRM à bas champ : élastographie, interaction IRM-Ultasons et polarisation dynamique nucléaire". Bordeaux 2, 2005. http://www.theses.fr/2005BOR21253.
Pełny tekst źródłaThis thesis deals with low field (0. 2 T) Magnetic Resonance Imaging (MRI). Magnetic Resonance Elastography allows to assess some viscoelastic properties of tissues by imaging of acoustic strain waves. In the next part, an ultrasonic transducer was calibrated using the comparison of the balance method and laser interferometry. Then, it was tried to modify the T1 contrast of tissues by spin-phonon interaction due to the application of ultrasound at the Larmor frequency. No modification was obtained, but an acoustic streaming was observed. The visualization of this streaming makes possible to calibrate transducers and to assess some properties of liquids. The last part was dedicated to set up Dynamic Nuclear Polarization experiments, based on the polarization transfer of unpaired electrons of free radicals to the protons of water. An enhancement of the NMR signal by a factor 30 was obtained on nitroxides
Bigot, Mathilde. "Élastographie par résonance magnétique multifréquence in vitro et ex vivo pour la caractérisation d’agrégats fibrillaires cérébraux". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1207.
Pełny tekst źródłaAmong several biological processes involved in dementia, fibrillar aggregation of endogenous proteins with altered conformation is an early characteristic of neurodegenerative diseases. Magnetic resonance elastography (MRE), an imaging technique that maps the mechanical properties of tissues, has recently been applied in neurodegenerative diseases. Although mechanical changes associated with these diseases have been detected, the mechanical effect of fibril has not yet been isolated in clinical or preclinical studies. This thesis work aims to exploit the fractal properties of fibrils to differentiate them from non-aggregated proteins. The exponent of the power law, obtained by adjusting multi-frequency MRE data acquired on phantom and rat brain ex vivo, could reveal at the macroscopic scale the presence of these fibrillar aggregates at the microscopic scale. During this thesis, an MRI elastography bench for imaging in vitro and ex vivo samples was developed. This device made it possible to implement a series of multi-frequency MRE measurements (400 to 1200Hz) on agarose samples containing two types of fibrils, α-Syn and Aβ, and a non-aggregated protein used as a control. The same device has made it possible to characterize with multi-frequency MRE (800 to 1200Hz) rat brains ex vivo previously injected with α-Syn in the striatum. For each rat, the contralateral striatum was injected with saline solution and used as a control. All MRE data were acquired on a 4.7T preclinical system using a modified RARE sequence. After a direct 3D inversion, the storage modulus, phase angle and wave velocity were extracted from the elastograms. The power law exponent is obtained by adjusting to the multi-frequency data. In inclusions containing fibrils, y was significantly higher than in those containing nonaggregated protein. This result is all the more interesting because the mono-frequency parameters were not affected much by the presence of fibrils: multi-frequency MRE provides information on the microstructure of tissues and makes it possible to characterize fibrillar proteins, however small they may be (a few μm). In rats, storage and loss modules decrease significantly over all frequencies studied compared to contralateral striatum. The parameters y and ϕ on the other hand do not allow discriminating between fibril injection and control injection. Further experiments would be needed to understand the absence of ex vivo detection. This thesis constitutes an original methodological contribution in the field of MRE, by isolating for the first time the biomechanical effect of fibrillar structures involved in neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease
Testu, Julien. "Mise en œuvre de l'élastographie par résonance magnétique multifréquentielle au Centre hospitalier universitaire de Sherbrooke". Mémoire, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11090.
Pełny tekst źródłaDebernard, Laëtitia. "Caractérisation des propriétés mécaniques des muscles avec la technique d'Élastographie par Résonance Magnétique (ERM)". Compiègne, 2011. http://www.theses.fr/2011COMP1974.
Pełny tekst źródłaThe objective of my thesis was to characterize the mechanical properties of the muscles of the thigh with magnetic resonance elastography (MRE) during physiological changes (growing muscle and age-related changes) and pathological process (Duchenne muscular dystrophy). This thesis depicted that shear modulus was a mechanical parameter more sensitive to the aged-related neuromuscular changes, while the attenuation coefficient was more related to the muscle quality, thus to the age and gender-related structural changes. Study of viscoelastic parameters of muscle tissue (vastus medialis and sartorius) and subcutaneous adipose tissue, with multi-frequency tests ERMs and rheological models (Voigt, Zener and Springpot) showed that the model Springpot was the best adapted for simulation of the viscoelastic properties. In addition, mapping of the shear modulus was correlated with the cartography of the muscle hardness, obtained by ultrasound elastography, thus validating the feasibility of the MRE to detect physiological changes in muscle. Finally, these data were used for the development of phantoms, reflecting muscle mechanical properties. All data, set up with that thesis, will be of use for the clinician to better determine the pathophysiology of neuromuscular disorder, to help in the choice of treatment (therapeutic or surgical) and in the evaluation of future treatments with a gain of function and tissue for the simulation the musculoskeletal system
Leclerc, Gwladys. "Identification expérimentale et numérique des propriétés mécanique des tissus biologiques avec la technique d'Elastographie par Résonance Magnétique (ERM) : application au tissu hépatique". Compiègne, 2012. http://www.theses.fr/2012COMP2038.
Pełny tekst źródłaMy research work was to identify experimentally and numerically the mechanical properties of the liver with Magnetic Resonance Elastography (MRE) technique. The first in vitro part of this project was to develop a phantom mimicking the mechanical properties of the liver. Hyper-viscoelastic properties of the phantom were identified with compression tests, and MRE tests performed with a multifrequency protocol using a hepatic driver generating waves within the liver. In parallel to this experimental identification, a finite element analysis of the propagation of the wave was made through a simplified 2D model, composed of the phantom, with the boundary conditions of MRE test (amplitude of displacement of the membrane, frequency), subsequently with a 3D model. An inverse method was also developed to numerically characterize the elastic properties of the phantom. The results obtained experimentally and numerically were similar (μ = 4 kPa), the identification process was validated and the phantom reveals the elastic properties of fibrotic liver tissue. The second in vivo part was focused on the study of the viscoelastic properties of healthy and fibrotic livers with multifrequency MRE tests. The elasticity increases with the stage of fibrosis. An analysis of the post-treatment (inversion algorithm, rheological models) showed different results of the viscosity with the stage of fibrosis. In addition, a 3D finite element model of the liver was reconstructed, with anatomical MRI slices, to simulate a MRE test and to analyze the behavior of the shear waves. These simulations enabled to adapt MRE protocols before the clinical phase
Hagot, Pascal. "Evaluation de l’interaction fluide-structure dans les Voies Aériennes Supérieures par Imagerie par Résonance Magnétique". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112059/document.
Pełny tekst źródłaObstructive Sleep Apnea (OSA) is a common disorder occurring in almost 3 million French people. However, current diagnosis methods are not sufficient to precisely define obstructing sites and doesn't take into account the fluid structure coupling which plays an important role during upper airway closing. During this thesis, we developed a series of tools exploring upper airway closing process. On the one hand, a screening tool of the structure and the mechanical properties of the upper airway, and on the other hand, a screening tool exploring with dynamic images of inert gases flow into the upper airway, were obtained using conventional hydrogen MRI coupled to magnetic resonance elastography (MRE) and helium-3 or fluor-19 gases MRI, respectively. Geometric and biomechanical data obtained using MRI/MRE are injected into a numerical model given the compliance and the state law of upper airway. Contributions of anatomical restriction on airway collapse are also investigated using a multi-compartmental two-dimensional fluid structure interaction model during a breath inspiration to predicted airway mechanical changes and collapse pressures. Furthermore, helium 3 and sulfur hexafluoride flow was modeled at steady state using commercial finite volume software to evaluate potential feasibility to image upper airway collapsibility during OSA. First dynamic MR imaging using sulfur hexafluoride (SF6) was obtained showing the feasibility of this technique. Using SF6, 6 times denser than air, shows a higher sensibility to upper airway obstruction. This thesis opens a new imaging modality to probe and to diagnose upper airway obstruction
Crézé, Maud. "Les muscles paravertébraux lombaires : de l’anatomie à l’étude en élastographie ultrasonore et par résonance magnétique, appliquées à la lombalgie chronique". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS182/document.
Pełny tekst źródłaKnowledge about the anatomy and the mode of action of the lumbar paraspinal muscles is major importance for the management of low back pain. Surgical experience shows that the paraspinal muscles constitute a voluminous muscle mass without large tendons and enclosed in an inextensible fascia. In biomechanics, the maximum strength of a muscle is positively correlated to the cross-sectional area of tendons and the muscle belly. Therefore, there is a paradox between the presumed high strength of the voluminous muscle belly and the low strength of the tendons. Traditional biomechanical models seem inappropriate for describing the mode of action of the paraspinal muscles. According to the beam theory, increasing elasticity within the paraspinal compartment would allow the stabilization of the spine.The work has two broad objectives. The first objective was to assess the assumption that there is an inconsistency betwenn the cross-sectional area of the tendon and of the belly of the main paraspinal muscles, i.e. the multifidus, the longissius and the iliocostalis. The second objective was to establish elastography protocols with magnetic resonance imaging and ultrasonography for the exploration of the elasticity of the paraspinal muscles at rest and in several different postures. Results of the anatomical studies show that the tendon-to-muscle area ratios of the longissimis and the iliocostalis were extremely small, as well as cross-sectional area of the belly of the multifidus. That suggests that paraspinal muscles are not able to provide the dorsal extension of the spine during muscle contraction. Rather, they seem to stabilize the spine by providing it with a certain rigidity ensured by a substantial muscle volume contained in an inextensible compartment. Through elastography, we have shown that the elasticity of the paraspinal muscles was the lowest at rest, in decubitus. Elasticity was not influenced by passive flexion or extension of the spine, nor by the stretching of the thoracolumbar fascia. Elasticity increased during sitting, standing, bending forward and bending backward the compared to decubitus. The biomechanical behaviour of the longissimus, the iliocostalis and multifidus differed according to the postures. This work confirms that there are significant changes in elasticity during standing postures. Low back pain is associated with stiffness changes of the spine and of the paraspinal muscles that have been observed through clinical examination. In the future, elastography could allow exploring low back pain
Kim, Kisoo. "Interventional MR Elastography for the monitoring of thermal ablations". Thesis, Strasbourg, 2019. https://publication-theses.unistra.fr/public/theses_doctorat/2019/Kim_Kisoo_2019_ED269.pdf.
Pełny tekst źródłaThermal ablation aims at damaging tumor cells by either heating or freezing tumoral tissue. MRI monitoring is a promising technique for ensuring the destruction of tumor cells while preserving the surrounding healthy tissue. Recently, the ICube team demonstrated the use of simultaneous realtime MR Elastography (MRE) and MR Thermometry (MRT). It allows monitoring temperature and mechanical properties of the targeted tissue simultaneously in realtime. In this Ph.D. thesis, we have presented two different developments in order to overcome some of the current limitations of interventional MRE and MRT, in terms of extending to the spatial coverage of the targeted region and developing a new method to monitor thermal ablations for all types of soft tissues, including fatty tissues. These contributions aim at improving the safety and efficiency of MR guided thermal ablation
Blanchard, Rémy. "Élastographie par résonance magnétique : contributions pour l’acquisition et la reconstruction du module de cisaillement : association avec l’élastographie ultrasonore quasi-statique pour l’étude de milieux pré-contraints". Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10030/document.
Pełny tekst źródłaThe term elastography refers to imaging techniques dedicated to the in vivo investigation of the mechanical properties of biological tissues. During this thesis, we focused on two elastography techniques. The first one is quasi-static ultrasound elastography, able to locally estimate tissue strain induced by a global deformation of a medium. The second one is Magnetic Resonance Elastography (MRE), able to measure the local shear modulus. In MRE, a shear wave is generated within the medium and imaged using a specific MRI sequence. The resulting wave images are then processed to estimate the local shear modulus. A new acquisition scheme of the shear wave images was proposed during this thesis. A method, based on local frequency estimation, was also developed for the estimation of the local shear modulus using the properties of a ratio of filters. Another research axis was the study of the effect of a prestrain application on the measured shear modulus. This effect was first studied with homogeneous media and then with heterogeneous test objects. In this last case, the use of quasi-static ultrasound elastography was necessary to locally access to the medium strain. This information was then combined with the information obtained using MRE to extract, for each region of interest, a strain/shear modulus curve
Yue, Jinlong. "L'élastographie par résonance magnétique et l'élastographie ultrasonore par ondes de cisaillement supersonic : simulation, comparaison expérimentale et l'application pour la caractérisation du foie". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS483/document.
Pełny tekst źródłaElastography is an emerging medical imaging modality which permits to measure the mechanical properties of human soft tissue. The measured mechanical properties can serve as potential biomarkers for improving the management of diseases, from early diagnosis, to severity evaluation and therapy response monitoring. Among different approaches, Magnetic Resonance Elastography (MRE) and Supersonic Shear Imaging (SSI) have shown particular interests. The two modalities have been widely investigated for multiple clinical applications. However, each modality is challenged by specific acquisition and reconstruction conditions which may induce intra- and inter-modality measurement biases and hence impede the interchangeability of the two modalities. The first part of my thesis focused on identifying the measurement biases between MRE and SSI. Through a thorough methodological comparison study, we recognized different frequency characteristics of generated shear waves for the two modalities and modality specific reconstruction validity issues as the main sources for the measurement biases between the two modalities. Then through a dedicated simulation study, we established an in silico abaci to identify the favorable range of number of voxels per wavelength which leads to accurate and precise MRE. Moreover, resampling was proven effective to regulate poorly defined number of voxels per wavelength to the favorable range. The overall outcome, which is usually computed from the three acquired motionencoded directions, may further be improved by appropriate weighting strategies that are based on curl of shear displacement field. For SSI, we referred to the quality parameter provided by the manufacturer to reasonably eliminate unreliable results so as to further improve the measurement quality. After establishing the potential measurement biases between MRE and SSI, we incorporated the proposed quality optimization strategies into both modalities in order to perform unbiased experimental comparison studies between the two modalities. First, in vitro studies were carried out on commercial calibrated phantoms as well as home-made polyvinyl alcohol phantoms. Experimental results corroborate well the simulation findings. MRE and SSI measurements agree well witheach other when theory, experiment, and reconstruction biases are minimized. In vivo studies were then performed on the livers of two healthy volunteers. We found that when the liver is quasi-elastic, the quality-guided MRE and SSI measurements agree well with each other and hence are interchangeable. In case of viscoelastic liver tissue, both MRE and SSI measurements are frequency dependent. Thus frequency-specific measurements are essential for cross-validating the measurements of these two modalities
Santarelli, Roberta. "Helium-3 Magnetic Resonance Elastography of the lung". Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112026/document.
Pełny tekst źródłaAccording to the American Lung Association, for the last few years, lung diseases have become the third most common cause of death worldwide after cardiovascular disease and tumors, and it is expected to rise up the ranking position in the next ten years. Lung diseases such as Chronic Obstructive Pulmonary Disease and interstitial fibrosis affect millions of people worldwide, killing thousands of them every year while new cases are reported. Today, there is no early diagnosis of these pulmonary diseases. They effectively manifest by a modification of the viscoelastic properties of the lung parenchyma which cannot be detected by usual techniques that are applied to other organs. X-ray computer tomography and surgical lung biopsy can state the disease. However, it is not yet possible to predict its progression, to determine the optimal length of the therapy, or to explore the administration of other agents potentially less toxic than those used nowadays. Causes and mechanisms of the disease, associated genetic factors are not determined yet. The social and medical issues are huge. The viscoelastic properties of lung tissue play a key role in the basic function of the organ. They could be very sensitive pulmonary biomarkers as they depend on the tissue structure, the biological conditions, and they are dramatically altered by most lung diseases like cancer, emphysema, asthma, or interstitial fibrosis. However, current auscultation and tactual explorations fail to regionally probe them in vivo.In this PhD work, a new modality was developed to regionally measure the viscoelastic properties of the lung parenchyma in order to detect, quantify, and classify diseases that modify them. This new imaging approach, hyperpolarized helium-3 Magnetic Resonance Elastography (MRE), benefit from the innocuity and the sensitivity of the technique as well as from the huge hyperpolarized helium-3 signal in the lung. First, the technique was validated on preserved pig lung phantoms. On the one hand, the assumptions of gas confinement and gas content independence that support quantitative helium-3 MRE were assessed. On the other hand, the sensitivity of the technique was challenged with respect to lung inflation and gravity dependence. Second, original means of mechanical excitation were developed and MR acquisition protocols were optimized to perform helium-3 MRE in vivo. First measurements of shear wave propagation were achieved in both rat and human lungs. Resulting shear elasticity agrees fairly well with stiffness values found ex vivo by alternative measurement techniques. This work opens up promising insights into lung pathophysiology in vivo
Boucneau, Tanguy. "Magnetic resonance imaging of respiratory mechanics". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS165.
Pełny tekst źródłaThe respiratory function in human cannot be separated from the deformation motion of the lung: the gas exchanges between the organism and its environment are made possible, during the inspiration, by the swelling of the alveoli in the pulmonary parenchyma, and during the expiration, by a passive return to the static equilibrium state of the lung. The viscoelastic properties of lung tissue play a key role in the function of this organ. These elements of respiratory mechanics may prove to be very sensitive biomarkers of the pathophysiological state of the lung since they depend on the structure of tissues and biological conditions that are considerably altered by most pulmonary diseases such as cancer, emphysema, asthma or interstitial fibrosis. Magnetic resonance imaging enables non-invasive measurement of three-dimensional anatomical images that allow, thanks to the accessible spatial and temporal resolutions as well as the rich contrasts observed in the soft tissues, the measurement of the deformation state of an organ at a given moment. Moreover, by applying motion encoding gradients, magnetic resonance elastography gives the possibility to follow, onto to the magnetic resonance phase signal, the mechanical strain response of organs to an external mechanical stress in order to reveal their viscoelastic properties, which makes possible a quantitative and spatially-resolved exploration of deep organs that are nor reachable by the medical doctor's hand. In the lung, conventional MRI is, however, relatively difficult: the low tissue density, the large differences in magnetic susceptibility at the interface between gas and tissue and, correlatively, the very short lifetimes of the magnetic resonance signal, lead to signal-to-noise ratios that are difficult to exploit. In addition, the durations of three-dimensional MRI scans are generally longer than the period of the respiratory motion, which requires consideration of this motion within the imaging process. This PhD project, carried out in collaboration with GE Healthcare, aims at circumventing the limitations mentioned above by using UTE and ZTE sub-millisecond echo-time acquisition techniques, combined with original and innovative approaches of intrinsic physiological motions monitoring as well as four-dimensional image reconstruction techniques taking into account the respiratory motion, the redundancy of information between the different data acquisition channels and the sparsity of the reconstructed images through some mathematical representations. The ultimate goal of this project is the development and the validation of local and quantitative techniques to explore the respiratory function, as well as dynamic magnetic resonance lung elastography, in order to extract local ventilation parameters and viscoelastic shear moduli in the lung during the breathing cycle
Zorgani, Ali. "Passive Elastography : Tomography and Mechanical Characterization of Biological Tissue". Electronic Thesis or Diss., Lyon, 2016. http://www.theses.fr/2016LYSE1191.
Pełny tekst źródłaThe aim of this thesis was the development of a new approach called passive elastography. This approach is inspired from noise correlation methods well developed in seismology and time reversal technics in acoustics. Passive elastography uses shear waves naturally induced in the human body to extract its mechanical properties of soft tissue. The feasibility of this method was tested in several applications. First in ultrasound, slow frame rate ultrasound scanner was used to monitor high intensity focused ultrasound treatment on porcine pancreas. Then, an ultrafast ultrasound scanner was used to retrieve shear wave speed map in a calibrated phantom and in-vivo. Second, Magnetic resonance elastography was implemented to image natural motion in the brain of healthy volunteers and conduct shear wavelength tomography. Third, of ophthalmological and dermatological applications, optical coherence passive elastography was tested in a phantom and a cornea of healthy mouse. Also, a fully optical setup was established to image surface wave for elastography applications. Finally, the resolution limit of elastography was measured using and ultrasound ultrafast scanner
Chakouch, Mashhour. "Viscoelastic properties of in vivo thigh muscle and in vivo phantom using magnetic resonance elastography (MRE)". Thesis, Compiègne, 2015. http://www.theses.fr/2015COMP2236/document.
Pełny tekst źródłaSummary of the vitro studies. The objective of this in vitro study was to create a phantom witch the same muscle architecture (fiber, aponeurosis …) and mechanical properties of muscle in passive and active states. Two homogeneous phantoms were manufactured with different concentrations of plastisol to simulate the muscle elastic properties in passive (50% of plastisol) and active (70% of plastisol) muscle conditions. Moreover, teflon tubing pipes (D = 0.9 mm) were thread in the upper part of the phantom (50%) to represent the muscle fibers and a plastic sheet (8 x 15 cm) was also included in the middle of the phantom to mimic the aponeurosis structure. Subsequently, MRE tests were performed at 90Hz with two different pneumatic drivers, tube and round shapes, to analyze the effect of the type of driver on the wave propagation. The wavelength was measured from the phase images and the elastic properties (shear modulus) were calculated. Both phantoms revealed elastic properties which were in the same range as in vivo muscle in passive (2.40 ± 0.18 kPa) and active (6.24 ± 0.21 kPa) states. The impact of the type of driver showed higher values with the tube (range: 1.2 kPa to 1.53 kPa). The analysis of the wave behavior revealed a sliding along the plastic sheet as it was observed for in vivo muscle study. The wave was also sensitive to the presence of the fibers where gaps were identified. A new post processing method was established to measure G’ and G” from experimental multi frequencies (60, 80, 100 Hz) MRE (MMRE) tests and rheological models. This method was tested on the phantom (50%) made without fiber. Cross validation of the viscoelastic (G’, G”) results was made with Hyper-Frequency Viscoelastic Spectroscopy (HFVS). Both techniques showed similar range of values for G’ and G” at the same frequencies. This last result validated our new data processing for the viscoelastic measurement. Summary of the in vivo studies. The objective of this in vivo study was to develop MRE protocols to characterize the elastic properties (shear modulus) of the nine thigh muscles. These tests were performed at a single frequency (90Hz). Different shear moduli were found between the muscles. The gracilis revealed the highest elastic properties compared to all the other muscles. These different elasticities may be due to different physiological and architectural compositions between the tissues. Then the viscoelastic properties of the ischio (ST, SM, and BC) and Gr muscles were determined based on our new data-processing method (validated on the phantom 50%) using MMRE tests (70, 90 and 120Hz) and rheological models. The results revealed that two rheological models, zener and springpot, can be used to measure the viscoelastic properties in passive state. A similar trend was found between the experimental ratios G”/G’ obtained at 90 Hz and the α value of the springpot model. The present MRE muscle protocol, and the viscoelastic data base, could be used as non-invasive diagnostic tools to evaluate tissue alterations, the progression of diseases, and the effect of treatments, such as the ongoing therapeutic trials for Duchenne muscular dystrophy
Ternifi, Redouane. "Mesure de la pulsatilité naturelle du tissu cérébral par ultrasons". Thesis, Tours, 2014. http://www.theses.fr/2014TOUR3306/document.
Pełny tekst źródłaThe study of biological tissues movement is currently, one of the major thematics in the medical imaging field. The challenge is to provide additional clinical information and allow for diagnostic assistance. The recently introduced elastographic techniques, provide ample opportunities for biomechanical tissues characterization, particularly of cerebral tissues. An innovative passive-elastographic methodology for assessing mechanical properties of brain tissue is proposed. The eventual aim is to allow for the diagnosis of neurodegenerative diseases
Bacle, Guillaume. "Les muscles infraspinatus et teres minor : anatomie, analyse de texture en imagerie IRM et comportement viscoélastique en élastographie ultrasonore". Thesis, Tours, 2016. http://www.theses.fr/2016TOUR3301/document.
Pełny tekst źródłaInfraspinatus and teres minor muscles are crucial functionally and are regularly impaired in the context of of the rotator cuff pathology. The proportion of fatty tissue in the infraspinatus is currently a strong prognosis criterion of functional outcomes of rotator cuff tendon repair. The goals of this work are to characterize these muscles anatomically, to provide a better exploration of their morphology by MRI, to use computer texture analysis to objectify their composition and finally to use the ultrasound elastography for analysing their viscoelastic behaviour under stress. Infraspinatus and teres minor muscles have a tripennate and parallel organization, respectively. Routine MRI acquisition criteria can be easily optimized to analyse more precisely the external rotator muscles. Texture analysis seems promising to assess the proportion of fatty tissue in the skeletal muscle. The ultrasound elastography allows us to estimate the degree of muscle anisotropy, and therefore the state of organization of the infraspinatus muscle
Zorgani, Ali. "Passive Elastography : Tomography and Mechanical Characterization of Biological Tissue". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1191/document.
Pełny tekst źródłaThe aim of this thesis was the development of a new approach called passive elastography. This approach is inspired from noise correlation methods well developed in seismology and time reversal technics in acoustics. Passive elastography uses shear waves naturally induced in the human body to extract its mechanical properties of soft tissue. The feasibility of this method was tested in several applications. First in ultrasound, slow frame rate ultrasound scanner was used to monitor high intensity focused ultrasound treatment on porcine pancreas. Then, an ultrafast ultrasound scanner was used to retrieve shear wave speed map in a calibrated phantom and in-vivo. Second, Magnetic resonance elastography was implemented to image natural motion in the brain of healthy volunteers and conduct shear wavelength tomography. Third, of ophthalmological and dermatological applications, optical coherence passive elastography was tested in a phantom and a cornea of healthy mouse. Also, a fully optical setup was established to image surface wave for elastography applications. Finally, the resolution limit of elastography was measured using and ultrasound ultrafast scanner
Balleyguier, Corinne. "Elastographie-IRM pour le diagnostic et la caractérisation des lésions du sein". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00824882.
Pełny tekst źródłaHoang, Dinh Au. "Développement et évaluation des paramètres quantitatifs de l’IRM de la prostate". Electronic Thesis or Diss., Lyon 1, 2015. http://www.theses.fr/2015LYO10210.
Pełny tekst źródłaThe purpose of this thesis is to develop and evaluate the quantitative methods of multiparametric MRI of prostate in discriminating Gleason score (GS) ≥7 cancers. We suppose that the quantitative parameter of MRI could help standardizer the diagnostic, reduce the inter-lecture and/ or inter-institution variation in diagnostic of prostate cancer. This thesis is divided into three chapters. The firs chapter, entilted « Quantitative T2 MRI of prostate » is a retrospective study on a database of prostate cancer patients before radical prostatectomy. The second chapter, entilted « Multi-parametric Quantitative MRI of prostate » is also a retrospective study before radical prostatectomy. The third chapter, entitled « MR elastography of prostate by transperineal approach », is an experimental study. Our first study shows that T2 value is robust between machines of different constructors. T2 value is significant predictor, but of weak performance, of aggressively cancer of prostate at 3T. Our second study shows that the combination of ADC_10th percentile with Time-to-peak (TTP) improved the diagnosis performance, and this model is also robust between two machines of different constructors. Our third study shows the initial results on elasticity of the prostate. These results show that MRI elastography of prostate at high excitation frequency (>100 Hz) by trans-perineale approach was feasible. The elastography may, in the future, be integrated in quantitative multi-parametric MRI to improve the diagnosis performance
Jaouen, Tristan. "Caractérisation du cancer de la prostate de haut grade à l’IRM multiparamétrique à l’aide d’un système de diagnostic assisté par ordinateur basé sur la radiomique et utilisé comme lecteur autonome ou comme second lecteur". Electronic Thesis or Diss., Lyon, 2022. http://www.theses.fr/2022LYSE1140.
Pełny tekst źródłaWe developed a region of interest-based (ROIs) computer-aided diagnosis system (CAD) to characterize International Society of Urological Pathology grade (ISUP) ≥2 prostate cancers at multiparametric MRI (mp-MRI). Image parameters from two multi-vendor datasets of 265 pre-prostatectomy and 112 pre-biopsy MRIs were combined using logistic regression. The best models used the ADC 2nd percentile (ADC2) and normalized wash-in rate (WI) in the peripheral zone (PZ) and the ADC 25th percentile (ADC25) in the transition zone (TZ). They were combined in the CAD system. The CAD was retrospectively assessed on two multi-vendor datasets containing respectively 158 and 105 pre-biopsy MRIs from our institution (internal test dataset) and another institution (external test dataset). Two radiologists independently outlined lesions targeted at biopsy. The Prostate Imaging-Reporting and Data System version 2 (PI-RADSv2) score prospectively assigned at biopsy and the CAD score were compared to biopsy findings. At patient level, the areas under the Receiver Operating Characteristic curve (AUC) of the PI-RADSv2 score were 82% (95% CI: 74-87) and 85% (95% CI: 79-91) in the internal and external test datasets respectively. For both radiologists, the CAD score had similar AUC results in the internal (82%, 95% CI: 76-89, p=1; 84%, 95% CI: 78-91, p=1) and external (82%, 95% CI: 76-89, p=0.82; 86%, 95% CI: 79-93, p=1) test datasets. Combining PI-RADSv2 and CAD findings could have avoided 41-52% of biopsies while missing 6-10% of ISUP≥2 cancers. The CAD system confirmed its robustness showing good discrimination of ISUP ≥2 cancers in a multicentric study involving 22 different scanners with highly heterogeneous image protocols. In per patient analysis, the CAD and the PI-RADSv2 had similar AUC values (76%, 95% CI: 70-82 vs 79%, 95% CI: 73-86; p=0.34) and sensitivities (86%, 95% CI: 76-96 vs 89%, 95% CI: 79-98 for PI-RADSv2 ≥4). The specificity of the CAD (62%, 95% CI: 53-70 vs 49%, 95% CI: 39-59 for PI-RADSv2 ≥4) could be used to complement the PI-RADSv2 score and potentially avoid 50% of biopsies, while missing 13% of ISUP ≥2 cancers. These findings were very similar to those reported in the single center test cohorts. Given its robustness, the CAD could then be exploited in more specific applications. The CAD first provided good discrimination of ISUP ≥2 cancers in patients under Active Surveillance. Its AUC (80%, 95% CI: 74-86) was similar to that of the PI-RADS score prospectively assigned by specialized uro-radiologists at the time of biopsy (81%, 95% CI: 74-87; p=0.96). After dichotomization, the CAD was more specific than the PI-RADS ≥3 (p<0.001) and the PI-RADS ≥4 scores (p<0.001). It could offer a solution to select patients who could safely avoid confirmatory or follow-up biopsy during Active Surveillance (25%), while missing 5% of ISUP≥2 cancers. Finally, the CAD was tested with the pre-prostatectomy mp-MRIs of 56 Japanese patients, from a population which is geographically distant from its training population and which is of interest because of its low prostate cancer incidence and mortality. The CAD obtained an AUC similar to the PI-RADSv2 score assigned by an experience radiologist in the PZ (80%, 95% CI: 71-90 vs 80%, 95% CI: 71-89; p=0.886) and in the TZ (79%, 95% CI: 66-90 vs 93%, 95%CI: 82-96; p=0.051). These promising and robust results across heterogeneous datasets suggest that the CAD could be used in clinical routine as a second opinion reader to help select the patients who could safely avoid biopsy. This CAD may assist less experience readers in the characterization of prostate lesions
Rocher, Laurence. "Imagerie Avancée du testicule : Echographie et IRM multiparamétriques". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS458.
Pełny tekst źródłaThe testicular imaging we developped in our department focused on two main subjects: infertility and tumoral characterization. It is based on multiparametric ultrasound and MRI. We defined diagnostic criteria of several pathologies, which may change the patient’s management, and we evaluated new modalities.We characterized Klinefelter patient’s testis.We determined the Color-Doppler features of Leydig cell tumors which are currently incidentally discovered and can benefit from monitoring or tumorectomy.We defined multiparametric US and MRI diagnostic’s criteria of burned out tumors in patients referred for US infertility screening.We demonstrated the ability of multiparametric MRI to improve the tumoral characterization using qualitative and quantitative enhancement parameters and apparent diffusion coefficient values.CEUS showed significant differences between the burned out tumors and other lesions.. Shear Wave Elastography (SWE) showed significant differences in testicular stiffness between normal, obstructive azoospermia on one side and non-obstructive azoospermic patients, but overlapped values seemed to minimize the potential clinical impact. Benign Leydig cell were softer compared to malignant tumors and burned out tumors. Association of B mode, color Doppler, and elastography allowed an optimal characterization.Ultrasensitive Doppler allowed a qualitative evaluation of the tumoral vascular architecture, a testicular vascularization assessment in case of acute scrotum, and a testicular perfusion quantification. We demonstrated a decreased testicular vascularization during the Valsalva maneuver confirming the hypoxic physiopathological explanation of the infertility process
Hoang, Dinh Au. "Développement et évaluation des paramètres quantitatifs de l’IRM de la prostate". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10210/document.
Pełny tekst źródłaThe purpose of this thesis is to develop and evaluate the quantitative methods of multiparametric MRI of prostate in discriminating Gleason score (GS) ≥7 cancers. We suppose that the quantitative parameter of MRI could help standardizer the diagnostic, reduce the inter-lecture and/ or inter-institution variation in diagnostic of prostate cancer. This thesis is divided into three chapters. The firs chapter, entilted « Quantitative T2 MRI of prostate » is a retrospective study on a database of prostate cancer patients before radical prostatectomy. The second chapter, entilted « Multi-parametric Quantitative MRI of prostate » is also a retrospective study before radical prostatectomy. The third chapter, entitled « MR elastography of prostate by transperineal approach », is an experimental study. Our first study shows that T2 value is robust between machines of different constructors. T2 value is significant predictor, but of weak performance, of aggressively cancer of prostate at 3T. Our second study shows that the combination of ADC_10th percentile with Time-to-peak (TTP) improved the diagnosis performance, and this model is also robust between two machines of different constructors. Our third study shows the initial results on elasticity of the prostate. These results show that MRI elastography of prostate at high excitation frequency (>100 Hz) by trans-perineale approach was feasible. The elastography may, in the future, be integrated in quantitative multi-parametric MRI to improve the diagnosis performance
Naïm, Cyrille. "Characterization of Carotid Plaques with Ultrasound Non-Invasive Vascular Elastography (NIVE) : Feasibility and Correlation with High-Resolution Magnetic Resonance Imaging". Thèse, 2013. http://hdl.handle.net/1866/9674.
Pełny tekst źródłaStroke is a leading cause of death and morbidity worldwide, and a significant proportion of strokes are caused by carotid atherosclerotic plaque rupture. Prevention of stroke in patients with carotid plaque poses a significant challenge to physicians, as risks and benefits of surgical or medical treatments remain equivocal. Many imaging techniques have been developed to identify and study vulnerable (high-risk) atherosclerotic plaques, but none is sufficiently validated or accessible for population screening. Non-invasive vascular elastography (NIVE) is a novel ultrasonic technique that maps carotid plaque strain (elasticity) characteristics to detect its vulnerability; it has not been clinically validated yet. The goal of this project is to evaluate the ability of ultrasound NIVE strain analysis to characterize carotid plaque composition and vulnerability in vivo in patients with significant plaque burden, as determined by the reference standard, high resolution MRI. To undertake this study, a thorough understanding of stroke, atherosclerosis, vulnerable plaque, and current non-invasive carotid plaque imaging techniques is required. Thirty-one subjects underwent NIVE and high-resolution MRI of internal carotid arteries. Of 31 plaques, 9 were symptomatic, 17 contained lipid and 7 were vulnerable on MRI. Strains were significantly lower in plaques containing a lipid core compared to those without lipid, with high sensitivity and moderate specificity. A quadratic fit was found between strain and lipid content. Strains did not discriminate symptomatic patients or vulnerable plaques. In conclusion, ultrasound NIVE is feasible in patients with significant carotid stenosis and can detect the presence of a lipid core. Further studies of plaque progression with NIVE are required to identify vulnerable plaques.