Conception et développement d’une sonde portable universelle pour l’imagerie 3D optoacoustique-ultrasonique

When the interest is in multiscale and multipurpose imaging, there exists such a will in integrating multi-modalilties into a synergistic paradigm in order to leverage the diagnostic values of the interrogating agents. Employing multiple wavelengths radiation, optoacoustic imaging benefits from the optical contrast to specifically resolve molecular structure of tissue in a non-invasive manner. Hybridizing optoacoustic and ultrasound imaging comes with the promises of delivering the complementary morphological, functional and metabolic information of the tissue. This dissertation is mainly devoted to the design and characterization of a hybridized universal handheld probe for optoacoustic ultrasound volumetric imaging and developing adaptive reconstruction algorithms toward the physical requirements of the designed system. The distinguishing features of this dissertation are the introduction of a new geometry for optoacoustic ultrasonic handheld probe and systematic assessments based on pre and post reconstruction methods. To avoid the biased interpretation, a de facto performance assessment being capable of evaluating the potentials of the designed probe in an unbiased manner must be practiced. The aforementioned features establish a framework for characterization of the imaging system performance in an accurate manner. Moreover, it allows further task performance optimization as well. Correspondingly, two advanced reconstruction algorithms have been elaborated towards the requirement of the designed optoacoustic-ultrasound (OPUS) imaging system in order to maximize its ability to produce images with homogeneous contrast and resolution over the entire volume of interest. This interest is mainly due to the fact that the medical data analysis pipeline is often carried out in challenging conditions, since one has to deal with noise, low contrast, limited projections and undesirable transformations operated by the acquisition system. The presented thesis shows how reconstruction artifacts can be reduced by compensating for the detecting aperture properties and alleviate artifacts due to sparse angular sampling. In pursuit of transferring this methodology to clinic and validating the theoretical results, a synthetic imaging platform was developed. Using the measurement system, the evolution of a novel sparse annular geometry and its dynamics has been investigated and a proof of concept was demonstrated via experimental measurement with the intention of benchmarking progress.La présente dissertation est principalement consacrée à la conception et à la caractérisation d’une sonde universelle pour l’imagerie volumétrique ultrasons-optoacoustique et le développement d’un algorithme de reconstruction adapté aux exigences physiques pour la conception du système. Les traits distinctifs de cette dissertation sont l’introduction d’une nouvelle géométrie pour les sondes manuelles ultrasons-optoacoustique et des évaluations systématiques basées sur des méthodes de pré-reconstruction et post-reconstruction. Pour éviter l’interprétation biaisée, une évaluation capable d’évaluer le potentiel de la sonde doit être faite. Les caractéristiques mentionnées établissent un cadre pour l’évaluation des performances du système d’imagerie d’une manière précise. En outre, elle permet d’optimiser les performances suivant l’objectif fixé. Ainsi, deux algorithmes de reconstruction anticipée ont été élaborés pour la conception du système OPUS (optoacoustique ultrasons) capables de produire des images avec un contraste et une résolution homogènes sur tout le volume d’intérêt. L’intérêt d’avoir de tels algorithmes est principalement dû au fait que l’analyse des données médicales est souvent faite dans des conditions difficiles, car on est face au bruit, au faible contraste, aux projections limités et à des transformations indésirables opérées par les systèmes d’acquisition. Cette thèse montre, aussi, comment les artefacts de reconstruction peuvent être réduits en compensant les propriétés d’ouverture et en atténuant les artefacts dus à l’échantillonnage angulaire parcimonieux. Afin de transférer cette méthodologie à la clinique et de valider les résultats théoriques, une plate-forme d’imagerie expérimentale a été développée. En utilisant le système de mesure développé, l’évolution d’une nouvelle géométrie annulaire parcimonieuse et sa dynamique ont été étudiées et une preuve de concept a été démontrée à travers des mesures expérimentales dans le but d’évaluer les progrès réalisés

Sparse sampling and reconstruction for an optoacoustic ultrasound volumetric hand-held probe

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Theoretical characterization of annular array as a volumetric optoacoustic ultrasound handheld probe

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Dual Frequency Band Annular Probe for Volumetric Pulse-echo Optoacoustic Imaging

International audienceOptoacoustic (OA) pulse echo (PE) imaging is a hybridized modality that is capable of providing physiological information on the basis of anatomical structure. In this work, we propose a dual frequency band annular probe for backward mode volumetric PE/OA imaging. The performance of this design is evaluated based on the spatio-temporal impulse response, three dimensional steerability of the transducer and point spread function. Optimum settings for number of elements in each ring and maximum steering are suggested. The transducer design and synthetic array beamforming simulation are presented. The resolution performance and reconstruction capabilities are shown with the in-silico measurements

Volumetric pulse echo and optoacoustic imaging by elaborating a weighted synthetic aperture technique

International audienceIntegrating the ultrasounic pulse-echo (PE) and optoacousic (OA) imaging is a potent approach in rendering the volumetric images of biological tissues. The deliverable information are essentially uncorrelated but highly complementary in learning about the optical and mechanical properties of the medium. Yet, owing to the inhomogeneities in acoustic velocity and the optical scattering, this synergistic approach suffers from the low depth resolution, low contrast and artifacts like off-axis contributions and phase distortion. In this work, an adaptive weighted dynamic focusing based reconstruction technique namely, weighted synthetic aperture (WSA), has been developed to address the aforementioned defects, in particular for annular array. Our findings show the efficiency of WSA method in 3D reconstruction of simulated phantom. We elaborate WSA to estimate the spatial location, size, reflectivity function and absorption coefficient of the insonified/illuminated targets for both imaging modalities. The phase distortion introduced by the separable delay approximation is addressed with an adaptive weighting factor that combines coherence factor (CF) and phase coherence factor (PCF). In addition, the weighting factor incorporates the spatial impulse response (SIR), which is associated with the properties of the transducer in order to inverse the effect of the transducer on imaging quality. Using numerical phantom, the simulation results demonstrate thatincorporating SIR into the weighting factor ensures the isotropic sensitivity while CF and PCF are suppressing the artifacts, grating lobe and phase aberration for both OA and PE images

Adaptive minimum variance coupled with sign and phase coherence factors in IQ domain for plane wave beamforming

International audienceIn the framework of PICMUS challenge, the objective comparison between steered plane waves beamforming is proposed on an external platform. Our beamforming proposal consists in a weighted minimum variance approach which combines a phase coherence factor calculation and a minimum variance beamforming. The computation is made in the IQ domain in order to reduce the calculation effort. An adaptive scheme is used to optimize the number of elements that are considered for the MV beamforming, which depends on the depth and the lateral position of the reconstructed pixel. Moreover, the coherence maps are filtered in order to avoid strong discontinuities and speckle penalty on the platform. The obtained results on the MIDAS platform demonstrates higher CNR and resolution compare to classical DAS approach. The main limitation of our weighted MV lies on the final axial resolution which is not improved and limits the overall performance of the method

Sparse hand-held probe for optoacoustic ultrasound volumetric imaging: an experimental proof-of-concept study

International audienceWe present an experimental proof-of-concept study on the performance of a sparse segmented annular array for optoacoustic imaging. A capacitive micromachined ultrasonic transducer was equipped with a negatively focused acoustic lens and scanned in an annular fashion to exploit the performance of the sparse array geometry proposed in our recent numerical studies [Biomed. Opt. Express 10, 1545 (2019); J. Biomed. Opt. 23, 025004 (2018)]. A dedicated water tank was made using a 3D printer for light delivery and mounting the sample. A phantom experiment was carried out to showcase the possibility of full-field optoacoustic ultrasound (OPUS) imaging and confirm the earlier numerical results. This proof of concept opens the door towards a prototype of OPUS imaging for (pre-) clinical studies