12 research outputs found
Microscopie par localisation ultrasonore dans les modÚles d'accidents vasculaires cérébraux
A stroke is a sudden loss of vascularization of a part of the brain. Patients must receive medical care within the first hour to reduce neuronal loss and long-term sequelae.Most strokes are hemorrhagic or ischemic, with similar symptoms but specific treatments. Early-phase diagnosis becomes vital and requires deep brain imaging through the skull bone.The development of Ultrasound Localization Microscopy (ULM) has widened applications for microvascular imaging by improving contrast, resolution, and penetration depth. Microbubbles are injected into the blood flow and localized to reconstruct the microvessels within few minutes.The main objective of this thesis is the application of 3D ULM for non-invasive stroke diagnosis in the early phase.A first study focuses on a quantitative comparison of localization algorithms for 2D ultrasound imaging. A set of standardized metrics and unified datasets were established to evaluate various algorithms with objective and reproducible criteria. Then a volumetric ULM system was set up to overcome the elevation projection of 2D imaging and increase the field of view. We performed a 3D angiography of a rat brain in vivo with a commercial scanner and a multiplexed ultrasonic probe. A few tens of micrometers resolution was obtained through the skull bone. This method didnât induce major modifications of the animalâs physiology and can be used for a pre-clinical study. Finally, this system was used to image induced strokes in a cohort of rats. It proved its ability to distinguish the effects of ischemia versus hemorrhage on brain vascularization. This first study shows the relevance of such imaging for the early diagnosis of stroke in humans by volumetric ULM, without the constraints and availability of MRI and CT.L'accident vasculaire cĂ©rĂ©bral (AVC) est une perte subite de la vascularisation d'une partie du cerveau. Une prise en charge rapide rĂ©duit considĂ©rablement les pertes neuronales et sĂ©quelles Ă long terme. Les hĂ©morragies cĂ©rĂ©brales et infarctus cĂ©rĂ©braux reprĂ©sentent les principaux types d'AVC avec des symptĂŽmes similaires mais des traitements trĂšs spĂ©cifiques. Le diagnostic prĂ©coce est primordial et nĂ©cessite une imagerie du cerveau en profondeur Ă travers le crĂąne.Le dĂ©veloppement de la microscopie par localisation ultrasonore (ULM) a ouvert de nouvelles possibilitĂ©s pour lâimagerie vasculaire en amĂ©liorant le contraste, la rĂ©solution et la profondeur de pĂ©nĂ©tration de lâĂ©chographie. Des microbulles sont injectĂ©es dans le sang et localisĂ©es pour reconstruire la microvascularisation en quelques minutes.L'objectif gĂ©nĂ©ral de cette thĂšse est l'application de lâULM 3D pour le diagnostic non invasif de lâAVC en phase prĂ©coce. Une premiĂšre Ă©tude porte sur une comparaison quantitative des algorithmes de localisation ultrasonore pour l'imagerie 2D. Un ensemble de mĂ©triques normĂ©es et de jeux de donnĂ©es universels ont Ă©tĂ© Ă©tablis pour Ă©valuer les diffĂ©rents algorithmes avec des critĂšres objectifs et reproductibles. Puis un systĂšme dâULM 3D a Ă©tĂ© dĂ©veloppĂ© pour pallier Ă la projection en Ă©lĂ©vation de lâimagerie 2D et Ă©largir le champ de vue. En utilisant une sonde multiplexĂ©e, une angiographie dâun cerveau de rat a Ă©tĂ© rĂ©alisĂ©e in vivo avec un systĂšme commercial. Une rĂ©solution de quelques dizaines de microns a Ă©tĂ© obtenue Ă travers le crĂąne, rĂ©duisant au minimum lâimpact de lâimagerie sur la physiologie de lâanimal en vue dâune Ă©tude prĂ©-clinique. Enfin, ce systĂšme a Ă©tĂ© utilisĂ© pour imager des AVC induits sur une cohorte de rats. Il a prouvĂ© sa capacitĂ© Ă distinguer les effets dâune ischĂ©mie par rapport Ă une hĂ©morragie sur la vascularisation du cerveau. Cette premiĂšre Ă©tude montre la pertinence dâune telle imagerie pour le diagnostic en phase prĂ©coce de lâAVC chez lâhumain par ULM volumĂ©trique en sâaffranchissant des contraintes et disponibilitĂ©s de lâIRM et du scanner
Microscopie par localisation ultrasonore dans les modÚles d'accidents vasculaires cérébraux
A stroke is a sudden loss of vascularization of a part of the brain. Patients must receive medical care within the first hour to reduce neuronal loss and long-term sequelae.Most strokes are hemorrhagic or ischemic, with similar symptoms but specific treatments. Early-phase diagnosis becomes vital and requires deep brain imaging through the skull bone.The development of Ultrasound Localization Microscopy (ULM) has widened applications for microvascular imaging by improving contrast, resolution, and penetration depth. Microbubbles are injected into the blood flow and localized to reconstruct the microvessels within few minutes.The main objective of this thesis is the application of 3D ULM for non-invasive stroke diagnosis in the early phase.A first study focuses on a quantitative comparison of localization algorithms for 2D ultrasound imaging. A set of standardized metrics and unified datasets were established to evaluate various algorithms with objective and reproducible criteria. Then a volumetric ULM system was set up to overcome the elevation projection of 2D imaging and increase the field of view. We performed a 3D angiography of a rat brain in vivo with a commercial scanner and a multiplexed ultrasonic probe. A few tens of micrometers resolution was obtained through the skull bone. This method didnât induce major modifications of the animalâs physiology and can be used for a pre-clinical study. Finally, this system was used to image induced strokes in a cohort of rats. It proved its ability to distinguish the effects of ischemia versus hemorrhage on brain vascularization. This first study shows the relevance of such imaging for the early diagnosis of stroke in humans by volumetric ULM, without the constraints and availability of MRI and CT.L'accident vasculaire cĂ©rĂ©bral (AVC) est une perte subite de la vascularisation d'une partie du cerveau. Une prise en charge rapide rĂ©duit considĂ©rablement les pertes neuronales et sĂ©quelles Ă long terme. Les hĂ©morragies cĂ©rĂ©brales et infarctus cĂ©rĂ©braux reprĂ©sentent les principaux types d'AVC avec des symptĂŽmes similaires mais des traitements trĂšs spĂ©cifiques. Le diagnostic prĂ©coce est primordial et nĂ©cessite une imagerie du cerveau en profondeur Ă travers le crĂąne.Le dĂ©veloppement de la microscopie par localisation ultrasonore (ULM) a ouvert de nouvelles possibilitĂ©s pour lâimagerie vasculaire en amĂ©liorant le contraste, la rĂ©solution et la profondeur de pĂ©nĂ©tration de lâĂ©chographie. Des microbulles sont injectĂ©es dans le sang et localisĂ©es pour reconstruire la microvascularisation en quelques minutes.L'objectif gĂ©nĂ©ral de cette thĂšse est l'application de lâULM 3D pour le diagnostic non invasif de lâAVC en phase prĂ©coce. Une premiĂšre Ă©tude porte sur une comparaison quantitative des algorithmes de localisation ultrasonore pour l'imagerie 2D. Un ensemble de mĂ©triques normĂ©es et de jeux de donnĂ©es universels ont Ă©tĂ© Ă©tablis pour Ă©valuer les diffĂ©rents algorithmes avec des critĂšres objectifs et reproductibles. Puis un systĂšme dâULM 3D a Ă©tĂ© dĂ©veloppĂ© pour pallier Ă la projection en Ă©lĂ©vation de lâimagerie 2D et Ă©largir le champ de vue. En utilisant une sonde multiplexĂ©e, une angiographie dâun cerveau de rat a Ă©tĂ© rĂ©alisĂ©e in vivo avec un systĂšme commercial. Une rĂ©solution de quelques dizaines de microns a Ă©tĂ© obtenue Ă travers le crĂąne, rĂ©duisant au minimum lâimpact de lâimagerie sur la physiologie de lâanimal en vue dâune Ă©tude prĂ©-clinique. Enfin, ce systĂšme a Ă©tĂ© utilisĂ© pour imager des AVC induits sur une cohorte de rats. Il a prouvĂ© sa capacitĂ© Ă distinguer les effets dâune ischĂ©mie par rapport Ă une hĂ©morragie sur la vascularisation du cerveau. Cette premiĂšre Ă©tude montre la pertinence dâune telle imagerie pour le diagnostic en phase prĂ©coce de lâAVC chez lâhumain par ULM volumĂ©trique en sâaffranchissant des contraintes et disponibilitĂ©s de lâIRM et du scanner
Ultrasound localization microscopy for the diagnosis of strokes
L'accident vasculaire cĂ©rĂ©bral (AVC) est une perte subite de la vascularisation d'une partie du cerveau. Une prise en charge rapide rĂ©duit considĂ©rablement les pertes neuronales et sĂ©quelles Ă long terme. Les hĂ©morragies cĂ©rĂ©brales et infarctus cĂ©rĂ©braux reprĂ©sentent les principaux types d'AVC avec des symptĂŽmes similaires mais des traitements trĂšs spĂ©cifiques. Le diagnostic prĂ©coce est primordial et nĂ©cessite une imagerie du cerveau en profondeur Ă travers le crĂąne.Le dĂ©veloppement de la microscopie par localisation ultrasonore (ULM) a ouvert de nouvelles possibilitĂ©s pour lâimagerie vasculaire en amĂ©liorant le contraste, la rĂ©solution et la profondeur de pĂ©nĂ©tration de lâĂ©chographie. Des microbulles sont injectĂ©es dans le sang et localisĂ©es pour reconstruire la microvascularisation en quelques minutes.L'objectif gĂ©nĂ©ral de cette thĂšse est l'application de lâULM 3D pour le diagnostic non invasif de lâAVC en phase prĂ©coce. Une premiĂšre Ă©tude porte sur une comparaison quantitative des algorithmes de localisation ultrasonore pour l'imagerie 2D. Un ensemble de mĂ©triques normĂ©es et de jeux de donnĂ©es universels ont Ă©tĂ© Ă©tablis pour Ă©valuer les diffĂ©rents algorithmes avec des critĂšres objectifs et reproductibles. Puis un systĂšme dâULM 3D a Ă©tĂ© dĂ©veloppĂ© pour pallier Ă la projection en Ă©lĂ©vation de lâimagerie 2D et Ă©largir le champ de vue. En utilisant une sonde multiplexĂ©e, une angiographie dâun cerveau de rat a Ă©tĂ© rĂ©alisĂ©e in vivo avec un systĂšme commercial. Une rĂ©solution de quelques dizaines de microns a Ă©tĂ© obtenue Ă travers le crĂąne, rĂ©duisant au minimum lâimpact de lâimagerie sur la physiologie de lâanimal en vue dâune Ă©tude prĂ©-clinique. Enfin, ce systĂšme a Ă©tĂ© utilisĂ© pour imager des AVC induits sur une cohorte de rats. Il a prouvĂ© sa capacitĂ© Ă distinguer les effets dâune ischĂ©mie par rapport Ă une hĂ©morragie sur la vascularisation du cerveau. Cette premiĂšre Ă©tude montre la pertinence dâune telle imagerie pour le diagnostic en phase prĂ©coce de lâAVC chez lâhumain par ULM volumĂ©trique en sâaffranchissant des contraintes et disponibilitĂ©s de lâIRM et du scanner.A stroke is a sudden loss of vascularization of a part of the brain. Patients must receive medical care within the first hour to reduce neuronal loss and long-term sequelae.Most strokes are hemorrhagic or ischemic, with similar symptoms but specific treatments. Early-phase diagnosis becomes vital and requires deep brain imaging through the skull bone.The development of Ultrasound Localization Microscopy (ULM) has widened applications for microvascular imaging by improving contrast, resolution, and penetration depth. Microbubbles are injected into the blood flow and localized to reconstruct the microvessels within few minutes.The main objective of this thesis is the application of 3D ULM for non-invasive stroke diagnosis in the early phase.A first study focuses on a quantitative comparison of localization algorithms for 2D ultrasound imaging. A set of standardized metrics and unified datasets were established to evaluate various algorithms with objective and reproducible criteria. Then a volumetric ULM system was set up to overcome the elevation projection of 2D imaging and increase the field of view. We performed a 3D angiography of a rat brain in vivo with a commercial scanner and a multiplexed ultrasonic probe. A few tens of micrometers resolution was obtained through the skull bone. This method didnât induce major modifications of the animalâs physiology and can be used for a pre-clinical study. Finally, this system was used to image induced strokes in a cohort of rats. It proved its ability to distinguish the effects of ischemia versus hemorrhage on brain vascularization. This first study shows the relevance of such imaging for the early diagnosis of stroke in humans by volumetric ULM, without the constraints and availability of MRI and CT
Microscopie par localisation ultrasonore dans les modÚles d'accidents vasculaires cérébraux
A stroke is a sudden loss of vascularization of a part of the brain. Patients must receive medical care within the first hour to reduce neuronal loss and long-term sequelae.Most strokes are hemorrhagic or ischemic, with similar symptoms but specific treatments. Early-phase diagnosis becomes vital and requires deep brain imaging through the skull bone.The development of Ultrasound Localization Microscopy (ULM) has widened applications for microvascular imaging by improving contrast, resolution, and penetration depth. Microbubbles are injected into the blood flow and localized to reconstruct the microvessels within few minutes.The main objective of this thesis is the application of 3D ULM for non-invasive stroke diagnosis in the early phase.A first study focuses on a quantitative comparison of localization algorithms for 2D ultrasound imaging. A set of standardized metrics and unified datasets were established to evaluate various algorithms with objective and reproducible criteria. Then a volumetric ULM system was set up to overcome the elevation projection of 2D imaging and increase the field of view. We performed a 3D angiography of a rat brain in vivo with a commercial scanner and a multiplexed ultrasonic probe. A few tens of micrometers resolution was obtained through the skull bone. This method didnât induce major modifications of the animalâs physiology and can be used for a pre-clinical study. Finally, this system was used to image induced strokes in a cohort of rats. It proved its ability to distinguish the effects of ischemia versus hemorrhage on brain vascularization. This first study shows the relevance of such imaging for the early diagnosis of stroke in humans by volumetric ULM, without the constraints and availability of MRI and CT.L'accident vasculaire cĂ©rĂ©bral (AVC) est une perte subite de la vascularisation d'une partie du cerveau. Une prise en charge rapide rĂ©duit considĂ©rablement les pertes neuronales et sĂ©quelles Ă long terme. Les hĂ©morragies cĂ©rĂ©brales et infarctus cĂ©rĂ©braux reprĂ©sentent les principaux types d'AVC avec des symptĂŽmes similaires mais des traitements trĂšs spĂ©cifiques. Le diagnostic prĂ©coce est primordial et nĂ©cessite une imagerie du cerveau en profondeur Ă travers le crĂąne.Le dĂ©veloppement de la microscopie par localisation ultrasonore (ULM) a ouvert de nouvelles possibilitĂ©s pour lâimagerie vasculaire en amĂ©liorant le contraste, la rĂ©solution et la profondeur de pĂ©nĂ©tration de lâĂ©chographie. Des microbulles sont injectĂ©es dans le sang et localisĂ©es pour reconstruire la microvascularisation en quelques minutes.L'objectif gĂ©nĂ©ral de cette thĂšse est l'application de lâULM 3D pour le diagnostic non invasif de lâAVC en phase prĂ©coce. Une premiĂšre Ă©tude porte sur une comparaison quantitative des algorithmes de localisation ultrasonore pour l'imagerie 2D. Un ensemble de mĂ©triques normĂ©es et de jeux de donnĂ©es universels ont Ă©tĂ© Ă©tablis pour Ă©valuer les diffĂ©rents algorithmes avec des critĂšres objectifs et reproductibles. Puis un systĂšme dâULM 3D a Ă©tĂ© dĂ©veloppĂ© pour pallier Ă la projection en Ă©lĂ©vation de lâimagerie 2D et Ă©largir le champ de vue. En utilisant une sonde multiplexĂ©e, une angiographie dâun cerveau de rat a Ă©tĂ© rĂ©alisĂ©e in vivo avec un systĂšme commercial. Une rĂ©solution de quelques dizaines de microns a Ă©tĂ© obtenue Ă travers le crĂąne, rĂ©duisant au minimum lâimpact de lâimagerie sur la physiologie de lâanimal en vue dâune Ă©tude prĂ©-clinique. Enfin, ce systĂšme a Ă©tĂ© utilisĂ© pour imager des AVC induits sur une cohorte de rats. Il a prouvĂ© sa capacitĂ© Ă distinguer les effets dâune ischĂ©mie par rapport Ă une hĂ©morragie sur la vascularisation du cerveau. Cette premiĂšre Ă©tude montre la pertinence dâune telle imagerie pour le diagnostic en phase prĂ©coce de lâAVC chez lâhumain par ULM volumĂ©trique en sâaffranchissant des contraintes et disponibilitĂ©s de lâIRM et du scanner
3D transcranial Ultrasound Localization Microscopy for discrimination between ischemic and hemorrhagic stroke in early phase
International audienceEarly diagnosis is a critical part of the emergency care of cerebral hemorrhages and ischemia. A rapid and accurate diagnosis of strokes reduces the delays to appropriate treatments and a better functional recovery. Currently, CTscan and MRI are the gold standards with constraints of accessibility, availability, and possibly some contraindications. The development of Ultrasound Localization Microscopy (ULM) has enabled new perspectives to conventional transcranial ultrasound imaging with increased sensitivity, penetration depth, and resolution. The possibility of volumetric imaging has increased the field-of-view and provided a more precise description of the microvascularisation. In this study, rats (n=9) were subjected to thromboembolic ischemic stroke or intracerebral hemorrhages prior to volumetric ULM at the early phases after onsets. Although the volumetric ULM performed in the early phase of ischemic stroke revealed a large hypoperfused area in the cortical area of the occluded artery, it showed a more diffused hypoperfusion in the hemorrhagic model. Respective computations of a Microvascular Diffusion Index highlighted different patterns of perfusion loss during the first 24h of these two strokes' subtypes. Our study provides the first proof that this methodology should allow early discrimination between ischemic and hemorrhagic stroke with a potential toward diagnosis and monitoring in clinic
3D Transcranial Ultrasound Localization Microscopy in the Rat Brain With a Multiplexed Matrix Probe
International audienceObjective: Ultrasound Localization Microscopy (ULM) provides images of the microcirculation in-depth in living tissue. However, its implementation in two-dimension is limited by the elevation projection and tedious plane-by-plane acquisition. Volumetric ULM alleviates these issues and can map the vasculature of entire organs in one acquisition with isotropic resolution. However, its optimal implementation requires many independent acquisition channels, leading to complex custom hardware.Methods: In this article, we implemented volumetric ultrasound imaging with a multiplexed 32 Ă 32 probe driven by a single commercial ultrasound scanner. We propose and compare three different sub-aperture multiplexing combinations for localization microscopy in silico and in vitro with a flow of microbubbles in a canal. Finally, we evaluate the approach for micro-angiography of the rat brain. The âlightâ combination allows a higher maximal volume rate than the âfullâ combination while maintaining the field of view and resolution.Results: In the rat brain, 100,000 volumes were acquired within 7 min with a dedicated ultrasound sequence and revealed vessels down to 31 ÎŒm in diameter with flows from 4.3 mm/s to 28.4 mm/s.Conclusion: This work demonstrates the ability to perform a complete angiography with unprecedented resolution in the living rat's brain with a simple and light setup through the intact skull.Significance: We foresee that it might contribute to democratize 3D ULM for both preclinical and clinical studies
Adaptive beamforming combined with decision theory-based detection for ultrasound localization microscopy
International audienceUltrasound Localisation Microscopy (ULM) is an imaging framework which consists in tracking microbubbles (MBs) on ultrasound (US) images to estimate their trajectory and thus the map of the vascular network. ULM algorithms takes as input US images usually beamformed with the delay-and-sum (DAS) method. In a previous study, we have shown that adaptive beamforming enhances the results of ULM on simulated data by detecting more MBs and localizing them more precisely. In another study, we introduced a new MB detection method based on decision theory. In this paper, adaptive beamformers such as Capon, pDAS and iMAP combined to this detection method are applied on in vivo rat brain data. Results show that this combination allow to identify more MBs and thus to represent more vessels in the ULM vascular network map
Adaptive beamforming combined with decision theory-based detection for ultrasound localization microscopy
International audienceUltrasound Localisation Microscopy (ULM) is an imaging framework which consists in tracking microbubbles (MBs) on ultrasound (US) images to estimate their trajectory and thus the map of the vascular network. ULM algorithms takes as input US images usually beamformed with the delay-and-sum (DAS) method. In a previous study, we have shown that adaptive beamforming enhances the results of ULM on simulated data by detecting more MBs and localizing them more precisely. In another study, we introduced a new MB detection method based on decision theory. In this paper, adaptive beamformers such as Capon, pDAS and iMAP combined to this detection method are applied on in vivo rat brain data. Results show that this combination allow to identify more MBs and thus to represent more vessels in the ULM vascular network map
Adaptive beamforming combined with decision theory-based detection for ultrasound localization microscopy
International audienceUltrasound Localisation Microscopy (ULM) is an imaging framework which consists in tracking microbubbles (MBs) on ultrasound (US) images to estimate their trajectory and thus the map of the vascular network. ULM algorithms takes as input US images usually beamformed with the delay-and-sum (DAS) method. In a previous study, we have shown that adaptive beamforming enhances the results of ULM on simulated data by detecting more MBs and localizing them more precisely. In another study, we introduced a new MB detection method based on decision theory. In this paper, adaptive beamformers such as Capon, pDAS and iMAP combined to this detection method are applied on in vivo rat brain data. Results show that this combination allow to identify more MBs and thus to represent more vessels in the ULM vascular network map