Introdução: Estudos pré-clínicos demonstraram que impulsos de alto índice mecânico (IM) de um transdutor de ultrassom diagnóstico durante uma infusão intravenosa de microbolhas (sonotrombólise) podem restaurar o fluxo epicárdico e microvascular no infarto agudo do miocárdio com supradesnivelamento do segmento ST (IAMCSST). Objetivo: Testamos a eficácia clínica da sonotrombólise em pacientes com IAMCSST medindo a taxa de recanalização coronariana precoce, tamanho do infarto do miocárdio por ressonância magnética e ecocardiograma e a evolução do defeito de perfusão e função ventricular esquerda à chegada, após a intervenção coronária percutânea (ICP), 72h a 96h e em um e seis meses de acompanhamento. Métodos: Pacientes com seu primeiro IAMCSST foram prospectivamente randomizados para receberem impulsos de alto IM guiados por ultrassom diagnóstico (grupo terapia) durante a infusão intravenosa de um agente de ultrassom antes e após a ICP ou para um grupo controle que recebeu apenas ICP (n = 50 em cada grupo). Um grupo de referência (n = 203) que chegou fora da janela de randomização também foi analisado. Recanalização angiográfica prévia à ICP, tamanho do infarto (TI) por ressonância magnética e alteração no defeito de perfusão e função sistólica pela ecocardiografia à chegada, após-ICP, 72h a 96h, em um e seis meses foram comparados. Resultados: A média de idade dos pacientes randomizados foi de 59 anos e não houve diferença de sexo, presença de diabetes, hipertensão arterial e dislipidemia entre os grupos estudados. Os tempos porta-balão não foram diferentes entre os grupos analisados (78 ± 32 minutos para o grupo controle versus 77 ± 26 minutos para o grupo terapia, p = 0,42), mas foram mais longos no grupo de referência (96 ± 49 minutos, p < 0,001 comparado aos grupos controle e terapia). A recanalização angiográfica foi de 48% no grupo terapia versus 20% no grupo controle e 21% no grupos de referência (p < 0,001). O TI foi reduzido (29 ± 22 gramas do grupo terapia versus 40 ± 20 gramas do grupo controle, p = 0,026). Da mesma forma, as taxas de fluxo TIMI 3 pré-ICP foram maiores no grupo terapia (32% versus 14% no grupo controle e 16% no grupo de referência, p = 0,02). Após a ICP, fluxo TIMI 3 foi observado no vaso culpado em 37/50 (74%) pacientes no grupo terapia e 30/50 (60%) pacientes do grupo controle. A fração de ejeção do ventrículo esquerdo (FEVE) não foi diferente entre os grupos antes do tratamento (44 ± 11% no grupo terapia versus 43 ± 10% no grupo controle, p = 0,39), mas aumentou imediatamente após a ICP no grupo terapia (p = 0,03) e permaneceu maior aos seis meses (p = 0,015). A correlação entre as medidas do tamanho do infarto (TI) em gramas por ressonância magnética e ecocardiografia com contraste, utilizando o coeficiente de correlação intraclasses foi de 0,672 (p < 0,001). Não houve diferença significativa na % de área acometida pelo infarto pelo ecocardiograma realizado pré-ICP, pós-ICP e durante a internação com 72h a 96h de evolução, mas no seguimento de 1 mês houve consolidação de maior redução da % de área infartada no grupo terapia 20,67 ± 8,99 a 11,87 ± 7,49 quando comparado ao grupo controle 19,16 ± 10,08 a 17,02 ± 10,02 (p = 0,016), mostrando uma diferença comportamental durante as avaliações temporais, com uma maior diminuição no tamanho do infarto no grupo terapia (p < 0,001). Ao comparar a porcentagem média de áreas infartadas naqueles pacientes com artérias coronárias obstruídas na primeira angiografia, houve um menor comprometimento microvascular naqueles do grupo terapia 12,99 ± 6,53 versus 18,87 ± 9,93 do grupo controle (p = 0,015 ). Ainda assim, como consequência das melhorias observadas na % do tamanho do infarto, notamos uma melhora progressiva na fração de ejeção nos pacientes do grupo terapia: 44,0% ± 11,0% para 53,0% ± 10% versus 43 % ± 10% para 48,0% ± 11,0% no grupo controles (p = 0,048) da chegada aos 6 meses de acompanhamento. Conclusões: A sonotrombólise adicionada à ICP melhora as taxas de recanalização e reduz o tamanho do infarto, resultando em melhorias sustentadas na perfusão miocárdica e na função sistólica após o IAMCSST / Background: Pre-clinical studies have demonstrated that high mechanical index (MI) impulses from a diagnostic ultrasound transducer during an intravenous microbubble infusion (sonothrombolysis) can restore epicardial and microvascular flow in acute ST-segment elevation myocardial infarction (STEMI). Objective: We tested the clinical effectiveness of sonothrombolysis in patients with STEMI by measuring early coronary recanalization rate, size of myocardial infarction by MRI and echocardiography and the evolution of the perfusion defect and left ventricular function at arrival, after PCI, 72h to 96h and at one- and six-months follow-up. Methods: Patients with their first STEMI were prospectively randomized to either diagnostic ultrasound-guided high MI impulses (therapy group) during an intravenous ultrasound agent infusion prior to, and following emergent percutaneous coronary intervention (PCI), or to a control group that received PCI only (n = 50 in each group). A reference group (n = 203) who arrived outside the randomization window was also analyzed. Angiographic recanalization prior to PCI, infarct size (IS) by magnetic resonance imaging, and change in perfusion defect and systolic function by echocardiography at arrival, post PCI, 72h to 96h, one and six months were compared. Results: The mean age of the randomized patients was 59 years and there was no difference in gender, presence of diabetes, arterial hypertension and dyslipidemia between the groups studied. Door to balloon times were not different between groups (78 ± 32 minutes for control versus 77 ± 26 minutes for therapy groups, p = 0.42), but were longer in the reference group (96 ± 49 minutes, p < 0.001 compared to control and therapy groups). Angiographic recanalization was 48% in therapy group versus 20% in control group and 21% in the reference group (p < 0.001). IS was reduced (29 ± 22 grams in therapy group versus 40 ± 20 grams in control group, p = 0.026). Likewise, pre-PCI TIMI 3 flow rates were higher in the therapy group (32% versus 14% in control group and 16% in the reference group, p = 0.02). After PCI, the TIMI 3 flow was observed in the culprit vessel in 37/50 (74%) patients in therapy group and 30/50 (60%) in patients in the control group. Left ventricular ejection fraction (LVEF) was not different between groups before treatment (44 ± 11% in therapy group versus 43 ± 10% in control group, p = 0.39), but increased immediately after PCI in the therapy group (p = 0.03) and remained higher at six months (p = 0.015). The correlation between the measurements of infarct size (IS) in grams by magnetic resonance and contrast echocardiography, using the intra-class correlation coefficient was 0.672 (p < 0.001). There was no significant difference in the % area affected by the infarction on echocardiography performed pre-PCI, post-PCI and during hospital stay with 72h to 96h of evolution, but in the follow-up of 1 month there was a consolidation of greater reduction of the % infarcted area in the therapy group 20.67 ± 8.99 to 11.87 ± 7.49 when compared to control group 19.16 ± 10.08 to 17.02 ± 10.02 (p = 0.016), showing a behavioral difference during the temporal evaluations, with a greater decrease in infarct size in the therapy group (p < 0.001). When comparing the mean % of infarcted areas in those patients with occluded coronary arteries at the first angiography, there was a lower microvascular impairment in those in the therapy group 12.99 ± 6.53 versus 18.87 ± 9,93 in control group (p = 0.015). Still, as a consequence of the improvements observed in the % of infarct size, we noticed a progressive improvement in the ejection fraction in patients in the therapy group 44.0% ± 11.0% to 53.0% ± 10% versus 43% ± 10% to 48.0% ± 11,0% in the control group (p = 0.048) from arrival to 6-month follow-up. Conclusions: Sonothrombolysis added to PCI improves recanalization rates and reduces infarct size, resulting in sustained improvements in myocardial perfusion and systolic function after STEMI

Introdução: As massas cardíacas (MC) podem ser tumores, trombos ou pseudotumores. A avaliação da vascularização poderá ser uma ferramenta adicional para o seu diagnóstico diferencial. Neste estudo, demonstrou-se o valor diagnóstico da ecocardiografia com perfusão na caracterização das MC or meio de análises qualitativas e quantitativas de perfusão. Métodos: Estudo prospectivo que envolveu 107 pacientes, classificados em quatro grupos: 33 trombos, 23 tumores malignos (TM), 24 tumores benignos (TB) e 6 pseudotumores; 21 pacientes foram excluídos por não terem diagnóstico definitivo confirmado. A avaliação de perfusão foi realizada pela ecocardiografia com perfusão em tempo real, utilizando contraste à base de microbolhas. Em um grupo selecionado de pacientes (32), o estudo foi complementado com dipiridamol para avaliação da reserva de fluxo da massa. A análise foi feita qualitativa e quantitativamente por dois observadores independentes. Na análise qualitativa, os parâmetros foram: intensidade da perfusão (escore 0 a 3), velocidade do repreenchimento microvascular (escore 0 a 2), padrão de perfusão central ou periférico (escore 0 a 2) e presença de áreas de necrose (escore 0 e 1). Os dois parâmetros de quantificação das massas foram: volume de sangue microvascular (A) e fluxo microvascular regional, que é o produto da velocidade de fluxo () e volume (A). Resultados: Na análise qualitativa, o padrão mais frequente para o grupo trombos foi: sem perfusão (81,9%), sem velocidade de perfusão (81,9%) e sem área de necrose (93,4%); nos tumores, predominou perfusão discreta (62,3%), com velocidade lenta (64,2%) e áreas de necrose (30,2%). Na análise qualitativa, a variação intraobservador para escore de perfusão e de velocidade foi de 20%, para áreas de necrose de 25% e para padrão de perfusão foi de 45%. Na análise quantitativa, o grupo trombos apresentou valores de A e Ax significativamente menores quando comparados ao grupo de tumores: Trombos: A = 0,08 (0,01-0,22dB); Ax = 0,03 (0,010,14dB/s-1); TM: A = 2,78 (1,31-7,0dB); Ax = 2,0 (0,995,58dB/s-1); TB: A = 2,58 (1,24-4,55dB); Ax = 1,18 (0,453,4dB/s-1). Quando comparados apenas os grupos de tumores com o uso de dipiridamol, os TM apresentaram volume sanguíneo microvascular (A) maiores: A = 4,18 (2,14-7,93dB); Ax = 2,46 (1,424,59dB/s-1), TB: A = 2,69 (1,11-4,26dB); Ax = 1,55 (0,555,50dB/s-1). Na análise com a curva ROC, a área sob a curva = 0,95, no parâmetro volume sanguíneo microvascular (A) < 0,65dB na ecocardiografia de perfusão com e sem uso de dipiridamol foi preditor para trombo, bem como o parâmetro fluxo sanguíneo microvascular (Ax) < 0,30dB/s-1, (área sob a curva = 0,94). Para distinguir entre TM de TB, o parâmetro volume sanguíneo microvascular (A), com o uso de dipiridamol > 3,28dB foi preditor de TM (área sob a curva = 0,75). Conclusão: O estudo ecocardiográfico para avaliação da perfusão das MC mostrou que a análise qualitativa é um método diagnóstico rápido e reprodutível para diagnosticar trombos. Os tumores cardíacos apresentam volume microvascular e fluxo sanguíneo regional maior se comparados com os trombos. O uso do dipiridamol foi útil na diferenciação entre os TM e TB / Background: Cardiac masses (CM) can be tumors, thrombi or pseudotumors. Evaluation of their vascularization might be an additional tool to perform a differential diagnosis. In the present study we demonstrated the diagnostic value of perfusion echocardiography for CM characterization, by qualitative and quantitative analyses of perfusion. Methods: We prospectively studied 107 patients, who were classified into 4 groups: 33 thrombus, 23 malignant tumors (MT), 24 benign tumors (BT) and 6 pseudotumors, of which 21 were excluded because no definitive diagnosis could be confirmed. Perfusion evaluation was performed by contrast echocardiography with real time perfusion imaging using microbubbles. A group of patients (32) was selected for a complementary study using dipyridamole to evaluate mass flow reserve. Qualitative and quantitative analyses were performed by two independent observers. Parameters for qualitative analysis were perfusion intensity (0-3 score), microvascular refilling velocity (0-2 score), central or peripheral perfusion pattern (0-2 score), and presence of areas of necrosis (0 or 1 score). The two parameters for quantification of masses were microvascular blood volume (A), and regional microvascular flow which is the product of blood flow velocity and vomume (A). Results: The most frequent pattern for the thrombi group in the qualitative analysis was absence of perfusion (81.9%), followed by no perfusion velocity (81.9%), and no areas of necrosis (93.4%), whilst among tumors there was predominance of discrete perfusion (62.3%), with slowed velocity (64.2%), and areas of necrosis (30.2%). Qualitative analysis, perfusion velocity showed intraobserver variability 20%, presence of areas of necrosis of 25% and perfusion pattern of 45%. In the quantitative analysis, the thrombi group was shown to have A and Ax values significantly smaller compared to the tumor group: Thrombi: A = 0.08 (0.01-0.22dB); Ax = 0.03 (0.010.14dB/s-1); MT: A = 2.78 (1.31-7.0dB); Ax = 2.0 (0.995.58dB/s-1); BT: A = 2.58 (1.24-4.55dB); Ax = 1.18 (0.453.4dB/s-1). When only the tumor groups with the use of dipyridamole were compared, MT was shown to have greater microvascular blood volume (A): A = 4.18 (2.14-7.93dB); Ax = 2.46(1.424.59dB/s-1), BT: A = 2.69 (1.11-4.265dB); Ax = 1.55 (0.555.50dB/s-1). Analysis of the ROC curve showed that an area of 0.95 for a microvascular blood volume of A < 0.65 dB predictive curve on perfusion echocardiography, both with and without dipyridamole, predicts thrombi, and so does a <0.30dB/s-1microvascular blood flow (Ax), area under curve = 0.94. In order to distinguish MT from BT, a >3.28dB microvascular blood volume (A) using dipyridamole was predictor of MT (area under curve = 0.75). Conclusion: The echocardiographic study to evaluate CM perfusion showed that qualitative analysis is reproducible diagnostic approach for diagnosing thrombi. Cardiac tumors show greater microvascular volume and regional blood flow when compared with thrombi. Dipyridamole quantitative stress mass perfusion was useful to differentiate MT from BT

Le développement de différentes formes colloïdales pour la thérapie et le diagnostic médical ultrasonore connait un intérêt croissant depuis de nombreuses années. En particulier, les microbulles de perfluorocarbone (PFC) sont des agents de contraste intéressants, car le gaz est un puissant réflecteur des ultrasons. Plus récemment, les gouttelettes de PFC ont été proposées pour de nouvelles applications acoustiques. Suite à une impulsion acoustique, les ultrasons induisent un changement de phase de l’état liquide à l’état gazeux. Ce phénomène est appelé la vaporisation acoustique de gouttelettes. Parallèlement à l’étude de nouvelles applications, le développement de nouvelles techniques de préparation offrant un meilleur contrôle lors de la production, reste un enjeu primordial. Ainsi, de nouvelles méthodes de préparation basées sur des dispositifs membranaires semblent être particulièrement intéressantes. L’objectif de la thèse porte donc sur le développement de nouvelles techniques à membrane pour la formulation de microbulles et de microgouttelettes de taille contrôlée pour des applications en imagerie et thérapie ultrasonore. Dans ce travail, l’émulsification membranaire directe avec un module membranaire de type cross-flow a été utilisé pour la préparation de microbulles stabilisées par des tensioactifs solubles, tandis qu’un module de type microkit a permis l’obtention de microbulles stabilisées par des phospholipides. Dans un second temps, l’émulsification membranaire par prémix a permis de formuler des microgouttelettes de PFC monodispersées. Pour les différentes formes colloïdales préparées, nous avons observé l’influence des paramètres du procédé (pression, débit et contrainte de cisaillement), des paramètres de formulation (molécules stabilisatrices, type de PFC de la phase dispersée) et des paramètres de la membrane (taille des pores) sur la formation des microbulles/ microgouttelettes. Par la suite, la caractérisation acoustique des microbulles/microgouttelettes a montré que ces systèmes présentent les propriétés nécessaires pour être utilisés comme agents de contraste ultrasonores / The development of various colloidal forms for therapy and diagnosis in ultrasound medical present a great interest for many years. In particular, microbubbles of perfluorocarbon (PFC) are interesting as contrast agents because the gas is a high ultrasound reflector. More recently, PFC droplets have been proposed for news acoustic applications. Indeed, after an acoustic pulse, the ultrasound waves induce a phase change from the liquid state to the gaseous state. This phenomenon is called the acoustic vaporization of droplets. In parallel with the study of new applications, the development of new process offering a better control during production, remains a key issue.Thus, the preparation using news methods based on membrane devices seem to be particularly interesting. The aim of the thesis is the development of new membrane process for the formulation of microbubbles and droplets with a size controlled for ultrasound applications in imaging and therapy. In this work, the direct membrane emulsification with a cross-flow membrane module was used for the preparation of microbubbles stabilized by soluble surfactants, while a microkit module allowed to obtain microbubbles stabilized by phospholipids. In a second step, the membrane emulsification by premix allowed to formulate monodispersed droplets of PFC. For the various colloidal forms prepared, we observed the influence of the process parameters (pressure, flow rate and shear stress), the formulation parameters (surfactants, type of PFC of the dispersed phase) and the membrane parameters (pore size) on the formation of microbubbles/droplets. Subsequently, the acoustic characterization of microbubbles/droplets has shown that these systems have the properties to be used as ultrasonic contrast agents

Introdução: As massas cardíacas (MC) podem ser tumores, trombos ou pseudotumores. A avaliação da vascularização poderá ser uma ferramenta adicional para o seu diagnóstico diferencial. Neste estudo, demonstrou-se o valor diagnóstico da ecocardiografia com perfusão na caracterização das MC or meio de análises qualitativas e quantitativas de perfusão. Métodos: Estudo prospectivo que envolveu 107 pacientes, classificados em quatro grupos: 33 trombos, 23 tumores malignos (TM), 24 tumores benignos (TB) e 6 pseudotumores; 21 pacientes foram excluídos por não terem diagnóstico definitivo confirmado. A avaliação de perfusão foi realizada pela ecocardiografia com perfusão em tempo real, utilizando contraste à base de microbolhas. Em um grupo selecionado de pacientes (32), o estudo foi complementado com dipiridamol para avaliação da reserva de fluxo da massa. A análise foi feita qualitativa e quantitativamente por dois observadores independentes. Na análise qualitativa, os parâmetros foram: intensidade da perfusão (escore 0 a 3), velocidade do repreenchimento microvascular (escore 0 a 2), padrão de perfusão central ou periférico (escore 0 a 2) e presença de áreas de necrose (escore 0 e 1). Os dois parâmetros de quantificação das massas foram: volume de sangue microvascular (A) e fluxo microvascular regional, que é o produto da velocidade de fluxo () e volume (A). Resultados: Na análise qualitativa, o padrão mais frequente para o grupo trombos foi: sem perfusão (81,9%), sem velocidade de perfusão (81,9%) e sem área de necrose (93,4%); nos tumores, predominou perfusão discreta (62,3%), com velocidade lenta (64,2%) e áreas de necrose (30,2%). Na análise qualitativa, a variação intraobservador para escore de perfusão e de velocidade foi de 20%, para áreas de necrose de 25% e para padrão de perfusão foi de 45%. Na análise quantitativa, o grupo trombos apresentou valores de A e Ax significativamente menores quando comparados ao grupo de tumores: Trombos: A = 0,08 (0,01-0,22dB); Ax = 0,03 (0,010,14dB/s-1); TM: A = 2,78 (1,31-7,0dB); Ax = 2,0 (0,995,58dB/s-1); TB: A = 2,58 (1,24-4,55dB); Ax = 1,18 (0,453,4dB/s-1). Quando comparados apenas os grupos de tumores com o uso de dipiridamol, os TM apresentaram volume sanguíneo microvascular (A) maiores: A = 4,18 (2,14-7,93dB); Ax = 2,46 (1,424,59dB/s-1), TB: A = 2,69 (1,11-4,26dB); Ax = 1,55 (0,555,50dB/s-1). Na análise com a curva ROC, a área sob a curva = 0,95, no parâmetro volume sanguíneo microvascular (A) < 0,65dB na ecocardiografia de perfusão com e sem uso de dipiridamol foi preditor para trombo, bem como o parâmetro fluxo sanguíneo microvascular (Ax) < 0,30dB/s-1, (área sob a curva = 0,94). Para distinguir entre TM de TB, o parâmetro volume sanguíneo microvascular (A), com o uso de dipiridamol > 3,28dB foi preditor de TM (área sob a curva = 0,75). Conclusão: O estudo ecocardiográfico para avaliação da perfusão das MC mostrou que a análise qualitativa é um método diagnóstico rápido e reprodutível para diagnosticar trombos. Os tumores cardíacos apresentam volume microvascular e fluxo sanguíneo regional maior se comparados com os trombos. O uso do dipiridamol foi útil na diferenciação entre os TM e TB / Background: Cardiac masses (CM) can be tumors, thrombi or pseudotumors. Evaluation of their vascularization might be an additional tool to perform a differential diagnosis. In the present study we demonstrated the diagnostic value of perfusion echocardiography for CM characterization, by qualitative and quantitative analyses of perfusion. Methods: We prospectively studied 107 patients, who were classified into 4 groups: 33 thrombus, 23 malignant tumors (MT), 24 benign tumors (BT) and 6 pseudotumors, of which 21 were excluded because no definitive diagnosis could be confirmed. Perfusion evaluation was performed by contrast echocardiography with real time perfusion imaging using microbubbles. A group of patients (32) was selected for a complementary study using dipyridamole to evaluate mass flow reserve. Qualitative and quantitative analyses were performed by two independent observers. Parameters for qualitative analysis were perfusion intensity (0-3 score), microvascular refilling velocity (0-2 score), central or peripheral perfusion pattern (0-2 score), and presence of areas of necrosis (0 or 1 score). The two parameters for quantification of masses were microvascular blood volume (A), and regional microvascular flow which is the product of blood flow velocity and vomume (A). Results: The most frequent pattern for the thrombi group in the qualitative analysis was absence of perfusion (81.9%), followed by no perfusion velocity (81.9%), and no areas of necrosis (93.4%), whilst among tumors there was predominance of discrete perfusion (62.3%), with slowed velocity (64.2%), and areas of necrosis (30.2%). Qualitative analysis, perfusion velocity showed intraobserver variability 20%, presence of areas of necrosis of 25% and perfusion pattern of 45%. In the quantitative analysis, the thrombi group was shown to have A and Ax values significantly smaller compared to the tumor group: Thrombi: A = 0.08 (0.01-0.22dB); Ax = 0.03 (0.010.14dB/s-1); MT: A = 2.78 (1.31-7.0dB); Ax = 2.0 (0.995.58dB/s-1); BT: A = 2.58 (1.24-4.55dB); Ax = 1.18 (0.453.4dB/s-1). When only the tumor groups with the use of dipyridamole were compared, MT was shown to have greater microvascular blood volume (A): A = 4.18 (2.14-7.93dB); Ax = 2.46(1.424.59dB/s-1), BT: A = 2.69 (1.11-4.265dB); Ax = 1.55 (0.555.50dB/s-1). Analysis of the ROC curve showed that an area of 0.95 for a microvascular blood volume of A < 0.65 dB predictive curve on perfusion echocardiography, both with and without dipyridamole, predicts thrombi, and so does a <0.30dB/s-1microvascular blood flow (Ax), area under curve = 0.94. In order to distinguish MT from BT, a >3.28dB microvascular blood volume (A) using dipyridamole was predictor of MT (area under curve = 0.75). Conclusion: The echocardiographic study to evaluate CM perfusion showed that qualitative analysis is reproducible diagnostic approach for diagnosing thrombi. Cardiac tumors show greater microvascular volume and regional blood flow when compared with thrombi. Dipyridamole quantitative stress mass perfusion was useful to differentiate MT from BT

Des bulles micrométriques sont utilisées dans divers domaines, notamment dans des applications médicales basées sur les ultrasons. Il est possible d’exploiter différents effets des bulles, comme par exemple leur résonance acoustique ou leur effet destructeur en cavitation inertielle. Un autre mécanisme exploitable est la génération de micro-écoulements, appelé microstreaming, induits autour d’une bulle. Ces écoulements sont relativement lents par rapport aux oscillations rapides de la bulle. Le microstreaming et les contraintes de cisaillement associées jouent un rôle important dans la perméabilisation d’une membrane cellulaire, mais il manque encore une compréhension détaillée de l’écoulement induit. Afin d’améliorer la compréhension des phénomènes physiques, ce travail se concentre sur les écoulements induits autour d’une bulle d’air dans piégée et excitée acoustiquement dans de l’eau et oscillante en modes de surface. La partie expérimentale se décompose de deux étapes. Dans un premier temps, il est nécessaire de contrôler la dynamique de la bulle, en particulier ses modes de surface et son orientation. Ceci est réalisé par coalescence entre deux bulles. Dans un second temps, le microstreaming est généré et enregistré simultanément à la dynamique de bulle. De cette manière il est possible de corréler les motifs d'écoulement aux oscillations de la bulle. Le grand nombre de motifs obtenus peut être classé selon le mode dominant et la taille de la bulle. Une étude plus détaillée de la dynamique de bulle permet de déduire les paramètres importants qui mènent à une telle variété de motifs de microstreaming. Afin de confirmer les résultats expérimentaux, un modèle analytique a été développé. Il est basé sur les équations de la mécanique des fluides de deuxième ordre et moyennées en temps, la dynamique d'interface de la bulle obtenue expérimentalement sert de donnée d’entrée au modèle. Ce manuscrit contient en supplément une section sur la génération de microjets par l'implosion d'agents de contraste. Ces jets peuvent apparaître en cas d’excitation acoustique suffisamment élevée. L’impact de ces jets sur parois présente un autre mécanisme responsable de la perméabilisation de membranes cellulaires. / Microbubbles find use in several domains, one of them being medical ultrasound applications. Different characteristics of those bubbles such as their acoustic resonance or their destructive effect during inertial cavitation can be exploited. Another phenomenon induced around acoustically excited bubbles is microstreaming, that means a relatively slow mean flow with respect to the fast bubble oscillations. Microstreaming and its associated shear stresses are commonly agreed to play a role in the permeabilization of cell membranes, a detailed understanding of the induced flows is however missing. To acquire basic physical knowledge, this work focuses on the characterization of streaming induced around an air bubble in water, more precisely around a single acoustically trapped and excited, nonspherically oscillating bubble. The experimental part consists of two steps. First, the bubble dynamics, in particular the triggered shape mode and the orientation of the bubble have to be controlled. For this, the use of bubble coalescence proves to be an adequate method. In a second step, the microstreaming is recorded in parallel to bubble dynamics. This allows to correlate the obtained streaming patterns to the respective shape oscillations. The large number of obtained pattern types can be classified, in particular with respect to the mode number and bubble size. A close investigation of the bubble dynamics allows furthermore deducing the important physical mechanisms which lead to such a variety of streaming patterns. In order to confirm the experimental findings, an analytical model has been developed. It is based upon time-averaged second-order fluid mechanics equations and the experimentally obtained bubble dynamics serves as input parameters. Supplementary to the microstreaming work, this manuscript contains a short section on directed jetting of contrast agent microbubbles, which might appear at high acoustic driving. The impact of those microjets on cell membranes presents another mechanism made responsible for the permeabilization of cell membranes.

Thesis deals with ultrasonographic contrast examinations, that are performed to assess tissue perfusion and non-invasive ultrasound method speckle tracking, overcoming the weaknesses of Doppler techniques used to scanning the movement of the tissue.

L'hypoxie est un mécanisme reconnu de résistance à la radiothérapie chez les tumeurs solides. Il a récemment été démontré que la cavitation de microbulles (MBs) ciblées par ultrasons (US) (UTMC) peut augmenter la perfusion sanguine dans les muscles squelettiques en déclenchant la signalisation du monoxyde d’azote (NO). Il est intéressant de noter que cet effet a été amplifié par une co-injection de nitrite de sodium et a réduit le spasme observé avec des ultrasons à haute pression et à long pulse. Comme il a été démontré que le nitrite de sodium montrait une synergie avec la radiothérapie, nous avons émis l'hypothèse que les MBSU avec une co-injection de nitrite de sodium pourraient radiosensibiliser davantage les tumeurs solides en augmentant la perfusion sanguine et ainsi réduire l'hypoxie tumorale. Nous avons évalué la capacité des MBSU avec et sans nitrite d’augmenter la perfusion dans les muscles (membres postérieurs de la souris) et les tumeurs en utilisant différentes longueurs de pulse et pressions et évalué l'efficacité de cette approche en tant que thérapie provasculaire administrée directement avant les traitements de radiothérapie. Des xénogreffes de prostate humaine (PC3) ont été cultivées bilatéralement chez des souris immunodéficientes : un côté a été traité avec des MBSU et le côté controlatéral a été utilisé comme témoin. Des transducteurs thérapeutiques (pulse long) ou cardiaques (pulse court) ont été utilisés pour traiter le tissu d'intérêt lors de l'injection de MBs par la veine caudale. Le nitrite a été injecté 5 minutes avant les MBSU lorsque cela était approprié. Les MBSU consistaient en 60 impulsions thérapeutiques, administrées à un intervalle (10-15 secondes) ajusté pour permettre le réapprovisionnement en MBs, tel que guidé par l'imagerie ultrasonore à contraste amélioré (CEUS) (Sequoia, Siemens), et était généralement administré en 15 minutes. L'augmentation de la perfusion dans la tumeur a été quantifiée par Burst Replenishment Imaging permettant une quantification longitudinale de la perfusion sanguine (A×β). Les souris ont été irradiées 10 minutes après les MBSU et la croissance tumorale a été suivie pendant 25 jours. Dans le muscle, l'augmentation de la perfusion sanguine après traitement de MBSU avec différents longs pulses était forte. 6 Dans les tumeurs soumises à de longs pulses, l'augmentation de la perfusion était significative à une faible pression (125 et 250 kPa) mais pas à plus haute pression (375, 500 et 750 kPa) par rapport au groupe contrôle (0 kPa). Lorsqu'associé à la radiothérapie, les MBSU avec des longs pulses à 250 kPa n'ont pas entraîné d'augmentation significative de l'efficacité du traitement. Les MBSU avec des pulses courts à haute pression (SONOS, 1500kPa) et co-injection de nitrite ont ensuite été validés dans le muscle. L'effet du traitement était fort. Cette augmentation de la perfusion était également visible dans les tumeurs soumises aux MBSU (SONOS) + nitrite et a duré au moins 10 minutes. Le nitrite seul n’a causé aucun changement de perfusion. De plus, les faibles réponses provasculaires observées pour les longs pulses à 750 kPa sans nitrite ont été renversées avec l'ajout de nitrite. Le SONOS a provoqué une augmentation de la perfusion, avec et sans nitrite. La validation histologique de la reperfusion dans les tumeurs traitées par SONOS + nitrite était également significative par rapport aux tumeurs recevant uniquement du nitrite. Enfin, il y a eu une amélioration de l'inhibition de la croissance pour le groupe 8 Gy + nitrite + MBSU (SONOS) lorsque comparé à 8 Gy + nitrite seul. Cet effet n'était pas significatif chez les souris traitées par MBSU (SONOS) + nitrite et recevant 0 Gy ou 2 Gy. En conclusion, la thérapie de MBSU + nitrite semble augmenter la perfusion sanguine conduisant à une efficacité accrue de la radiothérapie à 8 Gy dans notre modèle tumoral. / In solid tumors, hypoxia is a recognized mechanism of resistance to radiation therapy. It has recently been shown that ultrasound (US) targeted microbubbles (MBs) cavitation (UTMC) can increase blood perfusion in skeletal muscles by triggering nitric oxide signaling. Interestingly, this effect was amplified with a sodium nitrite co-injection and reduced the spasm observed with high pressure long tone burst ultrasound. Since sodium nitrite has been shown to synergize with radiotherapy, we hypothesized that UTMC with a sodium nitrite co-injection could further radiosensitize solid tumors by increasing blood perfusion and thus reduce tumor hypoxia. We evaluated the ability of UTMC with and without nitrite to increase perfusion in muscle (mouse hindlimbs) and tumors using different pulse lengths and pressure and evaluated the efficacy of this approach as a provascular therapy given directly before radiotherapy treatments. Human prostate xenografts (PC3) were grown bilaterally in immunodeficient mice: one side was treated with UTMC, and the contralateral side was used as a control. Therapeutic transducers (long pulses) or cardiac phased array (short pulses) were used to treat the tissue of interest during the injection of MBs via the tail vein. Nitrite was injected 5 minutes before UTMC when appropriate. UTMC consisted of 60 therapeutic pulses, given at a pulse interval (10-15 seconds) adjusted to allow MB replenishment, as guided by contrast enhanced US imaging (CEUS), and was typically given in 15 minutes. The increase in perfusion in the tumor was quantified by burst replenishment imaging allowing longitudinal quantification of blood perfusion (A×B). Mice were irradiated 10 minutes after UTMC, and tumor growth followed for 25 days. In muscle, the increase in blood perfusion following UTMC treatment with various long pulses was strong. In tumors subjected to long pulses, the increase in perfusion was significant at lower M.I. (125 and 250 kPa) but not at higher M.I. (375, 500 and 750 kPa) when compared to control (0 kPa). When combined with radiotherapy, UTMC with long pulses at 250 kPa did not result in a significant increase in treatment efficacy. UTMC with short pulses (SONOS, 1500 kPa) and nitrite co-injection was then validated in muscle. The effect of treatment was strong and significative. 8 This significant increase in perfusion was also visible in tumors subjected to UTMC (SONOS) + nitrite and lasted for at least 10 minutes but not for nitrite alone. The blunted provascular responses observed for long pulses at higher M.I. without nitrite was reversed with the addition of nitrite. SONOS with and without nitrite caused an increase in perfusion. Histological validation of reperfusion in SONOS + nitrite was also significant when compared to tumors receiving only nitrite alone. Finally, there was an improved growth inhibition for the 8 Gy + nitrite + UTMC group vs. 8 Gy + nitrite alone with the SONOS therapy. This effect was not significant with mice treated by UTMC + nitrite and receiving 0 Gy or 2 Gy. In conclusion, UTMC + nitrite seemed to increase blood flow leading to an increased radiotherapy efficacy at 8 Gy in our tumor model.

No description available.

Current research within the field of ultrasound contrast agents (UCAs) aims at developing capsules which are not only acoustically active, but also have a chemically modifiable surface. This enables use in new areas, including targeted drug delivery and theranostics. For such purposes, air-filled microbubbles (MBs) with a polyvinyl alcohol (PVA) shell are being studied. Ultrasound imaging velocimetry (UIV) is a technique used to evaluate various types of liquid flows by tracking patterns caused by UCAs across ultrasound images, and has shown great potential for flow measurements in terms of accuracy. The aim of this thesis was to implement a basic UIV program in Matlab to investigate the flow behavior of air-filled PVA MBs being pumped through a phantom, mimicking a blood vessel. The images were acquired using the programmable Verasonics research system by plane wave imaging with coherent compounding, and UIV was implemented as a post-processing technique. Three parameters were varied to study how the UIV performance and flow behavior of the MBs were affected: the concentration of MBs, the flow velocity, and the transducer voltage. The resulting velocity vector fields showed that it is possible to track PVA MBs using the implemented UIV program, and that the concentration 5·106 MBs/ml gave the best results out of the five concentrations tested. The generated velocity vector fields indicated a turbulent and pulsatile flow behavior, which was in line with the predicted flow behavior, although there was a disparity between the measured average flow velocity of the MBs and the predicted flow velocity. It was also observed that the MBs were increasingly pushed in the axial direction with increasing voltage, as according to theory. Even though a more advanced UIV algorithm could improve the accuracy of the velocity measurements, the results show possible use of air-filled PVA MBs in combination with UIV. / Nuvarande forskning inom ultraljudskontrastmedel syftar till att utveckla kapslar som inte bara är akustiskt aktiva, utan som även har en kemiskt modifierbar yta. Detta möjliggör användning inom nya områden, så som målinriktade läkemedel och theanostics. För detta syfte studeras luftfyllda mikrobubblor med ett skal av polyvinylalkohol (PVA). Ultrasound imaging velocimetry (UIV) är en teknik som används för att analysera olika typer av vätskeflöden genom att spåra mönster orsakade av ultraljudskontrastmedel över ett antal ultraljudsbilder. Metoden har visats ha stor potential för flödesmätningar, och hög noggrannhet har uppnåtts. Detta projekt syftade till att implementera ett grundläggande UIV-program i Matlab för att undersöka flödesbeteenden hos luftfyllda PVA-mikrobubblor som pumpas genom en modell av ett blodkärl. Ultraljudsbilderna togs med hjälp av det programmerbara forskningssystemet Verasonics, genom att använda planvågsavbildning och coherent compounding, och UIV implementerades som ett efterbearbetningsprogram. Tre parametrar varierades för att studera hur prestandan av UIV-programmet och flödesbeteendet hos mikrobubblorna påverkades: koncentrationen av mikrobubblor, flödeshastigheten, och spänningsamplituden hos ultraljudsproben. De resulterande hastighetsvektorfälten visade det möjligt att evaluera flödesbeteenden hos PVA-mikrobubblor med hjälp av det implementerade UIV-programmet. Bäst resultat erhölls genom att använda koncentrationen 5·106 mikrobubblor/ml, av de fem testade koncentrationerna. De genererade hastighetsvektorfälten indikerade ett turbulent och pulserande flöde, vilket överensstämde med teorin, trots att det fanns skillnader mellan genomsnittliga uppmätta flödeshastigheter och den beräknade flödeshastigheten. Det kunde också observeras att mikrobubblorna trycktes i den axiella riktningen när spänningsamplituden ökade, vilket överensstämde med teorin. Trots att metodens noggrannhet skulle kunna ökas genom att använda ett mer avancerat UIV-program, visade resultaten på möjligheten att använda luftfyllda PVA-mikrobubblor i kombination med UIV.

Ultrasound imaging systems are a safe and affordable imaging modality with the disadvantage of low spatial resolution, especially for assessing smaller vessels. However, with the implementation of super-resolution ultrasound imaging techniques, studies have shown promising results in achieving a resolution below the diffraction limit. Super-resolution ultrasound imaging techniques takes advantage of the point spread function to localize the centroid of the ultrasound contrast agents in an image. By superimposing thousands of these images, a super-resolved image of the localized and tracked contrast agents can be created, which presents an image where vessels down to a few micrometers can be resolved. The purpose of this master’s thesis was to implement super-resolution ultrasound imaging, test different localization methods and analyze them by using different ultrasound contrast agent concentrations. Grayscale ultrasound images were acquired using the Verasonics system for three different microbubble concentrations. The super-resolution ultrasound imaging program was executed on the grayscale images using three different localization methods, Gaussian fit, No-shift and Interpolation based scheme. The microbubbles were localized and tracked over several frames to create a super-resolved image which had the pixel resolution of a 10th of the wavelength. Significant improvements were demonstrated in the super-resolved images compared to the grayscale images. The higher microbubble concentrations resulted in a higher number of localized and tracked microbubbles. While the low concentration exhibited lower values. Comparing the methods, Gaussian fit and No-shift detected higher number of microbubbles than the method Interpolation. Although further analysis is needed, the thesis concluded that using Gaussian fit as a localization method and higher microbubble concentrations, a super-resolved image can be produced even if the program is tested on fewer images. / Ultraljudsavbildning är en säker och billig avbildningsmodalitet med en låg spatial upplösning, framför allt vid avbildning av mindre kärl. Men med implementering av ultraljudsavbildningstekniker med superupplösning har studier visat lovande resultat för att uppnå en upplösning under diffraktionsgränsen. Ultraljudsavbildningstekniker med superupplösning utnyttjar punktspridningsfunktionen för att lokalisera ett ultraljudskontrastmedels centerpunkt i en bild. Genom att överlagra tusentals av dessa bilder skapas en superupplöst bild av det lokaliserade och spårade kontrastmedlet. Med hjälp av superupplösta bilden kan kärl som är några mikrometer urskiljas. Syftet med denna masteruppsats var att implementera ultraljudsavbildning med superupplösning, testa olika lokaliseringsmetoder och analysera de genom att använda olika koncentrationer av mikrobubblor. Gråskale ultraljudsbilder samlades in med hjälp av Verasonics systemet för tre olika koncentrationer av mikrobubblor. Superupplösningsprogrammet var exekverad på gråskalebilderna för tre olika lokaliseringsmetoder, Gaussian fit, No-shift och Interpolation based scheme. Mikrobubblorna lokaliserades och spårades över flera bilder för att skapa en superupplöst bild vilket hade en tiondel av våglängden som pixelupplösning. Resultatet presenterade en märkbar förbättring i de superupplösta bilderna jämfört med gråskalebilderna. De högre koncentrationerna med flera mikrobubblor resulterade i ett högre antal lokaliserade och spårade mikrobubblor, medan den lägre koncentrationen gav färre lokaliserade mikrobubblor. Metoderna Gaussian fit och No-shift detekterade flera mikrobubblor än metoden Interpolation. Slutsatsen visade att användningen av lokaliseingsmetoden Gaussian fit med högre koncentrationer av mikrobubblor ger en superupplöst bild även om programmet exekveras på färre bilder.