Mudanças nas características mecânicas de tecidos biológicos geralmente estão relacionadas com algum tipo de patologia. Técnicas de imagens elastográficas são métodos quantitativos de se estimar as propriedades mecânicas de tecidos. Em geral, o objetivo destas técnicas de imagem é medir o movimento do tecido provocado por uma força interna ou externa. Por meio desse movimento, parâmetros viscoelásticos do meio em análise são reconstruídos. A força de excitação pode ser tanto quasi-estática, como dinâmica. O trabalho apresentado nesta tese aborda as técnicas de elastografia dinâmica e quasi-estática. Na abordagem quasi-estática, a elasticidade não-linear é estudada através de phantoms com características que simulam as do tecido humano. Na abordagem dinâmica, o movimento dinâmico promovido por força de radicação acústica é avaliado através de técnicas ultrassônicas e magnéticas. O desenvolvimento de materiais para serem usados como phantoms para elastografia por ultrassom é descrito. O comportamento elástico não-linear desses materiais foi analisado através de resultados de ensaios mecânicos. Esses materiais foram desenvolvidos para apresentarem uma relação tensão/deformação que não dependesse do módulo de cisalhamento para pequenas deformações, e foram projetados para serem usados em phantoms em que configurações heterogêneas são empregadas (por exemplo, phantoms com inclusões esféricas). O efeito da não-linearidade elástica dos materiais sobre o contraste, a relação sinal ruído e a relação contraste ruído de imagens elastográficas de um phantom contendo inclusões esféricas, sofrendo altas deformações (até 20%) foi investigada. Foi demonstrada a viabilidade de se medir movimentos vibratórios induzidos por feixes acústicos confocais através de um ultrassom Doppler que utiliza ondas contínuas. A interferência de feixes de ultrassom com pequena diferença de frequências provoca o aparecimento de uma força dinâmica no alvo. Foi demonstrada a formação de imagens de uma esfera rígida imersa em um phantom viscoelástico, através da varredura de ambos os transdutores (confocal e Doppler) pelo plano focal do transdutor confocal. O comportamento dinâmico de uma esfera magnetizada induzido por força de radicação acústica foi investigado. A esfera foi suspensa em água em configuração de pêndulo. Forcas estática de longa (poucos segundos) e curta (poucos milisegundos) duração foram utilizadas. O movimento da esfera foi medido através de um sensor magnetoresistivo. A partir da nova posição de equilíbrio em resposta à força de radicação de longa duração, a amplitude dessa força foi estimada. Para se estimar a viscosidade da água, o movimento de relaxação da esfera após a força ter sido desligada foi ajustado a um modelo de movimento-harmônico amortecido. O movimento de uma esfera rígida imersa em um phantom feito de gelatina, deslocada por força de radicação acústica, foi avaliado por meio de ecos ultrassônicas obtidos com um sistema pulso/eco. A teoria utilizada para se estimar os parâmetros viscoelásticos do phantom, usando o movimento induzido na esfera, é uma extensão da teoria usada para se estimar a viscosidade da água. / Changes in the mechanical properties of soft tissues may be related with pathological disorders. Elasticity imaging is a quantitative method of estimating the mechanical properties of the tissue. In general, the aim of this technique is to measure tissue motion caused by external or internal forces and use it to reconstruct the viscoelastic parameters of the medium. The excitation stress used can be (quasi-) static or dynamic. Both elastographic approaches are explored in this thesis work. In the quasi-static approach, the nonlinear elasticity is studied through tissue-mimicking phantom experiments. In the dynamic approach, the dynamic motion provided through acoustic radiation force is evaluated using ultrasonic and magnetic techniques. The development of phantom materials for elasticity imaging is reported. These materials were specifically designed to provide nonlinear stress/strain relationship that can be controlled independently of the small strain shear modulus of the material, and were designed for use in phantoms where heterogeneous configurations (e.g, spherical targets in a uniform background) are employed. The effects of phantom materials nonlinearity over the strain contrast, signal-to-noise ratio and contrast-to-noise ratio of a phantom containing spherical inclusions undergoing large deformations (up to 20%) were investigated.The feasibility of measuring vibration movement, through a mono-channel continuous wave Doppler system, induced by focused confocal beams, is demonstrated. The interference of two ultrasonic beams promotes a dynamic force to the target. The ability to form images of a rigid spherical inhomogeneity embedded in viscoelastic phantom by scanning both ultrasonic transducers (confocal and Doppler) across the confocal transducer focal plane is presented. The dynamic behavior of a rigid magnetic sphere induced by an acoustic radiation force was investigated. The sphere was suspended in water in a simple pendulum configuration. Steady forces of long (few seconds) and short (few milliseconds) durations were used. The movement of the magnetic sphere was tracked using a magnetoresistive sensor. From the new equilibrium position of the sphere in response to the long-duration static radiation force, the amplitude of this force was estimated. To access the water viscosity, the relaxation movement after the acoustic force had stopped was fitted to a harmonic-motion model. The motion of a rigid sphere embedded in gelatin phantom, displaced by acoustic radiation force, was evaluated using the ultrasonic echoes from a pulse-echo system. The theory used to estimate the viscoelastic parameters of the phantom, from the oscillation of the rigid sphere is an extension of the relation used to estimate the water viscosity.

A utilização do ultra som com a finalidade de acelerar o reparo tecidual é muito freqüente na prática clínica, embora as bases científicas para sua utilização não estejam bem estabelecidas. Este estudo analisou os efeitos do ultra som na cicatrização de tendões flexores de coelhos após tenorrafia. Foram utilizados 30 coelhos da raça Nova Zelândia, com peso médio de 2,7 Kg, divididos em dois grupos de 15 animais submetidos a tenotomia e tenorrafia com sutura tipo Kessler do tendão flexor profundo do terceiro dedo da pata dianteira direita. Após 24 horas foi iniciado em um dos grupos tratamento com ultra som, sendo o outro grupo utilizado para controle. A freqüência utilizada foi a de 3 MHz e a intensidade de 0,8 W/centímetro quadrado (SATA), por contato direto durante 7 dias consecutivos. Cada grupo foi dividido em subgrupos com 5 animais cada, e estes sacrificados em períodos distintos (8, 15 e 30 graus PO), e o tendão operado, dissecado e submetido à análise histológica pela microscopia de luz, analisando a reação inflamatória, grau de necrose, proliferação de fibroblastos, deposição de colágeno e formação de granuloma. Os resultados mostraram que o ultra som interferiu com o processo de reparo tecidual após a tenorrafia dos tendões flexores de coelhos / The use of ultrasound aiming to accelerate tissue healing is very frequent in clinical pratice, although the scientific basis to its use are not well established. This study analized the effects of ultrasound on the healing of rabbit’s flexor tendons after repair. It was used 30 New Zealand rabbits, with an average weight of 2.7 Kg, divided in two groups of 15 animal. They were submetted to tenotomy and repair with Kessler’s suture on deep flexor tendon of the middle right front claw. After 24 hour one of the groups started the ultrasound treatment, and the other was de control group. The ultrasound frequency used was 3 MHz and the intensity was 0.8 W/square cemtimeter (SATA), by direct contact during 7 consecutive days. Each group was divided in subgroups with 5 animals each, and these were killed in distincts periods (PO 8, 15 and 30), and the operated tendon was dissected and submitted to histologic analises by light microscopy, anlaysing the inflammatory reaction, necrosis degree, fibroblasts proliferation, colagen synthesis and granulom formation. The result showed that ultrasound interfere on the tissue healing process after repair on the rabbit’s flexor tendons

Ultrasound (US) imaging has made significant progress over the past 20 years in relation to its role in inflammatory arthritis, and in particular, Rheumatoid Arthritis. Modern US machines provide crisp, detailed images of superficial anatomical structures which has facilitated the uptake of US imaging as an important assessment tool within the Rheumatology department. Diagnostic and prognostic information can now assist clinicians decisions with the goal of improving patient treatment and subsequent outcome. In addition, 3D US imaging has recently been suggested as an additional imaging modality with potential benefits in the assessment of in?ammatory arthritis. Recent work has focused on providing a reliable, responsive US joint count which can be assimilated into routine care as well as providing a platform for clinical research. Thus, my first aim was to show that a defined limited US data set, including 2D and 3D imaging, shows acceptable reliability. I demonstrate that both imaging modalities are reliable in terms of reading and image acquisition when restricted to a limited US data set. My second aim, was to demonstrate that a limited US data set is responsive. Using both a physiological and pharmacological trigger, I demonstrate that both 2D and 3D imaging are responsive and that combining US endpoints with DAS28 (Disease Activity Score - 28) increased the effect size and identifies treatment effects early. Despite notable advances in musculoskeletal US research, there is still need for better understanding of the pathophysiological correlates of ultrasound imaging. Therefore my final aim was to examine the relationship of Power Doppler Signal (PDS) and gray-scale synovial thickening with histological features of synovitis at a single joint level and with an extended joint US data set. I Firstly show that the harvesting of synovial tissue, using a minimally invasive US-guided biopsy technique, is safe and well tolerated by patients and that the quality of tissue and RNA extracted is good. Using this tissue collection method, I demonstrate a good correlation of US and histological parameters of synovitis (specifically CD68+ sub-lining macrophages) at a single joint level, in both an early and established RA cohort. This relationship is maintained if the US assessment is extended to a discrete US joint data set. Furthermore, within the knee joint I demonstrated that PDS correlates well with synovial tissue expression of inflammatory mediators of neoangiogenesis and histological assessment of synovial vascular area.

Ultrasound irradiation of a protein or polymer solution at the air:water interface can be used to form hollow microspheres containing an air bubble. By introducing a layer of oil and sonicating the oil:water interface, microspheres containing an oil droplet are formed. The microspheres are stabilised by disulfide crosslinking, have diameters of between 1-20 mm and have a number of applications; gas filled protein microspheres are used as ultrasound contrast agents and oil filled microspheres are being developed for delivery of lipophilic drugs. This project extends the scope of sonochemically produced microspheres to include water-in-oil emulsion filled microspheres, which facilitate encapsulation of hydrophilic species, and polymer microspheres that release their contents in response to an external stimulus. Successful encapsulation of a water in oil emulsion phase is demonstrated using confocal microscopy. Release studies are reported for a number of hydrophilic species (in vitro) including 5,6-carboxyfluorescein, 5-fluorouracil and sodium chloride. Release can be triggered by sonochemical disruption of the microsphere shells or cleavage of the disulfide cross links. Thiol-ene coupling reactions initiated by ultrasound irradiation are reported. In water, ultrasound initiation of thiol-ene reactions with electron rich alkenes results in rates of reaction which compare favourably with conventional thermal initiation. Thiol-ene crosslinking is proposed as an alternative to disulfide crosslinking to stabilise sonochemically produced microspheres. Temperature responsive microspheres are produced via the sonochemical method using a block copolymer of N-isopropylacrylamide and thiolated methacrylic acid, P(MASH-b-NIPAm). The block co-polymer is synthesised using reversible addition-fragmentation transfer (RAFT) polymerisation and has a lower critical solution temperature (LCST) of 37 ºC. The microspheres formed from this block copolymer can be seen to rupture, releasing their internal oil phase, when heated above 37 ºC. These findings provide a basis from which to develop sonochemically produced polymer microspheres for responsive delivery of both hydrophilic and lipophilic species.

Ultrasonic instruments are used with the aid of an irrigant such as NaOCl in endodontic treatments to remove dentin debris and calculus from infected root canals. This cleaning process may be assisted by various factors, such as acoustic streaming, and the production of radicals and microjets from the collapse of transient cavitation bubbles. The aim of this project is to understand the principal factors affecting the performance of a number of different endosonic files in order to correlate to their cleaning efficiencies. Characterisation includes detecting transient cavitation activity, mapping the areas of cavitation, assessing the file vibration movements and the streaming effects produced by the files. Experiments to assess the cleaning efficiencies of the files include: emulsification, dye removal with a dental irrigant, ink and hydroxyapatite paste removal from model systems designed to mimic the structure of a tooth. The results show that there is a correlation between the sonochemical output and the cleaning efficiencies, and this brings in further study on the possible factors that may affect the production of transient cavitation and the vibration profiles of the endosonic files. Lastly, a series of computational simulation of the acoustic pressure fields from different endosonic files were performed. Correlations of the simulated and experimental results showed the difference in ultrasonic output of the endosonic files is strongly related to their design. This work provides the basis and techniques necessary to perform a comprehensive study on the design of the endosonic files in order to enhance and optimise their cleaning efficiencies during clinical use and to inform future endodontic practice.

The individual soft tissues in the human body, such as liver, prostate, thyroid and breast, can each be characterized by a set of mechanical properties. Among these properties, the stiffness, or Young’s modulus, is of particular interest, as disease processes or abnormal growths introduce changes in the tissue stiffness. For example, cirrhosis is associated with an increase in stiffness in the affected region(s) of the liver, and the severity has a strong positive correlation with the measured liver tissue stiffness. Although the conventional ultrasound image is produced by changes in acoustic properties, most notably acoustic impedance (equal to density times sound speed), it is in fact possible to measure tissue strain ultrasonically, by performing ultrasound imaging while the tissue region of interest is mechanically perturbed. Although in principle incorrect, such strain imaging methods are commonly referred to as ultrasound elastography imaging. While tissue strain can reveal the presence of stiffness changes, its diagnostic value is limited due to the inability to reveal the magnitude of the stiffness change. Still, strain imaging is a feature on several commercial scanners. There does in fact exist an elegant, but complex and quite expensive, quantitative ultrasound method of imaging the elasticity of soft tissues, called Supersonic Shear imaging (SSI). However, a much lower cost method of quantitatively imaging tissue elasticity would be useful, especially if the method can be implemented with only minor modifications to existing ultrasound scanner design. This dissertation research deals with an attempt of designing and testing such a method. Ultrasound elastography encompasses a number of diverse techniques, roughly categorized by the mechanical perturbation method into two main groups: quasi-static and dynamic methods. Dynamic elastography requires a vibrating source, either separate or integrated with a transducer, making the imaging system cumbersome, especially for the portable systems. Quasi-static elastography only requires conventional ultrasound hardware, however current techniques remain qualitative with unknown stress distribution. This dissertation focuses on the investigation of free hand quantitative quasi-static elastography, aiming to real time assessment. Our proposed low cost real-time ultrasound elastography system is based on determining an axial strain and an axial stress over a region of interest, i.e., an axial strain image and an axial stress image are required. By taking the axial stress/axial strain ratio for each pixel in the image, an actual elasticity image is established. To achieve this goal, our system needs to ultrasonically measure the mechanical strain fast and accurately over a specified image plane; likewise, the system needs to be able to calculate the mechanical stress over the same image plane in real time. Now, the stress imaging will require us to apply a quasi-static force function and also to be able to quantify this force function. There are two major research efforts we have made to implement a low cost real-time ultrasound elastography system. The first important topic of this dissertation involves the development of a novel displacement and strain estimator based on analytical phase tracking (APT), which has been demonstrated to give better performance in terms of accuracy, resolution and computational efficiency (approximately 40 times faster than the standard time domain cross correlation method). The second important topic is the stress field reconstruction, with efforts in: 1) integrate force sensors into a single linear array transducer probe, with the goal of quantifying the applied force function; 2) propose a superposition method based on Love’s analytical equation to calculate the stress distribution, where this solution is computationally fast enough to allow real time stress field estimation; 3) analyze the accuracy of the proposed stress method using finite element analysis as a reference on different simulated phantoms. The final objective is to combine the strain and stress information together for quantitative elastography. Correspondingly, we have implemented experiments to evaluate the method on homogeneous and inhomogeneous phantoms of various types. Results show that this method is able to distinguish medium with different stiffness. We have conducted experiments to study the feasibility and improve the accuracy of this estimation technique based on phantoms with known elasticity. In principle, such a technique could be used to image the distribution of Young’s modulus under quasi-static compression, with specific applications to medical imaging.

"This thesis presents an ultrasound technique for measuring the absolute integrated backscatter (IBS) of arterial wall structures through an intervening inhomogeneous soft tissue layer. The aberrating effect of this tissue layer is minimized by normalizing the measured IBS from the wall region of interest with the IBS from an adjacent range cell in blood. The technique may become a tool to differentiate between stable and vulnerable plaques in the carotid artery."

O trabalho buscou demonstrar o efeito benéfico do ultra-som no controle sintomático das osteorradionecroses (ORN) dos maxilares. Dez pacientes portadores de ORN dos maxilares foram avaliados e completaram o protocolo de tratamento proposto: um máximo de 40 aplicações de 20 minutos de ultra-som (US) de baixa intensidade sobre a área facial correspondente à região afetada pela ORN. O aparelho utilizado dispõe de transdutor composto por um disco cerâmico de PZT (Titanato de Zirconato de Chumbo) que emite ondas longitudinais, com freqüência de 1,5 Mhz e potência de 30 mW. Oito homens e duas mulheres compuseram a casuística, com idade média de 52,7 anos. Nove pacientes apresentavam ORN em mandíbula e um em maxila. Todos os pacientes mostraram resposta positiva ao tratamento com US, sendo que três foram tratados exclusivamente com US e sete submeteram-se a intervenção cirúrgica após as 40 aplicações de US. Extensão da casuística e pesquisas adicionais são indispensáveis ao melhor esclarecimento dos mecanismos de ação do US sobre o metabolismo ósseo, de sua interferência sobre o osso irradiado e para o estabelecimento de protocolos de tratamento clínico efetivos e cientificamente embasados. Concluímos que a terapia de US de baixa intensidade é eficiente no tratamento de ORNs dos maxilares, apresentando ausência de efeitos colaterais adversos e boa aceitação por parte dos pacientes. / The purpose of this research was to evaluate the effect of ultrasound (US) therapy upon symptomatic control of osteoradionecrosis (ORN) of the jaws. Ten ORN patients that completed the designed treatment protocol had their data analyzed. The treatment protocol consisted of a maximum of 40 sessions of 20-minute low intensity US application over the face in the area correspondent to the ORN lesion. The US device utilized was composed of a ceramic disc transducer (lead titanate zirconate) with 1.5 mHz frequency and 30 mW of power. Eight men and two women comprised the population studied, mean age 52.7 years. Nine patients presented the mandible and one patient the maxilla affected by ORN. All patients showed good results to US treatment. Three were treated exclusively by US and seven were submitted to a supplementary surgery intervention after the programmed 40 US applications. The extension of the casuistic and additional research are mandatory to enlighten the interactions between US waves and bone metabolism, the interferences of US upon irradiated bone and to the development of effective treatment protocols scientifically supported. It was concluded that US therapy is efficient to treat jaws osteoradionecrosis, generating no adverse effects and being well accepted by the patients.

Neste trabalho é analisada a medição de viscosidade de líquidos por ultrasom pelo método da reflexão de ondas de cisalhamento. O método baseiase na medição da magnitude e fase do coeficiente de reflexão quando as ondas de cisalhamento incidem na interface entre um sólido e o líquido testado. Foram analisados os conceitos teóricos do método da medição de viscosidade e desenvolvida a metodologia experimental a fim de evitar a influência indesejada de fatores externos, como a temperatura e a instabilidade da eletrônica, sobre a medição. Foram obtidos resultados com dois óleos alimentícios (azeite de oliva e óleo de milho) e quatro óleos automotivos do tipo SAE (40, 90, 140 e 250). Foi mostrado que para uma freqüência de operação baixa o suficiente para garantir comportamento Newtoniano do líquido, os valores de viscosidade têm excelente concordância numérica com os valores obtidos usando o viscosímetro rotacional, no caso dos óleos menos viscosos. Já no caso dos óleos mais viscosos, foram obtidos valores de viscosidade menores que os obtidos com viscosímetro rotacional, e o aumento no módulo elástico sugere um comportamento mais viscoelástico. Foi mostrado que o método de cálculo simplificado usado por alguns autores, que permite calcular a viscosidade a partir somente da magnitude do coeficiente de reflexão, não fornece os valores esperados de viscosidade. / This work deals with the ultrasonic measurement of liquids viscosity by means of the shear reflectance method. The method is based on the measurement of the magnitude and phase of the complex reflection coefficient of shear waves at a solidliquid sample interface. Basic concepts of the viscosity measurement method were analyzed and the experimental methodology was developed to avoid the undesired influence of external factors, such as temperature and electronic instability. Experimental results were obtained with two kinds of eatable oils (olive and corn oils) and four different automotive oils (SAE 40, 90, 140 e 250). For an operating frequency low enough to obtain Newtonian liquid behavior, as for less viscous liquids, it was shown that the viscosity results have good agreement with rotational viscometer measurements. In the case of more viscous liquids, the measured viscosity values were smaller than those obtained by the rotational viscometer, and the elastic modulus is increased, suggesting viscoelastic behavior. It is shown that a simplified model used by other authors, which obtains the viscosity without measuring the phase of the complex reflection coefficient, results in greater errors associated with the values obtained by the rotational viscometer.

O processo de separação da água em emulsões de petróleo é feita durante o processamento primário do petróleo e consiste na coalescência de gotas de água. Para minimizar o uso de desemulsificantes e acelerar o processo de separação da emulsão alguns equipamentos podem ser utilizados como os separadores acústicos. Neste trabalho a técnica de força de radiação produzida por ondas estacionárias de ultrassom é aplicada na segregação das fases líquidas de emulsões água em óleo. São desenvolvidas células de ultrassom que operam em frequências próximas de 1 MHz através de ressonadores piezelétricos visando a aplicação na coalescência de gotas de água em emulsões do tipo água-óleo. O trabalho envolve simulações do campo acústico através de modelos analíticos unidimensionais e bidimensionais e de um modelo numérico bidimensional pelo método dos elementos finitos para o estado plano de deformações. São realizadas verificações experimentais em protótipos de células de alta potência para separação em batelada através da comparação do potencial de radiação acústica e da impedância elétrica com resultados de modelos computacionais. Diversos ensaios de quebra de emulsões sintetizadas de petróleo são realizados utilizando um aparato experimental de laboratório aplicando potências de até 600 W=l. Um sistema de controle de frequência de operação é implementado para manter máxima transmissão de potência elétrica para a célula. Os resultados mostraram que a técnica empregada pode reduzir pela metade o uso de desemulsificante químico (de 20 a 10 ppm) ou diminuir o tempo de residência em até 60% (de 20 para 8 min). Uma análise da influência da frequência na eficiência de desemulsificação é realizada e indica que não há sensibilidade no resultado para a faixa de frequência entre 0.8 e 1.5 MHz a uma temperatura ambiente de aproximadamente 23 C. A metodologia empregada auxilia no projeto das células e na aplicação da técnica, mas é insuficiente para explicar integralmente os mecanismos de separação e as diferenças entre o protótipo e o modelo. A aplicação de ultrassom na coalescência de emulsões possui potencial para desenvolvimento em larga escala. / The oil water separation process of petroleum emulsions is performed during the primary processing of crude oil and consists of water droplets coalescence. To minimize the use of demulsifiers and accelerate the emulsion separation process some equipment may be used such as acoustic separators. In this work, a radiation force technique produced by ultrasound standing waves is applied to the water phase separation in oil emulsions. Ultrasound cells operating at ultrasonic frequencies near 1 MHz are developed using piezoelectric resonators applied to the coalescence of water droplets in oil emulsions. This work involves simulations of the acoustic field through one-dimensional and two-dimensional analytical models and a numerical model for two-dimensional plane strain finite element analysis. Furthermore, experimental verification is performed using high power prototypes for batch separation by comparing the acoustic radiation potential and electrical impedance with computational models results. Several tests of synthesized petroleum emulsions breaking are performed using an experimental laboratory apparatus applying up to 600 W=l. A frequency control system is implemented in order to maintain maximum electric power transmission to the cells. The results showed that the technique can halve the use of chemical demulsifier (from 20 to 10 ppm) or decrease the residence time of up to 60% (from 20 to 8 min). An analysis of the frequency influence on demulsification efficiency is performed and indicates that there is no parameter sensitivity in the frequency range between 0.8 and 1.5 MHz at room temperature of approximately 23 C. It is demonstrated that the design methodology is consistent and the application has potential for large-scale development.