Cardiac diseases and conduction disorders are associated with stroke, heart failure and sudden cardiac death and are a major health concern worldwide. In the US alone, more than 14 million people suffer from heart rhythm disorders. Current mapping and characterization techniques in the clinic involve invasive procedures, which are time-consuming, costly, and may involve ionizing radiation. In this dissertation, we introduce Electromechanical Wave Imaging (EWI) as a non-invasive, ultrasound-based treatment planning tool for pre-procedure characterization and assessment of arrhythmia in the clinic. In particular, standard EWI processing methods for mapping the electromechanical wave (EW), i.e. the onset of the mechanical activity following the depolarization of the heart, are described and detailed. Next, validation of EWI is performed with 3D electromechanical mapping and the EW propagation is shown to follow the electrical activation in all four chambers of the heart. Demonstration of the value of EWI for the characterization of cardiac arrhythmia is accomplished in vivo in a large animal model. First, EWI is shown capable of localizing the earliest region of activation in the ventricles during pacing from a standard pacemaker lead, as well as during pacing from a novel biological pacemaker. Repeatability is also demonstrated between consecutive cardiac cycle during normal sinus rhythm and during pacing. Then, in the atria, we demonstrate that EWI is capable of accurately identifying focal sources while pacing from several locations in both the left and right atria. In addition to being capable of localizing the focal source, EWI is also shown capable of differentiating between endocardial and epicardial focal sources. Finally, it is shown that EWI can correctly identify regions of infarction and monitor formation of infarcts over several days, after ligation of the left anterior descending coronary artery of canine hearts. Novel processing techniques aimed at extracting quantitative parameters from EWI estimates are then developed and implemented. Details of the implementation of processing methods for estimating the velocity of the EW propagation are presented, and a study of the EW velocity values in a canine heart before and after infarct formation is conducted. Electromechanical cycle length mapping (ECLM), which is aimed at extracting local rates of electromechanical activation in the heart, is then introduced and its implementation detailed. ECLM is subsequently validated in a paced canine heart in vivo. Finally, initial clinical feasibility is demonstrated. First, in the study of treatment of chaotic arrhythmia such as in the case of atrial fibrillation patients undergoing direct current cardioversion, ECLM is shown to be able to confirm acute treatment success. Then, the clinical value of EWI in the electrophysiology lab as a treatment planning tool for the characterization of focal arrhythmia is shown in ventricular tachycardia and Wolff-Parkinson-White patients. EWI is currently only a step away from real-world clinical application. As a non-invasive, ultrasound-based imaging modality, EWI is capable of providing relevant insights into the origins of an arrhythmia and has the potential to position itself in the clinic as a uniquely valuable pre-procedure planning tool for the non-invasive characterization of focal arrhythmias.

Over the past 10 years, Compressive Sensing has gained a lot of visibility from the medical imaging research community. The most compelling feature for the use of Compressive Sensing is its ability to perform perfect reconstructions of under-sampled signals using l1-minimization. Of course, that counter-intuitive feature has a cost. The lacking information is compensated for by a priori knowledge of the signal under certain mathematical conditions. This technology is currently used in some commercial MRI scanners to increase the acquisition rate hence decreasing discomfort for the patient while increasing patient turnover. For echography, the applications could go from fast 3D echocardiography to simplified, cheaper echography systems. Real-time ultrasound imaging scanners have been available for nearly 50 years. During these 50 years of existence, much has changed in their architecture, electronics, and technologies. However one component remains present: the beamformer. From analog beamformers to software beamformers, the technology has evolved and brought much diversity to the world of beam formation. Currently, most commercial scanners use several focalized ultrasonic pulses to probe tissue. The time between two consecutive focalized pulses is not compressible, limiting the frame rate. Indeed, one must wait for a pulse to propagate back and forth from the probe to the deepest point imaged before firing a new pulse. In this work, we propose to outline the development of a novel software beamforming technique that uses Compressive Sensing. Time-domain Compressive Beamforming (t-CBF) uses computational models and regularization to reconstruct de-cluttered ultrasound images. One of the main features of t-CBF is its use of only one transmit wave to insonify the tissue. Single-wave imaging brings high frame rates to the modality, for example allowing a physician to see precisely the movements of the heart walls or valves during a heart cycle. t-CBF takes into account the geometry of the probe as well as its physical parameters to improve resolution and attenuate artifacts commonly seen in single-wave imaging such as side lobes. In this thesis, we define a mathematical framework for the beamforming of ultrasonic data compatible with Compressive Sensing. Then, we investigate its capabilities on simple simulations in terms of resolution and super-resolution. Finally, we adapt t-CBF to real-life ultrasonic data. In particular, we reconstruct 2D cardiac images at a frame rate 100-fold higher than typical values.

Assegurar o bem-estar dos animais de laboratório e evitar a dor e o sofrimento desnecessários são as principais considerações na experimentação. Por isso, a investigação em busca de novos protocolos anestésicos que garantam um mínimo ou nulo desconforto dos animais tem-se convertido num tema prioritário. Neste estudo realizou-se a comparação do efeito da combinação de xilazina (X) e ketamina (K) com acepromazina (A) e opióides [metadona (Me), morfina (Mo) e tramadol (T)] com a finalidade de avaliar sua influência nos parâmetros fisiológicos de ratos de laboratório, para ambos os sexos, bem como seu poder analgésico e o efeito da oxigenação sobre os mesmos. A associação XKA para ratos machos e fêmeas e a associação XKMe para fêmeas foram as mais seguras e eficazes para procedimentos anestésicos. Porém, os resultados do teste de formalina com a medição da vocalização ultrassônica (VUS) sugerem que o protocolo de XKA tem um poder analgésico baixo, não sendo indicado para procedimentos que possam gerar dor moderada ou severa. Todas as associações anestésicas tiveram efeitos importantes como diurese, manutenção dos olhos abertos e hiperglicemia, os quais devem ser considerados quando possam influenciar nos resultados experimentais. Também, se conseguiu demonstrar que a oxigenação melhora a saturação de oxigênio (SO2) e os valores da pressão parcial de oxigênio (pO2) confirmando que sua utilização deveria ser sempre parte dos procedimentos experimentais com anestesia injetável para evitar a hipoxemia. Não obstante, observou-se uma acidose respiratória por aumento da pressão parcial do CO2 (pCO2) e diminuição do pH, cuja causa se relacionou à hipoventilação por depressão respiratória e acúmulo de CO2 durante o transcorrer da anestesia. Tal situação demonstra a necessidade de oxigenar os animais desde a indução da anestesia e de administrar medicamentos para reverter a depressão respiratória como a naloxona, bem como utilizar animais que não apresentem nenhum tipo de comprometimento respiratório. Portanto, a inclusão de analgesia e a oxigenação nos protocolos anestésicos injetáveis devem ser utilizadas de forma rotineira garantindo a mínima presença de dor e, com isso, resultados mais confiáveis nos procedimentos experimentais. / Ensuring the wellbeing of laboratory animals and avoiding unnecessary pain and suffering is one of the main considerations in experimentation. Therefore, the investigation of new anesthetic protocols that guarantee a minimum or null discomfort of the animals has become a priority theme. In this study, it was made an evaluation of the effect of the combination of xylazine (X) and ketamine (K) with acepromazina (A) and opioids [methadone (Me), morphine (Mo) e tramadol (T)] with the purpose of comparing their influence on the physiological parameters of laboratory rats, for both sexes, and evaluating their analgesic power and the effect of the oxygenation on them. The XKA protocol for male and females rats and the XKMe protocol for females were the safest and most effective for anesthetic procedures. However, the results of the formalin test with the measurement of the ultrasonic vocalization (VUS) suggest that the XKA protocol had a low analgesic power, and it is not indicated for procedures that can generate moderate or severe pain. All anesthetic protocols had important effects as diuresis, maintenance of open eyes, and hyperglycemia; these effects should be considered when they could influence in the experimental results. It was demonstrated that oxygenation improves oxygen saturation (SO2) and oxygen partial pressure (pO2) confirming that its use should be considered in the experimental procedures with injectable anesthesia to avoid hypoxemia. Nevertheless, a respiratory acidosis was observed due to the increase in partial pressure of CO2 (pCO2) and the decrease in pH, that could be caused for the hypoventilation due to respiratory depression and CO2 accumulation during the course of anesthesia. This leads to consider the need to pre-oxygenate animals from induction, to use drugs to reverse respiratory depression such as naloxone, and to work with animals that are not respiratory compromised. Therefore the inclusion of analgesia and oxygenation in anesthesia protocols should begin to be used routinely ensuring minimal presence of pain and thus more reliable results in the experimental procedures.

<p>The objective of this research is to develop recommendations on calibration standards, scanning procedures, and acceptance criteria for phased array ultrasonic testing (PAUT) of complete joint penetration butt welds within the AWS D1.5 Bridge Welding Code. These recommendations include the development of a rational acceptance criteria which is based in engineering analysis and fracture mechanics. It is expected that the updated scanning procedures and acceptance criteria will result in improved reliability for bridges and improved consistency in bridge fabrication quality.</p><p><br></p> <p> </p> <p>While PAUT was included in the 2015 edition of AWS D1.5 in Annex K, the acceptance criteria for this procedure was developed as an adaptation of an existing conventional ultrasonic testing (UT) acceptance criteria in AWS D1.1. Therefore, the acceptance criteria in AWS D1.5:2015 is a workmanship-based criteria and is not based on engineering analysis of the criticality of weld flaws. The scanning procedures and application of PAUT inspections of bridge welds according to this procedure differ greatly from the scanning procedures outlined in AWS D1.5 for conventional UT inspections. Previous research has shown that differences in flaw rejection are possible for PAUT and conventional UT ultrasonic methods under the AWS D1.5:2015 approach.</p><p><br></p> <p> </p> <p>In order to develop recommendations for improved calibration standards, scanning procedures, and acceptance criteria for PAUT within AWS D1.5, this research project utilized both analytical techniques and experimental testing. This research project included determination of target critical flaw sizes for routine detection and rejection through fitness-for-service evaluations. This was followed by a round robin ultrasonic testing program in order to collect data on the variability of inspection results of eleven weld samples with nineteen weld flaws using different ultrasonic inspection techniques. Next, calibration requirements were developed to account for differences in ultrasonic attenuation and shear wave velocity between calibration blocks and test objects. Development of these requirements included experimental testing of base metals and weld metals, along with simulations of ultrasonic inspection using commercial software. Finally, minimum requirements for weld scanning procedures, reference standard reflectors, and corresponding amplitude limits for detection and rejection of target critical weld flaws were developed using ultrasonic inspection simulations and verified through experimental testing of weld samples with known weld flaws.</p>

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (B.S.)--Massachusetts Institute of Technology, Dept. of Biology, 1978. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / B.S.

Os equipamentos dispóníveis para acompanhamento clínico de implantes dentários monitoram mudanças de estabilidade, mas não são capazes de quantificar o nível de osseointegração. A literatura mostra que a aplicação de ultra-som pulsado de baixa intensidade estimula o reparo de fraturas ósseas e o crescimento de tecido ósseo nos poros de implantes, indicando que um guia de onda ultra-sônico poderia ser usado tanto para monitorar o processo de osseointegração como também para diminuir o período de recuperação. Diversas dimensões e geometrias foram consideradas nas simulações dos guias ultra-sônicos, e o guia com formato degrau apresentou maior sensibilidade a mudanças na composição do meio que envolve o implante. Resultados obtidos por simulação sugerem que há uma relação linear entre a energia do sinal detectado e o grau de osseointegração. Foram realizados experimentos com guias de onda de titânio e alumínio, sendo necessário realizar mais testes com guias de dimensões reduzidas para a obtenção de um dispositivo adequado para uso clínico. / Available equipments for clinical assessment of dental implants monitor changes in stiffness but are not able to quantify the osseointegration level. Literature shows that the application of low-intensity pulsed ultrasound stimulates the healing of bone fractures and the bone ingrowth into implants pores, indicating that an ultrasonic waveguide could be used to monitor the osseointegration process as well as to shorten the healing period. Several dimensions and geometries were considered in the waveguides simulations, and the step-shaped waveguide showed more sensibility to changes in the surrounding media of the implant. Results obtained by simulation suggest there is a linear relation between the energy of the detected signal and the osseointegration level. Experiments with titanium and aluminum waveguides were conducted, being necessary to carry out more studies with reduced size waveguides in order to obtain a suitable device for clinical use.

Structures made of plate-like components are common in a variety of industries where the impacts of structural failures are severe. In many cases these structures are surrounded and only partially accessible, such as storage tanks and bridges, making them difficult to inspect frequently. The application of ultrasonic Guided Waves (GWs) in the evaluation and monitoring of relatively large plate-like structures is evermore a feasible option with the continuous development of transducer arrays. The use of transducer arrays is however complex due to directional control and the existence of many GW modes. Aimed at the evaluation of plate-like structures, in this research two piezoelectric transducer arrays respectively capable of omnidirectional and unidirectional control of the fundamental GW shear mode in plates (SH0) with above 20 dB mode purity are successfully designed, produced and validated. Omnidirectionality facilitates full structural evaluation coverage and can lead to defect mapping of large volumes with relatively few transducers. A unidirectional beam with relatively high mode purity facilitates evaluation of specific structural locations. Preference to the SH0 mode was given because of its non-dispersive and in-plane propagation properties making it more suitable than other GW modes to propagation in structures surrounded by fluid material. To enable the array development, a number of monolithic piezoelectric thickness-shear transducers of varied area were characterised with respect to GW mode directionality, amplitude and SH0 mode purity. The characterisation of each thickness-shear transducer allows for optimised superposition manipulation for specific applications. A single characterised shear transducer was selected for use in the development of omnidirectional and unidirectional SH0 mode transducer arrays. To aid development a linear superposition analysis model was produced and used to predict for a circular array design the optimum parameters for omnidirectional SH0 mode transmission with significant mode purity. A range of parameter combinations were evaluated and their predicted influence on array performance was characterised. The same method was employed to optimise a dual row linear array design for the unidirectional transducer array. All results were validated by FE models and later with empirical data. Both developed transducer arrays were characterised with respect to GW mode directionality, magnitude and SH0 mode purity. Both their detection sensitivity to pertinent defects and structures was validated, demonstrating relevance to Non Destructive Evaluation (NDE) and Structural Health Monitoring (SHM) applications.

Two different aluminium alloys, AA6111 (Al-Mg-Si) and AA7055 (Al-Mg-Zn), were chosen as the aluminium alloys to be welded with DC04, and two welding methods (USW and FSSW) were selected to prepare the welds. Selected pre-welded joints were then annealed at T=400 - 570oC for different times. Kinetics growth data was collected from the microstructure results, and the growth behaviour of the IMC layer was found to fit the parabolic growth law. A grain growth model was built to predict the grain size as a function of annealing time. A double-IMC phase diffusion model was applied, together with grain growth model, to predict the thickness of each phase as a function of annealing time in the diffusion process during heat treatment. In both material combinations and with both welding processes a similar sequence of IMC phase formation was observed during the solid state welding. η-Fe2Al5 was found to be the first IMC phase to nucleate. The IMC islands then spread to form a continuous layer in both material combinations. With longer welding times a second IMC phase, θ-FeAl3, was seen to develop on the aluminium side of the joints. Higher fracture energy was received in the DC04-AA6111 joints than in the DC04-AA7055 joints. Two reasons were claimed according to the microstructure in the two joints. The thicker IMC layers were observed in the DC04-AA7055 joints either before or after heat treatment, due to the faster growth rate of the θ phase. In addition, pores were left in the aluminium side near the interface as a result of the low melting point of AA7055.The modelling results for both the diffusion model and grain growth model fitted very well with the data from the static heat treatment. Grain growth occurred in both phases in the heat treatment significantly, and was found to affect the calculated activation energy by the grain boundary diffusion. At lower temperatures in the phases with a smaller grain size, the grain boundary diffusion had a more significant influence on the growth rate of the IMC phases. The activation energies for the grain boundary diffusion and lattice diffusion were calculated as 240 kJ/mol and 120 kJ/mol for the η phase, and 220 kJ/mol and 110 kJ/mol for the θ phase, respectively. The model was invalid for the growth of the discontinuous IMC layers in USW process. The diffusion model only worked for 1-Dimensional growth of a continuous layer, which was the growth behaviour of the IMC layer during heat treatment. However, due to the highly transient conditions in USW process, the IMC phases were not continuous and uniform even after a welding time of 2 seconds. Therefore, the growth of the island shaped IMC particles in USW was difficult to be predicted, unless the nucleation stage was taken into consideration.

Modern cancerous tumor diagnostics is nearly impossible without invasive methods, such as biopsy, that may require involved surgical procedures. In recent years some work has been done to develop alternative non-invasive methods of medical diagnostics. For this purpose, the data obtained from an ultrasound image of the body crosssection, has been analyzed using statistical models, including Rayleigh, Rice, Nakagami, and K statistical distributions. The homodyned-K (H-K) distribution has been found to be a good statistical tool to analyze the envelope and/or the intensity of backscattered signal in ultrasound tissue characterization. However, its use has usually been limited due to the fact that its probability density function (PDF) is not available in closed-form. In this work we present a novel closed-form representation for the H-K distribution. In addition, we propose using the first order approximation of the H-K distribution, the I-K distribution that has a closed-form, for the ultrasound tissue characterization applications. More specifically, we show that some tissue conditions that cause the backscattered signal to have low effective density values, can be successfully modeled by the I-K PDF. We introduce the concept of using H-K PDF-based and I-K PDF-based entropies as additional tools for characterization of ultrasonic breast tissue images. The entropy may be used as a goodness of fit measure that allows to select a better-fitting statistical model for a specific data set. In addition, the values of the entropies as well as the values of the statistical distribution parameters, allow for more accurate classification of tumors. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

Xie Jun. / "July 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 177-204). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.