Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

CAPES / A área de compressão de imagem é de grande importância para aplicações médicas. As técnicas de compressão têm sido muito estudadas por permitirem representar de forma eficiente os dados, reduzindo o espaço necessário para armazenamento e minimizando a demanda na transmissão através de canais de comunicação. A técnica de compressão JPEG usa a transformada discreta de cossenos bidimensional e as técnicas Joint Photographic Experts Group 2000 (JPEG2000), Set Partitioning in Hierarchical Trees (SPIHT) e Embedded Zerotree Wavelet (EZW) usam a Transformada Wavelet bidimensional. Neste trabalho, uma análise comparativa é feita usando as métricas Mean Squared Error (MSE), Peak Signal to Noise Ratio (PSNR), Cross Correlation (CC) e Structural Similarity (SSIM) assim como uma avaliação indireta de esforço computacional através do tempo de processamento. A análise usando a técnica de compressão JPEG usando blocos de tamanhos diferentes permite concluir sobre a influência da frequência central dos transdutores ultrassônicos nos detalhes da imagem assim como concluir que o uso de blocos de tamanho 8x8 e 16x16 pixeis tem o melhor desempenho que o uso de blocos de menos tamanho. Adicionalmente, ao avaliar matrizes de quantização alternativas propostas por Hamamoto, Veraswamy e Abu para a técnica de compressão JPEG introduzem melhorias na qualidade da imagem de ultrassom reconstruída quando comparadas a matriz de quantização tradicional considerada taxa de compressão constante na comparação. Para técnicas usando a transformada wavelet foi possível observar o impacto significativo na qualidade da imagem de ultrassom reconstruída em função dos filtros utilizados. Finalmente, pode-se concluir que o algoritmo JPEG2000 apresenta o melhor desempenho em relação à qualidade de imagem e ao tempo de processamento quando comparado com os algoritmos JPEG, SPIHT e EZW. / The area of image compression is of great importance for medical applications. Compression techniques have been studied for allowing to efficiently representing the data, reducing the required storage space and minimizing the demand on transmission through communication channels. The JPEG compression technique uses a two-dimensional discrete cosine transform and techniques Joint Photographic Experts Group 2000 (JPEG2000), Set Partitioning in Hierarchical Trees (SPIHT) and Embedded Zerotree Wavelet (EZW) use the two-dimensional wavelet transform. In this work, a comparative analysis is made using the metrics Mean Squared Error (MSE), Peak Signal to Noise Ratio (PSNR), Cross Correlation (CC) and Structural Similarity (SSIM) as well as an indirect assessment of computational effort through time processing. The analysis using the JPEG compression technique using blocks of different sizes allows us to conclude on the influence of the center frequency of the ultrasonic transducers in the details of the image so as to conclude that the use of blocks of size 8x8 and 16x16 pixels has better performance than the use of note less size. Additionally, in evaluating alternative quantization matrices proposed by Hamamoto, Veraswamy and Abu for JPEG compression technique is concluded that these introduce improvements in the quality of reconstructed ultrasound image when compared to traditional matrix quantization considered that given compression rate in comparison. Techniques for using the wavelet transform have been possible to observe a significant impact on the quality of the ultrasound image reconstructed on the basis of the filters used. Finally, it was concluded that the JPEG2000 algorithm has the best performance with respect to image quality and processing time compared with JPEG, EZW and SPIHT algorithms.

Diagnostic ultrasound has become invaluable to healthcare professions for the purpose of imaging soft tissue without the risk of exposure to damaging, ionizing radiation. However, the majority of commercially available transducers have rigid, fixed interfaces that cannot conform to the surface of the human body. Such limitations both introduce a potential air gap (requiring the application of ultrasound gel) and make long-term monitoring impractical. In this work, I propose a novel flexible 2D ultrasound phased array with adaptive phasing that is capable of compensating for the radius of curvature. I describe the phasing algorithm and illustrate the detrimental effect of a lack of phase correction through simulation. I conduct phase detection by using time of arrival (TOA) without additional external hardware. In addition to simulations, I provide details of the fabrication process of a flexible 16 by 16 element array. The manufactured array, with an operating frequency of 1.4MHz and bandwidth of 41.3%, was capable of generating pressures up to 600 kPa. Finally, I conduct an in-vivo human study to demonstrate the functionality of the array on a human humerus. Although visible without phase correction, the location of the bone can easily be tracked in real-time after applying the correction algorithm.

Recent studies have indicated that vascular stiffness is an important predictor of future cardiovascular disease. Hence, assessment of vascular stiffness would be of interest. Ultrasound is a good modality for assessment of vascular stiffness, due to its hight temporal resolution and non-invasive nature. Using ultrasound, various techniques have been proposedto estimate vascular stiffness, one of them being Pulse Wave Imaging. The ultimate goal of Pulse Wave Imaging is to provide a robust, qualitative and quantitative method to estimate and visualize clinically important parameters and phenomenonfor cardiovascular disease. The objective of this thesis limits itself to 1) expand Pulse Wave Imaging by going beyond just the diastolic stiffness, 2) utilize Pulse Wave Imaging in an atherosclerotic swine model to monitor plaque initiation and progression and 3) improve non-linear stiffness estimation at or near sites of reflections using Pulse Wave Imaging for clinical applications. In Aim 1, the question pursued was whether Pulse Wave Imaging can be utilized to monitor this non-linear behavior in-vivo. It was observed that in this mouse model, the compliance at diastolic pressure did not change significantly, whereas the compliance at end-systole did. Thus suggesting that Pulse Wave Imaging was able to monitor a change in non-linear stiffness, and that considering this, might be of importance. In Aim 2, the ability of Pulse Wave Imaging to monitor disease progression for atherosclerotic disease progression was assessed. Since human studies involve various compounding factors, animal models provide the opportunity to study the ability of methods in a more controlled manner. Swine is a good candidate due to its similarity with humans. To doso, first, the feasibility of Pulse Wave Imaging in swine needed to be assessed. While the cardiovascular system might be similar, various other factors, such as the location and depth of the carotid differs. It was revealed that PWI was feasible in swine and that we were able to generate atherosclerotic lesions within 9-months. Subsequently the ability of Pulse Wave Imaging and Vector Flow Imaging to monitor atherosclerotic progression leading to different type of lesions was assessed. The in-vivo findings were compared with histology and nanoidentation. The results indicated that Pulse Wave Imaging was shown to be able to separate to different disease progression pathways leading to different type of lesions. Finally in Aim 3, lessons learned from the animal models were attempted to be addressed by developing a more reflection robust approach for localized non-linear stiffness estimation for clinical application. First, improvements were proposed to a previously developed inverse problem approach that can resolve reflections within the field of view by including information from the flow velocity. To expand the approach to include non-linearity and reflections that occur outside the field of view, a physics-based neural network approach was considered. This might be of importance since most plaques are located at sites of significant reflections, such as the bifurcation. Chapter 6 revealed that artificial significant sources of reflections hindered its ability for sub-cm scale localized compliance measurements as indicated by an immediate increase in the number of detected segments after the ligation was induced. The approaches was validated using simulated data and feasibility was shown in in-vivo examples. With new progress, new issues tend to arise. Finally, the purpose of this sub-aim is to utilize the technique and investigate whether or not it can in fact better differentiate between different clinically relevant groups. The findings revealed no significant improvement concerning the mean compliance estimated, but appeared more robust against outliers when only the plaque segment was assessed. In conclusion, the results shown in this dissertation indicate that Pulse Wave Imaging is a promising approach to assess non-linear stiffness estimation for monitoring of vascular disease. Furthermore, an new methodology was proposed and feasibility was shown, which could further improve localized and non-linear stiffness estimation at or near sources of significant reflections, and which can be used as a starting point for further development.

Thesis (M.Eng. (Hons.)) -- University of Western Sydney, 2001. / Bibliography : leaves [185]-195 (v. 1).

Thesis (Ph. D.)--Ohio State University, 2006. / Available online via OhioLINK's ETD Center; full text release delayed at author's request until 2007 Jun 16

The objective of this research is to develop novel capacitive micromachined ultrasonic transducer (CMUT) arrays for intravascular ultrasonic (IVUS) imaging along with the fabrication processes to allow for monolithic integration of CMUTs with custom CMOS electronics for improved performance. The IVUS imaging arrays include dual-ring arrays for forward-looking volumetric imaging in coronary arteries and annular-ring arrays with dynamic focusing capabilities for side-looking cross sectional imaging applications. Both are capable of integration into an IVUS catheter 1-2 mm in diameter. The research aim of monolithic integration of CMUTs with custom CMOS electronics has been realized mainly through the use of sloped sidewall vias less than 5 µm in diameter, with only one additional masking layer as compared to regular CMUT fabrication. Fabrication of CMUTs has been accomplished with a copper sacrificial layer reducing isolation layers by 50%. Modeling techniques for computational efficient analysis of CMUT arrays were developed for arbitrary geometries and further expanded for use with larger signal analysis. Dual-ring CMUT arrays for forward-looking volumetric imaging have been fabricated with diameters of less than 2 mm with center frequencies at 10 MHz and 20 MHz, respectively, for an imaging range from 1 mm to 1 cm. These arrays, successfully integrated with custom CMOS electronics, have generated 3D volumetric images with only 13 cables necessary. Performance from optimized fabrication has reduced the bias required for a dual-ring array element from 80 V to 42 V and in conjunction with a full electrode transmit array, it was shown that the SNR can be improved by 14 dB. Simulations were shown to be in agreement with experimental characterization indicated transmit surface pressure in excess of 8 MPa. For side-looking IVUS, three versions of annular CMUT arrays with dynamic focusing capabilities have been fabricated for imaging 1 mm to 6 mm in tissue. These arrays are 840 µm in diameter membranes linked to form 8 ring elements with areas that deviate by less than 25 %. Through modeling and simulation undesirable acoustic cross between ring elements was reduced from -13 dB to -22 dB.

The purpose of this hermeneutic phenomenological study was to understand the essence of the lived experience of women after having an abnormal prenatal ultrasound. One hundred years ago, health disciplines had limited therapies for prenatal and neonatal disorders. During this period, the eugenics movement influenced leaders to involuntarily sterilize individuals who were sought to be "unfit" to prevent disorders in offspring. ... One of these contemporary reproductive genetic technologies is the use of ultrasound and serum bio-medical markers for detection of congenital, chromosome, and genetic disorders. When ultrasounds reveal abnormal findings, the perceived perfect pregnancy vanishes and gives way to feelings of shock, disbelief, fear, guilt, loss, and threats to self and their unborn baby. Twelve women who had an abnormal ultrasound were interviewed within the context of their cultural values and beliefs. The method of van Manen's hermeneutic phenomenology illuminated the meaning for these women in their life worlds. ... They endured this experience through their own coping mechanisms, but often felt uncertainty and emotional turmoil until the birth. The women also sought comfort through their cultural values, beliefs, and traditions. In coping with the risks found on this abnormal ultrasound, women often selected silence or blocking perceived threats. With these coping methods, they were alone in their suffering. ... Health providers, in not recognizing these women's misunderstandings and emotional fears, abandoned them in their psychosocial and cultural needs. The significance reveals that nurses and health providers need to infuse human caring ways of being, knowing, and doing within advanced technological environments. / by Jeanne Chatham Gottlieb. / Thesis (Ph.D.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Imagens térmicas, ou infravermelhas, contém somente informações funcionais do corpo e nenhuma informação anatômica. A falta de um referencial anatômico pode dificultar a inspeção visual da imagem em diagnósticos, motivo pelo qual imagens médicas funcionais são combinadas com imagens anatômicas, como no caso da fusão de imagens anatômicas de ressonância ou ultrassom com imagens funcionais de tomografia computadorizada e PET. Considerando isso, este trabalho apresenta um método para registro e fusão de imagens térmicas com imagens anatômicas, a fim de acrescentar referências anatômicas a imagens térmicas e facilitar a sua analise em diagnósticos. Devido as diferenças morfológicas entre as imagens anatômicas e funcionais a deformação de ao menos uma delas e necessária. Para isso foi adotado o método de transformação não rígida por interpolação utilizando B-splines com marcadores manualmente posicionados. Não há relatos da aplicação desta abordagem no registro e fusão de imagens térmicas em imagens de atlas anatômicos, apesar desta ser utilizada em outras áreas. Foi realizada uma serie de testes com imagens térmicas e anatômicas, essas últimas provindas de atlas anatômicos e fotografias de luz visível, de diferentes partes do corpo humano. O método apresentado e capaz de incluir informações de imagens anatômicas em imagens térmicas pelo registro e fusão destas, apresentando erros de posicionamento da ordem de 5 mm. / Thermal images, or infrared images, contain only functional information about the body, without anatomical information. The lack of an anatomical reference can compromise visual inspection. For this reason, functional medical images are combined with anatomical images, as in the case of the fusion of magnetic resonance or ultrasound anatomical images and PET functional images. Considering this, the present work presents a method for registration and fusion of thermal and anatomical images, with the purpose of providing anatomical references to thermal images and facilitate its analysis in diagnoses. Due to the morphological differences between the anatomical and functional images, it is necessary to transform at least one of them. For this purpose a method of non-rigid transformation with B-splines and manual landmarks was adopted. There are no reports of the application of this technique to thermal images and images from anatomical atlas, despite being used in other fields. Experiments were performed with thermal and anatomical images, the latter from atlas and visible light photographs, from different parts of the human body. The proposed method is capable of including information from anatomical images to thermal images through their registration and fusion, with errors in the order of 5 mm.

Este trabalho contribui para a busca de métodos rápidos para reconstrução esparsa em ultrassonografia. O objetivo é alcançado em três etapas: a validação de um modelo discreto de aquisição, uma avaliação comparativa de algoritmos adequados ao problema e uma proposição de aceleração para um dos métodos de melhor desempenho. A estratégia de validação do modelo consiste em reconstruções a partir de dados sintéticos de resultado conhecido e subsequente validação com dados reais, coletados por uma plataforma de pesquisa em ultrassom com um phantom de uso profissional. As reconstruções são realizadas por um conjunto selecionado de algoritmos iterativos de otimização convexa, que têm seus parâmetros, resultados e desempenhos analisados. O trabalho propõe a aceleração do método ADMM (Alternating Direction Method of Multipliers) que está entre os de melhor desempenho em termos de custo computacional, e que pode dobrar sua velocidade inicial de convergência com a modificação proposta. Como a aceleração também pode ser utilizada em outras aplicações do ADMM, a modificação proposta é validada em quatro casos de estudo, sendo dois em ultrassonografia e dois em imageamento por ressonância magnética. / This study contributes to the search for fast iterative methods for ultrasonic sparse image reconstruction. The goal is achieved in three steps: the validation of a discrete acquisition model, a comparative evaluation of algorithms suitable to the problem and an acceleration proposal for one of the best performing methods. The model validation strategy consists of image reconstructions from synthetic data with previously known results, and subsequent validation with real data, collected by an ultrasound research platform with a professional phantom. The reconstructions are performed by a selected set of iterative algorithms of convex optimization, which have their parameters, results and performances analyzed. This study proposes the acceleration of the ADMM (Alternating Direction Method of Multipliers), which is among the best performing methods in terms of computational cost, and which can have its initial convergence speed doubled by the proposed modification. Since the acceleration can also be used in other applications of ADMM, the proposed modification is validated in four cases of study: two in ultrasonography and two in magnetic resonance imaging.