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Doctoral Thesis
DOI
10.11606/T.59.2015.tde-22042015-153203
Document
Author
Full name
Alexandre Colello Bruno
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
Ribeirão Preto, 2015
Supervisor
Committee
Carneiro, Antonio Adilton Oliveira (President)
Machado, João Carlos
Miranda, Jose Ricardo de Arruda
Moraes, Eder Rezende
Oliveira, Ricardo Brandt de
Title in Portuguese
Aplicação do transdutor magnetoacústico em estudos gástricos: in vitro e in vivo
Keywords in Portuguese
magnetomotriz
Transdutor híbrido
Ultrassom
Abstract in Portuguese
A proposta deste trabalho foi desenvolver e avaliar as aplicações do transdutor magnetoacústico, em estudos in vitro e in vivo como ferramenta para o diagnóstico clínico, inicialmente para a análise de motilidade gastrintestinal. Na primeira etapa, a intensidade do campo magnético foi mapeada e ajustada, o melhor processamento para os dados foi definido e a viabilidade do uso de nanopartículas como marcadores foi contatada. Nos estudos in vivo, realizados em ratos, avaliou-se o potencial do transdutor híbrido para análise do esvaziamento gástrico, de alimentos marcado com partículas magnéticas, comparando os dados susceptométricos (padrão ouro) com os acústicos. O esvaziamento foi relacionado com a variação de área do estômago no tempo, que foi demarcada nas imagens de ultrassom usando a vibração das partículas como contraste. Outras variações e aplicações da ultrassonografia magnetomotriz foram investigadas, usando a excitação magnética pulsada (antes harmônica), aumentando a taxa de aquisição das imagens e gerando imagens elastográficas em fantomas. A produção e detecção de Shaer Waves (elastografia absoluta) também foi avaliada em outros fantomas com uma esfera de ferrita, sem e com uma inclusão mais rígida. A ultrassonografia magnetomotriz pulsada e o processamento vinculado a ela foram capazes de gerar as shear waves, através de puxões magnéticos na esfera de ferrita, e estimar a velocidade de propagação dessas. Com esta velocidade, estimaram-se os coeficientes elástico e viscoso dos meios de propagação. Portanto, o transdutor magnetoacústico, avaliado de diversas formas nesse trabalho, apresentou-se como uma potencial ferramenta para diagnóstico da motilidade gástrica in vivo, usando tanto a ultrassonografia magnetomotriz harmônica como a pulsada. As técnicas de processamento podem ser convencionais (modos Doppler, Power Doppler e elastográficos) ou dedicadas, as quais podem detectar deslocamentos, deformações ou propagação de ondas sísmicas; suas aplicações não se limitam ao estômago e nem os diagnósticos in vivo.
Title in English
Magnetoacústico transducer application in gastric studies: in vitro and in vivo.
Keywords in English
Hybrid probe
MMUs
Ultrasound
Abstract in English
The aim of this study was to develop and to evaluate applications magneto-acoustic transducer in phantoms and in vivo studies, as a tool for clinical diagnosis, initially for analysis of gastrointestinal motility. First step, the magnetic field intensity was adjusted and mapped; the best data and image processing was defined, and nanoparticles markers were studied to future applications. In experiments with rats (in vivo), we evaluated the hybrid transducer potential by gastric emptying analysis using foods labeled magnetic particles, comparing the susceptometric data (gold standard) with the acoustic. Others magneto motive ultrasonography variations and applications were investigated. The variations were the pulsed magnetic excitation and the high frame rate. The rats empty gastric were evaluated with solid and liquid food by pulsed magneto-motive ultrasound; the solid food took longer to leave the stomach, as was expected. Other applications based on the use of elastography techniques combined with pulsed magneto-motive ultrasound in phantoms were evaluated - the first potential application was the lesions detection in the colon wall (by elastography relative). In this case, harder inclusions were located by elastography based on deformations caused by the magnetic pulse and by the magnetic fluid inserted in the supposed colon. The second potential application was Shear Waves production and detection (Transient elastography) using a ferrite sphere inside the phantoms with a harder inclusion. The pulsed Magneto Motive Ultrasound was able to generate shear waves by magnetic "pushes" in the ferrite sphere and it estimated the speed propagation of these. Therefore, the Magneto-Acoustic transducer showed that it is a potential tool for gastric motility diagnosis in vivo, using the harmonic or pulsed Magneto-Motive Ultrasound. Their processing techniques can be conventional (Doppler, Power Doppler and elastography modes), or dedicated to detect displacements, strains and seismic waves propagation, and its applications are not limited to stomach and in vivo diagnostics.
 
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Publishing Date
2015-05-08
 
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