Arrays de Anillos Segmentados para la generación de imagen ultrasónica 3D

Nowadays ultrasonic imaging is one of the methods more frequently employed in clinical diagnosis and NDT applications. Ultrasonic commercial systems are mainly based on bidimensional images. Development of volumetric imaging systems based on array transducers has started at R&D laboratories a de...

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Detalles Bibliográficos
Autor: Martínez-Graullera, Óscar
Tipo de recurso: tesis doctoral
Fecha de publicación:2008
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/2943
Acceso en línea:http://hdl.handle.net/10261/2943
Access Level:acceso abierto
Palabra clave:ultrasonic imaging
2D arrays
GEUS
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spelling Arrays de Anillos Segmentados para la generación de imagen ultrasónica 3DMartínez-Graullera, Óscarultrasonic imaging2D arraysGEUSNowadays ultrasonic imaging is one of the methods more frequently employed in clinical diagnosis and NDT applications. Ultrasonic commercial systems are mainly based on bidimensional images. Development of volumetric imaging systems based on array transducers has started at R&D laboratories a decade ago. An array transducer is electronically controlled in order to steer the ultrasonic beam in any direction, avoiding mechanical scanning systems. Mainly rectangular MxN monolithic arrays have been proposed for 3D imaging. Unfortunately, these apertures need a large amount of elements (they can reach several thousands) to produce good quality images. For this reason, a great research effort has been addressed to develop subsampling techniques in order to reduce the number of active elements. But these techniques produce a drastic reduction of the emitted energy, so the image contrast is seriously limited. In this thesis 2D annular-segmented arrays are proposed as an alternative to the more common rectangular patterns. Annular segmented arrays have two main advantages: first, they present axial symmetry so the ultrasonic field shows almost invariant properties at any steered azimuth direction and a great symmetry with respect to the steering axis. Second, elements have a lower periodicity degree than rectangular arrays, and therefore grating lobes level is reduced. Consequently, we can increase the elements size holding at the same time a good quality in the acoustic field. With the purpose of reducing the number of elements with a full-active aperture, one of the objectives of this work is to find a criterion for array designing, in order to determine which is the aperture geometry that gives a good image quality with minimum electronic resources. Due to the scarce previous work devoted to 2D annular-segmented arrays, this thesis proposes innovative methods in the following aspects: • Computational methods valid for complex apertures. An exact solution based on the spatial impulse response, for the ultrasonic field radiated by annular sector transducers is presented. Nevertheless, due to the high computational cost associated to the exact solution, other approximated methods and algorithms are developed that reduce the computational cost in more than one order of magnitude. • Innovative methods to describe the field of annular-segmented arrays for several conditions of the aperture geometry, radiated pulse, field point position, etc. Quantitative and qualitative rules have been obtained to describe lateral response, side lobes and grating lobes in these conditions. • Designing rules for annular-segmented arrays. The influence of several array-designing parameters on the field quality is studied. The following parameters are studied: the elements interspacing, the aperture dimensions, the number and shape of the elements, the UT pulse, etc. From previous results, a theoretical comparative study between annular-segmented arrays and 2D rectangular apertures is presented. And finally, experimental work is done which validates theoretical results.Peer reviewed200820082008info:eu-repo/semantics/doctoralThesishttp://purl.org/coar/resource_type/c_db066564938 bytesapplication/pdfhttp://hdl.handle.net/10261/2943reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Españolinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/29432026-05-22T06:33:51Z
dc.title.none.fl_str_mv Arrays de Anillos Segmentados para la generación de imagen ultrasónica 3D
title Arrays de Anillos Segmentados para la generación de imagen ultrasónica 3D
spellingShingle Arrays de Anillos Segmentados para la generación de imagen ultrasónica 3D
Martínez-Graullera, Óscar
ultrasonic imaging
2D arrays
GEUS
title_short Arrays de Anillos Segmentados para la generación de imagen ultrasónica 3D
title_full Arrays de Anillos Segmentados para la generación de imagen ultrasónica 3D
title_fullStr Arrays de Anillos Segmentados para la generación de imagen ultrasónica 3D
title_full_unstemmed Arrays de Anillos Segmentados para la generación de imagen ultrasónica 3D
title_sort Arrays de Anillos Segmentados para la generación de imagen ultrasónica 3D
dc.creator.none.fl_str_mv Martínez-Graullera, Óscar
author Martínez-Graullera, Óscar
author_facet Martínez-Graullera, Óscar
author_role author
dc.subject.none.fl_str_mv ultrasonic imaging
2D arrays
GEUS
topic ultrasonic imaging
2D arrays
GEUS
description Nowadays ultrasonic imaging is one of the methods more frequently employed in clinical diagnosis and NDT applications. Ultrasonic commercial systems are mainly based on bidimensional images. Development of volumetric imaging systems based on array transducers has started at R&D laboratories a decade ago. An array transducer is electronically controlled in order to steer the ultrasonic beam in any direction, avoiding mechanical scanning systems. Mainly rectangular MxN monolithic arrays have been proposed for 3D imaging. Unfortunately, these apertures need a large amount of elements (they can reach several thousands) to produce good quality images. For this reason, a great research effort has been addressed to develop subsampling techniques in order to reduce the number of active elements. But these techniques produce a drastic reduction of the emitted energy, so the image contrast is seriously limited. In this thesis 2D annular-segmented arrays are proposed as an alternative to the more common rectangular patterns. Annular segmented arrays have two main advantages: first, they present axial symmetry so the ultrasonic field shows almost invariant properties at any steered azimuth direction and a great symmetry with respect to the steering axis. Second, elements have a lower periodicity degree than rectangular arrays, and therefore grating lobes level is reduced. Consequently, we can increase the elements size holding at the same time a good quality in the acoustic field. With the purpose of reducing the number of elements with a full-active aperture, one of the objectives of this work is to find a criterion for array designing, in order to determine which is the aperture geometry that gives a good image quality with minimum electronic resources. Due to the scarce previous work devoted to 2D annular-segmented arrays, this thesis proposes innovative methods in the following aspects: • Computational methods valid for complex apertures. An exact solution based on the spatial impulse response, for the ultrasonic field radiated by annular sector transducers is presented. Nevertheless, due to the high computational cost associated to the exact solution, other approximated methods and algorithms are developed that reduce the computational cost in more than one order of magnitude. • Innovative methods to describe the field of annular-segmented arrays for several conditions of the aperture geometry, radiated pulse, field point position, etc. Quantitative and qualitative rules have been obtained to describe lateral response, side lobes and grating lobes in these conditions. • Designing rules for annular-segmented arrays. The influence of several array-designing parameters on the field quality is studied. The following parameters are studied: the elements interspacing, the aperture dimensions, the number and shape of the elements, the UT pulse, etc. From previous results, a theoretical comparative study between annular-segmented arrays and 2D rectangular apertures is presented. And finally, experimental work is done which validates theoretical results.
publishDate 2008
dc.date.none.fl_str_mv 2008
2008
2008
dc.type.none.fl_str_mv info:eu-repo/semantics/doctoralThesis
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format doctoralThesis
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/2943
url http://hdl.handle.net/10261/2943
dc.language.none.fl_str_mv Español
language_invalid_str_mv Español
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv 6564938 bytes
application/pdf
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instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
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