Transducer Arrays for 3D Ultrasound Computed Tomography

Die Ultraschall-Computertomographie (USCT) ist ein vielversprechendes medizinisches Bildgebungsverfahren zur Früherkennung von Brustkrebs. Am Karlsruher Institut für Technologie wird derzeit ein Gerät der dritten Generation (3D-USCT-III) für 3D-Aufnahmen entwickelt. Unter den kritischsten und technologisch anspruchsvollsten Komponenten dieses Geräts sind die Schallwandlerarrays. Diese müssen eine pseudozufällige Positionierung einzelner Wandler ermöglichen, hohe Bandbreiten, große Öffnungswinkel und eine isotrope Schallabstrahlung aufweisen sowie den Vorschriften für Medizinprodukte genügen. In dieser Arbeit wird die Realisierung neuer Schallwandlerarrays (TAS-III) für die 3D-USCT-Bildgebung umfassend vorgestellt. Dies beinhaltet die Definition von Anforderungen, Systemdesign, automatisierte Fertigung, Charakterisierung und Entwurfsoptimierung. Kernelement des TAS-III-Designs sind Scheiben aus piezoelektrischen Verbundwerkstoffen, die 18 in Polymer eingebettete, räumlich verteilte piezokeramische Fasern enthalten. Zusätzliche Scheiben zur akustischenAnpassung und Dämpfung werden auf beiden Seiten angebracht, um die Arrays zu finalisieren. Für die Herstellung der benötigten 256 TAS-III wurde ein teilautomatisierter Fertigungsprozess entwickelt. Quantitative Qualitätsprüfungen ergaben, dass mehr als 96% der produzierten Wandler voll funktionsfähig waren. Die Amplitude und der Phasenwinkel des akustischen Feldes von 54 Wandlern wurden gemessen und ausgewertet. Die meisten der definierten Anforderungen wurden erfüllt. Es wurde eine mittlere Mittenfrequenz von 2,6 MHz, mit einer fraktionellen Bandbreite von 134% bei -10 dB ermittelt. Die Bandbreite resultiert dabei aus zwei unterschiedlichen Schwingungsmoden. Messungen in 3D zeigten isotrope Abstrahlcharakteristiken mit einem mittleren Öffnungswinkel von 42,8°. Für die Analyse und Optimierung des Designs wurden verschiedene Modellierungsansätze entwickelt. Geringfügige Änderungen der Länge und des Durchmessers der piezoelektrischen Fasern sowie eine höhere laterale Dämpfung konnten die Leistung in gewissem Maße verbessern. Der Umfang weiterer möglicher Verbesserungen zeigte jedoch, dass das TAS-III Design nahe am erreichbaren Optimum liegt. Alternative Wandlertechnologien wurden untersucht, umdie grundsätzlichen Grenzen von Verbundwerkstoffen bestehend aus piezoelektrischen Fasern in Bezug auf Öffnungswinkel und Bandbreite zu überwinden. Der Ersatz der Fasern durch einkristalline piezoelektrische Materialien verspricht eine Erhöhung der Bandbreite um 35%, erfordert jedoch umfangreiche Anpassungen in den Herstellungsprozessen. Die Charakterisierung von mikromechanischen Ultraschallwandlern ergab eine signifikante Vergrößerung des Öffnungswinkels, aber geringere erzeugte Schalldrücke. Dennoch machen die Eigenschaften und die verfügbare Designfreiheit diese Schallwandlertechnologie sehr vielversprechend für zukünftige 3D-USCT- Generationen. Die entworfenen und realisierten TAS-III erwiesen sich als rundum geeignet für den vorgesehenen Einsatz und wurden in zwei 3D-USCT-III-Geräten integriert. Ausführliche klinische Tests werden in naher Zukunft durchgeführt, um die Sensitivität und Spezifität dieser neuartigen 3D-Ultraschallbildgebungsmethode zu bewerten

Selected Papers from the 9th World Congress on Industrial Process Tomography

Industrial process tomography (IPT) is becoming an important tool for Industry 4.0. It consists of multidimensional sensor technologies and methods that aim to provide unparalleled internal information on industrial processes used in many sectors. This book showcases a selection of papers at the forefront of the latest developments in such technologies

MEMS Technology for Biomedical Imaging Applications

Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community

Applied Measurement Systems

Measurement is a multidisciplinary experimental science. Measurement systems synergistically blend science, engineering and statistical methods to provide fundamental data for research, design and development, control of processes and operations, and facilitate safe and economic performance of systems. In recent years, measuring techniques have expanded rapidly and gained maturity, through extensive research activities and hardware advancements. With individual chapters authored by eminent professionals in their respective topics, Applied Measurement Systems attempts to provide a comprehensive presentation and in-depth guidance on some of the key applied and advanced topics in measurements for scientists, engineers and educators

Two-phase slug flow measurement using ultra-sonic techniques in combination with T-Y junctions

The accurate measurement of multiphase flows of oil/water/gas is a critical element of oil exploration and production. Thus, over the last three decades; the development and deployment of in-line multiphase flow metering systems has been a major focus worldwide. Accurate measurement of multiphase flow in the oil and gas industry is difficult because there is a wide range of flow regimes and multiphase meters do not generally perform well under the intermittent slug flow conditions which commonly occur in oil production. This thesis investigates the use of Doppler and cross-correlation ultrasonic measurements made in different high gas void fraction flow, partially separated liquid and gas flows, and homogeneous flow and raw slug flow, to assess the accuracy of measurement in these regimes. This approach has been tested on water/air flows in a 50mm diameter pipe facility. The system employs a partial gas/liquid separation and homogenisation using a T-Y junction configuration. A combination of ultrasonic measurement techniques was used to measure flow velocities and conductivity rings to measure the gas fraction. In the partially separated regime, ultrasonic cross-correlation and conductivity rings are used to measure the liquid flow-rate. In the homogeneous flow, a clamp-on ultrasonic Doppler meter is used to measure the homogeneous velocity and combined with conductivity ring measurements to provide measurement of the liquid and gas flow-rates. The slug flow regime measurements employ the raw Doppler shift data from the ultrasonic Doppler flowmeter, together with the slug flow closure equation and combined with gas fraction obtained by conductivity rings, to determine the liquid and gas flow-rates. Measurements were made with liquid velocities from 1.0m/s to 2.0m/s with gas void fractions up to 60%. Using these techniques the accuracies of the liquid flow-rate measurement in the partially separated, homogeneous and slug regimes were 10%, 10% and 15% respectively. The accuracy of the gas flow-rate in both the homogeneous and raw slug regimes was 10%. The method offers the possibility of further improvement in the accuracy by combining measurement from different regimes

Development of a Focused Broadband Ultrasonic Transducer for High Resolution Fundamental and Harmonic Intravascular Imaging

Intravascular ultrasound (IVUS) is increasingly employed for detection and evaluation of coronary artery diseases. Tissue Harmonic Imaging provides different tissue information that could additionally be used to improve diagnostic accuracy. However, current IVUS systems, with their unfocussed transducers, may not be capable of operating in harmonic imaging mode. Thus, there is a need to develop suitable transducers and appropriate techniques to allow imaging in multi modes for complementary diagnostic information. Focused PVDF TrFE transducers were developed using MEMS (Micro-Electro-Mechanical-Systems) compatible protocols. The transducers were characterized using pulse-echo techniques and exhibited broad bandwidth (110 at -6dB) with axial resolutions of Such promising results suggest that focused, broadband PVDF TrFE transducers have opened up the potential to incorporate harmonic imaging modality in IVUS and also improve the image quality. In addition, the transducer\u27s multimodality imaging capability, not possible with the current systems, could enhance the functionality and thereby the clinical use of IVU

Development of a Focused Broadband Ultrasonic Transducer for High Resolution Fundamental and Harmonic Intravascular Imaging

Intravascular ultrasound (IVUS) is increasingly employed for detection and evaluation of coronary artery diseases. Tissue Harmonic Imaging provides different tissue information that could additionally be used to improve diagnostic accuracy. However, current IVUS systems, with their unfocussed transducers, may not be capable of operating in harmonic imaging mode. Thus, there is a need to develop suitable transducers and appropriate techniques to allow imaging in multi modes for complementary diagnostic information. Focused PVDF TrFE transducers were developed using MEMS (Micro-Electro-Mechanical-Systems) compatible protocols. The transducers were characterized using pulse-echo techniques and exhibited broad bandwidth (110 at -6dB) with axial resolutions of Such promising results suggest that focused, broadband PVDF TrFE transducers have opened up the potential to incorporate harmonic imaging modality in IVUS and also improve the image quality. In addition, the transducer\u27s multimodality imaging capability, not possible with the current systems, could enhance the functionality and thereby the clinical use of IVU