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As opposed to current Intraoperative Ultrasound (IOUS) systems and their relatively large probes and limited superficial high frequency imaging, the use of a biopsy needle with an integrated transducer that is capable of minimally invasive and high-resolution ultrasound imaging is proposed. Such a design would overcome the compromise between resolution and penetration depth which is associated with the use of a probe on the skins surface. It is proposed that during interventional procedures, a transducer array positioned at the tip of a biopsy needle could provide real-time image guidance to the clinician with regards to the needle position within the tissue, and aid in the safe navigation of needles towards a particular target such as a tumour in tissues such as the breast, brain or liver, at which point decisions surrounding diagnosis or treatment via in vivo tissue characterisation could be made. With this objective, challenges exist in the manufacturing these miniature scale devices and theirincorporation into needle packages. The reliable realisation of miniature ultrasound transducer arrays on fine-scale piezoelectric composites, and establishing interconnects to these devices which also fit into suitably sized biopsy needles are two such hurdles. In this thesis, the fabrication of miniature 15 MHz ultrasound transducers is presented. The first stage of development involved the production of single element transducers in needles ~2 mm inner diameter, using various piezoelectric materials as the active material. These devices were tested andcharacterised, and the expertise developed during their fabrication was used as the foundation upon which to design a wafer-scale fabrication process for the production of multiple 15 MHz transducer arrays. This process resulted in a 16 element 15 MHz array connected to a flexible printed circuit board and integrated into a breast biopsy needle. Characterisation tests demonstrated functionality of each of the 16 elements, both individually and combined as an array. To explore potential applications for these devices, the single element transducers were tested in fresh and Thiel embalmed cadaveric brain tissue. Plasticine targets were embedded in these brain models and the needle transducers were tested as navigational real-time imaging tools to detect these targets within the brain tissue. The results demonstrated feasibility of such devices to determine the location of the target as the needle devices were advanced or withdrawn from the tissue, showing promise for future devices enabling neurosurgical guidance of interventional tools in the brain. The application of breast imaging was also considered. Firstly, Thiel embalmed cadaveric breasts were assessed as viable breast models for ultrasound imaging. Following this, anatomical features, with diagnostic significance in relation to breast cancer i.e. axillary lymph nodes and milk ducts, were imaged using a range of ultrasound frequencies (6 – 40 MHz). This was carried out to determinepotential design parameters (i.e. operational frequency) of an interventional transducer in a biopsy needle probe which would best visualise these features and aid current breast imaging and diagnosis procedures.

Medical ultrasound technology accounts for over half of all imaging tests performed worldwide. In comparison to other methods, ultrasonic imaging is more portable and lower cost, and is becoming more accessible to remote regions where traditionally no medical imaging can be done. However, conventional ultrasonic imaging systems still rely on expensive PZT-based ultrasound probes that limit broader applications. In addition, the resolution of PZT based transducers is low due to the limitation in hand-fabrication methods of the piezoelectric ceramics. Capacitive Micromachined Ultrasonic Transducers (CMUTs) appears as an alternative to the piezoelectric (PZT) ceramic based transducer for ultrasound medical imaging. CMUTs show better ultrasound transducer design for batch fabrication, higher axial resolution of images, lower fabrication costs of the elements, ease of fabricating large arrays of cells using MEMS fabrication, and the extremely important potential to monolithically integrate the 2D transducer arrays directly with IC circuits for real-time 3D imaging. Currently most efforts on CMUTs are silicon based. Problems with current silicon-based CMUT designs include low pressure transmission and high-temperature fabrication processes. The pressure output from the silicon based CMUTs cells during transmission are too low when compared to commercially available PZT transducers, resulting in relatively blurry ultrasound images. The fabrication of the silicon-based cells, although easier than PZT transducers, still suffers from inevitable high temperature process and require specialized and expensive equipment. Manufacturing at an elevated temperature hinders the capability of fabricating front end analog processing IC circuits, thus it is difficult to achieve true 3D/4D imaging. Therefore novel low temperature fabrication with a low cost nature is needed. A polymer (Parylene) based CMUTs transducer has been investigated recently at UCF and aims to overcome limitations posted from the silicon based counterparts. This thesis describes the numerical simulation work and proposed fabrication steps of the Parylene based CMUT. The issue of transducer cost and pressure transmission is addressed by proposing the use of low cost and low temperature Chemical Vapor Deposition (CVD) fabrication of Parylene-C as the structural membrane plus graphene for the membrane electrodes. This study focuses mainly on comparing traditional silicon-based CMUT designs against the Parylene-C/Graphene CMUT based transducer, by using MEMS modules in COMSOL. For a fair comparison, single CMUT cells are modeled and held at a constant diameter and the similar operational frequency at the structural center. The numerical CMUT model is characterized for: collapse voltage, membrane deflection profile, center frequency, peak output pressure transmission over the membrane surface, and the sensitivity to the change in electrode surface charge. This study took the unique approaches in defining sensitivity of the CMUT by calculating the membrane response and the change in the electrode surface charge due to an incoming pressure wave. Optimal design has been achieved based on the simulation results. In comparison to silicon based CMUTs, the Parylene/Graphene based CMUT transducer produces 55% more in volume displacement and more than 35% in pressure output. The thesis has also laid out the detailed fabrication processes of the Parylene/Graphene based CMUT transducers. Parylene/Graphene based ultrasonic transducers can find wide applications in both medical imaging and Non destructive evaluation (NDE).

There is an urgent and unmet clinical need to improve accuracy and safety during needle-based interventional procedures including regional anaesthesia and cancer biopsy. In ultrasound guided percutaneous needle procedures, there is a universal problem of imaging the needle, particularly the tip, especially in dense tissues and steep insertion angles. Poor visualization of the needle tip can have serious consequences for the patients including nerve damage and internal bleeding in regional anaesthesia and, in the case of biopsy, mis-sampling, resulting in misdiagnosis or the need for repeat biopsy. The aim of the work was to design and develop an ergonomic ultrasound device to actuate standard, unmodified needles such that the visibility of needle can be enhanced when observed under colour Doppler mode of ultrasound imaging. This will make the needle procedures efficient through accurate needle placement while reducing the overall procedure duration. The research reported in this thesis provides an insight into the new breed of piezoelectric materials. A methodology is proposed and implemented to characterize the new piezocrystals under ambient and extreme practical conditions. For the first time, the IEEE standard method (1987) was applied to an investigation of this type with binary (PMN-PT) and ternary (PIN-PMN-PT) compositions of piezocrystals. Using the existing data and the data obtained through characterization, finite element analysis (FEA) were carried to adequately design the ultrasound device. Various configurations of the device were modelled and fabricated, using both piezoceramic and piezocrystal materials, in order to assess the dependency of device’s performance on the configuration and type of piezoelectric material used. In order to prove the design concept and to measure the benefits of the device, pre-clinical trials were carried out on a range of specimens including the soft embalmed Thiel cadavers. Furthermore, an ultrasound planar cutting tool with various configurations was also designed and developed as an alternative to the existing cumbersome ultrasonic scalpels. These configurations were based on new piezocrystals including the Mn-doped ternary (Mn:PIN-PMN-PT) material. It is concluded that the needle actuating device can significantly enhance the visibility of standard needles and additionally benefits in reducing the penetration force. However, in order to make it clinically viable, further work is required to make it compliant with the medical environment. The piezocrystals tested under practical conditions although offer extraordinary piezoelectric properties, are vulnerable to extreme temperature and drive conditions. However, it is observed that newer piezocrystals, especially Mn:PIN-PMN-PT have shown the potential to replace the conventional piezoceramics in high power and actuator applications. Moreover, the d31-mode based planar cutting tool contrasts with the cumbersome design of mass-spring transducer structure and has the potential to be used in surgical procedures.

付記する学位プログラム名: 充実した健康長寿社会を築く総合医療開発リーダー育成プログラム / 京都大学 / 新制・課程博士 / 博士(人間健康科学) / 甲第23127号 / 人健博第89号 / 新制||人健||6(附属図書館) / 京都大学大学院医学研究科人間健康科学系専攻 / (主査)教授 杉本 直三, 教授 黒木 裕士, 教授 松田 秀一 / 学位規則第4条第1項該当 / Doctor of Human Health Sciences / Kyoto University / DFAM

The aim of this thesis is to investigate an ultrasound transducer testing system calledProbeHunter and determine the limits of the device. This device requires custom configuratedfiles to adapt to and be applicable for new ultrasound probes. The task was to investigate theimprovement possibilities for the file creation and thus broaden the use of the system.The study shows that file creation is theoretically possible for certain models of probes. Ingeneral, there is a lack of files in Västmanland and that needs to improve to keep up with thelarge amounts of probes. Multiplexed array probes are, however, not possible to create files forat the state the system is in currently. / Introduktion: Sjukvården söker ständigt utveckling i sitt dagliga arbete för patientsäkerhet. Föratt uppnå detta behövs ett samarbete med externa företag som utvecklar system för att utföradessa kvalitetssäkringar. Medicinsk teknik i region Västmanland har under en längre tid varit påjakt efter en bra utrustning för test av ultraljudsprober och har använt sig av ett flertalundersökningsmetoder. ProbeHunter var en kandidat till flertal alternativ och kom att utnyttjasför att förbättra sjukvården. Syfte: Syftet med arbetet är att undersöka så många prob modeller med ProbeHunter sommöjligt. Identifiera vart gränserna med ProbeHunter går och därmed bredda på användningen avsystemet. Detta innebär inte nödvändigtvis att alla prober måste gå att testa men att man har gjorten rimlig procentökning. Metod: En mindre del av rapporten består av litteraturstudie tillsammans med mest praktisktarbete. Större del av rapportens källor för det primära arbetet består av intervjuer ochProbeHunters egna manualer. Som utgångspunkt hade det praktiska arbetet mycket fokus på atttesta så många prober som möjligt med systemet för att uppfylla de krav som var satta på arbetet. Resultat: Detta projekt gav möjligheten till en ökning av antal prober som kan testas på 11% avde 240 prober som finns i Västmanland sjukhus. Där 11% (= 27 prober) motsvarar de tester somhar blivit godkända. Medan de totalt skapade och editerade probespecifika filerna motsvara testav 27% (=65 prober av 240). Dessa filer inkluderar både fungerande och icke fungerande filer. Slutsats: ProbeHunter behöver förbättras ytterligare i några aspekter. Det är inte på något sättdet perfekta instrumentet men lyckas ändå ge bra resultat om rätt material är närvarande vidtestning. Aktiv utveckling krävs för att eliminera vissa nackdelar med systemet. ProbeHunter ärfortfarande en bra konkurrent till andra liknande system och kan komma att bli ännu bättre.

Proper design of bridge structures requires an appreciation for the possible failure mechanisms that can develop over the lifetime of the bridge, many of which are related to natural hazards. For example, scour is one of the most common causes of bridge failures. Scour occurs due to the erosion of soil and sediment within a channel with flowing water. During a flood event, the extent of scour can be so great that it can destabilize an existing bridge structure. In order to evaluate the scour potential of a bridge, it is necessary to have information regarding the substructure, particularly the bridge foundations. However, as of 2011 there are more than 40,000 bridges across United States with unknown foundations. Generally for these bridges there are no design or as-built plans available to show the type, depth, geometry, or materials incorporated into the foundations. Several non-destructive testing (NDT) methods have been developed to evaluate these unknown foundations. The primary objective of this research is to identify the most current and widely used NDT methods for determining the embedment depth of unknown bridge foundations and to compare these methods to an ultrasonic P-wave reflection imaging system. The ultrasonic P-wave reflection system has tremendous potential to provide more information and address several short-comings of other NDT methods. A laboratory study was initiated to explore various aspects related to the P-wave system performance, in order to characterize the limitations of the system in evaluation of unknown foundations prior to deployment in field studies. Moreover, field testing was performed using the P-wave system and a number of the current NDT methods at two selected bridge foundations to allow comparison between the results. / Civil Engineering

Chronic liver diseases are the eighth leading cause of death in Brazil and a major public health problem in the world. Liver biopsy is the best available reference standard for evaluating and classifying stages of liver diseases, but it presents limitations and complications that are common in invasive methods. In recent years, elasticity imaging methods have been the focus of intense research activity with the ability to measure mechanical properties of soft tissues in a non-invasive way. Shear wave elastography is one of the most promising methods because it enables to quantitatively assess tissue elasticity. However, the current depth range of shear wave elastography impedes its application in obese patients, which have a great risk of developing liver disease. The aim of this study is to investigate the use of shear wave elastography in deeper tissues using a two-dimensional ultrasound transducer array. An efficient transducer array arrangement was simulated, fabricated and characterized. The results show that the proposed transducer configuration presents enhanced transmitting capabilities for generating tissue displacement in deeper tissues. In addition, numerical simulations were performed in order to track the tissue deformation and reconstruct its elastic properties. / Doenças crônicas do fígado são a oitava causa de morte no Brasil e um dos principais problemas de saúde pública do mundo. A biópsia do fígado é o melhor padrão de referência disponível para avaliação e classificação dos estágios das doenças hepáticas, mas apresenta limitações e complicações que são comuns nos métodos invasivos. Nos últimos anos, métodos de imagem por elasticidade têm sido o foco de intensa atividade de pesquisa, pois têm a capacidade de medir propriedades mecânicas dos tecidos moles de maneira não invasiva. A elastografia por ondas de cisalhamento é um dos métodos mais promissores, pois permite avaliar quantitativamente a elasticidade do tecido. No entanto, a atual faixa de profundidade da elastografia por ondas de cisalhamento impede sua aplicação em pacientes obesos, que apresentam grande risco de desenvolver doença hepática. O objetivo deste estudo é investigar o uso da elastografia por onda de cisalhamento em tecidos mais profundos usando um transdutor de ultrassom bidimensional. Uma configuração eficiente de transdutores matriciais foi simulada, fabricada e caracterizada. Os resultados mostram que o transdutor proposto possui capacidade de transmissão melhorada para gerar deslocamento em tecidos profundos. Além disso, simulações numéricas foram realizadas para monitorar a deformação do tecido e reconstruir suas propriedades elásticas.

Chronic liver diseases are the eighth leading cause of death in Brazil and a major public health problem in the world. Liver biopsy is the best available reference standard for evaluating and classifying stages of liver diseases, but it presents limitations and complications that are common in invasive methods. In recent years, elasticity imaging methods have been the focus of intense research activity with the ability to measure mechanical properties of soft tissues in a non-invasive way. Shear wave elastography is one of the most promising methods because it enables to quantitatively assess tissue elasticity. However, the current depth range of shear wave elastography impedes its application in obese patients, which have a great risk of developing liver disease. The aim of this study is to investigate the use of shear wave elastography in deeper tissues using a two-dimensional ultrasound transducer array. An efficient transducer array arrangement was simulated, fabricated and characterized. The results show that the proposed transducer configuration presents enhanced transmitting capabilities for generating tissue displacement in deeper tissues. In addition, numerical simulations were performed in order to track the tissue deformation and reconstruct its elastic properties. / Doenças crônicas do fígado são a oitava causa de morte no Brasil e um dos principais problemas de saúde pública do mundo. A biópsia do fígado é o melhor padrão de referência disponível para avaliação e classificação dos estágios das doenças hepáticas, mas apresenta limitações e complicações que são comuns nos métodos invasivos. Nos últimos anos, métodos de imagem por elasticidade têm sido o foco de intensa atividade de pesquisa, pois têm a capacidade de medir propriedades mecânicas dos tecidos moles de maneira não invasiva. A elastografia por ondas de cisalhamento é um dos métodos mais promissores, pois permite avaliar quantitativamente a elasticidade do tecido. No entanto, a atual faixa de profundidade da elastografia por ondas de cisalhamento impede sua aplicação em pacientes obesos, que apresentam grande risco de desenvolver doença hepática. O objetivo deste estudo é investigar o uso da elastografia por onda de cisalhamento em tecidos mais profundos usando um transdutor de ultrassom bidimensional. Uma configuração eficiente de transdutores matriciais foi simulada, fabricada e caracterizada. Os resultados mostram que o transdutor proposto possui capacidade de transmissão melhorada para gerar deslocamento em tecidos profundos. Além disso, simulações numéricas foram realizadas para monitorar a deformação do tecido e reconstruir suas propriedades elásticas.

Extensions to k-Wave toolbox used for ultrasound modelling are described. Aim of extensions is to reduce time and space complexity by presenting alternative representations of tissues and transducers in simulation. This project clarifies basic principles and features of k-Wave, describes design of new representations and finally describes implementation of the suggested extensions.