Ultrasound metrology and phantom materials for validation of photoacoustic thermometry

High intensity focused ultrasound is an emerging non-invasive cancer therapy during which a focused ultrasound beam is used to destroy cancer cells within a confined volume of tissue. In order to increase its successful implementation in practice, an imaging modality capable of accurately mapping the induced temperature rise in tissue is necessary. Photoacoustic thermometry, a rapidly emerging technique for non-invasive temperature monitoring, exploits the temperature dependence of the Grüneisen parameter of tissues, which leads to changes in the recorded photoacoustic signal amplitude with temperature. However, the implementation of photoacoustic thermometry approaches is hindered by a lack of rigorous validation. This includes both the equipment and methodology used. This work investigates the effect of temperature on ultrasound transducers used in photoacoustic thermometry imaging as well as characterisation of potential phantom materials for its validation. The variation in transducer sensitivity with temperature is investigated using two approaches. The first one utilises a reference transducer whose output power is known as a function of temperature to characterise the sensitivity of the hydrophone. As the knowledge of variability of transducer output with temperature is not readily available, two standard metrology techniques using radiation force balances and laser vibrometry are extended beyond room temperature to characterise the effect of temperature on the output of PZT tranducers. For the second approach to transducer sensitivity calibration, a novel method is developed utilising water as a laser-generated ultrasound source and validated using the self-reciprocity calibration method. The calibrated hydrophone is then used to characterise the relevant temperature-dependent properties of several phantom materials in a custom-built setup. The measurement results are used to determine the most suitable phantom for photoacoustic thermometry. Finally, the phantom is heated and imaged in a proof-of-concept photoacoustic thermometry setup using a linear array. These contributions are of vital importance for allowing the translation of photoacoustic thermometry into clinical practice

Spin resonance excitation of Gd-based contrast agents for thermal energy deposition

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2016The theoretical and experimental investigation of electron spin-resonance relaxation to deposit thermal energy into liquid gadolinium-based contrast agents for cancer hyperthermia treatment is presented. Previous works suggest that using protons in water are inadequate, with a thermal deposition rate of approximately 1 ◦C per two years. A novel component of this research relies on the use of gadolinium-chelated molecules, which are currently used as contrast agents in clinical MRI scans. The chelating agents, or ligands, investigated are Gadobenate (MultiHance R ), Gadopentetate (Magnevist R ), Gadoterate (DotaremR ) and Gadoteridol (ProHance R ). The gadolinium atom has seven unpaired electrons in its inner f shell orbital and as a result has a 660 times stronger paramagnetic response when placed in an external magnetic field. The research tests the hypothesis that by using an appropriate external homogeneous DC magnetic field, together with a radiofrequency excited resonator, that a measurable amount of thermal energy is deposited into a liquid gadolinium-based contrast agent. The aim of this research is to ultimately discover a new cancer hyperthermia treatment. The research theory suggests that a temperature rate of 13.4 ◦C · s−1 can be achieved using the gadolinium-based contrast agents under certain experimental conditions, and a maximum of 29.4 ◦C · s−1 under more optimal conditions. The temperature rates are calculated using parameter values commonly found in literature and practice. The simulation and design of the DC magnetic field coil system is discussed, together with the simulation results and design parameters of the radiofrequency loop-gap resonator. The experimental results and analysis indicate that the selected contrast agents have varied responses based on their chemical nature and that only two out of the four contrast agents, Dotarem and ProHance, show a measurable effect albeit sufficiently small that statistical techniques were necessary to distinguish the effect from background. A model fit to the data is performed in order to determine the spin-lattice relaxation time of the contrast agents under the specified experimental conditions. The model estimate is significantly smaller than the values found in literature under similar conditions, with a spin-lattice relaxation time τ1e of approximately 0.2 ps compared to the literature value of 0.1 ns. Although the observed electron spin resonance heating rate is in the milli-Watt range it is still notably larger (167 000 times) compared to the heating rate obtained using protons. The low temperature rates suggest that a more suitable agent or molecule with a larger spin-relaxation time be used, in order to achieve clinical useful temperature rates in the range of 14 ◦C · s−1.MT201

Vocal fold vibratory and acoustic features in fatigued Karaoke singers

Session 3aMU - Musical Acoustics and Speech Communication: Singing Voice in Asian CulturesKaraoke is a popular singing entertainment particularly in Asia and is gaining more popularity in the rest of world. In Karaoke, an amateur singer sings with the background music and video (usually guided by the lyric captions on the video screen) played by Karaoke machine, using a microphone and an amplification system. As the Karaoke singers usually have no formal training, they may be more vulnerable to vocal fatigue as they may overuse and/or misuse their voices in the intensive and extensive singing activities. It is unclear whether vocal fatigue is accompanied by any vibration pattern or physiological changes of vocal folds. In this study, 20 participants aged from 18 to 23 years with normal voice were recruited to participate in an prolonged singing task, which induced vocal fatigue. High speed laryngscopic imaging and acoustic signals were recorded before and after the singing task. Images of /i/ phonation were quantitatively analyzed using the High Speed Video Processing (HSVP) program (Yiu, et al. 2010). It was found that the glottis became relatively narrower following fatigue, while the acoustic signals were not sensitive to measure change following fatigue. © 2012 Acoustical Society of Americapublished_or_final_versio

HIGH INTENSITY FOCUSED ULTRASOUND AND OXYGEN LOAD NANOBUBBLES: TWO DIFFERENT APPROCHES FOR CANCER TREATMENT

The study of applications based on the use of ultrasound in medicine and biology for therapeutic purposes is under strong development at international level and joins the notoriously well-established and widespread use of diagnostic applications [1]. In the past few years, High Intensity Focused Ultrasound (HIFU) has developed from a scientific curiosity to an accepted therapeutic modality. HIFU is a non invasive technique for the treatment of various types of cancer, as well as non-malignant pathologies, by inducing localized hyperthermia that causes necrosis of the tissue. Beside HIFU technology, other innovative therapeutic modalities to treat cancer are emerging. Among them, an extremely innovative technique is represented by oxygen loaded nanobubbles (OLNs): gas cavities confined by an appropriately functionalized coating. This is an oxygenating drugs aimed at re-oxygenation of cancerous tissue. Oxygen deficiency, in fact, is the main hallmark of cancerous solid tumors and a major factor limiting the effectiveness of radiotherapy. In this work, these two approaches to treat tumours are under study from a metrological point of view. In particular, a complete characterization of an HIFU fields regarding power, pressure and temperature is provided while oxygen load nanobubbles are synthesized, characterized and applied in in vitro and in vivo experiments

Frontier Research on the Processing Quality of Cereal and Oil Food

As everyone knows, cereal and oil are still the main part of our diet and provide essential nutrients and energy every day. With the progress of food processing technology, the quality of cereal and oil food is also improved significantly. Behind this, major nutrients of grain and oil, including protein, carbohydrate, lipid, and functional components, have experienced a variety of physical, chemical, and biological reactions during food processing. Moreover, research in this field also covers the multi-scale structural changes of characteristic components, such as component interaction and formation of key domains, which is essential for the quality enhancement of cereal and oil food. Based on the increasing consumer demand for nourishing, healthy, and delicious cereal and oil food, it might be interesting to report the latest research on the application of novel technology in food processing, multi-scale structural changes of characteristic components in food processing, structure-activity mechanism of food functional components. This book aimed to provide useful reference and guidance for the processing and utilization of cereal and oil food so as to provide technical support for the healthy development of cereal a oil food processing industry wordwide

Application of ultrasound in twin-screw extrusion and microinjection molding: improvements of properties of processed materials and nanocomposites : polymers and biopolymers

Pla de Doctorat Industrial, Generalitat de Catalunya, Aplicat embargament fins el dia 22 de novembre de 2022The plastics industry is in constant evolution looking to improve the properties of new materials and performance in different applications. Currently, the environmental impact associated with the use of plastics is one of the main concerns for the society. It was reflected in regulations at European level such as SUP Directive, Green Deal or studies such as Patents for tomorrow's plastics by European Patent Office on the trends reflected in research on alternative materials to conventional plastic. In order to transfer these new and more sustainable alternatives to an industrial and realistic environment, first applied research has to be carried out on both the development and processes of the materials to optimize their performance. In this thesis study, applied research was carried out using ultrasound technology on different nanocomposites and their transformation processes. Advances in the application of ultrasound for different transformation processes have been studied previously to ensure the approach of the practical study. This study focuses on the application of ultrasound in the process of obtaining new formulations by compounding extrusion and in injection molding, specifically in microinjection. The application of nanotechnology in the development of new materials will allow an improvement in performance and will open a range of new possibilities and applications. To explore the potential of ultrasonic molding (USM) technology, a preliminary process stability study was performed with polypropylene. The evaluation was carried out from a mechanical point of view, in which it was shown that, with an optimization of the process parameters and a correct design approach of the components with the nodal point allow a stability close to production was allowed. To deepen into the potential of USM technology in synergy with new nanocomposite formulations, a comparative study with the conventional microinjection process was performed. Two different nanocomposites based on a biopolymer matrix of poly 3-hydroxybutyrate with Cloisite 20 (organic modification), and with Cloisite 116 (unmodified) were studied. This research reveals that the USM technology, is stable obtaining micro-pieces, maintaining the chemical structure of the initial biocomposite without degrading and homogeneously achieving an exfoliation of both nanoclays. Conventional microinjection did show slight changes in the level of degradation and chemical structure, highlighting that it was not possible to micro-mold samples of the material with the unmodified nanoclay. The stabilization of the compounding extrusion assisted by an ultrasound system has been studied, with a design of a single component that allows the new approach to work in continuous condition and on pre-industrial equipment. Due to the success of the new component, it was possible to carry out the study of new formulations of polypropylene loaded with two different nanoclays (Cloisite 20 and Garamite 1958) and glass bubbles. The new nanocomposites reached the mechanical properties of a conventional material used for door panels in the automotive sector, but with a reduced density. The aim was to demonstrate that it is possible to reduce the weight of plastic components used in the automotive industry and reduce CO2 emissions for a standard vehicle. The research carried out in this thesis work has opened a new field of application to nanocomposites for weight reduction with improved mechanical properties when high level of dispersion is reached. In addition, the potential of USM technology for micro-molding applications has been demonstrated, showing high stability without material degradation during the process, and good dispersion of nano-reinforcements.El sector del plástico está en continuo cambio en busca de mejorar sus propiedades y rendimiento en diferentes aplicaciones. Actualmente. el impacto ambiental asociado al uso de los plásticos es una de las principales preocupaciones en el ámbito social. Se puede ver reflejado en regulaciones a nivel europeo como SUP Directive. Green Deal o estudios como el que efectúa la Oficina de Patentes Europeas Patents for tomorrow's plastics sobre las tendencias que reflejan las investigaciones en materiales alternativos al plástico convencional. Para poder llevar a un ambiente industrial y realista estas nuevas alternativas más sostenibles. primero se ha de llevar a cabo una investigación aplicada tanto del desarrollo de los materiales como de los procesos que pueden optimizar su rendimiento. En este estudio de tesis se lleva a cabo una investigación aplicada sobre diferentes nanocompuestos y sus procesos de transformación que pueden ser mejorados con la tecnología de ultrasonidos. Se ha estudiado los avances en la aplicación de ultrasonidos para diferentes procesos de transformación con el objetivo de enfocar correctamente el estudio práctico. Este estudio centra la aplicación de los ultrasonidos en el proceso de obtención de nuevas formulaciones por extrusión compounding y en el moldeo por inyección, concretamente en microinyeccion. La aplicación de nanotecnología en el desarrollo de nuevos materiales permitirá una mejora del rendimiento y abrirá un abanico de nuevas posibilidades y aplicaciones. Para explorar el potencial de la tecnología de microinyección por ultrasonidos (USM}, se realizó un estudio preliminar de estabilidad del proceso con un polipropileno. La evaluación fue llevada a cabo desde un punto de vista mecánico, en el que se demostró que con una optimización de los parámetros de proceso y un enfoque de diseño correcto de los componentes que hacen intervenir el punto nodal, se puede alcanzar un nivel de estabilidad cercano a producción. Para profundizar en el potencial de la tecnología USM en sinergia con nuevas formulaciones de nanocompuestos, se realizó un estudio comparativo con el proceso de microinyección convencional. Dos nanocompuestos basados en una matriz del biopolímero poli 3-hidroxibutirato con Cloisite 20 (modificación orgánica). Y con Cloisite 116 (sin modificar) fueron estudiados. Este estudio revela que la tecnología USM además de ser estable en la obtención de micropiezas, mantiene la estructura química del biocompuesto inicial sin llegar a degradación y alcanzando homogéneamente la exfoliación de ambas nanoarcillas. La microinyección convencional si mostro ligeros cambios a nivel de degradación y estructura química, destacando que no fue posible micromoldear muestras del material con la nanoarcilla sin modificar. La estabilización del proceso de extrusión compounding asistida por ultrasonidos ha sido estudiado, diseñando un componente único que permite al sistema de ultrasonidos trabajar en régimen continuo en equipos preindustriales. Gracias al éxito del nuevo componente, se ha podido llevar a cabo el estudio de nuevas formulaciones de polipropileno argado con dos nanoarcillas diferentes (Cloisite 20 y Garamite 1958) y esferas huecas. Los nuevos nanocompuestos alcanzaron las propiedades mecánicas de un material empleado para paneles de puerta en el sector automoción, pero con una densidad reducida. El objetivo fue demostrar que se puede reducir el peso de los componentes plásticos empleados en automoción y reducir las emisiones de CO2 para un vehículo estándar. La investigación llevada a cabo en este trabajo de tesis ha permitido abrir un nuevo campo de aplicación a los nanocompuestos para reducción de densidad con buenas propiedades mecánicas cuando la dispersión es alta. Además, se ha demostrado el potencial de la tecnología USM para aplicaciones de micromoldeo, mostrando alta estabilidad sin degradación del material durante el proceso, y buena dispersión de los nano-refuerzos.Polímers i biopolímer