Workshop on Smart Sensors - Instrumentation and Measurement: Program

On 18-19 February, the School of Engineering successfully ran a two-day workshop on Smart Sensors - Instrumentation and Measurement. Associate Professor Rainer Künnemeyer organised the event on behalf of the IEEE Instrumentation and Measurement Society, New Zealand Chapter. Over 60 delegates attended and appreciated the 34 presentations which covered a wide range of topics related to sensors, sensor networks and instrumentation. There was substantial interest and support from local industry and crown research institutes

Miniaturization of an optoelectronic holographic otoscope for measurement of nanodisplacements in tympanic membranes

An optoelectronic holographic otoscope (OEHO) is currently in use in a major hospital. The OEHO allows for nanometer-displacement measurements of the deformation of mammalian tympanic membrane (TM) under acoustic stimulation. The optical head of the current system is sufficient for laboratory use, but requires improved optical performance and a miniaturized size to be suitable for the clinic. A new optical head configuration is designed, aided by ray tracing analysis and research of the biomechanical and optical properties of the TM. A prototype is built and the optical performance quantified via developed image processing algorithms. The device is validated through comparison of analytical, computational, and experimental results and through interferometric chinchilla TM measurements

Optical correlation techniques for the investigation of colloidal systems

This review aims to provide a simple introduction to the application of optical correlation methods in colloidal science. In particular, I plan to show that full appraisal of the intimate relation between light scattering and microscopy allows designing novel powerful investigation techniques that combine their powers. An extended version of this paper will appear in "ColloidalFoundations of Nanoscience", edited by D. Berti and G. Palazzo, Elsevier (ISBN 978-0-444-59541-6). I am very grateful to the publisher for having granted me the permission to post this preprint on arXiv.Comment: 19 pages, 5 figure

Time domain, near-infrared diffuse optical methods for path length resolved, non-invasive measurement of deep-tissue blood flow

The non-invasive and, often, continuous measurement of the hemodynamics of the body, and for the main purposes of this thesis, the brain, is desired because both the instantaneous values and their changes over time constantly adapt to the conditions affecting the body and its environment. They are altered in pathological situations and in response to increased function. It is desirable for these measurements to be continuous, reliable, minimally invasive, and relatively inexpensive. In recent years, optical techniques that, by using diffusing and deep-reaching (up to few centimeters) light at skin-safe levels of intensity, combine the aforementioned characteristics, have increasingly become used in clinical and research settings. However, to date there is, on one side the need to expand the number and scope of translational studies, and, on the other, to address shortcomings like the contamination of signals from unwanted tissue volumes (partial volume effects). A further important goal is to increase the depth of penetration of light without affecting the non-invasive nature of diffuse optics. My PhD was aimed at several aspects of this problem; (i) the development of new, more advanced methods, i.e. the time/pathlength resolved, to improve the differentiation between superficial and deeper tissues layers, (ii) the exploration of new application areas, i.e. to characterize the microvascular status of bones, to study the functional response of the baby brain, and (iii) to improve the quality control of the systems , i.e. by introducing a long shelf-life dynamic phantom. In conceptual order, first I introduce long shelf-life reference standards for diffuse correlation spectroscopy. Secondly, I describe the use of an existing hybrid time domain and diffuse correlation spectroscopy system to monitor the changes that some pathological conditions, in this case osteoporosis and human immunodeficiency virus infection, may have on many aspects of the human bone tissue that are currently not easy to measure (i.e. invasively assessed) by conventional techniques. Thirdly, I describe the development of a novel time domain optical technique that intimately combines, introducing many previously unmet advancements, the two previously cited optical spectroscopy techniques. For the first time I was able to produce a time domain device and protocol that can monitor the blood flow in vivo in the head and muscles of healthy humans. Lastly, I describe a device and method that I have used to monitor changes in blood flow in healthy human infants of three to five months of age, for the first time in this age bracket, as a marker of activation following visual stimulation. Overall, this work pushes the limit of the technology that makes use of diffuse light to minimally invasively, continuously, and reliably monitor endogenous markers of pathological and physiological processes in the human body.La medición no invasiva y, a menudo, continua de la hemodinámica del cuerpo, y para los propósitos principales de esta tesis, del cerebro, es conveniente porque tanto los valores instantáneos como sus variaciones en el tiempo se adaptan constantemente a las condiciones que afectan el cuerpo humano y su entorno. Estas suelen alterarse en situaciones patológicas o como respuesta a una mayor función. Es deseable que estas mediciones sean continuas, confiables, mínimamente invasivas y relativamente asequibles. En los últimos años, las técnicas ópticas que, mediante el uso de luz difusa para medir los tejidos en profundidad (hasta unos pocos centímetros) mediante niveles de intensidad que son seguros para la piel, combinan las características arriba mencionadas, se han utilizado cada vez más tanto en entornos clínicos como de investigación. Sin embargo, al día de hoy hay, por un lado, la necesidad de ampliar el número y el ámbito de los estudios translacionales y, por el otro, de suplir a las deficiencias como por ejemplo la contaminación de volúmenes de tejido no deseados (efectos de volumen parcial). Otro objetivo importante es aumentar la profundidad de penetración de la luz sin afectar la naturaleza no invasiva de la óptica difusa. Mi doctorado está destinado a mejorar varios aspectos de este problema; (i) el desarrollo de nuevos métodos más avanzados, es decir, el método resuelto en el tiempo/trayectoria de los fotones, para mejorar la diferenciación entre los tejidos superficiales y profundos, (ii) la exploración de nuevas áreas de aplicación, es decir, para caracterizar el estado microvascular de los huesos, para estudiar la respuesta funcional del cerebro en los niños, y (iii) para mejorar el control de calidad de los sistemas, es decir, mediante la introducción de un phantom dinámico de larga vida útil. En orden conceptual, primero voy a introducir estándares de referencia de larga vida útil para la espectroscopia de correlación difusa (DCS). En segundo lugar, voy a describir el uso de un sistema híbrido espectroscopia tiempo-resuelta (TRS) con DCS ya existente para monitorizar los cambios que algunas condiciones patológicas, en este caso la osteoporosis y la infección por el virus de la inmunodeficiencia humana, pueden comportar para muchos aspectos del tejido óseo humano que actualmente no se pueden medir con facilidad (es decir, se van evaluado de forma invasiva) mediante técnicas convencionales. En tercer lugar, voy a describir el desarrollo de una novedosa técnica óptica en el dominio temporal que combina íntimamente, introduciendo muchos avances previamente no cumplidos, TRS y DCS. Por primera vez pude producir un dispositivo y un protocolo tiempo-resueltos para medir el flujo de la sangre en la cabeza y en los músculos de seres humanos sanos. Por último, en esta tesis voy a describir un dispositivo y un método que he usado para monitorear los cambios en el flujo sanguíneo como marcadores de activación del cerebro debida a estímulos visivos en bebés entre tres y cinco meses de edad. En general, este trabajo amplia los limites de la tecnología que hace uso de la luz difusa para monitorizar, de forma mínimamente invasiva, continua y confiable los marcadores endógenos de procesos patológicos y fisiológicos en el cuerpo humano.Postprint (published version

Some applications of holographic interferometry and Speckle correlation techniques to the study of plant growth and physiology

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Strain Mapping in Teeth with Variable Remaining Tooth Structure

Problem: The effect of remaining tooth structure on strain in compromised teeth is not fully understood. Different remaining tooth quantities may affect stress and strain concentration within the remaining structure and potentially the longevity of the related restoration. Objectives: The aim of this project was to map and evaluate tooth strain levels at different stages and areas of structural tooth loss created by dental preparation (simulating caries created lesions) or soft drink demineralisation (simulating external acid erosion lesions), before and after restoration, and to evaluate and compare different strain measurement techniques: strain gauges (SG), the surface displacement field measured using digital image correlation (DIC), electronic speckle pattern interferometry (ESPI), and finite element analysis (FEA). In addition, testing teeth affected by erosion required testing and verifying different acid demineralisation protocols. Material and methods: Part I: Enamel samples (sound, polished) were subjected to extended 25 hours (hr) soft drink immersion protocols (accelerated, prolonged) with different salivary protection conditions (no saliva, artificial saliva, and natural saliva) to compare enamel surface loss. Moreover, enamel surface loss of extended erosion periods simulating different levels of clinical erosion lesions was calculated by different imaging methodologies. Microscopic analysis was performed to compare subsurface changes of early and extended erosion protocols. Part II: Strain under static loading was compared in teeth with different stages of unrestored occlusal and buccal accelerated soft drink demineralisation lesions and after restoration using different techniques (strain gauges, electronic speckle pattern interferometry, and finite element analysis). Part III: Strain under static loading was compared in prepared teeth with different remaining tooth dimensions and different restorations using strain gauges and digital image correlation techniques. Results: Part I: No statistical significance was detected in enamel thickness loss between sound and polished enamel samples in the accelerated erosion groups under all salivary conditions or between early and extended erosion groups tested. Part II: All testing methodologies measured an increased strain reading after 1 day in occlusal erosion group followed by gradual decrease, while, continuous increase in strain was observed with buccal erosion progression. For both groups, all restorative materials used were able to restore strain close to pre-treatment level. However, strain distribution pattern was more favourable in ceramic and gold occlusal onlays than composite onlays. Part III: for both strain gauges and digital image correlation, remaining tooth height ≥ 3 mm and width of 1 to 1.5 mm of the remaining tooth structure had a positive effect on strain. Tooth compositions of enamel and dentine resisted strain better than dentine counterparts at all dimensions. Both core restorations (with and without cuspal coverage) were found to support the remaining tooth structure and reduce strain. However, only cuspal coverage recorded significantly lower strain than their unrestored counterparts. Conclusion: Restorations bonded to advanced erosion induced lesions restored strain levels to pre-treatment condition and produced a more favourable strain distribution pattern highlighting the role of adhesion in reducing strain. Remaining tooth structure suffers less strain under loading when enamel is part of the structure and when the minimum dimension of 3 mm in height and 1.5 mm in width is preserved. Bonding of core restoration or cusp coverage aids in reducing strain under loading. All strain measuring methodologies were comparable, where similar strain behaviour was recorded. Remineralisation of enamel and dentine is effective in the management of initial erosion

Non Contact Heart Monitoring

Electrocardiograms are one of the most widely used methods for evaluating the structure-function relationships of the heart in health and disease. This book is the first of two volumes which reviews recent advancements in electrocardiography. This volume lays the groundwork for understanding the technical aspects of these advancements. The five sections of this volume, Cardiac Anatomy, ECG Technique, ECG Features, Heart Rate Variability and ECG Data Management, provide comprehensive reviews of advancements in the technical and analytical methods for interpreting and evaluating electrocardiograms. This volume is complemented with anatomical diagrams, electrocardiogram recordings, flow diagrams and algorithms which demonstrate the most modern principles of electrocardiography. The chapters which form this volume describe how the technical impediments inherent to instrument-patient interfacing, recording and interpreting variations in electrocardiogram time intervals and morphologies, as well as electrocardiogram data sharing have been effectively overcome. The advent of novel detection, filtering and testing devices are described. Foremost, among these devices are innovative algorithms for automating the evaluation of electrocardiograms. Permanenet links: Full chapter: http://www.intechopen.com/articles/show/title/non-contact-heart-monitoring Book: http://www.intechopen.com/books/show/title/advances-in-electrocardiograms-methods-and-analysi

A modeling-based assessment of acousto-optic sensing for monitoring high-intensity focused ultrasound lesion formation

Real-time acousto-optic (AO) sensing - a dual-wave modality that combines ultrasound with diffuse light to probe the optical properties of turbid media - has been demonstrated to non-invasively detect changes in ex vivo tissue optical properties during high-intensity focused ultrasound (HIFU) exposure. The AO signal indicates the onset of lesion formation and predicts resulting lesion volumes. Although proof-of-concept experiments have been successful, many of the underlying parameters and mechanisms affecting thermally induced optical property changes and the AO detectability of HIFU lesion formation are not well understood. In thesis, a numerical simulation was developed to model the AO sensing process and capture the relevant acoustic, thermal, and optical transport processes. The simulation required data that described how optical properties changed with heating. Experiments were carried out where excised chicken breast was exposed to thermal bath heating and changes in the optical absorption and scattering spectra (500 nm - 1100 nm) were measured using a scanning spectrophotometer and an integrating sphere assembly. Results showed that the standard thermal dose model currently used for guiding HIFU treatments needs to be adjusted to describe thermally induced optical property changes. To model the entire AO process, coupled models were used for ultrasound propagation, tissue heating, and diffusive light transport. The angular spectrum method was used to model the acoustic field from the HIFU source. Spatial-temporal temperature elevations induced by the absorption of ultrasound were modeled using a finite-difference time-domain solution to the Pennes bioheat equation. The thermal dose model was then used to determine optical properties based on the temperature history. The diffuse optical field in the tissue was then calculated using a GPU-accelerated Monte Carlo algorithm, which accounted for light-sound interactions and AO signal detection. The simulation was used to determine the optimal design for an AO guided HIFU system by evaluating the robustness of the systems signal to changes in tissue thickness, lesion optical contrast, and lesion location. It was determined that AO sensing is a clinically viable technique for guiding the ablation of large volumes and that real-time sensing may be feasible in the breast and prostate