This thesis is focussed on extending the use of phased array radiofrequency (RF) coils for use in magnetic resonance imaging (MRI). Phased arrays are very useful as receiver coils and have been used over the last 15 years or so to improve receiver coil coverage and to speed up image acquisition. These arrays have almost invariably been constructed and used at mid- to highfrequency (&lt128 MHz), thus there is clearly an opportunity to increase the operating frequency of the phased array and also use these systems in transceive mode. Using phased array coils in transceive mode has the advantage of gaining better spatial specificity of excited regions. Also as the operating wavelength in high field strength is shortened by the dielectric properties of the patient and approaches the size of conventional transmitter coils, there are distinct advantages in using the smaller coils in the phased array system for transmission. In addition, with the ability to independently control the magnitudes and phases of the transmission power on each element of a transceiver phased array system, RF focussing or shimming can be performed during RF transmission. The research work presented in this thesis is therefore, primarily focussed on designing and analysing high frequency phased array coils for MRI applications with transceive and RF focussing capability and investigating the possibility of using focussing transceive phased array coils to ameliorate image distortions that appear in high field MR images. The second major area of work concerns evaluation of the performance of partial parallel imaging when used at high field strength and the compatibility with transceive phased array systems. Common to both areas are investigation into other approaches for the design of high field RF coils, exploring the possibility of new mutual decoupling techniques and the consideration of other numerical computational methods that can assist in designing future high frequency phased array coils and help evaluate the complex field-tissue interactions at high field strength.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The Electrocardiograph (EKG or ECG) measures electrical changes of tissue surrounding the heart to create a time-based representation of the physical operation of the heart. The purpose of this paper is to explore the future of ECG telemetry systems and how they are used in health care. The initial goal is to develop an inexpensive, efficient, and robust real-time ECG telemetry system. The future goal is to create a wireless network of miniature body sensors capable of measuring ECG data and other vital signs.

A fundus camera a complex optical system that makes use of the principle of reflex free indirect ophthalmoscopy to image the retina. Despite being in existence as early as 1900's, little has changed in the design of a fundus camera and there is minimal information about the design principles utilized. Parameters and specifications involved in the design of fundus camera are determined and their affect on system performance are discussed. Fundus cameras incorporating different design methods are modeled and a performance evaluation based on design parameters is used to determine the effectiveness of each design strategy. By determining the design principles involved in the fundus camera, new cameras can be designed to include specific imaging modalities such as optical coherence tomography, imaging spectroscopy and imaging polarimetry to gather additional information about properties and structure of the retina. Design principles utilized to incorporate such modalities into fundus camera systems are discussed. Design, implementation and testing of a snapshot polarimeter fundus camera are demonstrated.

<p>Optical coherence tomography (OCT) is a non-invasive imaging modality that uses low coherence interferometry to generate three-dimensional datasets of a sample's structure. OCT has found tremendous clinical applications in imaging the retina and has demonstrated great utility in the diagnosis of various retinal diseases. However, such diagnoses rely upon the ability to observe abnormalities in the structure of the retina caused by pathology. By the time an ocular disease has progressed to the point of affecting the morphology of the retina, irreversible vision loss in the eye may already occur. Changes in the functionality of the tissue often precede changes to the structure. Thus, if imaging methods are developed to provide additional functional information about the behavior and response of the retinal tissue and vasculature, earlier treatment for disease may be prescribed, thus preserving vision for the patient. </p><p>Within the last decade, significant technological advances in OCT systems have enabled high-speed and high sensitivity image acquisition using either spectral domain OCT (SDOCT) or swept-source OCT (SSOCT) configurations. Such systems use Fourier processing to extract structural information of a sample from interferometric principles. But such systems also have access to the optical phase information, which allows for functional analysis of sample dynamics. This dissertation details the development and application of methods using both intensity and phase information as a tool for studying interesting biological phenomena. The goal of this work is an extension of techniques to image the vasculature in the retina and enhance the clinical utility of OCT.</p><p>I first outline basic theory necessary for understanding the principles of OCT. I then describe OCT phase imaging in cellular applications as a demonstration of the ability of OCT to provide functional information on biological dynamics. Phase imaging methods suffer from an artifact known as phase wrapping, and I have developed a software technique to overcome this problem in OCT, thus extending its usefulness in providing quantitative information. I characterize the limitations in measuring moving scatterers with Doppler OCT in both SDOCT and SSOCT system. I also show the ability to image the vasculature in the retina using variance imaging with a high-speed retinal imaging system and software based methods to correct for patient motion and create a widefield mosaic in an automated manner. Finally, future directions for this work are discussed.</p> / Dissertation

A prototype sensor array was developed for use with laboratory automation to permit closed-loop control of liquid-levels in a multiwell microplate geometry. A simple electrical model for non-contact capacitance-based fluid sensors was extended to describe a fluid-level dependency. The new model shows that a charge-transfer based capacitance transducer employing a liquid-specific calibration can be used to obtain an output signal that varies linearly with the liquid-level when fringe-field effects are negligible. The calibration also compensates for liquid-to-liquid conductivity and permittivity differences. / The sensor was tested using sodium chloride (NaCl) and ethanol solutions to simulate the range of conductivity and permittivity typical in biological and chemical research. Measured capacitance was a second-order function of liquid volume due to fringe-field effects and was compensated for by adding a hardware-based calibration. Liquid-volume measurement error averaged 0.2% of the 120mul fill volume with a standard deviation of 0.6% (&lt; mul). The maximum absolute error for all liquids was 2.7% (3mul).

No description available.

A Pressão intracraniana (PIC) é um dos principais parâmetros fisiológicos em animais e humanos e sua morfologia é extremamente importante. Entretanto, todos os métodos de monitoramento existentes no mercado são invasivos, existindo uma ampla demanda por sistemas não invasivos, expandindo assim o campo de pesquisas acerca desse importante parâmetro neurológico, que só não é melhor estudado devido a forma invasiva de ser monitorado. A motivação é fazer com que o monitoramento da PIC seja tão comum e tão essencial quanto é hoje o monitoramento da pressão arterial, facilitando o diagnóstico e até prognóstico de diversas doenças. Este trabalho analisa e implementa melhorias de um sistema não invasivo de monitoramento da pressão intracraniana, baseado em extensometria. Um dos objetivos, no que tange o desenvolvimento do produto, é analisar o equipamento como um todo - Sensor, Hardware, Firmware e Software - e propor melhorias a partir dos testes realizados. Os testes realizados In vivo mostraram uma boa correlação do sinal com um sistema Gold Stardard, evidenciando o potencial promissor do método. / The intracranial pressure (ICP) is one of the main physiological parameters in animals and humans and its morphology is extremely important. However, all monitoring methods available in the market are invasive and there is a large demand for non-invasive systems, thus expanding the scope of research on this important neurological parameter, that just is not further studied because of the invasive method of monitoring. The motivation is to make monitoring the ICP as common and as essential, as monitoring the blood pressure is nowadays, facilitating diagnosis and even prognosis of various diseases. This work analyzes and implements improvements in a non-invasive intracranial pressure monitoring system based on extensometer. One of the goals, regarding product development, is to analyze the unit as a whole- Sensor, Hardware, Firmware and Software- and propose improvements from the tests. The in vivo tests showed a good correlation with a Gold Stardard system signal showing the promising potential of the method.

A pressão intracraniana (PIC) é um dos principais parâmetros neurológicos em animais e humanos. A PIC é uma função da relação entre o conteúdo da caixa craniana (parênquima cerebral, líquido cefalorraquiano e sangue) e o volume do crânio. O aumento da PIC (hipertensão intracraniana) pode acarretar graves efeitos fisiológicos ou até mesmo o óbito em pacientes que não receberem rapidamente os devidos cuidados, os quais incluem o monitoramento em tempo real da PIC. Todos os métodos de monitoramento da PIC atualmente utilizados são invasivos, ou seja, é necessário introduzir um sensor de pressão no sistema nervoso central, acarretando aos pacientes riscos de infecções e traumas decorrentes do método. Neste trabalho desenvolvemos um método minimamente invasivo de monitoramento da pressão intracraniana, que consiste na utilização de sensores de deformação do tipo strain gauge fixados sobre a calota craniana. Os sinais oriundos deste sensor foram amplificados, filtrados e enviados para um computador com software apropriado para análise e armazenamento dos dados. O trabalho aqui apresentado objetivou os testes &quot;in vivo&quot; do sistema, onde foi utilizada mais de uma centena de animais em diversos testes, sendo que em todos os casos os resultados foram satisfatórios, apontando a eficácia do método. / The intracranial pressure (ICP) is one of the most important neurological parameter in animals and humans. The ICP is a function of the relation between the contents of the skull (brain parenchyma, cerebrospinal fluid and blood) and the volume of the skull. The increase in ICP (intracranial hypertension) may cause serious physiological effects and death in patients that do not receive appropriate care quickly, which includes real-time monitoring of ICP. All monitoring methods currently used in ICP are invasive, ie requiring invasion of the central nervous system by a pressure sensor, causing infections and traumas risks to patients. In this work we present a new minimally invasive method to monitor the intracranial pressure. This uses strain gauge deformation sensors, externally glued on the skull. The signal from this sensor is amplified, filtered and sent to a computer with appropriate software for analysis and data storage. &quot;In vitro&quot; and &quot;in vivo&quot; experiments let to the following results: (1) Our minimally invasive system is capable of adequately monitoring the ICP. (2) The measurements are in real and online time providing excellent signal and stability. (3) Simultaneous comparison with invasive methods not only validated our results but showed increased performance. The equipment cost effective will allow the use of our system in the Public Health System, with a important social aspect of our contribution.

A Pressão intracraniana (PIC) é um dos principais parâmetros fisiológicos em animais e humanos e sua morfologia é extremamente importante. Entretanto, todos os métodos de monitoramento existentes no mercado são invasivos, existindo uma ampla demanda por sistemas não invasivos, expandindo assim o campo de pesquisas acerca desse importante parâmetro neurológico, que só não é melhor estudado devido a forma invasiva de ser monitorado. A motivação é fazer com que o monitoramento da PIC seja tão comum e tão essencial quanto é hoje o monitoramento da pressão arterial, facilitando o diagnóstico e até prognóstico de diversas doenças. Este trabalho analisa e implementa melhorias de um sistema não invasivo de monitoramento da pressão intracraniana, baseado em extensometria. Um dos objetivos, no que tange o desenvolvimento do produto, é analisar o equipamento como um todo - Sensor, Hardware, Firmware e Software - e propor melhorias a partir dos testes realizados. Os testes realizados In vivo mostraram uma boa correlação do sinal com um sistema Gold Stardard, evidenciando o potencial promissor do método. / The intracranial pressure (ICP) is one of the main physiological parameters in animals and humans and its morphology is extremely important. However, all monitoring methods available in the market are invasive and there is a large demand for non-invasive systems, thus expanding the scope of research on this important neurological parameter, that just is not further studied because of the invasive method of monitoring. The motivation is to make monitoring the ICP as common and as essential, as monitoring the blood pressure is nowadays, facilitating diagnosis and even prognosis of various diseases. This work analyzes and implements improvements in a non-invasive intracranial pressure monitoring system based on extensometer. One of the goals, regarding product development, is to analyze the unit as a whole- Sensor, Hardware, Firmware and Software- and propose improvements from the tests. The in vivo tests showed a good correlation with a Gold Stardard system signal showing the promising potential of the method.

Iontophoresis is a method to enhance and regulate the transdermal drug delivery by application of an electric field to the skin. Application of small electric current (µ A) enhances transport of both charged and neutral molecules across the skin. Reverse of this process enables extraction of analytes across the skin for noninvasive sensing and diagnosis. Hence it is planned to conduct detailed studies on Reverse Iontophoresis. An invitro model is developed to study the extraction of glucose across the skin. Effects of magnitude of electric current, time of application, pH etc. on the extraction of glucose are studied. It is observed that extraction of glucose at the cathode is higher than at the anode. Advantage of invitro model is the possibility of varying parameters to an extent which is impossible invivo. Instrumentation suitable for continuous monitoring of reverse iontophoresis invivo in human subjects is developed. It supplies the required current and acquires the potential profile of the skin during reverse iontophoresis. Potential profiles showed that skin resistance decreases with the application of current. Experimental results revealed that the application of pulsed DC tends to make the reverse iontophoresis more effective by enhancing the flow of analytes which is proved by the fact that skin resistance decreases and stabilizes faster in comparison to the one with direct current reverse iontophoresis. Present work emphasizes the importance of selecting an appropriate duty cycle and frequency for reverse iontophoresis. Duty cycle around 95% and frequency of 250 mHz are good for low frequency reverse iontophoresis. Effect of reverse iontophoresis on the skin recovery is observed by monitoring the potential profiles at the end of the process. In all the reverse iontophoresis experiments, safety of the patient is ensured by fixing a compliance voltage level. Finally, Instrumentation to measure the capacitance of biosensors is developed based on frequency domain technique with a sinusoidal input. Accuracy in capacitance measurements is ±5%. Glucose measurement is demonstrated with the developed instrument using a capacitance type biosensor. The obtained results are in good agreement with the standard UV-Visible spectroscopic measurements based on phenol-sulphuric acid assay method.