published_or_final_version / Medicine / Master / Doctor of Medicine

This dissertation investigates the application of the frequency-scanned beam of a microstrip leaky wave antenna (LWA) to track humans in the two-dimensional (2-D) range-azimuth plane. The history, operating principles and frequency-scanned properties of a microstrip LWA are first reviewed. The basic concept of using a microstrip LWA to track humans is verified by designing, building and testing a broadband microstrip LWA, developing the necessary processing algorithm, and collecting data using a vector network analyzer. A number of topics are then investigated to further advance the concept. First, the idea of combining the frequency-scanned antenna with a short-pulse ultra-wideband (UWB) radar is developed to realize a portable, real-time system for human tracking. The radar concept and the components of the system are discussed in detail. Line-of-sight and through-wall measurements of a human subject are carried out to demonstrate the performance. Second, a new LWA structure is proposed to achieve a narrower azimuth beam, which requires both a small leaky-wave attenuation constant and a long aperture. The transverse resonance method (TRM) is applied to analyze the proposed structure and the results are verified with measurements of a built prototype. Third, a new signal processing technique, compressive sensing, is applied to further improve the resolution in both the azimuth and down range dimensions. The technique is tested with simulation and measurement data and is shown to produce sharper target responses in both the down range and azimuth dimensions. Lastly, the radar cross-section (RCS) of a microstrip LWA is studied. The antenna mode scattering and structural mode scattering are modeled separately. A ray picture is provided to explain the observed time-domain features using the group delay of the leaky wave. / text

To date, elastographic imaging techniques such as magnetic resonance elastography (MRE) have primarily been considered isotropic material properties, despite the fact that most biological tissues tend to have some anisotropic qualities. In this thesis, a finite-element based orthotropic, incompressible material model is used as the basis for the in vitro MRE gelatin phantom. This study includes the use of biologically based orthotropic gelatin phantoms, with MRI data acquisition and boundary conditions suitable to describe the orthotropic material behavior. Fabricating a biological gelatin phantom using pineapple for MRE in vitro testing is a novel technique which was developed specially for this study. Multiple motion measurements from the pineapple gelatin phantom were made by applying directionally independent boundary conditions within the 85-125 Hz frequency range. Such multiple, orthogonal excitation data is needed to provide a complete description of the mechanical properties of this anisotropic phantom, given the potential for non-uniqueness of the reconstructed property estimates. Orthotropic image reconstructions were then carried out to map orthotropic elasticity properties in 3-D based on MR detected motion datasets captured from the pineapple gelatin phantom. The subzone based orthotropic incompressible reconstruction algorithm was based on the Conjugate Gradient optimization method, to gain computational efficiency, and used total volitional (TV) regularization techniques to constraint the solution process. The adjoint-residual method was utilized to improve the efficiency of the gradient descent based algorithm. The elasticity image reconstruction results presented for the orthotropic incompressible phantom are also correlated with isotropic property reconstructions for the same phantom.

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The adaptation of a general purpose laboratory minicomputer for nuclear medicine imaging is described. Electronic interfaces have been designed and constructed to link nucleonic equipment to a PDP 12 computer. A computer television display system has been developed to facilitate interactive processing of scintigraphic data. The main features of the television system are that it is relatively inexpensive and reliable. A domestic quality receiver has been adapted for use as a colour monitor. Any instrument that records data will produce a distorted or degraded version of the input signal. Generally, imaging equipment will produce a blurred image of the object, and in the case of scintigraphic imaging the blurs may be comparable to the size of the physiological structures being investigated. The process of refocussing the recorded data is called, in mathematical terms, deconvolution. In this study Fourier transform techniques have been developed as methods of implementing deconvolution. It is shown that the restoration of images in the presence of noise is likely to be a mathematically unstable process. Four methods of accommodating the problems associated with noise are described. Each method has built in optimisation of one form or another so that mathematically stable algorithms are used to implement deconvolution. This means that all the parameters used by the computer programs are determined automatically so that the computer operator is not required to select any parameters manually. A brief description of two dimensional digital filtering is given to enable comparison between filtering and deconvolution of scintigrams. A two dimensional lowpass filter is developed which automatically defines the passband frequency response appropriate to a particular scintigram. Finally, all the signal processing methods are tested on both simulated and clinical data. Results show that deconvolution offers advantages over digital filtering particularly for scintigrams obtained from morphic structures. Some of the problems of deconvolving certain types of scintigram are discussed.

This thesis presents an investigation into the application of electrodynamic sensors to a tornographic imaging system. Several sensing mechanisms for measurement using non-intrusive techniques are discussed and their relevance to pneumatic conveying considered. Electrical charge tomography systems are shown to be worthy of investigation. Electrodynamic sensors are inherently low cost and simple in concept. This sensor is used to detect the inherent charge on dry, moving solids. Models are developed to predict the sensitivity of circular and rectangular electrodes. The spatial filtering effect of these sensors is investigated. Cross correlation is briefly reviewed and a software program is presented and tested. For tomographic imaging the forward problem for the individual sensors is modelled, used to solve the inverse problem and derive the linear back projection and filtered back projection algorithms. The design of the electronic circuitry which forms the transducer is presented. The gravity drop flow rig is described and the relationship between sand flow and plastic bead flow relative to the flow indicator setting determined. The dual 16-channel sensor array measurement section is described. Flow models are developed and used to predict the relative output voltage profiles expected from the sensor arrays. The linearity and frequency bandwidth of the sensor electronics is measured. The effect of sensor size on sensitivity and spatial filtering are investigated for circular and rectangular electrodes. Estimates of the solid concentration of flowing particles are made using individual sensors. Concentration profiles are generated and compared with predicted values. Peripheral velocities of the flowing material are determined from transit times calculated by cross correlation of upstream and downstream sensor signals. Concentration profiles are calculated using linear back projection and filtered back projection algorithms from data measured by the sensor arrays. Velocity profiles are obtained by cross correlation of upstream and downstream pixel concentration values. Estimates of the mass flow rate are obtained by combining concentration and velocity profiles. Suggestions for further work on electrodynamic sensors and tomographic measurements are made.

The research for this dissertation project began with the goal to construct a snapshot imaging spectropolarimeter forthe visible spectrum. The instrument integrates a channeled spectropolarimeter (CHSP) into a computed tomographicimaging spectrometer (CTIS), the result being an instrument that measures the complete spatially- andspectrally-resolved Stokes vectors of a scene. It is not the first of its kind, since a similar instrument has beenbuilt before for use in the short-wave infrared. However, that instrument encountered severe difficulties due tolimitations of available hardware. Visible spectrum work generally enjoys the best instrumentation available, providingan ideal place to attempt a proof-of-concept demonstration.The main body of the research is focused on finding ways to improve the CTIS measurement technique, especially in waysallowing it to integrate with channeled spectropolarimetry. The first effort is a careful analysis and reworking of thecalibration procedure for the instrument, followed by a survey and comparison of ideas for alternative CTIS designs.The second effort makes use of the new calibration approach to develop an alternative way of thinking about CTISreconstructions based on the geometry and physics of the instrument rather than on abstract matrix mathematics. Thisopens up ways to improve their accuracy and to achieve reconstructions at a much higher speed.Experimental results from the instrument illustrate the improvements obtained from using the new methods, showing itscurrent capabilities and limitations.