Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 25 for “"contrast to noise ratio"”.
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Assessment of New Innovations In Pet/Ct For Respiratory Motion Correction
<p>In oncological imaging, Positron Emission Tomography/Computed Tomography (PET/CT) is a vital tool used for stating and treatment response assessment of patients due to its ability to visualize and accurately quantify the bio-distribution of radiolabeled pharmaceuticals. However, due to the long …
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Backscatter Spatial Coherence for Ultrasonic Image Quality Characterization: Theory and Applications
<p>Adaptive ultrasound systems, designed to automatically and dynamically tune imaging parameters based on image quality feedback, represent a promising solution for reducing the user-dependence of ultrasound. The efficacy of such systems, however, depends on the ability to accurately and reliably …
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Improved Techniques For Acquisition and Analysis of Dynamic Contrast-Enhanced Magnetic Resonance Imaging For Detecting Vascular Permeability In The Central Nervous System
<p>Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a noninvasive technique for quantitative assessment of the integrity of blood-brain barrier and blood-spinal cord barrier (BSCB) in the presence of central nervous system pathologies. However, the results of DCE-MRI show …
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Detection of improvised explosive devices at long-range using coded aperture imaging of backscattered X-rays with dynamic reconstruction
… above a few meters and with a source-detector system moving in relation to the target. The aim of this study is to determine the feasibility of a large-area, Coded-Aperture Imaging (CAI) system using X-Ray backscatter as the source of radiation. A moving source-detector system required …
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Development and Optimisation of Radial Techniques for Sodium Magnetic Resonance Imaging
The goal of this work was to provide techniques and hardware for 23Na MRI of the human brain, heart and muscle in a clinical scanner at 1.5T. For this purpose, radiofrequency (RF) coils were developed and a transmit/receive switch was adapted to 16.84 MHz. A 3D radial gradient echo (GRE) sequence …
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FMRI In Patients With Implanted Electrodes: Mitigating Imaging Artifacts
This thesis explores the integration of intracranial EEG (icEEG) with functional MRI (fMRI) in epilepsy patients with implanted electrodes, aiming to mitigate susceptibility artifacts in the resulting fMRI images and thus enhance diagnostic accuracy. Epilepsy is a complex disorder requiring precise …
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On the dynamics of magnetic fluids in magnetic resonance imaging
… past twenty years that these fluids have begun to be used in magnetic resonance imaging (MRI) where they have found application as contrast agents, improving the contrast to noise ratio of the received MR intensity. The major goal of this work was to assess the feasibility of modulating the …
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Novel Chemically Selective Rapid Magnetic Resonance Imaging Techniques and the Clinical Applications
… chemically selective imaging methods for the generation of high quality fat-only or water-only images in short scan durations. High quality fat imaging is mainly used for human fat distribution measurements. The study of fat distribution is important for both clinical diagnosis and basic research. …
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Task-specific observer performance and image quality : direct and indirect relationships in low-dose CT images
Aim: The aim of this research was to examine image quality in low-dose CT images, as determined by a range of image quality measures (IQM), in addition to psychophysical assessment, and look at direct or indirect relationships. Method: CT images of an anthropomorphic chest phantom were obtained …
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Null subtraction imaging technique for biomedical ultrasound imaging
… results in an improved image with less distortion and fewer artifacts. In general, apodization is used to lower sidelobes in exchange for increasing the width of the mainlobe and thus decreasing lateral resolution. Null subtraction imaging (NSI) is a nonlinear image processing technique …
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Spatial Coherence-Based Adaptive Acoustic Output Selection for Diagnostic Ultrasound
<p>The US Food and Drug Administration (FDA) provides guidelines for maximum acoustic output for diagnostic ultrasound imaging through metrics such as intensity, Mechanical Index (MI), and Thermal Index (TI). However, even within these guideline values, if the acoustic exposure levels used do not …
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Quantifying Neuromelanin Content Across Varying Magnetic Field Strengths: A Comparative Analysis
… in the substantia nigra of the human brain. Due to its paramagnetic nature, NM can be imaged using MRI in the form of neuromelanin sensitive contrast. This method, known as Neuromelanin Sensitive Magnetic Resonance Imaging (NM-MRI) allows non-invasive imaging of the human substantia nigra through …
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Improvements In Four-Dimensional and Dual Energy Computed to mography
<p>Dual energy and 4D computed tomography (CT) seek to address some of the limitations in traditional CT imaging. Dual energy CT, among other purposes, allows for the quantification and improved visualization of contrast materials, and 4D CT is often used in radiation therapy applications as it …
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AP pelvis x-ray imaging on a trolley: the impact of trolley design, mattress design and radiographer practices on image quality and radiation dose
… exist between imaging a patient on an x-ray tabletop and imaging a patient on a trolley. The aim of this thesis was to evaluate the impact of trolley design, mattress design and radiographer practice on image quality and radiation dose for AP pelvis imaging on a trolley in order to optimise this …
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Design study of a two-panel head-and-neck cancer dedicated position emission tomography system
… mucosal surfaces inside the head and neck. Due to the complex anatomy and vital physiological role of the tumor-involved regions, the goal of HNC treatment is not only to improve survival outcomes but also to preserve organ function. Whole-body (WB) positron emission tomography (PET) has been …
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Image Quality Optimisation and Dose Management in CT, SPECT/CT, and PET/CT
… in life. The overall objective of this work was to evaluate and optimise different approaches for minimising patient radiation absorbed dose and maintaining or improving image quality in CT, SPECT/CT, and PET/CT. One way to achieve optimisation is to use automatic exposure control (AEC) systems …
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Dynamic state-space estimation of the hemodynamic response with Near-Infrared Spectroscopy
… been the use of signals from small source-detector separation (1 cm) optodes as regressors. Since those additional measurements are mainly sensitive to superficial layers in adult humans, they help in removing the systemic interference present in longer separation measurements (3 cm). Encouraged …
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Digital radiography: image acquisition and scattering reduction in x-ray imaging.
… X-ray imaging devices have evolved and adapted to the needs of individual applications, leading to the appearance of digital image capture devices. Digital technologies introduced the possibility of separating the image acquisition and image processing steps, allowing their individual …
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Dual energy image reconstruction and systems for application in proton therapy treatment planning
Proton therapy is the use of a proton beam rather than a traditional X-ray beam in the treatment of cancer. This technique is being developed all over the world due to the unique Bragg peak feature of proton beams. In order to guarantee accurate dose delivery to the tumour, the stopping power ratio …
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Development of High-speed Photoacoustic Imaging technology and Its Applications in Biomedical Research
Photoacoustic (PA) tomography (PAT) is a novel imaging modality that combines the fine lateral resolution from optical imaging and the deep penetration from ultrasonic imaging, and provides rich optical-absorption–based images. PAT has been widely used in extracting structural and functional …
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