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Medical Biophysics Commons

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Applications Of Ct Perfusion-Based Triaging And Prognostication In Acute Ischemic Stroke, Eric A. Wright 2018 The University of Western Ontario

Applications Of Ct Perfusion-Based Triaging And Prognostication In Acute Ischemic Stroke, Eric A. Wright

Electronic Thesis and Dissertation Repository

CT Perfusion (CTP) is a minimally invasive imaging technique that aids acute ischemic stroke (AIS) triage and prognostication by determining tissue viability based on hemodynamic parameters. The goals of this research are to determine: 1) CTP thresholds for estimation of infarct and penumbra volume, 2) how CTP scan duration impacts infarct and penumbra volume estimates, and 3) reliability of CTP for predicting functional outcomes following intra-arterial therapy (IAT).

Chapter 2 introduced an experimental study for determining ischemia-time dependent thresholds for brain infarction using multimodal imaging in a porcine stroke model that is easier to implement than previous large animal stroke ...


Multi-Scale Peripheral Vasculopathy With Metabolic Syndrome, Kent Lemaster 2018 The University of Western Ontario

Multi-Scale Peripheral Vasculopathy With Metabolic Syndrome, Kent Lemaster

Electronic Thesis and Dissertation Repository

The combination of cardiovascular and metabolic risk factors including obesity, dyslipidemia, hypertension, and insulin resistance, in combination with a prothrombotic and proinflammatory state, is a condition termed Metabolic Syndrome (METS). Twenty percent of the adult population is afflicted with METS which increases the risk of type-2 diabetes mellitus and cardiovascular disease. Further, the presence of peripheral vascular disease (PVD) is tightly coupled with METS which is a perfusion-demand mismatch of blood supply to active skeletal muscle resulting in painful claudication and a late-stage potential for amputation. The underlying contributors of METS associated micro-vasculopathies in the skeletal muscle, their impact on ...


Quantitative Analysis Of Three-Dimensional Cone-Beam Computed Tomography Using Image Quality Phantoms, Rudy Baronette 2018 The University of Western Ontario

Quantitative Analysis Of Three-Dimensional Cone-Beam Computed Tomography Using Image Quality Phantoms, Rudy Baronette

Electronic Thesis and Dissertation Repository

In the clinical setting, weight-bearing static 2D radiographic imaging and supine 3D radiographic imaging modalities are used to evaluate radiographic changes such as, joint space narrowing, subchondral sclerosis, and osteophyte formation. These respective imaging modalities cannot distinguish between tissues with similar densities (2D imaging), and do not accurately represent functional joint loading (supine 3D imaging). Recent advances in cone-beam CT (CBCT) have allowed for scanner designs that can obtain weight-bearing 3D volumetric scans. The purpose of this thesis was to analyze, design, and implement advanced imaging techniques to quantify image quality parameters of reconstructed image volumes generated by a commercially-available ...


Validation Of A Hyperspectral Nirs Method For Measuring Tissue Oxygen Saturation, Matthew Kewin 2018 The University of Western Ontario

Validation Of A Hyperspectral Nirs Method For Measuring Tissue Oxygen Saturation, Matthew Kewin

Electronic Thesis and Dissertation Repository

Brain injury during preterm infancy can cause serious intellectual and behavioral disabilities, as such, measurements of cerebral health are needed to aid in the diagnosis and treatment of these injuries. Near infrared spectroscopy (NIRS) is considered ideal for this purpose because it is non-invasive and provides a continuous measure of tissue oxygen saturation (StO2), a key marker of cerebral health. Current commercial NIRS systems have considerable variability between devices and between infants restricting them to monitoring trends. Time-resolved (TR) NIRS is considered the gold standard in biomedical optics for quantifying tissue optical properties, but the technology is more complex ...


Effects Of Maternal Protein Restriction On The Pulmonary Surfactant System During The Early Life And Adulthood, Reza Khazaee 2018 The University of Western Ontario

Effects Of Maternal Protein Restriction On The Pulmonary Surfactant System During The Early Life And Adulthood, Reza Khazaee

Electronic Thesis and Dissertation Repository

Fetal growth restriction (FGR) is defined by low birth weight and contributes to a variety of adult-onset diseases with different severities between males and females. However, the effects of FGR on the pulmonary surfactant are not fully elucidated. In this thesis, first, we investigated the FGR effects on the lung function and the surfactant system at the early postnatal life. It was hypothesized that FGR contributes to alterations of lung mechanics and the surfactant system during the neonatal period. Second, we assessed the FGR effects on the surfactant system in response to sepsis in adulthood. It was hypothesized that FGR ...


An Integrated Approach To Analyzing Arteriolar Network Hemodynamics., Zahra Farid 2018 The University of Western Ontario

An Integrated Approach To Analyzing Arteriolar Network Hemodynamics., Zahra Farid

Electronic Thesis and Dissertation Repository

The objective of this thesis was to optimize our technique for studying blood flow in arteriolar networks by including capillary resistance and venular network geometry. We aimed to validate our technique using experimental flow measurements and Murray’s law. First, arteriolar and venular networks were reconstructed from intravital videomicroscopy (IVVM) images of the gluteus maximus muscle, and capillary resistance was estimated and distributed to each terminal arteriole (TA) segment according to its diameter. Resistance for small arterioles and venules that were likely missed in our IVVM experiments were also added to each TA segment in our reconstructed networks based on ...


Development And Validation Of A Stand-Alone Dcs System For Monitoring Absolute Cerebral Blood Flow., Mahro Khalid 2018 The University of Western Ontario

Development And Validation Of A Stand-Alone Dcs System For Monitoring Absolute Cerebral Blood Flow., Mahro Khalid

Electronic Thesis and Dissertation Repository

Premature infants are at high risk of neonatal brain injury due to poor cerebrovascular regulation, leading to periods of dangerously low cerebral blood flow (CBF) and possible injury. However, there are currently no established bedside methods of monitoring CBF to alert the intensive care staff to cerebrovascular dysfunction. Diffuse correlation spectroscopy (DCS) is an emerging noninvasive optical technique for monitoring relative CBF. I developed a stand-alone DCS method of monitoring absolute CBF by incorporating a quantitative dynamic contrast-enhanced (DCE) technique. This required modifying a DCS system to capture multi-distance data to measure the tissue optical properties and to perform DCE ...


Diffusion And Functional Mri Of The Brain Following Sports-Related Impacts And Concussion, Kathryn Y. Manning 2018 The University of Western Ontario

Diffusion And Functional Mri Of The Brain Following Sports-Related Impacts And Concussion, Kathryn Y. Manning

Electronic Thesis and Dissertation Repository

Concussion is a prevalent injury associated with contact sports, however the underlying brain changes associated with concussion remain poorly understood. Therefore it is critical to (a) understand the complex sequelae that underlie concussion, (b) when or if the brain recovers, and (c) if there are brain changes associated with contact sports in general. Advanced imaging techniques may be sensitive to changes that persist beyond relatively prompt symptom recovery and clearance to return to play.

Resting state functional MRI (RS-fMRI) and diffusion tensor imaging (DTI) data was acquired on the 3T at Robarts Research Institute from healthy and concussed athletes from ...


Toward Optimization Of Target Planning For Magnetic Resonance Image-Targeted, 3d Transrectal Ultrasound-Guided Fusion Prostate Biopsy, Peter Martin 2018 The University of Western Ontario

Toward Optimization Of Target Planning For Magnetic Resonance Image-Targeted, 3d Transrectal Ultrasound-Guided Fusion Prostate Biopsy, Peter Martin

Electronic Thesis and Dissertation Repository

The current clinical standard for diagnosis of prostate cancer (PCa) is 2D transrectal ultrasound (TRUS)-guided biopsy. However, this procedure has a false negative rate of 21-47% and therefore many patients return for repeat biopsies. A potential solution for improving upon this problem is “fusion” biopsy, where magnetic resonance imaging (MRI) is used for PCa detection and localization prior to biopsy. In this procedure, tumours are delineated on pre-procedural MRI and registered to the 3D TRUS needle guidance modality. However, fusion biopsy continues to yield false negative results and there remains a gap in knowledge regarding biopsy needle target selection ...


Equipment To Address Infrastructure And Human Resource Challenges For Radiotherapy In Low-Resource Settings, Rachel McCarroll 2018 The University of Texas M D Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences

Equipment To Address Infrastructure And Human Resource Challenges For Radiotherapy In Low-Resource Settings, Rachel Mccarroll

UT GSBS Dissertations and Theses (Open Access)

Millions of people in low- and middle- income countries (LMICs) are without access to radiation therapy and as rate of population growth in these regions increase and lifestyle factors which are indicative of cancer increase; the cancer burden will only rise. There are a multitude of reasons for lack of access but two themes among them are the lack of access to affordable and reliable teletherapy units and insufficient properly trained staff to deliver high quality care. The purpose of this work was to investigate to two proposed efforts to improve access to radiotherapy in low-resource areas; an upright radiotherapy ...


Optimization Of Decision Making In Personalized Radiation Therapy Using Deformable Image Registration, Jason Vickress 2018 The University of Western Ontario

Optimization Of Decision Making In Personalized Radiation Therapy Using Deformable Image Registration, Jason Vickress

Electronic Thesis and Dissertation Repository

Cancer has become one of the dominant diseases worldwide, especially in western countries, and radiation therapy is one of the primary treatment options for 50% of all patients diagnosed. Radiation therapy involves the radiation delivery and planning based on radiobiological models derived primarily from clinical trials. Since 2015 improvements in information technologies and data storage allowed new models to be created using the large volumes of treatment data already available and correlate the actually delivered treatment with outcomes. The goals of this thesis are to 1) construct models of patient outcomes after receiving radiation therapy using available treatment and patient ...


Methods For The Investigation Of Microvascular Control Of Oxygen Distribution, Richard Sove 2018 The University of Western Ontario

Methods For The Investigation Of Microvascular Control Of Oxygen Distribution, Richard Sove

Electronic Thesis and Dissertation Repository

The purpose of this thesis was to develop tools for studying oxygen-dependent regulation of red blood cell (RBC) flow distribution in the microcirculation. At the microvascular level, arterioles dictate the distribution of oxygen (O2) carrying RBCs to downstream capillaries, a process which needs to be tightly regulated and coupled to O2 off loading from capillaries to the tissue. To investigate potential regulatory mechanisms, an O2 exchange platform was developed to manipulate the RBC hemoglobin O2 saturation (SO2) at the muscle surface while limiting the changes in SO2 to only a single capillary network. Decreasing ...


Behavior Coding Strategies: Population Coupling And The Functional Role Of Excitatory/Inhibitory Balance In Primary Motor Cortex, Patrick Aaron Kells 2018 University of Arkansas, Fayetteville

Behavior Coding Strategies: Population Coupling And The Functional Role Of Excitatory/Inhibitory Balance In Primary Motor Cortex, Patrick Aaron Kells

Theses and Dissertations

The complexities of an organism’s experience of- and interaction with the world are emergent phenomena produced by large populations of neurons within the cerebral cortex and other brain regions. The network dynamics of these populations have been shown to be sometimes synchronous, with many neurons firing together, and sometimes asynchronous, with neurons firing more independently, leading to a decades-old debate within the neuroscience community. This discrepancy comes from viewing the system at two different scales; at the single cell level, the spiking activity of two neurons within cortex tend to be rather independent, but when the average activity of ...


Development Of 3d-Printed Patient Specific Bolus For Clinical Use In Total Scalp Irradiation, Garrett Baltz 2018 The University of Texas M D Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences

Development Of 3d-Printed Patient Specific Bolus For Clinical Use In Total Scalp Irradiation, Garrett Baltz

UT GSBS Dissertations and Theses (Open Access)

Total scalp irradiation (TSI) is a specialized radiation therapy technique that aims to deliver a uniform dose to the entire scalp. Original electron-based TSI techniques had limited homogeneity due to hot and cold spots created at field junctions due to the multiple matched fields that were required to treat the entire scalp. The transition to photon volumetric-modulated arc therapy based TSI techniques has improved homogeneity, to the point where non-conformal bolus is now a limiting factor. Bolus is required to build-up full dose to the scalp surface in total scalp irradiation. Creating bolus that is conformal to the scalp is ...


Design And Development Of A Phantom For Tomosynthesis With Potential For Automated Analysis Via The Cloud., David Goodenough, Josh Levy, Hildur Olafsdottir, Ingvi Olafsson 2018 George Washington University

Design And Development Of A Phantom For Tomosynthesis With Potential For Automated Analysis Via The Cloud., David Goodenough, Josh Levy, Hildur Olafsdottir, Ingvi Olafsson

Radiology Faculty Publications

This paper describes Development of a Phantom for Tomosynthesis with Potential for Automated Analysis via the Cloud. Several studies are underway to investigate the effectiveness of Tomosynthesis Mammographic Image Screening, including the large TMIST project as funded by the National Cancer Institute https://www.cancer.gov/about-cancer/treatment/clinical-trials/nci-supported/tmist. The development of the phantom described in this paper follows initiatives from the FDA, the AAPM TG245 task group, and European Reference Organization (EUREF) for Quality Assured Breast Screening and Diagnostic Services Committee report noting, that no formal endorsement nor recommendation for use has been sought, or granted by ...


Imaging Biomarkers Of Pulmonary Structure And Function, Dante Capaldi 2018 The University of Western Ontario

Imaging Biomarkers Of Pulmonary Structure And Function, Dante Capaldi

Electronic Thesis and Dissertation Repository

Asthma and chronic obstructive pulmonary disease (COPD) are characterized by airflow limitations resulting from airway obstruction and/or tissue destruction. The diagnosis and monitoring of these pulmonary diseases is primarily performed using spirometry, specifically the forced expiratory volume in one second (FEV1), which measures global airflow obstruction and provides no regional information of the different underlying disease pathologies. The limitations of spirometry and current therapies for lung disease patients have motivated the development of pulmonary imaging approaches, such as computed tomography (CT) and magnetic resonance imaging (MRI). Inhaled hyperpolarized noble gas MRI, specifically using helium-3 (3He) and xenon-129 ...


High Performance Optical Computed Tomography For Accurate Three-Dimensional Radiation Dosimetry, Kurtis Hendrik Dekker 2018 The University of Western Ontario

High Performance Optical Computed Tomography For Accurate Three-Dimensional Radiation Dosimetry, Kurtis Hendrik Dekker

Electronic Thesis and Dissertation Repository

Optical computed tomography (CT) imaging of radiochromic gel dosimeters is a method for truly three-dimensional radiation dosimetry. Although optical CT dosimetry is not widely used currently due to previous concerns with speed and accuracy, the complexity of modern radiotherapy is increasing the need for a true 3D dosimeter. This thesis reports technical improvements that bring the performance of optical CT to a clinically useful level. New scanner designs and improved scanning and reconstruction techniques are described.

First, we designed and implemented a new light source for a cone-beam optical CT system which reduced the scatter to primary contribution in CT ...


Analysis Of Subchondral Bone And Microvessels Using A Novel Vascular Perfusion Contrast Agent And Optimized Dual-Energy Computed Tomography, Justin J. Tse 2018 The University of Western Ontario

Analysis Of Subchondral Bone And Microvessels Using A Novel Vascular Perfusion Contrast Agent And Optimized Dual-Energy Computed Tomography, Justin J. Tse

Electronic Thesis and Dissertation Repository

Osteoarthritis (OA), is a chronic debilitating disease that affects millions of individuals and is characterized by the degeneration of joint subchondral bone and cartilage. These tissue degenerations manifest as joint pain, limited range of joint motion, and overall diminished quality of life. Currently, the exact mechanism(s) and cause(s) by which OA initiates and progresses remain unknown. The multi-factorial complex nature of OA (i.e. age, diabetes, obesity, and prior injuries have all been shown to play a role in OA) contributes to the current lack of a cure or effective long-term treatment for OA.

One re-emerging and interesting ...


Optimization Of Design Procedures For Delta Relaxation Enhanced Magnetic Resonance, Daniel J. Martire 2018 The University of Western Ontario

Optimization Of Design Procedures For Delta Relaxation Enhanced Magnetic Resonance, Daniel J. Martire

Electronic Thesis and Dissertation Repository

Delta relaxation enhanced magnetic resonance (dreMR) is a magnetic resonance imaging (MRI) method that produces contrast based on longitudinal relaxation dispersion. Through modulation of the magnetic field using an actively-shielded, field-cycling insert coil, this technique increases probe specificity and suppresses remaining signal. However, significant improvements are needed. This thesis addresses two advancements in dreMR with a focus on optimizing design procedures. A general procedure was developed to design split power solenoid magnets. The procedure was then applied to the design of a switched-field exposure system. A coil was constructed and the method was validated. This procedure can be used for ...


Advances In Dual-Energy Computed Tomography Imaging Of Radiological Properties, Dong Han 2018 Virginia Commonwealth University

Advances In Dual-Energy Computed Tomography Imaging Of Radiological Properties, Dong Han

Theses and Dissertations

Dual-energy computed tomography (DECT) has shown great potential in the reduction of uncertainties of proton ranges and low energy photon cross section estimation used in radiation therapy planning. The work presented herein investigated three contributions for advancing DECT applications. 1) A linear and separable two-parameter DECT, the basis vector model (BVM) was used to estimate proton stopping power. Compared to other nonlinear two-parameter models in the literature, the BVM model shows a comparable accuracy achieved for typical human tissues. This model outperforms other nonlinear models in estimations of linear attenuation coefficients. This is the first study to clearly illustrate the ...


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