Medical Sciences Commons^™

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

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

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 …

Wearable Sensors And Total Knee Arthroplasty: Assessing Quantitative Function To Improve The Patient Experience, Megan Fennema

Electronic Thesis and Dissertation Repository

Osteoarthritis (OA) is a chronic degenerative disease for which the only long-term solution is total knee arthroplasty (TKA), though many patients are not satisfied with their TKA. Satisfaction in TKA patients is not well understood. Subjective questionnaires and objective functional tests have been previously used to assess TKA outcomes, but both have disadvantages. Wearable sensors have facilitated affordable biomechanical measurement in OA and TKA populations. The objective of this work was to use wearable sensors alongside functional tests with TKA patients to identify quantitative function that related to subjective function and satisfaction. A wearable sensor-setup was validated before implementation in …

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 …

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

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 measured …

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

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

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. Within-tumour …

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 …

Investigating The Cortical, Metabolic And Behavioral Effects Of Transcranial Direct Current Stimulation In Preparation For Combined Rehabilitation, Kayla N. Ryan

Electronic Thesis and Dissertation Repository

The goal of this thesis was to determine the cortical reorganization that occurs in patients with cervical spondylotic myelopathy (CSM) after surgical decompression and to implement this knowledge into a new rehabilitation strategy. Transcranial direct current stimulation (tDCS) is a non-invasive technique to modulate human behavior. Due to the novel electrode montage used, it was first pertinent that we determine how tDCS would modulate cortical, metabolic and motor behavior in healthy individuals.

We observed the longitudinal functional adaptations that occur in patients with CSM using functional MRI. Enhanced excitation of supplementary motor area (SMA) was observed following surgical decompression and …

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 …

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 …

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

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 hypothesis …

Acute Pharmacologic Modulation Of Glioblastoma Ph Monitored By Chemical Exchange Saturation Transfer Magnetic Resonance Imaging, Mohammed Albatany

Electronic Thesis and Dissertation Repository

The response of tumor intracellular pH (pH_i) to a pharmacological challenge could help identify aggressive cancer. In addition, tumor pH_i may influence cell proliferation, apoptosis, chemotherapy resistance, and thermosensitivity. Chemical exchange saturation transfer (CEST) is a novel MRI contrast mechanism that is sensitive to cellular pH. More specifically, a CEST method called amine and amide concentration-independent detection (AACID) produces images weighted by intracellular pH (pH_i) and can be used to study pharmacologic pH modulation in tumours.

The overall goal of this thesis was to maximize the magnitude of intracellular tumour acidification using pharmacologic agents. Several …

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 …