Medicine and Health Sciences Commons^™

The Impact Of Simulated Image Acquisition Time Reduction On Image Quality And Parameters Of Myocardial Perfusion Imaging Using A Dedicated Cardiac Camera, Alireza Khatami

Electronic Thesis and Dissertation Repository

Heart disease is the second leading cause of death in Canada, highlighting the crucial role of early diagnosis in disease management. Myocardial perfusion imaging (MPI), is widely employed for this purpose, involves injecting a radiopharmaceutical into the body, imaging its distribution with a gamma camera, and revealing cardiac blood flow patterns. A significant challenge in MPI is the lengthy 8 to 10 minutes required for stress and rest imaging, potentially causing patient discomfort and compromising image quality due to movement. In a clinical study with 26 patients, post-processed data manipulation simulated a reduction in MPI imaging time. The findings indicated …

Development Of Ph-Weighted Magnetic Resonance Imaging In The Spinal Cord: Application In Degenerative Cervical Myelopathy, Alicia E. Cronin

Electronic Thesis and Dissertation Repository

Degenerative cervical myelopathy (DCM) is a degenerative disease of the spinal cord that can lead to neurological dysfunction. It has been hypothesized that ischemia and hypoxia in the spinal cord at the site of compression could impact functional recovery after decompression surgery. Unfortunately, direct in-vivo quantification of hypoxia and ischemia in the spine has been limited in humans. Magnetic resonance imaging (MRI) can be utilized to measure hypoxia indirectly in soft tissue. Specifically, chemical exchange saturation transfer (CEST) is an MRI contrast that can be derived from the transfer of magnetization from selectively excited endogenous protons to bulk water protons. …

Assessing The Sensitivity Of Cerebral Blood Flow And Oxygenation To High Intracranial Pressure With Near-Infrared Light, Sule Karagulleoglu Kunduraci

Electronic Thesis and Dissertation Repository

Premature birth is associated with increased susceptibility to cerebral injuries because of the compounded effects of underdeveloped cerebral vascular and unstable hemodynamics. Notably, premature infants are highly vulnerable to intraventricular hemorrhage, which often leads to hydrocephalus and subsequently to high intracranial pressure (ICP). Current monitoring methods such as ultrasonography can only detect injuries that have already occurred, highlighting the need for prognostic tools. We hypothesize that concomitant measures of cerebral blood flow (CBF), blood oxygenation, and oxygen metabolism will be sensitive to high ICP. To test this hypothesis, experiments were conducted in a piglet model of high ICP using a …

Eosinophilic Asthma Response To Therapy: 129xe Magnetic Resonance Imaging And Computed Tomography, Marrissa Joan Mcintosh

Electronic Thesis and Dissertation Repository

Novel biologic therapies, such as anti-interleukin-5 receptor α (anti-IL-5Rα) or benralizumab, have been developed to treat patients with severe eosinophilic asthma who experience frequent exacerbations, poor quality of life and increased risk of mortality. Whether this therapy results in disease modifying activity, specifically in the asthmatic airways and pulmonary vasculature, is still poorly understood. Pulmonary structure and function may be evaluated using computed tomography (CT) and hyperpolarized noble gas magnetic resonance imaging (MRI), respectively. Computed tomography has previously been utilized to measure airway dimensions, mucus occlusions and pulmonary blood volumes. In contrast, hyperpolarized gas MRI allows for the in vivo …

Water-Fat Magnetic Resonance Imaging For The Assessment Of Human Fetal Adipose Tissue, Stephanie A. Giza

Electronic Thesis and Dissertation Repository

Adipose tissue is crucial for providing heat and energy to infants, especially at transitions such as birth and therefore must begin developing in utero. This development may be altered due to an adverse uterine environment, increasing the risk of developing later-life metabolic diseases such as obesity. An early assessment of fetal adipose tissue development through lipid accumulation could be key to understanding metabolic programming and minimizing this risk.

Water-fat magnetic resonance imaging (MRI) can non-invasively measure the lipid concentration of tissues and can therefore monitor the development of adipose tissue via tissue lipid concentration. This work demonstrated the feasibility …

Predicting Brain Metastasis Response To Stereotactic Radiosurgery Using Magnetic Resonance Imaging Radiomics And Machine Learning, David A. Devries

Electronic Thesis and Dissertation Repository

Brain metastases (BMs) represent advanced cancer, and so BM patients must be treated quickly and effectively while minimizing treatment toxicities. Stereotactic radiosurgery (SRS) uses conformal, ablative radiation doses to treat BMs, but with failure rates up to 30%. A predictive model of BM progression post-SRS would therefore aid in BM treatment selection and SRS planning. Previous studies have used pre-treatment T1-weighted contrast-enhanced magnetic resonance imaging (T1w-CE MRI) to predict SRS outcomes, through quantitative radiomic analysis with machine learning (ML) and qualitative appearance analysis. Comparison of these methods is not well understood, and ML methods have not been studied for sensitivity …

Assessment Of A Novel High-Density, Full-Head Coverage, Time-Resolved Near-Infrared Spectroscopy (Nirs) Device For Intraoperative Neuromonitoring, Farah Kamar

Electronic Thesis and Dissertation Repository

Neuromonitoring during surgery is used to detect early indications of cerebral injury before permanent damage occurs. A commonly used technology is cerebral oximetry; however, current systems only monitor one brain region and have limited depth sensitivity. A newly developed NIRS system, Kernel Flow, offers the possibility to address both limitations by providing full-head coverage and time-resolved detection to enhance sensitivity to the brain. This work aimed to assess Kernel Flow’s sensitivity to regional cerebral oxygenation changes. Two experiments were conducted. In the first, decreases in cerebral oxygenation caused by transient carotid compression were measured in healthy volunteers. The second was …

In Utero Magnetic Resonance Relaxometry For Fetal Tissue Development, Simran Sethi

Electronic Thesis and Dissertation Repository

Fetal life is a significant period of human development because organ systems that sustain life outside the uterus begin to develop during this time. A necessary process that begins during fetal life is myelination, which is the process by which myelin, a lipid-rich substance, is wrapped around neurons in the brain to increase the speed of action potential transmission. Since myelination is critical for the normal function of the central nervous system, fetal myelin assessment is important for understanding neurodevelopment and neurodegeneration, such as intrauterine growth restriction (IUGR).

Magnetic resonance imaging (MRI) is an excellent tool for visualizing fetal anatomy …

Development And Validation Of Mechatronic Systems For Image-Guided Needle Interventions And Point-Of-Care Breast Cancer Screening With Ultrasound (2d And 3d) And Positron Emission Mammography, Claire Ks Park

Electronic Thesis and Dissertation Repository

The successful intervention of breast cancer relies on effective early detection and definitive diagnosis. While conventional screening mammography has substantially reduced breast cancer-related mortalities, substantial challenges persist in women with dense breasts. Additionally, complex interrelated risk factors and healthcare disparities contribute to breast cancer-related inequities, which restrict accessibility, impose cost constraints, and reduce inclusivity to high-quality healthcare. These limitations predominantly stem from the inadequate sensitivity and clinical utility of currently available approaches in increased-risk populations, including those with dense breasts, underserved and vulnerable populations.

This PhD dissertation aims to describe the development and validation of alternative, cost-effective, robust, and high-resolution …

Advancing Non-Invasive Imaging Techniques For Tracking Cellular Therapeutics In Vivo, Olivia C. Sehl

Electronic Thesis and Dissertation Repository

Cell therapies, including mesenchymal stem cells (MSC) and regulatory T cells (Tregs) have shown potent and long-lasting therapeutic benefit in several disease applications. Unfortunately, the effectiveness of these therapies is variable and following administration, it is largely unknown where therapeutic cells traffic and how many persist over time. This thesis aims to advance and compare iron- and fluorine-19 (¹⁹F)-based magnetic resonance imaging (MRI) and magnetic particle imaging (MPI) for therapeutic cell tracking.

First, we developed a trimodal imaging approach to study MSC fate in vivo. In a mouse model, iron-labeled MSC were detected by MRI and MPI, …

Development Of Magnetic Particle Imaging For Quantitative Immune Cell Tracking, Julia J. Gevaert

Electronic Thesis and Dissertation Repository

The Foster lab has been developing cellular MRI tools for well over a decade using superparamagnetic iron oxide (SPIO)-based contrast agents for numerous applications cell tracking applications. SPIO are used to label cells which are indirectly detected as regions of signal loss. The main challenge with this technique is quantification of cell number, which is important for applications such as dendritic cell (DC)-based immunotherapies where cell number is used as a predictor of immunotherapeutic response.

Magnetic particle imaging (MPI) is a novel pre-clinical modality that shows promise for cell tracking. MPI directly detects the nonlinear magnetization response of superparamagnetic iron …

Spatiotemporal Optimization Of Intratumoural Electric Field Modulation For Cancer Therapy, Erin Iredale

Electronic Thesis and Dissertation Repository

The use of anti-cancer non-ablative electric fields is an expanding area of research that includes clinically available external devices for the treatment of glioblastoma (GBM), and a pre-clinical internal system called Intratumoural Modulation Therapy (IMT). IMT uses multiple electrodes implanted within the tumour to apply low intensity electric fields (~1 V/cm) focused on the target region, anywhere in the brain, with no externally visible devices. In this thesis, multi-electrode spatiotemporally dynamic IMT is investigated through computer simulation, numerical optimization, brain phantom and in vitro validation methods. These planning and validation strategies are hypothesized to improve tumour coverage with the necessary …

In Vivo Multi-Modal Imaging Approaches For Cancer, Stem And Immune Cells, Nourhan Shalaby

Electronic Thesis and Dissertation Repository

Introduction: Molecular imaging allows for non-invasive longitudinal visualization of cellular functions in vivo. This area of research has provided better understanding of fundamental molecular and biochemical processes, enabled optimization of pre-clinical and clinical assessments for new treatments, and allowed for more accurate and early detection of many pathologies. Extensive research for novel imaging techniques and emerging technologies have rapidly advanced the field. However, an ideal single imaging modality or approach does not exist. Alternatively, multi-modal imaging approaches are commonly applied to overcome limitations of individual technologies. In this thesis, we design, develop, validate, and image various cell types using …

Investigating Cellular Imaging Techniques For Cancer Cell Tracking, Natasha Knier

Electronic Thesis and Dissertation Repository

Introduction: Breast cancer remains a leading cause of mortality among women due to the propensity of breast tumours to spread and metastasize to distant sites, including the brain. Early detection of metastatic disease has been challenging, and typical methods of treatment often fail. A significant roadblock in advancing the detection and treatment of breast cancer brain metastases is the lack of representative experimental preclinical models and methods of studying its progression in vivo. Methods: First, we use iron-based cellular MRI to noninvasively track the progression of a brain metastatic breast cancer cell line in murine models with varying immune …

Evaluating The Biomechanical, Functional, And Clinical Outcomes Of Bicruciate Stabilized Total Knee Arthroplasty, Jordan S. Broberg

Electronic Thesis and Dissertation Repository

Total knee arthroplasty (TKA) is the only solution for treating arthritis of the knee joint. Although it is successful at reducing pain and returning function to affected joints, one in five patients still report dissatisfaction following their operation. Bicruciate stabilized (BCS) TKA was developed to improve outcomes by replicating normal knee structure and function. The biomechanical, functional, and clinical outcomes for the BCS design were investigated in this thesis through radiographic imaging techniques, wearable sensor systems, and questionnaires in a cohort of TKA patients.

A stereo x-ray technique, called radiostereometric analysis (RSA), assesses implant fixation by tracking micromotion of TKA …

Building A Magnetosome-Like Nanoparticle For Magnetic Resonance Imaging, Qin Sun

Electronic Thesis and Dissertation Repository

With its superb spatial and temporal resolution, magnetic resonance imaging (MRI) has great potential to track cellular activities that define early stages of disease. To improve molecular imaging techniques, we are developing MRI reporter gene expression based on the magnetosome. In magnetotactic bacteria (MTB), magnetosome formation compartmentalizes iron biominerals in membrane-enclosed vesicles. We hypothesize that essential magnetosome proteins interact in any cell type to form rudimentary magnetosome-like nanoparticles, providing a genetically-controlled contrast agent for molecular MRI.

MTB genes mamE, mamB, mamI, and mamL were cloned from M. magneticum sp. AMB-1 genomic DNA by PCR and inserted into …

Assessing Inflammation In The Pathology Of Knee Osteoarthritis, Zachary J. Koudys

Electronic Thesis and Dissertation Repository

Osteoarthritis (OA) is a joint disease that causes pain, stiffness, and loss of function. Inflammation of the synovium plays a role in the pathology of OA. Macrophages are the dominant immune cells in synovial tissue. Activated macrophages over-express the translocator protein (TSPO). [¹⁸F]FEPPA is a 2^nd generation positron emission tomography (PET) tracer that can target TSPO with high specificity. Hybrid [¹⁸F]FEPPA PET/MRI may enable accurate quantification of macrophage activity in vivo. In this work, [¹⁸F]FEPPA tracer uptake in knee synovial tissue was measured ex vivo using autoradiography and was validated to correlate to …

Novel 129xe Magnetic Resonance Imaging And Spectroscopy Measurements Of Pulmonary Gas-Exchange, Alexander M. Matheson

Electronic Thesis and Dissertation Repository

Gas-exchange is the primary function of the lungs and involves removing carbon dioxide from the body and exchanging it within the alveoli for inhaled oxygen. Several different pulmonary, cardiac and cardiovascular abnormalities have negative effects on pulmonary gas-exchange. Unfortunately, clinical tests do not always pinpoint the problem; sensitive and specific measurements are needed to probe the individual components participating in gas-exchange for a better understanding of pathophysiology, disease progression and response to therapy.

In vivo Xenon-129 gas-exchange magnetic resonance imaging (¹²⁹Xe gas-exchange MRI) has the potential to overcome these challenges. When participants inhale hyperpolarized ¹²⁹Xe gas, it …

Depth-Dependent Analysis Of Human Ocular Dominance Columns Using Fmri With Phase Regression, Brett T. Liem

Electronic Thesis and Dissertation Repository

High-resolution fMRI using gradient-echo blood-oxygen-level-dependent (BOLD) contrast is beneficial for the non-invasive study of neural microcircuits. However, the signal spatial specificity of the BOLD contrast severely limits the ability to localize regions of neural activity at the mesoscopic scale in the cortex due to signal contamination from large veins. Phase regression is a venous bias correction technique that uses the correlation between magnitude and phase data in large veins to estimate and supress their contribution to the BOLD signal. This thesis further investigates the performance of phase regression by examining the laminar BOLD signal in human ocular dominance columns. Phase …

Longitudinal Computed Tomography Airway Measurements In Ex-Smokers With And Without Chronic Obstructive Pulmonary Disease, Paulina V. Wyszkiewicz

Electronic Thesis and Dissertation Repository

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease characterized by chronic airflow obstruction, emphysematous destruction, and airway remodeling. Thoracic CT has previously revealed abnormalities in the small airways, where disease onset is believed to initiate. In previous COPD cohort studies, airway wall thinning and diminished total airway count (TAC) were observed with increasing disease severity. However, longitudinal insights are lacking. Accordingly, the objective of this thesis was to evaluate longitudinal CT airway measurements at baseline and after three-years in ex-smokers. I observed that CT TAC was decreased only in ex-smokers with COPD, whilst airway walls were thinner in both …

Exploring Novel Intradialytic Techniques To Identify & Ameliorate Of Hemodialysis-Induced Myocardial Ischemic Injury, Jarrin D. Penny

Electronic Thesis and Dissertation Repository

Patients with chronic kidney disease requiring hemodialysis to sustain life have extremely high rates of cardiovascular morbidity/mortality. This is both a consequence of the disease process and treatment. Hemodialysis induces systemic circulatory stress is largely due to the extracorporeal circuit and volume removal. The stress induced by intermitted hemodialysis is repetitive with cumulative cardiovascular effect and is the principal driver of heart failure and sudden death in this vulnerable population. The insults imposed by hemodialysis result in left ventricular regional wall motion abnormalities and lead to myocardial stunning with permanent damage to the vasculature and myocardium. Currently, the adversity caused …

Improving The Reliability And Accessibility Of Ct Perfusion Imaging In Acute Ischemic Stroke, Kevin J. Chung

Electronic Thesis and Dissertation Repository

CT perfusion (CTP) imaging is a validated treatment decision support tool in acute ischemic stroke. Automated analysis of CTP cerebral blood flow (CBF) and Tmax maps produces estimates of ischemic core and penumbra volumes used to determine target mismatch profiles for treatment. However, availability and utilization of CTP is low due to diagnostic variability between CTP software and technical, logistical, and radiation dose considerations that may limit its routine adoption. The objective of this doctoral research was to improve the reliability and accessibility of CTP by (1) improving diagnostic agreement between CTP software, (2) enabling perfusion imaging with standard acute …

An Evaluation Of A Deep Learning Approach For Radiation Dose Reduction In 18f-Fdg Pet/Mri Pediatric Epilepsy Imaging, Confidence Raymond

Electronic Thesis and Dissertation Repository

Epilepsy is a degenerative brain disease characterized by abruption of neural activities that result in seizures. The onset of epileptic seizures are usually from a primary source - the epileptogenic foci (EF) which could be distributed to nearby neurons and tissues. Accurate localization of EF is critical in epilepsy cases where drug treatment has failed, and surgery is indicated to resect the EF to alleviate seizure. Typically, hybrid positron emission tomography (PET) and computed tomography (CT) imaging are performed to functionally localize the EF in drug-resistant epilepsy for surgical planning when anatomical abnormalities representing the EF cannot be identified on …

The Characterization Of Hemodialysis Membranes In Miniaturized Dialyzers, Mehrshad Moradshahi

Electronic Thesis and Dissertation Repository

Lack of an appropriate animal model prevents rapid evaluation of health outcomes associated with hemodialysis. We developed a miniaturized dialyzer for use in small rats. The aim of this study was to investigate whether the miniaturized dialyzers can differentiate performance characteristics representing hemodialysis membrane and fiber design. We evaluated internal filtration, water permeability, sieving coefficient (SC) and clearance of solutes, in the Medium Cut Off (MCO) and conventional High Flux (HF) miniaturized dialyzers. We found statistically significant differences between miniaturized MCO and conventional HF dialyzers with respect to ultrafiltration coefficient, clearance of Beta-2 Microglobulin (B2M), and SC of B2M.These outcomes …

Simulated And Experimental Approaches To The Development Of Novel Test Phantoms For Radiofrequency Heating Of Implanted Medical Devices, Amgad M. Louka

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging (MRI) has cemented itself as the gold standard for imaging of soft tissues and is only increasing in popularity. Given the rising number of MRI scanners and medical device being implanted into patients, it is becoming increasingly likely that patients undergoing MRI will have an implanted medical device (IMD). The presence of an elongated metallic IMD inside a scanner could result in dangerous interactions with the radiofrequency fields during MRI, thus some of these IMDs preclude the patients from being scanned.

Orthopedic devices typically fall into this category due to their high potential for RF induced heating, …

Technical Adaptations For Cardiac Sodium Mri, Taylor L. Marcus

Electronic Thesis and Dissertation Repository

Cardiac sodium (Na⁺) MRI has the potential to unveil relationships between chronic kidney disease (CKD) and cardiovascular disease (CVD). Unfortunately, this modality requires many technical adaptations before it’s possible to extract and compare image data between individuals. This study investigated whether cardiac electrocardiogram (ECG) gating could improve image quality, and whether a uniform phantom could increase signal uniformity if a surface coil is used to acquire the image. Healthy participants were imaged with a custom-built surface coil and 3.0-T MR system. Cardiac gated images presented with a decreased signal-to-noise ratio (SNR), but intensity correction significantly increased image signal …

Multi-Scale Computational Modeling Of Coronary Blood Flow: Application To Fractional Flow Reserve., Jermiah Joseph

Electronic Thesis and Dissertation Repository

Introduction. Fractional flow reserve (FFR) is presently an invasive coronary clinical index. Non-invasive CT imaging combined with computational coronary flow modelling may reduce the patient’s burden of undergoing invasive testing.

Research statement. The ability to obtain information of the hemodynamic significance of detected lesions would streamline decision making in escalation to invasive angiography.

Methods. A reduced order (lumped parameter) model of the coronary vasculature was further developed. The model was used in the assessment of the roles of structure and function on the FFR. Sophisticated methods were used to elicit numerical

solutions. Further, CT imaging (n = …

Anatomical And Functional Lung Imaging With Volumetric Computed Tomography In Non-Small Cell Lung Cancer, Heather Young

Electronic Thesis and Dissertation Repository

Non-small cell lung cancer (NSCLC) is one of the most diagnosed cancers in Canada, and the leading cause of cancer deaths. A significant challenge in treating NSCLC is balancing aggressive treatment with the potentially severe side effects. In radiation therapy, the management of respiratory motion and the risks of radiation-induced lung injury (RILI) pose significant challenges. 4-dimensional computed tomography (4D-CT) is an important part of motion management, but images often suffer from motion-induced artifacts. Volumetric CT scanners with wide axial field-of-view (aFOV) may reduce these artifacts and present an opportunity to advance CT-based functional lung imaging.

Chapter 2 presents a …

Atrial Fibrillation And Cognitive Decline: A Computational Hemodynamics Investigation, Timothy J. Hunter

Electronic Thesis and Dissertation Repository

Background: Atrial fibrillation (AF) is a prevalent cardiac disease which has been associated with increased risk of dementia and cognitive decline. We hypothesize that atrial fibrillation leads to regional transient hypoperfusion events in the brain, and that geometric variations in the arterial structure called the Circle of Willis (CoW) play a role in these events.

Methods: A computational model was developed to simulate cerebral blood flow in six common variations of the CoW. Risk was assessed based on frequency of beat-wise regional hypoperfusion events during AF, and sensitivity analysis was performed with respect to this model output.

Results …

Software And Hardware-Based Tools For Improving Ultrasound Guided Prostate Brachytherapy, Nathan Orlando

Electronic Thesis and Dissertation Repository

Minimally invasive procedures for prostate cancer diagnosis and treatment, including biopsy and brachytherapy, rely on medical imaging such as two-dimensional (2D) and three-dimensional (3D) transrectal ultrasound (TRUS) and magnetic resonance imaging (MRI) for critical tasks such as target definition and diagnosis, treatment guidance, and treatment planning. Use of these imaging modalities introduces challenges including time-consuming manual prostate segmentation, poor needle tip visualization, and variable MR-US cognitive fusion. The objective of this thesis was to develop, validate, and implement software- and hardware-based tools specifically designed for minimally invasive prostate cancer procedures to overcome these challenges.

First, a deep learning-based automatic 3D …