Case – 18F-Dcfpyl-Positron Emission Tomography/Computed Tomography (Pet/Ct) Time Of Imaging, Golmehr Sistani, Ur Metser, Glenn S. Bauman, David T. Laidley, Stephen E. Pautler, Katherine A. Zukotynski

Medical Biophysics Publications

No abstract provided.

Cortical Thickness Estimation In Individuals With Cerebral Small Vessel Disease, Focal Atrophy, And Chronic Stroke Lesions, Miracle Ozzoude, Joel Ramirez, Pradeep Reddy Raamana, Melissa F. Holmes, Kirstin Walker, Christopher J.M. Scott, Fuqiang Gao, Maged Goubran, Donna Kwan, Maria C. Tartaglia, Derek Beaton, Gustavo Saposnik, Ayman Hassan, Jane Lawrence-Dewar, Dariush Dowlatshahi, Stephen C. Strother, Sean Symons, Robert Bartha, Richard H. Swartz, Sandra E. Black

Medical Biophysics Publications

Background: Regional changes to cortical thickness in individuals with neurodegenerative and cerebrovascular diseases (CVD) can be estimated using specialized neuroimaging software. However, the presence of cerebral small vessel disease, focal atrophy, and cortico-subcortical stroke lesions, pose significant challenges that increase the likelihood of misclassification errors and segmentation failures. Purpose: The main goal of this study was to examine a correction procedure developed for enhancing FreeSurfer’s (FS’s) cortical thickness estimation tool, particularly when applied to the most challenging MRI obtained from participants with chronic stroke and CVD, with varying degrees of neurovascular lesions and brain atrophy. Methods: In 155 CVD participants …

Detection And Quantification Of Cells Using Magnetic Particle Imaging And Magnetic Microspheres, Kierstin P. Melo

Electronic Thesis and Dissertation Repository

Magnetic particle imaging (MPI) is an emerging imaging modality that specifically detects superparamagnetic iron oxide nanoparticles (SPIOs). Our lab has shown that cell tracking with magnetic resonance imaging (MRI) has very high sensitivity, but low specificity and quantification of iron labeled cells is difficult. MPI cell tracking could overcome these limitations. A Momentum^TM MPI system was installed at Robarts in August 2019 and this is the first project to be completed using MPI. In Chapter 2 a series of in vitro experiments are reported which tested the repeatability and reproducibility of imaging SPIO labeled cell samples. There are no …

Improving Hydrid Pet/Mri Cardiovascular Imaging With Improved Hardware Design And Attenuation Correction Coefficient, Adam Helmy Farag

Electronic Thesis and Dissertation Repository

According to the World Health Organization (WHO) report in 2019, cardiovascular diseases (CVD) cause 52% of all illness-related deaths globally and are considered to be the second most common cause of death in Canada. CVD is also estimated to cost the Canadian economy about $21.2 billion in direct and indirect costs. With these figures, it is vital to develop the most effective and accurate methods and tools to diagnose accurately CVD and their causes. One of the promising tools for accurate diagnostic and therapeutic of CVD is the integrated Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) PET/MRI technology, …

Histologic Tissue Components Provide Major Cues For Machine Learning-Based Prostate Cancer Detection And Grading On Prostatectomy Specimens, Wenchao Han, Carol Johnson, Mena Gaed, José A. Gómez, Madeleine Moussa, Joseph L. Chin, Stephen Pautler, Glenn S. Bauman, Aaron D. Ward

Medical Biophysics Publications

Automatically detecting and grading cancerous regions on radical prostatectomy (RP) sections facilitates graphical and quantitative pathology reporting, potentially benefitting post-surgery prognosis, recurrence prediction, and treatment planning after RP. Promising results for detecting and grading prostate cancer on digital histopathology images have been reported using machine learning techniques. However, the importance and applicability of those methods have not been fully investigated. We computed three-class tissue component maps (TCMs) from the images, where each pixel was labeled as nuclei, lumina, or other. We applied seven different machine learning approaches: three non-deep learning classifiers with features extracted from TCMs, and four deep learning, …

A Telescope Gwas Analysis Strategy, Based On Snps-Genes-Pathways Ensamble And On Multivariate Algorithms, To Characterize Late Onset Alzheimer’S Disease, Margherita Squillario, Giulia Abate, Federico Tomasi, Veronica Tozzo, Annalisa Barla, Daniela Uberti, Michael W. Weiner, Paul Aisen, Ronald Petersen, Jack R. Clifford, William Jagust, John Q. Trojanowki, Arthur W. Toga, Laurel Beckett, Robert C. Green, Andrew J. Saykin, John Morris, Leslie M. Shaw, Zaven Khachaturian, Greg Sorensen, Maria Carrillo, Lew Kuller, Marc Raichle, Steven Paul, Peter Davies, Howard Fillit, Franz Hefti, Davie Holtzman, M. Marcel Mesulam, William Potter, Peter Snyder, Tom Montine

Medical Biophysics Publications

Genome–wide association studies (GWAS) have revealed a plethora of putative susceptibility genes for Alzheimer’s disease (AD), with the sole exception of APOE gene unequivocally validated in independent study. Considering that the etiology of complex diseases like AD could depend on functional multiple genes interaction network, here we proposed an alternative GWAS analysis strategy based on (i) multivariate methods and on a (ii) telescope approach, in order to guarantee the identification of correlated variables, and reveal their connections at three biological connected levels. Specifically as multivariate methods, we employed two machine learning algorithms and a genetic association test and we considered …

Challenges And Opportunities With Causal Discovery Algorithms: Application To Alzheimer’S Pathophysiology, Xinpeng Shen, Sisi Ma, Prashanthi Vemuri, Gyorgy Simon, Michael W. Weiner, Paul Aisen, Ronald Petersen, Clifford R. Jack, Andrew J. Saykin, William Jagust, John Q. Trojanowki, Arthur W. Toga, Laurel Beckett, Robert C. Green, John Morris, Leslie M. Shaw, Zaven Khachaturian, Greg Sorensen, Maria Carrillo, Lew Kuller, Marc Raichle, Steven Paul, Peter Davies, Howard Fillit, Franz Hefti, David Holtzman, M. Marcel Mesulam, William Potter, Peter Snyder, Adam Schwartz, Tom Montine, Ronald G. Thomas

Medical Biophysics Publications

Causal Structure Discovery (CSD) is the problem of identifying causal relationships from large quantities of data through computational methods. With the limited ability of traditional association-based computational methods to discover causal relationships, CSD methodologies are gaining popularity. The goal of the study was to systematically examine whether (i) CSD methods can discover the known causal relationships from observational clinical data and (ii) to offer guidance to accurately discover known causal relationships. We used Alzheimer’s disease (AD), a complex progressive disease, as a model because the well-established evidence provides a “gold-standard” causal graph for evaluation. We evaluated two CSD methods, Fast …

Fam222a Encodes A Protein Which Accumulates In Plaques In Alzheimer’S Disease, Tingxiang Yan, Jingjing Liang, Ju Gao, Luwen Wang, Hisashi Fujioka, Michael W. Weiner, Norbert Schuff, Howard J. Rosen, Bruce L. Miller, David Perry, Paul Aisen, Paul Aisen, Arthur W. Toga, Gustavo Jimenez, Michael Donohue, Devon Gessert, Kelly Harless, Jennifer Salazar, Yuliana Cabrera, Sarah Walter, Lindsey Hergesheimer, Arthur W. Toga, Karen Crawford, Scott Neu, Lon S. Schneider, Sonia Pawluczyk, Mauricio Becerra, Liberty Teodoro, Bryan M. Spann, Ronald Petersen, Clifford R. Jack, Matthew Bernstein

Medical Biophysics Publications

Alzheimer’s disease (AD) is characterized by amyloid plaques and progressive cerebral atrophy. Here, we report FAM222A as a putative brain atrophy susceptibility gene. Our cross-phenotype association analysis of imaging genetics indicates a potential link between FAM222A and AD-related regional brain atrophy. The protein encoded by FAM222A is predominantly expressed in the CNS and is increased in brains of patients with AD and in an AD mouse model. It accumulates within amyloid deposits, physically interacts with amyloid-β (Aβ) via its N-terminal Aβ binding domain, and facilitates Aβ aggregation. Intracerebroventricular infusion or forced expression of this protein exacerbates neuroinflammation and cognitive dysfunction …

Social Cognition Impairment In Genetic Frontotemporal Dementia Within The Genfi Cohort, Lucy L. Russell, Caroline V. Greaves, Martina Bocchetta, Jennifer Nicholas, Rhian S. Convery, Katrina Moore, David M. Cash, John Van Swieten, Lize Jiskoot, Fermin Moreno, Raquel Sanchez-Valle, Barbara Borroni, Robert Laforce, Mario Masellis, Maria Carmela Tartaglia, Caroline Graff, Emanuela Rotondo, Daniela Galimberti, James B. Rowe, Elizabeth Finger, Matthis Synofzik, Rik Vandenberghe, Alexandre De Mendonça, Fabrizio Tagliavini, Isabel Santana, Simon Ducharme, Chris Butler, Alex Gerhard, Johannes Levin, Adrian Danek, Markus Otto, Jason D. Warren

Medical Biophysics Publications

A key symptom of frontotemporal dementia (FTD) is difficulty interacting socially with others. Social cognition problems in FTD include impaired emotion processing and theory of mind difficulties, and whilst these have been studied extensively in sporadic FTD, few studies have investigated them in familial FTD. Facial Emotion Recognition (FER) and Faux Pas (FP) recognition tests were used to study social cognition within the Genetic Frontotemporal Dementia Initiative (GENFI), a large familial FTD cohort of C9orf72, GRN, and MAPT mutation carriers. 627 participants undertook at least one of the tasks, and were separated into mutation-negative healthy controls, presymptomatic mutation carriers (split …

Optimization Of Multi-Electrode Implant Configurations And Programming For The Delivery Of Non-Ablative Electric Fields In Intratumoral Modulation Therapy., Erin Iredale, Andrew Deweyert, Douglas A Hoover, Jeff Z Chen, Susanne Schmid, Matthew O Hebb, Terry M Peters, Eugene Wong

Medical Biophysics Publications

PURPOSE: Application of low intensity electric fields to interfere with tumor growth is being increasingly recognized as a promising new cancer treatment modality. Intratumoral modulation therapy (IMT) is a developing technology that uses multiple electrodes implanted within or adjacent tumor regions to deliver electric fields to treat cancer. In this study, the determination of optimal IMT parameters was cast as a mathematical optimization problem, and electrode configurations, programming, optimization, and maximum treatable tumor size were evaluated in the simplest and easiest to understand spherical tumor model. The establishment of electrode placement and programming rules to maximize electric field tumor coverage …

Brain Metabolite Levels In Sedentary Women And Non-Contact Athletes Differ From Contact Athletes, Amy L. Schranz, Gregory A. Dekaban, Lisa Fischer, Kevin Blackney, Christy Barreira, Timothy J. Doherty, Douglas D. Fraser, Arthur Brown, Jeff Holmes, Ravi S. Menon, Robert Bartha

Medical Biophysics Publications

White matter tracts are known to be susceptible to injury following concussion. The objective of this study was to determine whether contact play in sport could alter white matter metabolite levels in female varsity athletes independent of changes induced by long-term exercise. Metabolite levels were measured by single voxel proton magnetic resonance spectroscopy (MRS) in the prefrontal white matter at the beginning (In-Season) and end (Off-Season) of season in contact (N = 54, rugby players) and non-contact (N = 23, swimmers and rowers) varsity athletes. Sedentary women (N = 23) were scanned once, at a time equivalent to the Off-Season …

Impact Of Graded Passive Cycling On Hemodynamics, Cerebral Blood Flow, And Heart Function In Healthy Adults And Septic Icu Patients, Jennifer Chen

Electronic Thesis and Dissertation Repository

Sepsis is a life-threatening dysregulation of host response to an infectious insult, which often leads to multi-organ failure. Sepsis survivors suffer from post-intensive care syndrome in part due to their prolonged bed rest and lack of mobility. Although early mobilization has been championed as a mechanism to counter the adverse effects associated with ICU immobility, due to sedation and mechanical ventilation, active early mobilization is not often administered in septic patients due to worries of hemodynamic instability and potential for inducing adverse events. Passive exercise is a mobilization modality that circumvents the need for patients to be conscious and participatory …

Neural Effects Of Oxytocin And Mimicry In Frontotemporal Dementia: A Randomized Crossover Study, Lindsay D. Oliver, Chloe Stewart, Kristy Coleman, James H. Kryklywy, Robert Bartha, Derek G.V. Mitchell, Elizabeth C. Finger

Medical Biophysics Publications

OBJECTIVE: To determine whether intranasal oxytocin, alone or in combination with instructed mimicry of facial expressions, would augment neural activity in patients with frontotemporal dementia (FTD) in brain regions associated with empathy, emotion processing, and the simulation network, as indexed by blood oxygen-level dependent (BOLD) signal during fMRI. METHODS: In a placebo-controlled, randomized crossover design, 28 patients with FTD received 72 IU intranasal oxytocin or placebo and then completed an fMRI facial expression mimicry task. RESULTS: Oxytocin alone and in combination with instructed mimicry increased activity in regions of the simulation network and in limbic regions associated with emotional expression …

Chronic Neurological Impairment In Patients With Thrombotic Thrombocytopenic Purpura: Findings In Quantitative Mri, Jeffrey Hamilton

Electronic Thesis and Dissertation Repository

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening, microvascular blood disorder that affects approximately 5 people per million per year. The disorder is characterized by insufficient activity in ADAMTS13 (a disintegrin-like and metalloprotease with thrombospondin type 1 repeats 13), which is an important enzyme in hemostasis because it prevents thrombosis. Along with blood clotting, other predominant symptoms are fever, anaemia, kidney failure, and neurological changes. Neurological changes may include confusion and decreased levels of consciousness, as well as depression and increased risk of seizures or stroke. However, little is known about the general pathology of these neurological changes and this forms …

Metabolic Syndrome Impairs Cerebrovascular Tone And Behaviour In Obese Zucker Rats, Brayden D. Halvorson

Electronic Thesis and Dissertation Repository

Metabolic syndrome is associated with cerebrovascular disease and cognitive impairment. We determined vascular reactivity in middle cerebral arteries (MCA), and performed cognitive testing using an operant conditioning chamber (OCC) and Morris Water Maze (MWM). Male obese Zucker rats (OZR) were used to test the hypothesis that the pro-inflammatory environment present in the OZR impairs cerebrovascular tone regulation and is associated with neuroinflammation of the white matter and cognitive impairment. Dilation of MCA following challenge with acetylcholine was blunted, whereas constrictor responses were enhanced. Learning was impaired in the MWM and a shift in swim strategy towards increased allocentric navigation was …

Higher Csf Strem2 Attenuates Apoe4-Related Risk For Cognitive Decline And Neurodegeneration, Nicolai Franzmeier, M. Suárez-Calvet, Lukas Frontzkowski, Annah Moore, Timothy J. Hohman, Estrella Morenas-Rodriguez, Brigitte Nuscher, Leslie Shaw, John Q. Trojanowski, Martin Dichgans, Gernot Kleinberger, Christian Haass, Michael Ewers, Michael Weiner, Paul Aisen, Gerald Novak, Robert C. Green, Tom Montine, Ronald Petersen, Anthony Gamst, Ronald G. Thomas, Michael Donohue, Sarah Walter, Devon Gessert, Tamie Sather, Laurel Beckett, Danielle Harvey, John Kornak, Clifford R. Jack, Anders Dale, Matthew Bernstein, Joel Felmlee

Medical Biophysics Publications

Background: The Apolipoprotein E ϵ4 allele (i.e. ApoE4) is the strongest genetic risk factor for sporadic Alzheimer's disease (AD). TREM2 (i.e. Triggering receptor expressed on myeloid cells 2) is a microglial transmembrane protein brain that plays a central role in microglia activation in response to AD brain pathologies. Whether higher TREM2-related microglia activity modulates the risk to develop clinical AD is an open question. Thus, the aim of the current study was to assess whether higher sTREM2 attenuates the effects of ApoE4-effects on future cognitive decline and neurodegeneration. Methods: We included 708 subjects ranging from cognitively normal (CN, n = …

The Development Of Bacterial Magnetic Resonance Imaging For Microbiota Analyses, Sarah C. Donnelly

Electronic Thesis and Dissertation Repository

Current microbial analyses to assess either the commensal microbiota or microorganism infection and disease typically require ex vivo techniques that risk contamination and are not undertaken in real time. The possibilities for employing imaging techniques in the microbiology field is becoming more prominent as studies expand on the use of positron emission tomography, ultrasound and numerous microscopy techniques. However, magnetic resonance imaging (MRI), a non-invasive in vivo modality that can produce real-time results is falling behind. Here, we examined the feasibility of detecting bacteria using clinical field strength MRI. Commensal, probiotic and uropathogenic Escherichia coli were scanned by 3 Tesla …

A Novel Salvage Option For Local Failure In Prostate Cancer, Reirradiation Using External Beam Or Stereotactic Radiation Therapy: Systematic Review And Meta-Analysis, Mark T. Corkum, Lucas C. Mendez, Joseph Chin, David D'Souza, R. Gabriel Boldt, Glenn S. Bauman

Medical Biophysics Publications

Purpose: Reirradiation (re-RT) using external beam radiation therapy (EBRT) is a novel salvage strategy for local failure in prostate cancer. We performed a systematic review describing oncologic and toxicity outcomes for salvage EBRT/stereotactic radiation therapy (SBRT) re-RT. Methods and Materials: A International Prospective Register of Systematic Reviews registered (#141466) systematic review, meta-analysis, and meta-regression was conducted using preferred reporting items for systematic reviews and meta-analyses guidelines. PubMed and EMBASE were searched from inception through September 2019. Outcome measures included local control (LC), biochemical relapse free survival (BRFS), and ≥grade 3 genitourinary (GU)/gastrointestinal (GI) toxicity. EBRT and SBRT data were collected …

A 3d Microvessel Model For The Study Of Endothelial Cell Transluminal Pillar Formation, Emma Kate Prescott

Electronic Thesis and Dissertation Repository

BACKGROUND: Endothelial cells (ECs) line the blood vessel lumen and respond to fluid shear stress. ECs are also responsible for initiating the formation of new blood vessels. These new vessels can form either by sprouting angiogenesis or intussusceptive, or splitting, angiogenesis. The latter is poorly understood but recent evidence suggests that intussusception occurs with altered blood flow. However, the biomechanical and biochemical mechanisms of intussusceptive angiogenesis remain largely unknown and in vitro models do not exist.

The purpose of this thesis was to develop a three-dimensional EC culture model capable of forming transluminal pillars, a key step in angiogenesis, and …

Tspo Pet Detects Acute Neuroinflammation But Not Diffuse Chronically Activated Mhcii Microglia In The Rat, Nassir Al-Khishman

Electronic Thesis and Dissertation Repository

Abstract

Background

Accurate and sensitive imaging biomarkers are required to study the progression of white matter (WM) microglial activation in neurological diseases in vivo. The translocator protein (TSPO) is considered a sensitive target for imaging microglial activation with positron emission tomography (PET). This study aimed to test the ability of TSPO to detect WM microglial activation marked by major histocompatibility complex class II (MHCII) molecules in rat models of prodromal Alzheimer’s disease and acute subcortical stroke.

Methods

Fischer 344 wild-type (n = 12) and TgAPP21 (n = 11) rats were imaged with [¹⁸F]FEPPA PET and MRI to …

A Clinically Representative Rat Model Of Hip Hemiarthroplasty, Adam Dm Paish

Electronic Thesis and Dissertation Repository

Joint replacement is an increasingly common surgery with over 130,000 procedures performed annually in Canada. Although joint replacement surgery is highly successful, implants do not last a lifetime, and often have to be replaced via costly revision surgeries. Before innovations aimed at extending the life of implants are applied to the clinic, testing must be performed in animal models. Clinically representative small-animal models of joint replacement would be ideal in the initial stages of research and development, due to ease of handling and low costs, but few such models have been established in the literature. Thus, we describe the development …

Ontario Neurodegenerative Disease Research Initiative (Ondri): Structural Mri Methods And Outcome Measures, Joel Ramirez, Melissa F. Holmes, Christopher J.M. Scott, Miracle Ozzoude, Miracle Ozzoude, Sabrina Adamo, Gregory M. Szilagyi, Maged Goubran, Fuqiang Gao, Stephen R. Arnott, Jane M. Lawrence-Dewar, Jane M. Lawrence-Dewar, Derek Beaton, Stephen C. Strother, Douglas P. Munoz, Mario Masellis, Richard H. Swartz, Robert Bartha, Sean P. Symons, Sandra E. Black, Michael Strong, Peter Kleinstiver, Natalie Rashkovan, Susan Bronskill, Sandra E. Black, Michael Borrie, Elizabeth Finger, Corinne Fischer, Andrew Frank, Morris Freedman, Sanjeev Kumar, Stephen Pasternak

Medical Biophysics Publications

The Ontario Neurodegenerative Research Initiative (ONDRI) is a 3 years multi-site prospective cohort study that has acquired comprehensive multiple assessment platform data, including 3T structural MRI, from neurodegenerative patients with Alzheimer's disease, mild cognitive impairment, Parkinson's disease, amyotrophic lateral sclerosis, frontotemporal dementia, and cerebrovascular disease. This heterogeneous cross-section of patients with complex neurodegenerative and neurovascular pathologies pose significant challenges for standard neuroimaging tools. To effectively quantify regional measures of normal and pathological brain tissue volumes, the ONDRI neuroimaging platform implemented a semi-automated MRI processing pipeline that was able to address many of the challenges resulting from this heterogeneity. The purpose …

A Hybrid Pet/Mri Brain Connectivity Approach For Improving Epilepsy Surgical Evaluation, Stefan E. Poirier

Electronic Thesis and Dissertation Repository

Hybrid PET/MRI can non-invasively improve epileptic focus (EF) localization prior to surgical resection in drug-resistant epilepsy (DRE), especially when MRI is negative. In this thesis, we developed an ¹⁸F-fluorodeoxyglucose (FDG) PET-guided diffusion tractography (PET/DTI) approach to assess white matter (WM) integrity in MRI-negative DRE and evaluated its potential impact on epilepsy surgical planning. To validate the potential of PET/MRI, we first evaluated the diagnostic competence of PET/MRI in DRE and found that PET/MRI provides similar diagnostic information as PET/CT (current clinical standard). For the PET/DTI approach, we used asymmetry index (AI) mapping of FDG-PET to guide WM fiber tractography …

Glutamate And Dysconnection In The Salience Network: Neurochemical, Effective Connectivity, And Computational Evidence In Schizophrenia, Roberto Limongi, Peter Jeon, Michael Mackinley, Tushar Das, Kara Dempster, Jean Théberge, Robert Bartha, Dickson Wong, Lena Palaniyappan

Medical Biophysics Publications

Background: Functional dysconnection in schizophrenia is underwritten by a pathophysiology of the glutamate neurotransmission that affects the excitation-inhibition balance in key nodes of the salience network. Physiologically, this manifests as aberrant effective connectivity in intrinsic connections involving inhibitory interneurons. In computational terms, this produces a pathology of evidence accumulation and ensuing inference in the brain. Finally, the pathophysiology and aberrant inference would partially account for the psychopathology of schizophrenia as measured in terms of symptoms and signs. We refer to this formulation as the 3-level hypothesis. Methods: We tested the hypothesis in core nodes of the salience network (the dorsal …

Longitudinal Changes Of Brain Microstructure And Function In Nonconcussed Female Rugby Players, Kathryn Y. Manning, Jeffrey S. Brooks, James P. Dickey, Alexandra Harriss, Lisa Fischer, Tatiana Jevremovic, Kevin Blackney, Christy Barreira, Arthur Brown, Robert Bartha, Tim Doherty, Douglas Fraser, Jeff Holmes, Gregory A. Dekaban, Ravi S. Menon

Medical Biophysics Publications

ObjectiveTo longitudinally assess brain microstructure and function in female varsity athletes participating in contact and noncontact sports.MethodsConcussion-free female rugby players (n = 73) were compared to age-matched (ages 18-23) female swimmers and rowers (n = 31) during the in- and off-season. Diffusion and resting-state fMRI (rs-fMRI) measures were the primary outcomes. The Sports Concussion Assessment Tool and head impact accelerometers were used to monitor symptoms and impacts, respectively.ResultsWe found cross-sectional (contact vs noncontact) and longitudinal (in- vs off-season) changes in white matter diffusion measures and rs-fMRI network connectivity in concussion-free contact athletes relative to noncontact athletes. In particular, mean, axial, …

Exploring The Effects Of Hemodialysis On Renal And Hepatic Blood Flow And Function Using Ct Perfusion Imaging, Raanan Marants

Electronic Thesis and Dissertation Repository

Hemodialysis (HD) is the most common form of renal replacement therapy for end-stage renal disease. However, patients develop complications that are driven by HD-induced circulatory stress from rapidly removing large fluid volumes during HD, making various vascular beds vulnerable to ischemia. By assessing how HD-induced circulatory stress affects different organs, it may be possible to characterize the mechanisms behind these complications and evaluate therapeutic interventions. This thesis aims to explore how HD affects renal and hepatic blood flow and function using CT perfusion imaging. For this work, patients received either standard or cooled HD first in a two-visit, crossover study …

Neurite Orientation Dispersion And Density Imaging In A Rodent Model Of Mild Traumatic Brain Injury, Patrick Mccunn

Electronic Thesis and Dissertation Repository

Mild traumatic brain injury (mTBI) has become a focal point within the medical community due to its increased prevalence in recent years. Unfortunately, there is currently no neuroimaging technique able to accurately diagnose and monitor mTBI in-vivo. One technique that has shown great promise is neurite orientation dispersion and density imaging (NODDI). NODDI is a diffusion MRI (dMRI) technique used to characterize microstructural complexity through the compartmental modelling of neural water fractions into Intra-neurite, Extra-neurite and CSF volume fractions. The overreaching theme of this thesis was to validate NODDI in a preclinical setting to then be applied to imaging …

Kinetic Analysis Of Dynamic Pet For Molecular, Functional And Physiological Characterization Of Diseases, Fiona Li

Electronic Thesis and Dissertation Repository

PET with targeted probes may better elucidate the molecular and functional basis of diseases. The widely used standardized uptake value from static imaging, however, cannot quantify the probe uptake processes like perfusion, permeability, binding to and disassociation (k₄) from target. The overarching thesis goal is to develop a model to enable kinetic analysis of dynamic imaging to separate these processes.

As perfusion delivery is not modelled in the current standard two tissue compartment (S2TC) model, I developed a flow modified two tissue compartment (F2TC) model that incorporates the blood flow effect. The model’s performances were investigated with simulation. …

Quantitative Dynamic Pet & Ct Perfusion For Cancer Imaging: Diagnosis & Monitoring Treatment Response, Dae-Myoung (Danny) Yang

Electronic Thesis and Dissertation Repository

Hybrid PET/CT imaging is a newer cancer imaging modality which allows contemporaneous PET metabolic/molecular and CT anatomical imaging during a single diagnostic session on a single device. However, current PET imaging has relied heavily on measuring the tracer accumulation in the tumour as a surrogate of the pathologic activity targeted by the tracer while CT is limited to measuring tumour size or visualizing tumour enhancement pattern, all of which lack sensitivity and specificity in detecting cancer and assessing treatment response. Therefore, it is critical to develop pharmacokinetic techniques for assessing the physiologic/molecular characteristics of tumours with clinical PET/CT scanners to …

A Novel System And Image Processing For Improving 3d Ultrasound-Guided Interventional Cancer Procedures, Derek J. Gillies

Electronic Thesis and Dissertation Repository

Image-guided medical interventions are diagnostic and therapeutic procedures that focus on minimizing surgical incisions for improving disease management and reducing patient burden relative to conventional techniques. Interventional approaches, such as biopsy, brachytherapy, and ablation procedures, have been used in the management of cancer for many anatomical regions, including the prostate and liver. Needles and needle-like tools are often used for achieving planned clinical outcomes, but the increased dependency on accurate targeting, guidance, and verification can limit the widespread adoption and clinical scope of these procedures. Image-guided interventions that incorporate 3D information intraoperatively have been shown to improve the accuracy and …