Medicine and Health Sciences Commons^™

Cognitive Decline In Thrombotic Thrombocytopenic Purpura Survivors: The Role Of White Matter Health As Assessed By Mri., F Hannan, J Hamilton, C J Patriquin, K Pavenski, M T Jurkiewicz, L Tristao, A M Owen, P K Kosalka, S C L Deoni, J Théberge, J Mandzia, S H S Huang, J D Thiessen

Department of Medicine Publications

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare condition caused by severe ADAMTS13 deficiency, leading to platelet aggregation and thrombosis. Despite treatment, patients are prone to cognitive impairment and depression. We investigated brain changes in iTTP patients during remission using advanced magnetic resonance imaging (MRI) techniques, correlating these changes with mood and neurocognitive tests. Twenty iTTP patients in remission (30 days post-haematological remission) were compared with six healthy controls. MRI scans, including standard and specialized sequences, were conducted to assess white matter health. Increased T1 relaxation times were found in the cingulate cortex (p < 0.05), and elevated T2 relaxation times were observed in the cingulate cortex, frontal, parietal and temporal lobes (p < 0.05). Pathological changes in these areas are correlated with impaired cognitive and depressive scores in concentration, short-term memory and verbal memory. This study highlights persistent white matter damage in iTTP patients, potentially contributing to depression and cognitive impairment. Key regions affected include the frontal lobe and cingulate cortex. These findings have significant implications for the acute and long-term management of iTTP, suggesting a need for re-evaluation of treatment approaches during both active phases and remission. Further research is warranted to enhance our understanding of these complexities.

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 …

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 …

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, …

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, …

Noninvasive Quantification Of Tissue Sodium Concentration In The Kidney Disease Spectrum Using 23na Magnetic Resonance Imaging, Fabio R. Salerno

Electronic Thesis and Dissertation Repository

Chronic kidney disease (CKD), especially when requiring kidney replacement therapy (hemodialysis (HD) and peritoneal dialysis (PD)), is associated with extracellular water expansion with increased total body sodium. Sodium can also be accumulated in tissues independently of extracellular water. Sodium-23 magnetic resonance imaging (²³Na MRI) can quantify the concentration of sodium nuclei in tissues. Applied to the human leg, quantification of tissue sodium concentrations mainly at the skin and muscle level is possible. We hypothesized that increased tissue sodium concentrations exert toxic effects in CKD and dialysis. We aimed to (1) compare tissue sodium concentrations in adults, children and …

Quantitative Mri And 3d-Printing For Monitoring Periprosthetic Joint Infection, Greg Hong

Electronic Thesis and Dissertation Repository

Joint replacements are becoming increasingly commonplace with over 130,000 joint arthroplasties being performed annually in Canada. Although joint replacement surgery is highly successful, implants do occasionally fail and need to be replaced via costly and difficult revision surgery. Periprosthetic joint infection (PJI) has recently become the leading reason for revision of both hip and knee replacements, which is unfortunate because PJI is difficult to diagnose and treat effectively; diagnosis is made particularly difficult by the lack of established non-invasive (imaging) means of evaluating PJI. This thesis aims to demonstrate that magnetic resonance imaging (MRI) has potential for diagnosing and monitoring …

Examining The Association Between Brain Mri Measures At 7 Tesla And Cognition Following Covid-19 Infection, Helma Heidari

Electronic Thesis and Dissertation Repository

The long-term neuropsychological, cognitive, and neurobiological effects of the severe acute respiratory syndrome (SARS-CoV-2) in survivors with milder symptoms are still poorly understood. In this thesis we evaluated cognitive and psychological changes approximately five weeks after a wide range of symptoms in COVID-19 illness and determined whether advanced diffusion magnetic resonance imaging measures within subcortical brain structures of the limbic system were related to neurological, respiratory, psychiatric, and gastric symptoms experienced during the acute phase of illness. Cognitive and neuropsychological evaluations were performed in 45 participants who experienced neurological symptoms during the acute phase of COVID-19 illness. Participants also underwent …

Automation Through Deep-Learning To Quantify Ventilation Defects In Lungs From High-Resolution Isotropic Hyperpolarized 129xe Magnetic Resonance Imaging, Tuneesh Kaur Ranota

Electronic Thesis and Dissertation Repository

Obstructive lung diseases are characterized by heterogenous ventilation. Hyperpolarized ¹²⁹Xe gas lung magnetic resonance imaging (MRI) can examine lung ventilation heterogeneity by acquiring high-resolution isotropic images. The current gold standard of semi-automated (SA) segmentation can be used to quantify non-isotropic ¹²⁹Xe lung images to generate ventilation defect percent (VDP), however, this method is not suitable for analysis of isotropic voxel ¹²⁹Xe images due to the large number of slices. Therefore, we used a fully automated deep learning-based (DL) lung algorithm to calculate VDP from isotropic images. SNR, SA and DL-based VDP were calculated, showing a strong positive …

Visualization And Manual Segmentation Of The Post-Mortem Human Amygdala Subnuclei Using Ultra High Field Magnetic Resonance Imaging, Sara M. Pac

Electronic Thesis and Dissertation Repository

The human amygdala is composed of 13 functionally and anatomically distinct subnuclei. Because most nuclei are difficult to distinguish at the microanatomical level, they are also challenging to discern macroscopically. In low field strength magnetic resonance imaging (MRI) studies, the amygdala can be identified only in its entirety. Higher resolution scans can be acquired by employing ultra-high field strength MRI acquisition techniques. We present a step-by-step guide for the manual segmentation of the amygdala subnuclei at ultra-high field 9.4T MRI. Post-mortem human brain specimen amygdala prosections fit for the 9.4T MRI bore allowed for the collection of high resolution T2-weighted …

Ex Vivo Thrombus Magnetic Resonance Imaging Features And Patient Clinical Data Enable Prediction Of Acute Ischemic Stroke Cause, Spencer D. Christiansen, Junmin Liu, Maria Bres Bullrich, Manas Sharma, Sachin K. Pandey, Melfort Boulton, Sebastian Fridman, Luciano A. Sposato, Maria Drangova

Robarts Vascular Research Publications

The cause of ischemic stroke often remains elusive even after full stroke workup is completed. Cardioembolic mechanisms in particular are frequently presumed but challenging to definitively diagnose. Quantitative thrombus texture analysis is emerging as a powerful tool for stroke characterization, having shown the ability to predict response to stroke treatment,1 but its ability to predict stroke cause and complement machine learning models built from standard clinical features has not been studied.2, 3 The purpose of this study is to evaluate the ability of radiomics features extracted from quantitative magnetic resonance images of retrieved ischemic stroke thrombi (R2*(=1/T2*), …

Repetitive Mild Traumatic Brain Injury In Mice Triggers A Slowly Developing Cascade Of Long-Term And Persistent Behavioral Deficits And Pathological Changes, Xiaoyun Xu, Matthew Cowan, Flavio Beraldo, Amy Schranz, Patrick Mccunn, Nicole Geremia, Zalman Brown, Maitray Patel, Karen L. Nygard, Reza Khazaee, Lihong Lu, Xingyu Liu, Michael J. Strong, Gregory A. Dekaban, Ravi Menon, Robert Bartha, Mark Daley, Haojie Mao, Vania Prado, Marco A.M. Prado, Lisa Saksida, Tim Bussey, Arthur Brown

Medical Biophysics Publications

We have previously reported long-term changes in the brains of non-concussed varsity rugby players using magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI) and functional magnetic imaging (fMRI). Others have reported cognitive deficits in contact sport athletes that have not met the diagnostic criteria for concussion. These results suggest that repetitive mild traumatic brain injuries (rmTBIs) that are not severe enough to meet the diagnostic threshold for concussion, produce long-term consequences. We sought to characterize the neuroimaging, cognitive, pathological and metabolomic changes in a mouse model of rmTBI. Using a closed-skull model of mTBI that when scaled to human leads …

The Effects Of Resistance Training On Cognition And Brain Health In Older Adults At Risk For Diabetes: A Pilot Feasibility Study, Joyla Furlano

Electronic Thesis and Dissertation Repository

Type 2 diabetes is associated with neurocognitive deficits and increased risk for dementia, with high prevalence of diabetes occurring in old age. There are many known risk factors for diabetes, including physical inactivity, obesity, and prediabetes. Studies show that individuals who are at risk for diabetes (i.e., have one or more risk factors) already experience some brain deficits seen in diabetes. One way to combat these deficits is aerobic exercise; however, the effects of resistance exercise in this population are relatively unknown. The objectives of this thesis were to report on the current evidence of brain deficits in prediabetes, and …

Mri Of Structural & Functional Changes Associated With Western Diet Consumption, Lauren M. Smith

Electronic Thesis and Dissertation Repository

The Western diet (WD) is a high-fat, high-sugar diet increasingly common in the Western world and is associated with adverse effects in many organs, though the mechanisms behind these changes are unclear. Magnetic resonance imaging (MRI) techniques that provide structural and functional information non-invasively were used to investigate the effect of the WD on the liver and placenta in a guinea pig model.

The WD leads to a manifestation of the metabolic syndrome in the liver known as non-alcoholic fatty liver disease (NAFLD). Fat-fraction MRI was used to confirm the onset of NAFLD in a guinea pig model fed a …

Survival Benefit For Individuals With Constitutional Mismatch Repair Deficiency Syndrome And Brain Tumors Who Undergo Surveillance Protocol. A Report From The International Replication Repair Consortium, Ayse Bahar Ercan, Carol Durno, Vanessa J. Bianchi, Melissa Edwards, Melyssa Aronson, Eric Bouffet, Abeer Al-Battashi, Musa Alharbi, Donald Basel, Elizabeth Cairney

Paediatrics Publications

BACKGROUND

Constitutional mismatch repair deficiency syndrome (CMMRD) is a severe cancer predisposition syndrome resulting in early onset central nervous system (CNS) and other cancers. International guidelines for surveillance exist but no study has systematically evaluated the efficacy of this protocol. METHODS

We surveyed all confirmed CMMRD patients in the International Replication Repair Deficiency Consortium. A surveillance protocol consisting of frequent biochemical, endoscopic and imaging (CNS and total body MRI) studies were employed. Survival analyses and efficacy of each method were assessed. RESULTS

Surveillance data were collected from 105 CMMRD individuals from 41 countries. Of the 193 malignant tumors, CNS malignancies …

Examining Brain Connectivity And Reading Ability In Children, Alexandra M. Cross

Electronic Thesis and Dissertation Repository

In this thesis, I investigated the relationship between functional and structural connectivity and reading ability in children. Prior research has tended to use single word reading measures or composite measures, however this is problematic as reading is a complex skill relying on multiple subskills, such as decoding efficiency, sight word reading efficiency, reading comprehension, and rapid automatized naming. As a result, the multi-faceted relationship between brain connectivity and reading ability is not well understood. I aimed to address this issue by considering multiple reading subskills while examining the neural substrates of reading. In Chapter 2, I examined how individual differences …

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 …

Quantitative Magnetic Resonance Imaging Of Knee Articular Cartilage And Effusion-Synovitis: The Structural Response To Changes In Joint Loading, Hayden F. Atkinson

Electronic Thesis and Dissertation Repository

Knee osteoarthritis (OA) is a progressive degenerative condition that can affect all tissues within the joint. Methods to measure early changes in joint structures and the effect of interventions are required. The purpose of this thesis was to investigate aspects of quantitative magnetic resonance imaging (MRI) as outcome measures in knee OA studies. Specifically, changes in articular cartilage composition and/or effusion-synovitis were examined in people with or at risk for knee OA and healthy controls, and after altering joint loads.

Chapter 2 is a systematic review that studied articular cartilage composition using MRI T2 and T1ρ relaxation in patients at …

Fev1 And Mri Ventilation Defect Reversibility In Asthma And Copd, Hana Serajeddini, Rachel L Eddy, Christopher Licskai, David G Mccormack, Grace Parraga

Medical Biophysics Publications

The underlying pathophysiological determinants of asthma and chronic obstructive pulmonary disease (COPD) are related in complex ways. Importantly however, post-bronchodilator FEV1- reversibility may occur in approximately 50% of COPD patients whilst epidemiological and magnetic-resonance-imaging (MRI) studies suggest that in asthmatics, FEV1-reversibility may diminish over time. As compared to patients with asthma or COPD alone, patients with coexisting asthma and COPD report worse clinical outcomes and increased healthcare costs and burden.

Pulmonary Xenon-129 Mri: New Opportunities To Unravel Enigmas In Respiratory Medicine, Rachel L Eddy, Grace Parraga

Medical Biophysics Publications

No abstract provided.

Does An Acute Achilles Tendon Rupture Become A Patient's Achilles Heel In The Long-Term?, Michaela Cm Khan

Electronic Thesis and Dissertation Repository

It is unknown if deficits in the involved limb following acute Achilles tendon rupture (AATR) persist in the long-term, or differ between patients treated operatively or non-operatively. This study investigated 43 patients 15±1 years post-AATR from a previous randomized controlled trial (RCT) that compared operative and non-operative treatment. Structural characteristics in the Achilles tendon and surrounding musculature were assessed using magnetic resonance imaging. We also performed physical examinations and evaluated performance-based and patient-reported outcomes. Overall, there were substantial differences between the involved and uninvolved limbs in most outcomes. Some outcomes improved over time from the initial RCT to the final …

Investigating In Vivo Brain Metabolite Levels In Concussed Female Athletes And A Murine Model Of Repetitive Closed Head Injury, Amy L. Schranz

Electronic Thesis and Dissertation Repository

After a concussion there is a complex cascade of events, termed the neurometabolic cascade, that includes changes in ion flux, neurotransmission, and cellular energetics. How this pathophysiological process translates into cognitive deficits remains poorly understood. Magnetic resonance spectroscopy (MRS) provides a non-invasive technique that allows for the quantification of brain metabolites that are involved in these processes, including glutamate and glutamine, which are involved in neurotransmission. Moreover, female athletes are underrepresented in studies on concussion, limiting our knowledge and understanding of sex differences. The overall goal of this thesis was to examine metabolite changes using MRS in female athletes before …

Ultra-High Field Magnetic Resonance Imaging For Stereotactic Neurosurgery, Jonathan Lau

Electronic Thesis and Dissertation Repository

Stereotactic neurosurgery is a subspecialty within neurosurgery concerned with accurate targeting of brain structures. Deep brain stimulation (DBS) is a specific type of stereotaxy in which electrodes are implanted in deep brain structures. It has proven therapeutic efficacy in Parkinson’s disease and Essential Tremor, but with an expanding number of indications under evaluation including Alzheimer’s disease, depression, epilepsy, and obesity, many more Canadians with chronic health conditions may benefit. Accurate surgical targeting is crucial with millimeter deviations resulting in unwanted side effects including muscle contractions, or worse, vessel injury. Lack of adequate visualization of surgical targets with conventional lower field …

The Canadian Dementia Imaging Protocol: Harmonization Validity For Morphometry Measurements, Olivier Potvin, Isabelle Chouinard, Louis Dieumegarde, Robert Bartha, Pierre Bellec, D. Louis Collins, Maxime Descoteaux, Rick Hoge, Joel Ramirez, Christopher J.M. Scott, Eric E. Smith, Stephen C. Strother, Sandra E. Black, Simon Duchesne

Medical Biophysics Publications

© 2019 The Authors The harmonized Canadian Dementia Imaging Protocol (CDIP) has been developed to suit the needs of a number of co-occurring Canadian studies collecting data on brain changes across adulthood and neurodegeneration. In this study, we verify the impact of CDIP parameters compliance on total brain volume variance using 86 scans of the same individual acquired on various scanners. Data included planned data collection acquired within the Consortium pour l'identification précoce de la maladie Alzheimer - Québec (CIMA-Q) and Canadian Consortium on Neurodegeneration in Aging (CCNA) studies, as well as opportunistic data collection from various protocols. For images …

Effect Of Ultrafiltration During Hemodialysis On Hepatic And Total-Body Water: An Observational Study., Claire J Grant, Trevor P Wade, Charles A Mckenzie, Guido Filler, Christopher W Mcintyre, Huang S. Shih-Han

Paediatrics Publications

Background

The hepatic circulation is involved in adaptive systemic responses to circulatory stress. However, it is vulnerable to both chronic hypervolemia and cardiac dysfunction. The influence of hemodialysis (HD) and ultrafiltration (UF) upon liver water content has been understudied. We conducted a detailed pilot study to characterize the effects of HD upon liver water content and stiffness, referenced to peripheral fluid mobilization and total body water.

Methods

We studied 14 established HD patients without liver disease. Magnetic resonance imaging (MRI) together with ultrasound-based elastography and bioimpedance assessment were employed to measure hepatic water content and stiffness, body composition, and water …

Retrospective Motion Correction In Magnetic Resonance Imaging Of The Brain, Patricia Johnson

Electronic Thesis and Dissertation Repository

Magnetic Resonance Imaging (MRI) is a tremendously useful diagnostic imaging modality that provides outstanding soft tissue contrast. However, subject motion is a significant unsolved problem; motion during image acquisition can cause blurring and distortions in the image, limiting its diagnostic utility. Current techniques for addressing head motion include optical tracking which can be impractical in clinical settings due to challenges associated with camera cross-calibration and marker fixation. Another category of techniques is MRI navigators, which use specially acquired MRI data to track the motion of the head.

This thesis presents two techniques for motion correction in MRI: the first is …

In Vivo Tracking Of Tumour Associated Macrophages In Breast Cancer With Magnetic Resonance Imaging, Ashley V. Makela

Electronic Thesis and Dissertation Repository

Introduction: The environment in which a tumour exists and functions is called the tumour microenvironment (TME). In breast cancer, the presence of tumour associated macrophages (TAMs) in the TME is associated with tumour aggressiveness and poor outcomes. Despite evidence for a link between TAM content and outcome, there are few strategies to measure TAMs and no in vivo approach. Iron or fluorine-19 (¹⁹F)-based MRI can be used to detect macrophages post intravenous injection of either an iron or perfluorocarbon (PFC) agent. Iron-based MRI is sensitive but difficult to quantify. ¹⁹F MRI is specific and signal is proportional …

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 …

Magnetic Resonance Imaging In The Diagnosis Of White Matter Signal Abnormalities., Ravi Datar, Asuri Narayan Prasad, Keng Yeow Tay, Charles Anthony Rupar, Pavlo Ohorodnyk, Michael Miller, Chitra Prasad

Paediatrics Publications

Background White matter abnormalities (WMAs) pose a diagnostic challenge when trying to establish etiologic diagnoses. During childhood and adult years, genetic disorders, metabolic disorders and acquired conditions are included in differential diagnoses. To assist clinicians and radiologists, a structured algorithm using cranial magnetic resonance imaging (MRI) has been recommended to aid in establishing working diagnoses that facilitate appropriate biochemical and genetic investigations. This retrospective pilot study investigated the validity and diagnostic utility of this algorithm when applied to white matter signal abnormalities (WMSAs) reported on imaging studies of patients seen in our clinics. Methods The MRI algorithm was applied to …