Medicine and Health Sciences Commons^™

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, …

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 …

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 …

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 …

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 …

Development Of Anatomical And Functional Magnetic Resonance Imaging Measures Of Alzheimer Disease, Samaneh Kazemifar

Electronic Thesis and Dissertation Repository

Alzheimer disease is considered to be a progressive neurodegenerative condition, clinically characterized by cognitive dysfunction and memory impairments. Incorporating imaging biomarkers in the early diagnosis and monitoring of disease progression is increasingly important in the evaluation of novel treatments. The purpose of the work in this thesis was to develop and evaluate novel structural and functional biomarkers of disease to improve Alzheimer disease diagnosis and treatment monitoring. Our overarching hypothesis is that magnetic resonance imaging methods that sensitively measure brain structure and functional impairment have the potential to identify people with Alzheimer’s disease prior to the onset of cognitive decline. …

Magnetic Resonance Imaging Of Breast Cancer Brain Metastasis Progression And Responses To Radiotherapy, Donna H. Murrell

Electronic Thesis and Dissertation Repository

Introduction: The incidence of brain metastasis due to breast cancer is increasing and prognosis is poor. Treatment is challenging for this disease because systemic therapy has limited efficacy due to the presence of the blood-brain barrier. In addition, it is thought that disseminated dormant cancer cells persist in metastatic organs and may evade treatment, thereby facilitating a mechanism for later recurrence. Methods: In this thesis, we use contrast-enhanced MRI and high resolution anatomical MRI to characterize blood-brain barrier integrity associated with the development of brain metastases due to HER2+ breast cancer in the SUM-190-BR3, JIMT-1-BR3, and MDA-MB-231-BR-HER2 experimental models. We …

Characterization Of Maga Expression And Iron Uptake In P19 Cells: Implications For Use As A Gene-Based Contrast Agent, Linshan Liu

Electronic Thesis and Dissertation Repository

Magnetic resonance imaging (MRI) is one of the non-invasive imaging modalities used in longitudinal cell tracking. Previous studies suggest that MagA, a putative iron transport protein from magnetotactic bacteria, is a useful gene-based magnetic resonance contrast agent. Hemagglutinin (HA)-tagged MagA was stably expressed in undifferentiated embryonic mouse teratocarcinoma, multipotent P19 stem cells to provide a suitable model for tracking these cells during differentiation. Western blot and immunocytochemistry confirmed the expression and membrane localization of MagA-HA in P19 cells. Elemental iron analysis using inductively-coupled plasma mass spectrometry revealed significant iron uptake in both parental and MagA-HA-expressing P19 cells, cultured in the …

Mri Relaxation Rates: A Quantitative Approach To Track Tumour Cells Expressing Maga, Anindita Sengupta

Electronic Thesis and Dissertation Repository

Using magnetic resonance imaging, relaxation rate measurements were

performed in cancer cells overexpressing a magnetotactic bacterial gene, MagA.

Measurements of magnetic resonance relaxation rates in this expression

system is important for optimizing cell detection and specificity, for developing

quantification methods, and for refinement of gene-based iron contrast using

magnetosome associated genes. We measured the total transverse

relaxation rate (R2^*), its irreversible and reversible components (R2 and R2^′,

respectively) and the longitudinal relaxation rate (R1) in MDA-MB-435 tumor cells.

Clonal lines overexpressing MagA were cultured in the presence and absence of

iron supplementation, and mounted in a …

In Vivo Cellular Mri In Experimental Traumatic Spinal Cord Injury, Laura E. Gonzalez-Lara

Electronic Thesis and Dissertation Repository

Spinal cord injury (SCI) remains one of the most devastating conditions in medicine; it is a complex medical condition with no cure currently available. Inflammation plays an important role in SCI as it can have both beneficial and detrimental effects. Cell therapy has emerged as a promising treatment for SCI due to the potential for stem cells, including multipotent mesenchymal stromal cells (MSC), for tissue regeneration and immunomodulation of the inflammatory cascade after the initial trauma. However, there are still important, unresolved questions regarding cell therapy that magnetic resonance imaging (MRI) can help to address by producing high-resolution images with …

From Isolated Tumour Cells To Overt Lymph Node Metastases: Biological And Imaging Studies On The Development Of Experimental Lymph Node Metastases, Michael M. Lizardo

Electronic Thesis and Dissertation Repository

Metastatic colonization and establishment of overt lymph node (LN) tumours indicates poor prognosis for cancer patients. However, the basic biology that influences the development of LN metastasis is poorly understood due to the lack of basic animal models. The following work provides a new lymph node experimental metastasis assay (LEMA) that permits the assessment of tumour cell fate after they arrest in draining LNs. In using this new model, we discovered that only 8% of the tumour cells that arrive in the LN are successful in forming overt tumours. This work also explored the use of imaging approaches to monitor …