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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 …

Towards A Comprehensive Software Suite For Stereotactic Neurosurgery, Greydon Gilmore

Electronic Thesis and Dissertation Repository

Stereotactic neurosurgery is a subspeciality within neurosurgery that relies on accurately targeting structures within the brain for diagnostic and therapeutic purposes. Surgical implantation of electrodes is a common procedure in stereotactic neurosurgery. For instance, deep brain stimulation (DBS) is an effective treatment option for individuals living with movement disorders while stereoelectroencephalography (SEEG) provides invaluable information from individuals living with drug-resistant epilepsy. In both procedures, electrophysiology data is acquired and used to identify brain characteristics such as surgical target location in DBS surgery and the seizure onset zone in SEEG surgery. Accurate surgical targeting of the electrodes is crucial, with millimeter …

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 …