Medicine and Health Sciences Commons^™

Mobilising Expertise And Resources To Close The Radiotherapy Gap In Cancer Care., D Rodin, J Longo, T Sherertz, M M Shah, O Balagun, N Wendling, Jacob Van Dyk, C N Coleman, M J Xu, S Grover

Oncology Publications

Closing the gap in cancer care within low- and middle-income countries and in indigenous and geographically isolated populations in high-income countries requires investment and innovation. This is particularly true for radiotherapy, for which the global disparity is one of the largest in healthcare today. New models and paradigms and non-traditional collaborations have been proposed to improve global equity in cancer control. We describe recent initiatives from within the radiation oncology community to increase access to treatment, build the low- and middle-income countries' radiation oncology workforce, mobilise more professionals from within high-income countries and raise awareness of the global need for …

Analysis Of Global Radiotherapy Needs And Costs By Geographic Region And Income Level., E Zubizarreta, Jacob Van Dyk, Y Lievens

Oncology Publications

Recent years have seen various reviews on the lack of access to radiotherapy often based on geographic regions of the world such as Africa, Asia Pacific, Europe, Latin America and North America. Countries are often defined by their national income per capita levels based on World Bank definitions of high income, upper middle income, lower middle income and low income. Within the world regions, there are significant variations in gross national income (GNI) per capita among the different countries, and even within similar income levels, large variations exist. This report presents the actual status of radiotherapy and analyses the current …

Characterization Of N-Butyl Cyanoacrylate (Nbca) Glue Polymerization For The Embolization Of Brain Arteriovenous Malformations (Avms), Bill H. Wang

Electronic Thesis and Dissertation Repository

Brain AVMs are abnormal connections between arteries and veins. Endovascular glue embolization with NBCA is an accepted form of treatment. The reported complication rates of NBCA embolization varies widely from 2-15%, and timing of polymerization plays a major role.

Polymerization time was measured for mixtures of lipiodol/NBCA of 50/50, 70/30, 60/40. The influence of pH, temperature and presence of biological catalysts on polymerization time was investigated in-vivo. PVA-C, silicone and endothelium surfaces were compared. High-speed video analysis of glue injection through a microcatheter was performed.

Polymerization rate increases with pH and temperature. A hydrophilic surface such as PVA-C better mimics …

Accuracy Requirements And Uncertainties In Radiotherapy: A Report Of The International Atomic Energy Agency., Debbie Van Der Merwe, Jacob Van Dyk, Brendan Healy, Eduardo Zubizarreta, Joanna Izewska, Ben Mijnheer, Ahmed Meghzifene

Oncology Publications

BACKGROUND: Radiotherapy technology continues to advance and the expectation of improved outcomes requires greater accuracy in various radiotherapy steps. Different factors affect the overall accuracy of dose delivery. Institutional comprehensive quality assurance (QA) programs should ensure that uncertainties are maintained at acceptable levels. The International Atomic Energy Agency has recently developed a report summarizing the accuracy achievable and the suggested action levels, for each step in the radiotherapy process. Overview of the report: The report seeks to promote awareness and encourage quantification of uncertainties in order to promote safer and more effective patient treatments. The radiotherapy process and the radiobiological …

Radiation Oncology Quality And Safety Considerations In Low Resource Settings: A Medical Physics Perspective, Jacob Van Dyk, Ahmed Meghzifene

Oncology Publications

The last few years have seen a significant growth of interest in the global radiation therapy crisis. Various organizations have quantified the need and are providing aid in support of addressing the shortfalls existing in many low-to-middle income countries (LMICs). With the tremendous demand for new facilities, equipment and personnel, it is very important to recognize the quality and safety challenges and to address them directly. An examination of publications on quality and safety in radiation therapy indicates a consistency in a number of the recommendations; however, these authoritative reports were generally based on input from high-resourced contexts. Here we …

Multi-Nuclear Magnetic Resonance Imaging Of Obstructive Lung Disease, Khadija Sheikh

Electronic Thesis and Dissertation Repository

Obstructive lung diseases such as chronic-obstructive-lung-disease (COPD), bronchiectasis, and asthma are characterized by airflow obstruction. They affect over six million Canadians costing the economy $12 billion/year. Despite decades of research, therapies that modify obstructive-lung-disease progression and control are lacking because patient diagnosis, monitoring, and response to therapy are currently made using airflow measurements that may conceal the independent contributions of underlying pathologies. One goal of obstructive-lung-disease research is to develop ways to identify patients with specific underlying pathological phenotypes to improve patient care and outcomes. Thoracic computed-tomography (CT) and magnetic-resonance-imaging (MRI) provide ways to regionally identify the underlying pathologies associated …

Design And Evaluation Of A Catheter Contact-Force Controller For Cardiac Ablation Therapy., Daniel Gelman, Allan C Skanes, Mohammad A Tavallaei, Maria Drangova

Medical Biophysics Publications

GOAL: Maintaining a constant contact force (CF) of an ablation catheter during cardiac catheter ablation therapy is clinically challenging due to inherent myocardial motion, often resulting in poor ablation of arrhythmogenic substrates. To enable a prescribed contact force to be applied during ablation, a catheter contact force controller (CCFC) was developed.

METHODS: The system includes a hand-held device attached to a commercial catheter and steerable sheath. A compact linear motor assembly attaches to an ablation catheter and autonomously controls its relative position within the shaft of the steerable sheath. A closed-loop control system is implemented within embedded electronics to enable …

Effect Of Left Atrial Wall Thickness On Radiofrequency Ablation Success., Jiro Inoue, Allan C Skanes, Lorne J Gula, Maria Drangova

Medical Biophysics Publications

INTRODUCTION: Radiofrequency (RF) ablation in thicker regions of the left atrium (LA) may require increased ablation energy in order to achieve effective transmural lesions. Consequently, many cases of recurrent atrial fibrillation (AF) postablation may be due to thicker-than-normal atrial tissue. The aim of this study was to test the hypotheses that patients with recurrent AF have thicker tissue overall and that electrical reconnection is more likely in regions of thicker tissue.

METHODS AND RESULTS: Retrospective analysis was performed on 86 CT images acquired preoperatively from a cohort of 119 patients who had undergone RF ablation for AF. Of these, 33 …

Energy Subtraction Methods As An Alternative To Conventional X-Ray Angiography, Christiane S. Burton

Electronic Thesis and Dissertation Repository

Digital subtraction angiography (DSA) is a technique that is widely used to enhance the visibility of small vessels obscured by background structures by subtracting a mask and contrast image. However, DSA is generally unsuccessful for imaging the heart due to the motion that occurs between mask and contrasted images which cause motion artifacts. An alternative approach known as energy subtraction angiography (ESA) exploits the iodine k-edge by acquiring contrast images with a low and high kV in rapid succession to bring the benefits of DSA without motion artifacts. However, it was concluded that image quality for ESA could not compete …

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. …

Global Access To Radiation Therapy For Cervical Cancer: The Cost Of Inaction, Jacob Van Dyk, D Rodin, Timothy Paul Hanna, E Burger, Eduardo Zubizarreta, Mei Ling Yap, Michael Barton, Rifat Atun, Felicia Marie Knaul, Y Lievens, Mary K. Gospodarowicz, D A. Jaffray, M Milosevic

Oncology Publications

No abstract provided.

Carotid Artery Atherosclerosis In Patients With Active Rheumatoid Arthritis: Predictors Of Plaque Occurrence And Progression Over 24 Weeks, Janet E Pope, Tatiana Nevskaya, Lillian Barra, Grace Parraga

Medical Biophysics Publications

INTRODUCTION: This study evaluated the prevalence and progression of subclinical carotid artery atherosclerosis in active rheumatoid arthritis (RA).

METHODS: Carotid arteries of RA patients were scanned using 3D ultrasound at baseline and 24 weeks for total plaque area, vessel wall volume, and intima-media thickness (IMT), as well as arterial stiffness measured using pulse wave velocity. Variables related to inflammation, lipids and cardiovascular (CV) risk were assessed for associations with plaque progression. Of 195 screened patients, 31 met inclusion criteria (66 Swollen joint count (SJC) plus 68 Tender joint count (TJC)≥8 OR SJC plus TJC≥4 with elevated acute phase reactants) and …

Design, Development And Evaluation Of A Compact Telerobotic Catheter Navigation System., Mohammad Ali Tavallaei, Daniel Gelman, Michael Konstantine Lavdas, Allan C Skanes, Douglas L Jones, Jeffrey S Bax, Maria Drangova

Medical Biophysics Publications

BACKGROUND: Remote catheter navigation systems protect interventionalists from scattered ionizing radiation. However, these systems typically require specialized catheters and extensive operator training.

METHODS: A new compact and sterilizable telerobotic system is described, which allows remote navigation of conventional tip-steerable catheters, with three degrees of freedom, using an interface that takes advantage of the interventionalist's existing dexterity skills. The performance of the system is evaluated ex vivo and in vivo for remote catheter navigation and ablation delivery.

RESULTS: The system has absolute errors of 0.1 ± 0.1 mm and 7 ± 6° over 100 mm of axial motion and 360° of …

Characterizing The Role Of The Neuropeptide Y-Y5r System In Breast Cancer, Jenna Kara

Electronic Thesis and Dissertation Repository

Studies have demonstrated a correlation between stress and an increased risk of breast cancer. Neuropeptide Y (NPY) is up- regulated in chronic stress and induces proliferation and chemotaxis of 4T1 breast cancer cells via Y5 receptor (Y5R) activation. In the studies performed in this thesis, we characterize NPY-Y5R as a regulatory system that promotes breast cancer metastasis. We compared three cancer cell sublines derived from the same murine mammary fat pad tumour, that greatly differ in metastatic potential (67NR, 168FARN, and 4T1) in addition to a 4T1-Y5R knockdown established in our labs. In this thesis we demonstrate significance of up-regulation …

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 …

Radiomics For Response Assessment After Stereotactic Radiotherapy For Lung Cancer, Sarah A. Mattonen

Electronic Thesis and Dissertation Repository

Stereotactic ablative radiotherapy (SABR) is a guideline-specified treatment option for patients with early stage non-small cell lung cancer. After treatment, patients are followed up regularly with computed tomography (CT) imaging to determine treatment response. However, benign radiographic changes to the lung known as radiation-induced lung injury (RILI) frequently occur. Due to the large doses delivered with SABR, these changes can mimic the appearance of a recurring tumour and confound response assessment. The objective of this work was to evaluate the accuracy of radiomics, for prediction of eventual local recurrence based on CT images acquired within 6 months of treatment. A …

Digging Deeper With Diffuse Correlation Spectroscopy, Kyle J. Verdecchia

Electronic Thesis and Dissertation Repository

Patients with neurological diseases are vulnerable to cerebral ischemia, which can lead to brain injury. In the intensive care unit (ICU), neuromonitoring techniques that can detect flow reductions would enable timely administration of therapies aimed at restoring adequate cerebral perfusion, thereby avoiding damage to the brain. However, suitable bedside neuromonitoring methods sensitive to changes of blood flow and/or oxygen metabolism have yet to be established.

Near-infrared spectroscopy (NIRS) is a promising technique capable of non-invasively monitoring flow and oxygenation. Specifically, diffuse correlation spectroscopy (DCS) and time-resolved (TR) NIRS can be used to monitor blood flow and tissue oxygenation, respectively, and …

Optimizing Respiratory Gated Intensity Modulated Radiation Therapy Planning And Delivery Of Early-Stage Non-Small Cell Lung Cancer, Ilma Xhaferllari

Electronic Thesis and Dissertation Repository

Stereotactic ablative body radiotherapy (SABR) is the standard of care for inoperable early-stage non-small cell lung cancer (NSCLC) patients. However, thoracic tumours are susceptible to respiratory motion and, if unaccounted for, can potentially lead to dosimetric uncertainties. Respiratory gating is one method that limits treatment delivery to portions of the respiratory cycle, but when combined with intensity-modulated radiotherapy (IMRT), requires rigorous verification. The goal of this thesis is to optimize respiratory gated IMRT treatment planning and develop image-guided strategies to verify the dose delivery for future early-stage NSCLC patients.

Retrospective treatment plans were generated for various IMRT delivery techniques, including …

Quantitative Pet-Ct Perfusion Imaging Of Prostate Cancer, Adam R. Blais

Electronic Thesis and Dissertation Repository

Functional imaging of ¹⁸F-Fluorocholine PET holds promise in the detection of dominant prostatic lesions. Quantitative parameters from PET-CT Perfusion may be capable of measuring choline kinase activity, which could assist in identification of the dominant prostatic lesion for more accurate targeting of biopsies and radiation dose escalation.

The objectives of this thesis are: 1) investigate the feasibility of using venous TACs in quantitative graphical analysis, and 2) develop and test a quantitative PET-CT Perfusion imaging technique that shows promise for identifying dominant prostatic lesions.

Chapter 2 describes the effect of venous dispersion on distribution volume measurements with the Logan …

Arthrokinematics Of The Distal Radioulnar Joint In The Normal Wrist And Following Distal Radius Malunion, Braden M. Gammon

Electronic Thesis and Dissertation Repository

Contact patterns in the distal radioulnar joint (DRUJ) are not well understood for normal anatomy or with distal radius deformity. This thesis presents three studies which investigate the arthrokinematics of the DRUJ for these conditions. The first study compared casting and Tekscan, two standard methods for contact measurement, with a novel technique of proximity mapping termed Inter-cartilage Distance (ICD). The relative benefits, limitations and role for ICD in DRUJ contact assessment were examined and discussed. The second study used ICD to characterize contact patterns in the native DRUJ. Contact was found to be maximal in 10 degrees of supination and …

Hyperpolarized 3he Magnetic Resonance Imaging Ventilation Defects In Asthma: Relationship To Airway Mechanics, Del Leary, Sarah Svenningsen, Fumin Guo, Swati Bhatawadekar, Grace Parraga, Geoffrey N Maksym

Medical Biophysics Publications

In patients with asthma, magnetic resonance imaging (MRI) provides direct measurements of regional ventilation heterogeneity, the etiology of which is not well-understood, nor is the relationship of ventilation abnormalities with lung mechanics. In addition, respiratory resistance and reactance are often abnormal in asthmatics and the frequency dependence of respiratory resistance is thought to reflect ventilation heterogeneity. We acquiredMRIventilation defect maps, forced expiratory volume in one-second (FEV1), and airways resistance (Raw) measurements, and used a computational airway model to explore the relationship of ventilation defect percent (VDP) with simulated measurements of respiratory system resistance (Rrs) and reactance (Xrs).MRIventilation defect maps were …

Optimizing The Rehabilitation Of Elbow Lateral Collateral Ligament Injuries, Ranita Harpreet Kaur Manocha

Electronic Thesis and Dissertation Repository

Elbow lateral collateral ligament (LCL) injuries frequently arise following trauma, and can result in disabling instability. Typically such injuries are managed with immobilization followed by a graduated exercise regime; however there is minimal biomechanical evidence to support current treatment protocols. This investigation examines the in vitro effectiveness of several rehabilitation techniques using a custom elbow motion simulator. It was found that active range of motion is safest in the overhead position (n = 7). Early motion in this position may reduce the incidence of elbow stiffness without compromising ligament healing following LCL injury. Forearm pronation and active motion stabilize …

Imaging How And Where We Breathe Oxygen: Another Big Short?, Dante P I Capaldi, Fumin Guo, Grace Parraga

Medical Biophysics Publications

The Big Short tells the story of a small group of skeptics who profited from the financial crisis in 2007 by betting against collateralized (mortgage) debt obligations (CDO). Importantly, the novel paints a clear picture of the eccentric nature of contrarians who think divergently and against the grain or bet against an accepted truth or “sure” thing. In a similar manner, Ishii and co-workers’ recent work describes their team’s development of a pulmonary imaging technology that provides divergent and disruptive in vivo lung measurements of oxygen partial pressure in the context of the prevailing and longstanding consensus around FEV1 as …

Pulmonary Ct And Mri Phenotypes That Help Explain Chronic Pulmonary Obstruction Disease Pathophysiology And Outcomes, Eric A Hoffman, David A Lynch, R Graham Barr, Edwin J R Van Beek, Grace Parraga

Medical Biophysics Publications

Pulmonary x-ray computed tomographic (CT) and magnetic resonance imaging (MRI) research and development has been motivated, in part, by the quest to subphenotype common chronic lung diseases such as chronic obstructive pulmonary disease (COPD). For thoracic CT and MRI, the main COPD research tools, disease biomarkers are being validated that go beyond anatomy and structure to include pulmonary functional measurements such as regional ventilation, perfusion, and inflammation. In addition, there has also been a drive to improve spatial and contrast resolution while at the same time reducing or eliminating radiation exposure. Therefore, this review focuses on our evolving understanding of …

This Is What Copd Looks Like, Khadija Sheikh, Harvey O Coxson, Grace Parraga

Medical Biophysics Publications

Despite decades of research, and the growing healthcare and societal burden of chronic obstructive pulmonary disease (COPD), therapeutic COPD breakthroughs have not occurred. Sub-optimal COPD patient phenotyping, an incomplete understanding of COPD pathogenesis and a scarcity of sensitive tools that provide patient-relevant intermediate endpoints likely all play a role in the lack of new, efficacious COPD interventions. In other words, COPD patients are still diagnosed based on the presence of persistent airflow limitation measured using spirometry. Spirometry measurements reflect the global sum of all the different possible COPD pathologies and perhaps because of this, we lose sight of the different …

Pulmonary Imaging Biomarkers Of Gas Trapping And Emphysema In Copd: (3)He Mr Imaging And Ct Parametric Response Maps, Dante P I Capaldi, Nanxi Zha, Fumin Guo, Damien Pike, David G Mccormack, Miranda Kirby, Grace Parraga

Medical Biophysics Publications

PURPOSE: To directly compare magnetic resonance (MR) imaging and computed tomography (CT) parametric response map (PRM) measurements of gas trapping and emphysema in ex-smokers both with and without chronic obstructive pulmonary disease (COPD).

MATERIALS AND METHODS: Participants provided written informed consent to a protocol that was approved by a local research ethics board and Health Canada and was compliant with the HIPAA (Institutional Review Board Reg. #00000940). The prospectively planned study was performed from March 2014 to December 2014 and included 58 ex-smokers (mean age, 73 years ± 9) with (n = 32; mean age, 74 years ± 7) and …

Design And Evaluation Of An Mri-Compatible Linear Motion Stage., Mohammad Ali Tavallaei, Patricia M Johnson, Junmin Liu, Maria Drangova

Medical Biophysics Publications

PURPOSE: To develop and evaluate a tool for accurate, reproducible, and programmable motion control of imaging phantoms for use in motion sensitive magnetic resonance imaging (MRI) appli cations.

METHODS: In this paper, the authors introduce a compact linear motion stage that is made of nonmagnetic material and is actuated with an ultrasonic motor. The stage can be positioned at arbitrary positions and orientations inside the scanner bore to move, push, or pull arbitrary phantoms. Using optical trackers, measuring microscopes, and navigators, the accuracy of the stage in motion control was evaluated. Also, the effect of the stage on image signal-to-noise …