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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Diagnostic Performance of a Prototype Dual-energy Chest Imaging System

Mehdizadeh Kashani, Hany 31 May 2011 (has links)
Purpose: To assess the performance of a Dual-Energy chest radiography system. Methods: A cohort of 129 patients was recruited from population referred for CT guided biopsy of a lung lesion. Digital radiography (DR) and Dual Energy (DE) images were acquired. Receiver operating characteristic (ROC) tests were performed to evaluate performance of DE images compared to DR. Five chest radiologists scored images. Performance was analyzed for all cases pooled and sub groups based on gender, nodule size, density, location, and chest diameter. Results: There was no significant difference between DE and DR for all cases (p = 0.61). There was a significant advantage for DE imaging of small nodules, and nodules located in right-upper lobe. (p = 0.02 and 0.01) Conclusions: DE imaging demonstrated significant improvement in diagnosis of sub-centimeter lung nodules and lesions in the upper lung zones which are common characteristic of early stage lung malignancy.
2

Diagnostic Performance of a Prototype Dual-energy Chest Imaging System

Mehdizadeh Kashani, Hany 31 May 2011 (has links)
Purpose: To assess the performance of a Dual-Energy chest radiography system. Methods: A cohort of 129 patients was recruited from population referred for CT guided biopsy of a lung lesion. Digital radiography (DR) and Dual Energy (DE) images were acquired. Receiver operating characteristic (ROC) tests were performed to evaluate performance of DE images compared to DR. Five chest radiologists scored images. Performance was analyzed for all cases pooled and sub groups based on gender, nodule size, density, location, and chest diameter. Results: There was no significant difference between DE and DR for all cases (p = 0.61). There was a significant advantage for DE imaging of small nodules, and nodules located in right-upper lobe. (p = 0.02 and 0.01) Conclusions: DE imaging demonstrated significant improvement in diagnosis of sub-centimeter lung nodules and lesions in the upper lung zones which are common characteristic of early stage lung malignancy.
3

Blood Velocity and Volumetric Flow Rate Calculated from Dynamic 4D CT Angiography using a Time of Flight Approach

Barfett, Joseph 17 March 2014 (has links)
Purpose: A time of flight approach to the analysis of 4D CT angiography is examined to calculate blood flow in arteries. Materials and Methods: Software was written to track contrast bolus TOF along a central vessel axis. Time density curves were analyzed to determine bolus time to peak at successive vessel cross-sections which were plotted against vessel path length. A line of best fit was plotted through the resulting data and 1/slope provided a measurement of velocity. Results: Validation was successful in simulation and in flow phantoms, though quality of results depended strongly on quality of curve fit. In phantoms and in vivo, accuracy and reproducibility of measurements improved with longer path lengths and, in vivo, depended on the avoidance of venous contamination. Conclusions: Quantitative functional intravascular information such as blood velocity and flow rate may be calculated from 4D CT angiography.
4

Blood Velocity and Volumetric Flow Rate Calculated from Dynamic 4D CT Angiography using a Time of Flight Approach

Barfett, Joseph 17 March 2014 (has links)
Purpose: A time of flight approach to the analysis of 4D CT angiography is examined to calculate blood flow in arteries. Materials and Methods: Software was written to track contrast bolus TOF along a central vessel axis. Time density curves were analyzed to determine bolus time to peak at successive vessel cross-sections which were plotted against vessel path length. A line of best fit was plotted through the resulting data and 1/slope provided a measurement of velocity. Results: Validation was successful in simulation and in flow phantoms, though quality of results depended strongly on quality of curve fit. In phantoms and in vivo, accuracy and reproducibility of measurements improved with longer path lengths and, in vivo, depended on the avoidance of venous contamination. Conclusions: Quantitative functional intravascular information such as blood velocity and flow rate may be calculated from 4D CT angiography.
5

A Theoretical Analysis of the Field of Human Simulation and the Role of Emotion and Affect in the Work of Standardized Patients

McNaughton, Nancy 30 August 2012 (has links)
Standardized Patients (SPs) are lay persons who are employed extensively within health professional education to help teach and assess a range of clinical skills. Individuals trained to take on the physical, historical and emotional aspects of patient stories are integral to the dissemination of collective attitudes, values, and beliefs about what it means to be a competent health professional. As an embodied affective presence literally in front of and often in physical contact with health professionals SPs are a fertile site of knowledge production as well as transformative learning. Their unique contribution is a corollary of both their location as non-clinicians and their pedagogical facility with embodied emotions and affect. SPs in medical education teach about emotion and affect, engage affectively in the presentation of clinical material and as a professionalizing group have developed an educational methodology for facilitating understanding and experience of emotion and affect. In this thesis I examine the field of human simulation and the work of standardized patients (SPs) through critical theoretical perspectives seeking to broaden our understanding of their contributions as a present and future force in health professional education, specifically medical education. Central to my examination is the constitutive role of emotion and affect as they are conceived both within medical education and engaged by standardized patients as media through which different knowledges are produced. My analysis is shaped by poststructuralist feminist writers on emotion, Michel Foucault’s genealogical historical approach, and principally Gilles Deleuze and Felix Guattari’s alternative nomadology as theorized in a thousand plateaus (1987). I intend an alternative reading of the advent of SPs in medical education through a process of mapping rhizomatic networks that include acting, emotion, affect, medicine, and the place of women patients and standardized patients in medical arenas. I have located the current study within an ongoing project of embodied ethical practice and nomadic subjectivity within education specific to human simulation and standardized patients.
6

Flexible Radial Data Acquisition and Image Reconstruction Strategies for Breast Magnetic Resonance Imaging

Chan, Rachel Wai-Chung 20 August 2012 (has links)
Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has a high sensitivity (71- 100%) for detecting breast cancers. DCE-MRI is approximately twice as sensitive as mammography for patients who are genetically predisposed to breast cancer, who have an elevated lifetime risk (up to 85%) of contracting the disease, and who require rigorous screening. However, current methods of DCE-MRI often have difficulty distinguishing malignant from benign tumours, resulting in low positive predictive values (on average, PPV = 45%). The research in this thesis is motivated by the need for improvement in the ability of MRI to differentiate breast lesions. It is believed that the differentiation of malignant from benign lesions can be improved by acquiring images of high spatial resolution for visualizing morphological features of tumours and those of high temporal resolution for characterizing contrast-kinetic curves. However, simultaneously achieving high spatial and temporal resolution is limited by the inherent trade-off between speed and quality in MRI, requiring one to choose a particular balance of spatial and temporal resolution. In this thesis, novel techniques are presented that reduce the need to choose a spatiotemporal resolution before the scan. Flexible methods are presented that allow images to be retrospectively reconstructed with different balances of spatial and temporal resolution from the same dataset. Flexibility is achieved through radial sampling of k-space data, with 3D radial directions based on Multidimensional Golden Means (MGM) and Halton sequences. Radial sampling also allows constrained image reconstruction techniques such as Compressed Sensing and Prior-Image Constrained Compressed Sensing to be incorporated for reducing undersampling artifacts in high-temporalresolution images. This thesis demonstrates in 2D how such reconstruction algorithms are influenced by acquisition schemes and shows how reconstruction algorithms work in synergy with flexible radial sampling to provide improvements in the quality of breast MR images. The flexibility to choose any spatiotemporal resolution combined with better image quality in fast images could potentially improve the characterization of breast lesions screened by MRI.
7

Flexible Radial Data Acquisition and Image Reconstruction Strategies for Breast Magnetic Resonance Imaging

Chan, Rachel Wai-Chung 20 August 2012 (has links)
Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has a high sensitivity (71- 100%) for detecting breast cancers. DCE-MRI is approximately twice as sensitive as mammography for patients who are genetically predisposed to breast cancer, who have an elevated lifetime risk (up to 85%) of contracting the disease, and who require rigorous screening. However, current methods of DCE-MRI often have difficulty distinguishing malignant from benign tumours, resulting in low positive predictive values (on average, PPV = 45%). The research in this thesis is motivated by the need for improvement in the ability of MRI to differentiate breast lesions. It is believed that the differentiation of malignant from benign lesions can be improved by acquiring images of high spatial resolution for visualizing morphological features of tumours and those of high temporal resolution for characterizing contrast-kinetic curves. However, simultaneously achieving high spatial and temporal resolution is limited by the inherent trade-off between speed and quality in MRI, requiring one to choose a particular balance of spatial and temporal resolution. In this thesis, novel techniques are presented that reduce the need to choose a spatiotemporal resolution before the scan. Flexible methods are presented that allow images to be retrospectively reconstructed with different balances of spatial and temporal resolution from the same dataset. Flexibility is achieved through radial sampling of k-space data, with 3D radial directions based on Multidimensional Golden Means (MGM) and Halton sequences. Radial sampling also allows constrained image reconstruction techniques such as Compressed Sensing and Prior-Image Constrained Compressed Sensing to be incorporated for reducing undersampling artifacts in high-temporalresolution images. This thesis demonstrates in 2D how such reconstruction algorithms are influenced by acquisition schemes and shows how reconstruction algorithms work in synergy with flexible radial sampling to provide improvements in the quality of breast MR images. The flexibility to choose any spatiotemporal resolution combined with better image quality in fast images could potentially improve the characterization of breast lesions screened by MRI.
8

A Theoretical Analysis of the Field of Human Simulation and the Role of Emotion and Affect in the Work of Standardized Patients

McNaughton, Nancy 30 August 2012 (has links)
Standardized Patients (SPs) are lay persons who are employed extensively within health professional education to help teach and assess a range of clinical skills. Individuals trained to take on the physical, historical and emotional aspects of patient stories are integral to the dissemination of collective attitudes, values, and beliefs about what it means to be a competent health professional. As an embodied affective presence literally in front of and often in physical contact with health professionals SPs are a fertile site of knowledge production as well as transformative learning. Their unique contribution is a corollary of both their location as non-clinicians and their pedagogical facility with embodied emotions and affect. SPs in medical education teach about emotion and affect, engage affectively in the presentation of clinical material and as a professionalizing group have developed an educational methodology for facilitating understanding and experience of emotion and affect. In this thesis I examine the field of human simulation and the work of standardized patients (SPs) through critical theoretical perspectives seeking to broaden our understanding of their contributions as a present and future force in health professional education, specifically medical education. Central to my examination is the constitutive role of emotion and affect as they are conceived both within medical education and engaged by standardized patients as media through which different knowledges are produced. My analysis is shaped by poststructuralist feminist writers on emotion, Michel Foucault’s genealogical historical approach, and principally Gilles Deleuze and Felix Guattari’s alternative nomadology as theorized in a thousand plateaus (1987). I intend an alternative reading of the advent of SPs in medical education through a process of mapping rhizomatic networks that include acting, emotion, affect, medicine, and the place of women patients and standardized patients in medical arenas. I have located the current study within an ongoing project of embodied ethical practice and nomadic subjectivity within education specific to human simulation and standardized patients.
9

Neuroanatomical Correlates of Depressive Symptoms Following Acute Ischemic Stroke

Francis, Philip 24 August 2011 (has links)
This study investigated the hypothesis that severity of depressive symptoms following acute ischemic stroke is associated with degree of tissue infarction and severity of white matter changes (WMCs). It employed a novel quantitative region-based approach considering both infarction and WMCs. Of 54 ischemic stroke patients recruited, 50 (72.3 ± 12.8 years, 52.0% male) had useable CT scans. The typical patient was recruited within 3 weeks of their stroke (19.7 ± 31.0 days), exhibited minor cognitive impairment (MMSE score 25.8 ± 4.6), and had mild to moderate stroke severity (NIHSS score 6.5 ± 5.4). 28.0% of patients screened positive for clinical depression with a CES-D score ≥16. While neither degree of infarction nor severity of WMCs (ARWMC score) in the 12 brain regions correlated with depressive symptoms (CES-D score), stroke severity was a significant predictor of depressive symptoms. This stressor, related to physical disability, was a predominant predictor over lesion characteristics.
10

Neuroanatomical Correlates of Depressive Symptoms Following Acute Ischemic Stroke

Francis, Philip 24 August 2011 (has links)
This study investigated the hypothesis that severity of depressive symptoms following acute ischemic stroke is associated with degree of tissue infarction and severity of white matter changes (WMCs). It employed a novel quantitative region-based approach considering both infarction and WMCs. Of 54 ischemic stroke patients recruited, 50 (72.3 ± 12.8 years, 52.0% male) had useable CT scans. The typical patient was recruited within 3 weeks of their stroke (19.7 ± 31.0 days), exhibited minor cognitive impairment (MMSE score 25.8 ± 4.6), and had mild to moderate stroke severity (NIHSS score 6.5 ± 5.4). 28.0% of patients screened positive for clinical depression with a CES-D score ≥16. While neither degree of infarction nor severity of WMCs (ARWMC score) in the 12 brain regions correlated with depressive symptoms (CES-D score), stroke severity was a significant predictor of depressive symptoms. This stressor, related to physical disability, was a predominant predictor over lesion characteristics.

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