Dissertations / Theses on the topic 'Magnetic Resonance Imaging Biomarkers'
To see the other types of publications on this topic, follow the link: Magnetic Resonance Imaging Biomarkers.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Magnetic Resonance Imaging Biomarkers.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Stephen, Renu M. "Magnetic Resonance Imaging Biomarkers For Targeted Cancer Therapies." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194845.
Full textAbstract:
In 2007, there will be an estimated 178,480 new cases of breast cancer diagnosed in women in the United States. The elucidation of the vast heterogeneity of individual tumors has led to a paradigm shift from a one-size fits all treatment strategy to more individualized treatment based on the molecular profile of the tumor. Identifying biomarkers that respond to or predict the action of drugs is important in identifying efficacious targets and drugs that will improve clinical outcome. To examine this, we first identified two breast cancer cell lines (ACC-3199 and ACC-3171) from a panel of low passage breast cells lines that were capable of growing serially as tumor xenografts. This was followed by the in vivo molecular characterization of these two cell lines. In ACC-3199 tumors, we identified a gain of pAKT expression compared to cultured cells. Based on this finding, we investigated the role of diffusion-weighted (DW) and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) as potential imaging biomarkers in identifying early response to PX-866, a PI3K inhibitor, in ACC-3199 tumors as represented by changes in tumor cellularity and hemodynamic parameters, respectively. Our results indicated that DW-MRI was able to identify an early response to PX-886 in ACC-3199 tumors as defined by an increase in the apparent diffusion coefficient (ADC) value of the tumors prior to changes in tumor volumes. Using DCE-MRI, we were able to conclude that PX-866 was not an effective anti-angiogenic agent as indicated by an increase in tumor permeability following therapy. Based on the VEGFR2 expression observed in ACC-3171 tumor xenografts, we examined the response of MDA-MB-231/GFP and ACC-3171 tumor xenografts to the anti-angiogenic agent, sunitinib, using the same imaging modalities. DW-MRI was able to detect increases in ADC values as early as 12 h post-treatment in both MDA-MB-231/GFP and ACC-3171 tumors. Thus, it appears that DW-MRI may be a useful clinical test in predicting the early response to PI3K and anti-angiogenic inhibitors. These imaging approaches, in addition to the further molecular characterization of breast tumors may lead to the improvement and development of medical therapies for breast cancer patients.
2
Johnston, Edward William. "Developing multiparametric and novel magnetic resonance imaging biomarkers for prostate cancer." Thesis, University College London (University of London), 2017. http://discovery.ucl.ac.uk/10039809/.
Full textAbstract:
Whilst biomarker research is gaining momentum within the cancer sciences, disappointingly few biomarkers are successfully translated into clinical practice, which is partly due to lack of rigorous methodology. In this thesis, I aim to systematically study several quantitative magnetic resonance imaging (MRI) biomarkers (QIBs), at various stages of biomarker development for use as tools in the assessment of local and metastatic prostate cancer according to clinical need. I initially focus on QIBs derived from conventional multiparametric (mp) prostate MRI sequences, namely T2 weighted (T2W), apparent diffusion coefficient (ADC) and dynamic contrast enhanced (DCE). Firstly, by optimising analytical methods used throughout the thesis, deciding which approach is more reliable between single-slice region-of-interest vs. contouring the whole tumour volume using two different software packages. I then consider whether metric reproducibility can be improved by normalisation to different anatomical structures, and assess whether it is preferable to use statistics derived from imaging histograms rather than the current convention of using mean values. I combine multiple QIBs in a logistic regression model to predict a Gleason 4 component in known prostate cancer, which represents an unmet clinical need, as noninvasive tools to distinguish these more aggressive tumours do not currently exist. I subsequently ‘technically validate’ a novel microstructural diffusion-weighted MRI technique called VERDICT (Vascular, Extracellular and Restricted Diffusion for Cytometry in Tumours) to detect aggressive prostate cancer as part of a prospective cohort study. I assess the image quality, contrast-to-noise ratio, repeatability and performance of quantitative parametric VERDICT maps to discriminate between Gleason grades vs. the current best performing, but still imperfect tool of ADC. In the final two results chapters, motivated by the limited diagnostic accuracy of the prostate cancer staging modalities in current clinical use, I investigate the ability of mp whole-body (WB) MRI to stage aggressive cancer outside the prostate in patients with a high risk of metastases at primary diagnosis, and in biochemical failure following prostatectomy.
3
Latifoltojar, Arash. "Developing whole-body magnetic resonance imaging biomarkers for the assessment of haematological malignancies." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10055800/.
Full textAbstract:
Whole body magnetic resonance imaging (WB-MRI) is being recognised as an alternative to conventional computed tomography, isotope bone scan and PET-CT scan. Advances in MR imaging have enabled sophisticated whole body protocols interrogating and imaging different facets of tumour biology. Furthermore, these multi-sequence WB-MRI protocols can be applied within patient friendly examination times. Qualitative and quantitative evaluation of WB-MRI examinations can now readily be performed, and form the focus of ongoing research into clinical utility for disease staging and response assessment. Quantitative WB-MRI research has mainly concentrated on diffusion weighted imaging (DWI) derived apparent diffusion coefficient (ADC), a parameter broadly representative of tumour cellularity. This thesis focuses on evaluating WB-MRI in the setting of lymphoma and multiple myeloma (haematological malignancies) through a series of translational imaging biomarker developmental studies. The first study retrospectively evaluates the diagnostic accuracy of WB-MRI (performed at 1.5 T) for the staging of paediatric Hodgkin’s lymphoma (HL) (Chapter 3) and determines ADC quantitative thresholds for disease detection (Chapter 4). Following this, a clinical trial of WB-MRI with prospective application of quantitative ADC thresholds for staging and response assessment of paediatric HL is described (Chapter 5). The final 3 chapters describe the WB-MRI studies conducted at 3.0 T – exploring the potential value of higher field strengths, and the reliability of novel quantitative imaging biomarkers for the diagnosis and response assessment of lymphoma and multiple myeloma.
4
Rahman, Rifaquat M. "Magnetic Resonance Imaging for Prediction and Assessment of Treatment Response in Bevacizumab-Treated Recurrent Glioblastoma." Thesis, Harvard University, 2014. http://etds.lib.harvard.edu/hms/admin/view/65.
Full textAbstract:
Glioblastoma is the most common primary brain tumor in adults, and it is associated with a dismal prognosis with a median survival of 15 months. Despite treatment with chemotherapy, radiation therapy and surgery, patients inevitably have disease recurrence. Bevacizumab is a monoclonal humanized antibody that inhibits vascular endothelial growth factor signaling, and it has been shown to be effective in recurrent glioblastoma with respect to prolonging progression-free survival (PFS). The use of bevacizumab and other anti-angiogenic agents in recurrent glioblastoma have created novel challenges in interpreting magnetic resonance imaging (MRI) of patients. Furthermore, since only some patients appear to have a durable benefit from bevacizumab, there is a need for imaging biomarkers that can reliably identify this subgroup of patients.
Partly due to the challenges created by anti-angiogenic agents, the Response Assessment in Neuro-Oncology (RANO) was proposed to address some of the limitations with traditional response assessment criteria. In the first part of this project, we attempted to validate the RANO criteria by performing a comparative analysis of the RANO criteria vs. the Macdonald criteria using imaging from the phase II BRAIN trial. As we hypothesized, the RANO criteria yielded a significantly decreased PFS by identifying a subset of patients who had progression of nonenhancing tumor evident on T2-weighted imaging. Additionally, response and progression as defined by the RANO criteria correlated with subsequent overall survival (OS) in landmark analyses. While this supports the implementation of RANO criteria for response assessment in glioma clinical trials, future research will be necessary to further improve response assessment by incorporating advanced techniques such as volumetric anatomic assessment, perfusion-weighted MR (PWI-MR), diffusion-weighted MR (DWI-MR), MR spectroscopy (MRS) and positron emission tomography (PET).
Advanced imaging techniques are becoming increasingly recognized for their ability to provide objective, non-invasive assessment of treatment response but also to serve as predictive and prognostic biomarkers allowing for stratification of patient subgroups with better treatment outcome. In the second part of the project, we attempted to perform volumetric analysis of tumor size based on conventional MRI, as well as a histogram analysis of apparent diffusion coefficients (ADC) derived from diffusion-weighted MRI, to evaluate imaging parameters as predictors for PFS and OS in a single institution database of recurrent glioblastoma patients initiated on bevacizumab. Volumetric percentage change and absolute early post-treatment volume (3-6 weeks after initiation) of enhancing tumor can stratify survival for patients with recurrent glioblastoma receiving bevacizumab therapy. ADC histogram analysis using a multi-component curve-fitting technique within both enhancing and nonenhancing components of tumor prior to the initiation of bevacizumab can also be used to stratify OS in recurrent glioblastoma patients. While prospective studies are necessary to validate findings, future studies will increasingly incorporate multiparametric approaches to elucidate biomarkers that combine the value of conventional MRI with advanced techniques such as DWI-MR, PWI-MR, MRS and PET to obtain better predictors for PFS and OS in recurrent glioblastoma.
5
Hiscox, Lucy Victoria. "Early characterisation of neurodegeneration with high-resolution magnetic resonance elastography." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31198.
Full textAbstract:
This thesis contributes to recent interest within medical imaging regarding the development and clinical application of magnetic resonance elastography (MRE) to the human brain. MRE is a non-invasive phase-contrast MRI technique for measurement of brain mechanical properties in vivo, shown to reflect the composition and organisation of the complex tissue microstructure. MRE is a promising imaging biomarker for the early characterisation of neurodegeneration due to its exquisite sensitivity to variation among healthy and pathological tissue. Neurodegenerative diseases are debilitating conditions of the human nervous system for which there is currently no cure. Novel biomarkers are required to improve early detection, differential diagnosis and monitoring of disease progression, and could also ultimately improve our understanding of the pathophysiological mechanisms underlying degenerative processes. This thesis begins with a theoretical background of brain MRE and a description of the experimental considerations. A systematic review of the literature is then performed to summarise brain MRE quantitative measurements in healthy participants and to determine the success of MRE to characterise neurological disorders. This review further identified the most promising acquisition and analysis methods within the field. As such, subsequent visits to three brain MRE research centres, within the USA and Germany, enabled the acquisition of exemplar phantom and brain data to assist in discussions to refine an experimental protocol for installation at the Edinburgh Imaging Facility, QMRI (EIF-QMRI). Through collaborations with world-leading brain MRE centres, two high-resolution - yet fundamentally different - MRE pipelines were installed at the EIF-QMRI. Several optimisations were implemented to improve MRE image quality, while the clinical utility of MRE was enhanced by the novel development of a Graphical User Interface (GUI) for the optimised and automatic MRE-toanatomical coregistration and generation of MRE derived output measures. The first experimental study was performed in 6 young and 6 older healthy adults to compare the results from the two MRE pipelines to investigate test-retest agreement of the whole brain and a brain structure of interest: the hippocampal formation. The MRE protocol shown to possess superior reproducibility was subsequently applied in a second experimental study of 12 young and 12 older cognitively healthy adults. Results include finding that the MRE imaging procedure is very well tolerated across the recruited population. Novel findings include significantly softer brains in older adults both across the global cerebrum and in the majority of subcortical grey matter structures including the pallidum, putamen, caudate, and thalamus. Changes in tissue stiffness likely reflect an alteration to the strength in the composition of the tissue network. All MRE effects persist after correcting for brain structure volume suggesting changes in volume alone were not reflective of the detected MRE age differences. Interestingly, no age-related differences to tissue stiffness were found for the amygdala or hippocampus. As for brain viscosity, no group differences were detected for either the brain globally or subcortical structures, suggesting a preservation of the organisation of the tissue network in older age. The third experiment performed in this thesis finds a direct structure-function relationship in older adults between hippocampal viscosity and episodic memory as measured with verbal-paired recall. The source of this association was located to the left hippocampus, thus complementing previous literature suggesting unilateral hippocampal specialisation. Additionally, a more significant relationship was found between left hippocampal viscosity and memory after a new procedure was developed to remove voxels containing cerebrospinal fluid from the MRE analysis. Collectively, these results support the transition of brain MRE into a clinically useful neuroimaging modality that could, in particular, be used in the early characterisation of memory specific disorders such as amnestic Mild Cognitive Impairment and Alzheimer's disease.
6
Royle, Natalie Anne. "Quantifying structural changes in the ageing brain from magnetic resonance imaging." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/15835.
Full textAbstract:
Understanding the ageing process is of increasing importance to an ageing society and one aspect of this is investigating what role the brain has in this process. Cognitive ability declines as we age and it is one of the most distressing aspects of getting older. Brain tissue deterioration is a significant contributor to lower cognitive ability in late life but the underlying biological mechanisms in the brain are not yet fully understood. One reason for this is the difficulty in obtaining accurate measures of potential ageing-related brain biomarkers. The chapters in this thesis explore the difficulties of quantifying brain changes in the ageing brain from Magnetic Resonance Imaging (MRI), and how the changes identified are related to cognition in later life. The data was acquired as part of the second wave of the longitudinal Lothian Birth Cohort 1936 study in which 866 people aged 73 years, returned for cognitive and medical assessment. At this stage of the study 702 underwent MR imaging resulting in 627 complete datasets across all testing. The entire data, a randomly chosen subset of 150 and 416 freely available data were used to investigate global and regional measurement methods in older brains and how the resultant measurements related to cognitive performance. Furthermore the presence of early life cognitive data in the form of a general intelligence test sat at age 11, served as an indicator of cognitive ability prior to the potential influence of the ageing process. The chapters concerning global measures at first establish, that a measure of intracranial volume (ICV) serves as both a way of correcting for individual differences in brain size between participants and as a proxy premorbid measure of brain size. The analysis, utilising freely available cross-sectional MRI data (http://www.oasis-brains.org) revealed that ICV differed very little between 18-28 year olds and 84-96 year olds where as total brain tissue volume (TBV) differed by 14.1% between the two groups, which was more than twice the standard deviation across the entire age range (18-96 years). Second a validated, reliable method for measuring ICV was investigated using 150 people randomly chosen from the LBC1936 study. Automated and semi-automated methods were validated against reference measurements the results of which showed that common ageing features make automated and semi-automated methods that do not have an additional manual editing step, ineffective at producing accurate ICV measurements. This analysis also highlighted the need to employ additional spatial overlap assessment to volumetric comparison of measurement methods to reduce the effect of false-positives and false-negatives skewing apparent discrepancies between methods. Using the information gained here ICV and TBV from the entire LBC1936 cohort were analysed in a structural equation model, alongside cognitive ability measures at both age 11 and age 73. We found that TBV was a stronger predictor of later life cognitive ability, after accounting for early life ability, but that a modest association remained between ICV and late life cognition. This suggests that early life factors pay a role in how well we age, though the relationship is complex. The regional measures chapters look at two brain regions commonly associated with ageing, the hippocampus and the frontal lobes. Measuring either of these brain regions in large samples of healthy older adults is challenging for many reasons. The hippocampus is small and as with all brain regions shows greater variation in older age, this makes employing automated methods that have the advantage of being fast and reproducible difficult. Following the results of our systematic review of automated methods for measuring the hippocampus, the two most commonly used and available automated methods were validated against reference standard measurements. The results indicated that although automated methods present an attractive alternative to laborious manual measurements they still require manual editing to produce accurate measurements in older adults. The modified strategy employed across the LBC1936 was to use an automated method and then manually edit the output; these segmentations were used to investigate the potential of multimodal image analysis in clarifying associations between the hippocampus and cognitive ability in old age. The analysis focused on associations between longitudinal relaxation time (T1), magnetization transfer ratio (MTR), fractional anisotropy (FA) and mean diffusivity (MD) in the hippocampus and general factors of fluid intelligence, cognitive processing speed and memory. The findings show that multi-modal MRI assessments were more sensitive than volumetric measurements at detecting associations with cognitive measures. The difficulty with producing a relevant frontal lobe measure was made apparent when the result of a large systematic review looking at the manual protocols used revealed 19 methods and 15 different landmarks had been employed. This resulted in an analysis that took the 5 most common boundaries reported and applied them to 10 randomly selected participants from the LBC1936. The results showed significant differences between the resultant volumes, with the smallest measurement when using the genu as the posterior marker representing only 35% of the measurement acquired using the central sulcus. The results from the studies presented in this thesis strongly highlight the need to develop age specific methods when using brain MRI to study ageing. Furthermore the implications of using unstandardised protocols, making assumptions about a methods performance based on validation in younger samples and the need to account for early life factors in this area of research have been made clearer. Studies building on these findings will be beneficial in elucidating the role of the brain in ageing.
7
Heise, Verena. "How can magnetoencephalography and magnetic resonance imaging improve our understanding of genetic susceptibility to Alzheimer's disease?" Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:a3c670f3-aef5-4f34-b983-37f21d0019ad.
Full textAbstract:
The Apolipoprotein E (APOE) ε4 allele is the best-established genetic risk factor for sporadic Alzheimer's disease (AD) while the ε2 allele confers a reduced risk compared with the most common ε3 allele. Neuroimaging studies using magnetic resonance imaging (MRI) have shown that APOE genotype affects brain structure and function. The aims of the research presented in this DPhil thesis were twofold: 1) to investigate the effect of APOE genotype on brain function in healthy adults using magnetoencephalography (MEG), which is a direct measure of neuronal activity and 2) to explore interactions between the AD risk factors APOE ε4 allele, age and female gender and their effects on brain structure and function using resting-state functional MRI and diffusion tensor imaging. MEG revealed similar neuronal activity at rest for APOE ε2 and ε4 carriers, i.e. those with opposite AD risk, indicating a more general effect on the functional architecture of the brain that is not directly linked to AD risk. However, differences between APOE ε2 and ε4 carriers became apparent when reactivity to stimuli was explored using the excellent temporal resolution of MEG. APOE ε4 carriers showed faster sensory pro- cessing and APOE genotype effects were found for functional networks associated with attention. In the second part of this project, female APOE ε4 carriers showed overall significantly reduced functional connectivity between the hippocampus and precuneus and a significant age-related decrease in connectivity of these regions. Increased vulnerability of this connection might be one reason for increased AD risk and interventions targeting hippocampal connectivity might be especially effective in at-risk populations. The research presented in this DPhil thesis showed a complex pattern of APOE genotype effects on brain structure and function. While global APOE genotype effects on functional and structural connectivity do not follow patterns of AD risk, more specific measures of connectivity and task-related brain function could be of use in the development of preclinical markers for AD development.
8
Jia, Guang. "MR imaging biomarkers for benign prostatic hyperplasia pharmacotherapy." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1164686290.
Full text
9
Chaney, Aisling. "Investigating imaging biomarkers of neuroinflammation and neurodegeneration in rodent models of Alzheimer's disease." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/investigating-imaging-biomarkers-of-neuroinflammation-and-neurodegeneration-in-rodent-models-of-alzheimers-disease(16750cf1-eb30-49c5-b9eb-9f01d4a0560f).html.
Full textAbstract:
Alzheimer’s disease (AD) is a progressive neurodegenerative disease resulting in alterations in memory, language, executive function and emotional behaviour. Although it can be characterised by symptoms, by the time they arise significant pathological alterations have already emerged in the central nervous system, namely increased amyloid plaques, neurofibrillary tangles and neuronal loss. Despite known pathological hallmarks the exact aetiology of AD is poorly understood and no current treatments are available. However, there is growing interest in the role of neuroinflammation in AD, with increases observed in the early stages of disease and with disease progression. Moreover, it has been suggested that peripheral inflammation can influence neuroinflammation and worsen neurodegeneration. Using Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRS) we can non-invasively measure biomarkers of neuroinflammation and degeneration allowing multi-modal investigation of its role in normal aging and AD. Considering this the objectives of this study were to (i) Use PET and MRS to investigate neuroinflammatory and metabolite alterations in transgenic (TG) models of AD and their wildtype (WT) animals. (ii) Assess rates of cognitive decline in these models using memory based tests. (iii) Investigate relatively new TgF344AD rat as an AD model by characterising younger time-points than previously reported. (iv) Investigate the contribution of peripheral inflammation on AD progression. PET and MRS imaging was carried out longitudinally in the APPswe×PS1de9 mouse. Neuroinflammation was confirmed ex vivo and cognitive ability was assessed by behavioural tests. Results revealed significantly increase hippocampal and thalamic neuoinflammation in old TG mice as assessed by [18F]DPA-714 PET and supported by immunohistochemistry. Reduced neuronal marker N-acetlyaspartate was seen with age and was exacerbated in the TG mice. Accelerated cognitive decline was also seen in TG mice. PET and MRS imaging was carried out at 6 and 12 months in the TgF344AD model, which expresses amyloid and tau pathology as well as neuronal loss. No cognitive decline was observed in TG rats; however increased anxiety behaviour was seen. Increased [18F]DPA-714 PET was observed as an effect of gene in the thalamus at 6 months and the hypothalamus at 12 months. Increases in glutamate were seen with age in the TG rats but not the WTs. Increased inflammation and metabolite alterations were seen with aging. The effect of peripheral urinary tract infection (UTI) on cognition and imaging out was assessed. Imaging was carried out prior to and after re-current UTI. Infection induced cognitive decline in infected TG but not WT rats. Infection had an increasing effect on hypothalamic neuroinflammation in WT rats but a decreasing effect on TG rats, which masked the original gene differences. This thesis is set out in the alternative format with each experimental study represented as a chapter. Results in this thesis implicate neuroinflammation in AD development and progression. In addition, we report systemic infection-CNS interactions accelerating cognitive decline in AD and highlight the importance of understanding the effects of comorbidities in disease.
10
Wright, Caroline. "Magnetic Resonance Imaging (MRI) biomarkers of placental structure and function in normal and growth restricted pregnancy." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/magnetic-resonance-imaging-mri-biomarkers-of-placental-structure-and-function-in-normal-and-growth-restricted-pregnancy(288b4214-b346-4a31-8bdd-1d4afaf65178).html.
Full textAbstract:
Fetal growth restriction (FGR) is a serious complication of human pregnancy where the fetus fails to reach its genetically pre-determined growth potential. It is a common condition, affecting 5 -15% of all pregnancies (Gardosi 2009) and is linked to a third of all antepartum deaths (CEMACH 2008). An ongoing problem for obstetricians is the difficulty in diagnosing and predicting FGR and those at highest risk of poor outcomes. Placental insufficiency is a major cause of FGR and specific abnormalities in placental morphology and function occur in this condition; constituting an abnormal FGR placental phenotype (Sibley, Turner et al. 2005). Magnetic Resonance Imaging (MRI) is a powerful tool that allows quantitative analysis of several indices relating to tissue structure and function and, therefore, is of potential use in identifying this phenotype. We hypothesised that a range of MR indices would be feasible in the placenta at 1.5 T, that these indices would be altered in FGR and that there would be correlations with relevant parameters of placental morphology. Ultimately, we aimed to assess whether these indices could be used in the assessment of FGR in utero.Using MRI we estimated placental volume, widths, length and depths in groups of women with normal and FGR pregnancies. We also measured placental relaxation times, T1 and T2, which relate to tissue composition and assessed parameters relating to blood flow using Intra-Voxel Incoherent Motion (IVIM) and Arterial Spin Labelling (ASL). We demonstrated an FGR placental phenotype that was reduced in volume but increased in depth, by around 10mm, with a shorter T2 relaxation time and lower values of D (the diffusion coefficient) measured by IVIM. A trend for reduced perfusion measured by ASL was observed in pregnancies with birthweights less than 10th centile (Gardosi, Chang et al. 1992). T2 and D also correlated with stereological indices of placental morphology.In conclusion, the studies in this thesis illustrate these MRI indices show great potential asbiomarkers for identifying the FGR placenta
11
Lam, Ching Yin. "Biomarkers to assess an anti-inflammatory treatment for irritable bowel syndrome : mast cell assays and magnetic resonance imaging." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/28803/.
Full textAbstract:
Irritable bowel syndrome (IBS) remains a heterogeneous condition and is a common condition. The causes of IBS remain poorly understood and there is a lack in biomarkers to distinguish this condition. Recently, there have been reports on the release of immune mediators leading to symptoms of irritable bowel syndrome. Mast cells, which can be activated by allergy or stress, are thought to be important cause of symptoms in some IBS patients because they can release chemicals, which cause pain and diarrhoea. Currently, there are few effective treatments available to alleviate these symptoms. Recent small studies have shown that Mesalazine, an ‘anti-inflammatory’ drug, may be able to modify and reverse the symptoms of IBS with diarrhoea. One small study suggested Mesalazine reduced mast cell numbers. This current study is one of the largest studies looking at the use of Mesalazine as a form of treatment for IBS with diarrhoea. Unfortunately, this study did not show any beneficial effect of Mesalazine treatment in unselected patients with IBS and diarrhoea. Potentially, there is a subgroup of IBS patients who developed their symptoms following a bout of gastroenteritis who appeared to benefit from Mesalazine treatment but a larger study is needed to confirm this. In this study, the mast cell mediators released from mucosal biopsies was not a useful marker of disease since it failed to correlate with any symptoms. Magnetic resonance imaging (MRI) is a potentially useful tool to assess the physiology of the gastrointestinal tract in patients with functional gut disorders as it does not involve radiation and is not invasive. So far, there is a lack of biomarkers to assist in diagnosis and treatment of irritable bowel syndrome. The MRI marker pill used in the multiple studies in Chapter 3 to assess whole gut transit time is very promising as it is now applied, in the research setting, to patients with chronic constipation such as slow transit constipation and irritable bowel syndrome with constipation. Further use of the MRI and adding a stimulus such as laxative in patients with chronic constipation is helpful to distinguish between functional constipation and irritable bowel syndrome with constipation; thus helping with its medical management. The use of MRI as a biomarker for diagnosis of irritable bowel syndrome remains promising although it was not demonstrated in this thesis.
12
Harry, Vanessa N. "A study of novel MRI techniques as biomarkers of early treatment response in advanced cervical and ovarian cancer." Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=186762.
Full textAbstract:
The management of advanced cervical and ovarian cancers remains a significant challenge as many women fail to respond to recommended therapy, resulting in disease progression and ultimately patient death. Because of tumour heterogeneity, it is rare for all cancers of a particular type to respond to a specific therapy. Many patients therefore receive treatment from which they derive little or no benefit, leading to increased morbidity and costs. A marker that could rapidly predict disease outcome would clearly be beneficial in allowing the administration of tailored therapy while reducing toxicity and cost. Novel functional imaging techniques have the ability to characterise biological tissues and non-invasively integrate physical and metabolic information. These include diffusion weighted MRI (DW-MRI), which is particularly sensitive to the microscopic motion of water molecules and changes in tissue cellularity, as well as dynamic contrast-enhanced MRI (DCE-MRI) which can assess tumour vascular characteristics during the passage of a paramagnetic contrast agent through tissues. Both imaging techniques have demonstrated potential as biomarkers of tumour response in various malignancies such as brain tumours, but have not been fully explored in gynaecological cancers.
13
Durst, Markus [Verfasser], Axel [Akademischer Betreuer] [Gutachter] Haase, and Franz [Gutachter] Pfeiffer. "Efficient Acquisition Strategies for Nuclear Magnetic Resonance Imaging with Hyperpolarised Biomarkers / Markus Durst ; Gutachter: Axel Haase, Franz Pfeiffer ; Betreuer: Axel Haase." München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/1136422587/34.
Full text
14
Bargiotas, Ioannis. "Development of Image Processing Methods to Extract Biomarkers of Aortic Aging from MRI and Applanation Tonometry." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066338.
Full textAbstract:
Aorte est l'artère qui amortit et conduit le flux sanguin éjecté par le cœur en flux continu vers la périphérie. Avec l’âge, l'élasticité aortique diminue en association avec des altérations fonctionnelles et hémodynamiques de l’aorte et du cœur. Alors que l'hémodynamique artérielle a été largement étudiée par l'analyse des courbes de pression, les modifications de l’onde de débit aortique n’ont été que très peu explorées. L’imagerie IRM, couplée à une segmentation appropriée, permet une évaluation non-invasive et précise du débit sanguin aortique. Cette thèse combine ce débit mesuré en IRM avec les pressions tonométriques afin de proposer des indices quantitatives de rigidité artérielle. Ainsi, ce travail comprend: Une nouvelle approche, basée sur les ondelettes, pour estimer le temps de transit entre les ondes de flux provenant de deux sites aortiques. Ce dernier a permis de calculer la vitesse de l'onde de pouls dans la crosse, qui s’est avérée être un marqueur fort de la rigidité et de l’âge. Une analyse d'impédance aortique dans le domaine fréquentiel pour quantifier la charge pulsatile et les réflexions qui augmentent la charge exercée sur le cœur. Une quantification de la forme de l'onde de débit aortique, dont l’association avec les changements géométriques du cœur a été montrée. Une cartographie des pressions intra-aortiques absolues en utilisant les équations de Navier-Stokes. Ces nouveaux indices ont été testés sur 70 sujets sains et leur complémentarité en termes de caractérisation de l’âge et du couplage entre l'aorte et le cœur a été montrée. De futures études sur l'hypertension artérielle permettront de démontrer l'utilité clinique de nos indicesAorta is the artery which immediately accommodates the blood flow ejected from the heart. It buffers blood’s pulsatile momentum and conducts it smoothly towards periphery. With physiological aging, aortic elasticity diminishes significantly in association with aortic or cardiac functional and hemodynamic alterations. While aortic hemodynamics were widely studied through pressure curves analysis, proximal aorta flow patterns were only little investigated. Recent developments of cardiovascular magnetic resonance imaging (MRI) and image segmentation tools, enable an accurate non-invasive evaluation of proximal aortic blood flow. This thesis combined MRI with central pressure measurements by applanation tonometry to propose flow-indices of arterial stiffness. Indeed our work proposed: A new wavelet-based method, which enables temporal localization of signal frequencies to estimate transit-time between flow waves from two aortic sites, in order to derive aortic arch pulse wave velocity, which is a strong marker of stiffening and aging. An aortic impedance analysis in frequency domain to provide indices which reflect changes in aortic pulsatile load and wave reflection, which augments the load on the heart Quantitative flow-morphology indices which were shown to be associated with age-related changes in left heart geometry. Absolute intra-aortic pressure mapping using the Navier-Stokes equations. These new indices have been tested on 70 healthy volunteers and findings indicated their complementary nature in characterizing aging and aortic-heart coupling. Further investigations in the context of hypertension will prove the clinical usefulness of our indices
15
Patel, Bhavini. "Searching for surrogate markers of cognitive impairment in small vessel disease: a magnetic resonance imaging and blood biomarker study." Thesis, St George's, University of London, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.617005.
Full textAbstract:
Cerebral small vessel disease (SVD) is a chronic disease of the small cerebral blood vessels and a common cause of dementia. Surrogate markers for cognitive impairment are required for future treatment trials. Patients with SVD have similar risk factors and MRI features as Alzheimer's disease. Blood biomarkers would be useful for diagnostic and prognostic purposes. St George's Cognition and Neuroimaging Study (SCANS) is a longitudinal study investigating the potential of MRI as a surrogate marker for cognitive impairment. This report examines the baseline data from SCANS. 121 patients with lacunar stroke and white matter hyperintensities had multi modal MRI, neuropsychological testing and had blood sampling for biomarkers of endothelial activation . Patient group performed worse in executive function and information processing speed compared to normative data. Patients had more white matter lesions, smaller whole brain volumes and lower fractional anisotropy and higher mean diffusivity on diffusion tensor imaging. Multiple regression, suggested brain volume was the best predictor of impaired information speed processing (P=0.001) and median white matter FA for executive dysfunction (p=0.004). High numbers (>9) of cerebral microbleeds were associated with impaired executive dysfunction. Blood biomarkers were tested in 106 patients. Patients had lower tissue factor (TF), tissue plasminogen activator (tPA) antigen and plasmin activation inhibitor-1 than controls. TF was associated with lesion volume and tPA was associated with the number of clinical strokes.
16
Wang, Silun, and 王思倫. "Diffusion tensor MR imaging as a biomarker for the evaluation of whitematter injury in rodent models." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43085416.
Full text
17
Burman, Joachim. "Curing Multiple Sclerosis : How to do it and how to prove it." Doctoral thesis, Uppsala universitet, Neurologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-221888.
Full textAbstract:
Hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment for multiple sclerosis (MS) with now more than 600 documented cases in the medical literature. Long-term remission can be achieved with this therapy, but when is it justified to claim that a patient is cured from MS? In attempt to answer this question, the outcome of the Swedish patients is described, mechanisms behind the therapeutic effect are discussed and new tools for demonstration of absence of disease have been developed. In Swedish patients treated with HSCT for aggressive MS, disease free survival was 68 % at five years, and no patient progressed after three years of stable disease. Presence of gadolinium enhancing lesions prior to HSCT was associated with a favorable outcome (disease free survival 79 % vs 46 %, p=0.028). There was no mortality and no patient required intensive care. The immune system of twelve of these patients was investigated further. In most respects HSCT-treated patients were similar to healthy controls, demonstrating normalization. In the presence of a potential antigen, leukocytes from HSCT-treated patients ceased producing pro-inflammatory IL-17 and increased production of the inhibitory cytokine TGF-β1 suggesting restoration of tolerance. Cytokine levels and biomarkers of tissue damage were investigated in cerebrospinal fluid from a cohort of MS patients. The levels were related to clinical and imaging findings. A cytokine signature of patients with relapsing-remitting MS could be identified, characterized by increased levels of CCL22, CXCL10, sCD40L, CXCL1 and CCL5 as well as down-regulation of CCL2. Further, we could demonstrate that active inflammation in relapsing-remitting MS is a tissue damaging process, with increased levels of myelin basic protein and neurofilament light. Importantly, relapsing-remitting MS patients in remission displayed no tissue damage. In secondary progressive MS, moderate tissue damage was present without signs of active inflammation. From a clinical vantage point, it seems that we confidently can claim cure of relapsing-remitting MS patients after five years absence of disease activity. The new tools for evaluation of disease can strengthen this assertion and may enable earlier prediction of outcome.
18
Iima, Mami. "Apparent Diffusion Coefficient as an MR Imaging Biomarker of Low-Risk Ductal Carcinoma in Situ: A Pilot Study." Kyoto University, 2014. http://hdl.handle.net/2433/188640.
Full text
19
Prowle, John Richard. "Renal blood flow and the pathophysiology of acute kidney injury." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607649.
Full text
20
Arrambide, García Georgina. "Study of diagnostic and prognostic clinical, biological, and magnetic resonance imaging markers at the time of a clinically isolated syndrome." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/384610.
Full textAbstract:
En este trabajo estudiamos marcadores con valor diagnóstico o pronóstico en el momento de presentar un síndrome clínico aislado (CIS, del inglés clinically isolated syndrome). Dado que presentar un CIS representa un riesgo para desarrollar esclerosis múltiple (EM), se considera crucial identificar qué pacientes tendrán un segundo brote y determinar el grado de acumulación de discapacidad a medio y largo plazo. Por ello, aún se considera necesario identificar marcadores que representen los diferentes aspectos de esta enfermedad, especialmente si se demuestra su utilidad en la práctica clínica diaria. Así, nuestro objetivo fue determinar el valor diagnóstico y pronóstico de marcadores clínicos, biológicos y radiológicos en el momento del CIS.
Primero, dado que el espectro de enfermedades de la neuromielitis óptica (NMOSD, del inglés neuromyelitis optica spectrum disorders) es uno de los principales diagnósticos diferenciales de la EM, decidimos evaluar la utilidad de determinar sistemáticamente la presencia de anticuerpos NMO-IgG en el momento del CIS, observando que tal abordaje no es necesario ya que la determinación de este anticuerpo fue negativa en la mayoría de los pacientes. Por tanto, otras características clínicas y radiológicas también deben considerarse durante el diagnóstico diferencial y esta determinación podría realizarse en casos indeterminados. Posteriormente se estableció una colaboración con Aurélie Ruet y Bruno Brochet [Centre Hospitalo-Universitaire (CHU) de Bordeaux, INSERM-CHU centre d’Investigation Clinique, Université de Bordeaux en Francia] para evaluar más a fondo el valor añadido de presentar dos o más factores predictivos de EM, previamente identificados por ellos, en pacientes con CIS que no cumplen los criterios diagnósticos de 2010 para diseminación en espacio, observando que si bien es más bajo, los pacientes con combinaciones de estos factores aún presentan un riesgo de desarrollar EM y deberían ser monitorizados más estrechamente. De igual forma, la utilidad de realizar una RM medular en el momento del CIS se considera un tema controvertido. Por tanto, analizamos su valor diagnóstico y pronóstico añadido, observando que aunque su aportación a los criterios diagnósticos es más bien modesta, la presencia de lesiones medulares representa un riesgo aumentado para evolucionar a una EM y para desarrollar una mayor discapacidad. También establecimos otra colaboración con la compañía israelí Glycominds, Inc., para validar el valor predictivo del gMS-Classifier2, un algoritmo que incorpora anticuerpos anti-glicano IgM en suero, diseñado con el objetivo de identificar pacientes con CIS en riesgo de presentar un segundo brote. El gMS-Classifier2 resultó ser un factor de riesgo independiente para EM, si bien los hallazgos en la RM representan un riesgo más elevado. Finalmente, valoramos varios marcadores biológicos en líquido cefalorraquídeo durante una fase de screening y una de validación que requirió trabajos colaborativos con Jens Kuhle, Ludwig Kappos (Department of Neurology, University Hospital Basel, en Suiza), Luisa María Villar y José Carlos Álvarez-Cermeño [Departamentos de Inmunología y Neurología del Hospital Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) en Madrid]. De todos los biomarcadores testados, los niveles basales de NfL resultaron ser factores independientes de riesgo para desarrollar una EM, siendo los hallazgos de RM nuevamente los mayores indicadores de riesgo. Además, los NfL presentaron fuertes correlaciones con los cambios en el volumen cerebral a los cinco años de seguimiento.The present work is concerned with finding diagnostic and prognostic markers at the time of a clinically isolated syndrome (CIS). Given that presenting a CIS indicates the possibility of developing multiple sclerosis (MS), it is considered crucial to identify which patients will present a second attack and to determine the degree of disability accumulation over the medium to long-term. Therefore, the search for markers that capture the different aspects of this disease is still considered necessary, particularly if they demonstrate to be useful in the daily clinical practice. Therefore, we aimed to determine the diagnostic and prognostic value of a number of clinical, biological, and radiological markers available at the time of the CIS. First, considering neuromyelitis optica spectrum disorders (NMOSD) as one of the main differential diagnoses of MS after a first attack, we decided to assess the value of systematically determining NMO-IgG status at the time of a CIS, observing that such approach is not necessary since the antibody determination was negative in most patients. Therefore, other clinical and radiological characteristics should also be taken into account during the differential diagnosis and this test could be considered in indeterminate cases. Next, a collaborative work was established with Drs. Aurélie Ruet and Bruno Brochet [Centre Hospitalo-Universitaire (CHU) de Bordeaux, INSERM-CHU centre d’Investigation Clinique, Université de Bordeaux, France] to further assess the added value of presenting ≥2 predictive factors for MS, previously identified by them, in patients not fulfilling the 2010 criteria for dissemination in space, and observed that although lower, patients with combinations of these predictive factors are still at risk of developing MS and should be monitored closely. Likewise, the usefulness of a baseline spinal cord MRI at the time of a CIS is still somewhat controversial. Therefore, we analysed its added diagnostic and prognostic value, observing that although the diagnostic value is modest, presence of spinal cord lesions do pose an increased and independent risk for both evolution to MS and disability accumulation. One more collaboration was established with the Israeli company Glycominds, Inc., to validate the predictive value of gMS-Classifier2, an algorithm incorporating serum IgM anti-glycan antibodies, designed with the aim of identifying CIS patients at risk of a second demyelinating attack. gMS-Classifier2 turned out to be an independent risk factor for clinically definite MS, although MRI findings still posed a higher risk. Finally, we evaluated a number of biological markers in cerebrospinal fluid during a screening and a validation phase that involved a couple of collaborative works with Jens Kuhle, Ludwig Kappos (Department of Neurology, University Hospital Basel, in Switzerland), Luisa María Villar, and José Carlos Álvarez-Cermeño (Departments of Neurology and Immunology, Multiple Sclerosis Unit, Hospital Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS) in Madrid). Of all biomarkers, only baseline neurofilament light chain levels were independent risk factors for MS with MRI findings again posing the highest risk but, interestingly, they showed very strong correlations with brain volume changes at five years of follow-up.
21
Wirth, Anna Maria [Verfasser], and Mark W. [Akademischer Betreuer] Greenlee. "Structural magnetic resonance imaging in amyotrophic lateral sclerosis: cortical morphometry, diffusion properties and lesion detection as potential biomarkers for the state and progression of amyotrophic lateral sclerosis / Anna Maria Wirth ; Betreuer: Mark W. Greenlee." Regensburg : Universitätsbibliothek Regensburg, 2019. http://d-nb.info/1188026658/34.
Full text
22
Hassel, Erika, and Mark Thorpe. "Hur kan magnetisk resonanstomografi användas för tidig diagnos av autism : Konsekvenser för röntgensjuksköterskor." Thesis, Luleå tekniska universitet, Institutionen för hälsovetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-67294.
Full textAbstract:
Inledning: Autism eller Autismspektrumtillstånd (AST) kännetecknas av varierande svårigheter inom tre områden: förmåga till ömsesidigt socialt samspel, förmåga till ömsesidig kommunikation och föreställningsförmåga, flexibilitet och variation i beteende och intressen. AST drabbar cirka 1 % av barnen i Sverige och anses uppkomma till följd av avvikelser i vissa delar av hjärnan. Diagnosen AST görs vanligen efter två års ålder med hjälp av intervjuer med närstående och observationer av barnets beteende. Sökandet efter abnormiteter i hjärnan hos barn med AST har pågått sedan 1980-talet. Tekniska framsteg i datorer och magnetisk resonanstomografi (MR) innebär att forskare kan kartlägga hjärnan som aldrig tidigare. Syftet: Syftet med studien var att sammanställa och beskriva den senaste forskningen om MRs användning för tidig diagnos av autism och beskriva konsekvenser för röntgensjuksköterskans yrke. Metod: Studien har gjorts som en allmän litteraturöversikt. Fjorton vetenskapliga artiklar kvalitetsgranskades och analyserades. Resultat: Resultaten delades först upp i tre olika grupper: fynd från strukturell MR, fynd från funktionell MR och konsekvenser för röntgensjuksköterskor. Dessa grupper delades ytterligare till ett antal underkategorier. Slutsats: Ett flertal avvikelser i hjärnan hittades hos barn som senare utvecklar AST. Avvikelser i hjärnvolymen, extra-axiell vätska, corpus callosum, anisotropiska värden, bearbetning av ljud och visuell orienteringsförmåga. Det verkar troligt att efter mer forskning blir dessa biomarkörer tillräckligt pålitliga att användas som diagnostiskt verktyg. Om MR undersökningar av barn med AST blir rutinmässiga kommer röntgensjuksköterskor att behöva ny kunskap och ny kompetens framför allt med hantering av barn med AST.Introduction: Autism or Autism spectrum disorder (ASD) is characterized by varying degrees of difficulty in three areas: mutual social interaction, mutual communication and imagination, flexibility and variety of behavior and interests. ASD affects approximately 1% of children in Sweden and is thought to be due to deviations in certain regions of the brain. A diagnosis is usually made after the age of two with the help of interviews with family members and observations of the child’s behaviour. The search for abnormalities in the brains of children with ASD had been going on since the 1980s. Technical advances in computers and magnetic resonance imaging (MRI) mean that researchers can map the brain like never before. Aim: The aim of this study was to compile and describe the latest research on MRI's use for the early diagnosis of autism and describe the consequences for the radiology nurse's profession. Method: The study has been conducted as a literature review. Fourteen scientific articles were quality controlled and analyzed. Results: The results were first divided into three different groups: findings from structural MRI, findings from functional MRI and consequences for radiology nurses. These groups were then divided further into a number of subgroups. Conclusion: A number of abnormalities were found in the brains of children who later develop ASD. Abnormalities were found in brain volume, extra-axial fluid, corpus callosum, fractional anisotropy values, processing of sound and visual orientation. It seems probable that after more research these biomarkers will become reliable enough to be used as a diagnostic tool. If MRI examinations of children with ASD become routine then radiology nurses will need new knowledge and skills above all in the handling of children with ASD.
23
Avancini, Tiffany Moukbel Chaim. "Acurácia diagnóstica em sujeitos adultos com TDAH e transtorno bipolar: classificação individual de imagens de ressonância magnética de crânio." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/5/5142/tde-06062017-103414/.
Full textAbstract:
INTRODUÇÃO: O transtorno de déficit de atenção com hiperatividade (TDAH) persistente em adultos apresenta prevalência significativa na população geral. Nota-se também uma alta taxa de comorbidade com outros quadros psiquiátricos, especialmente o transtorno bipolar (TB). Entretanto, ainda hoje discutem-se as próprias definições do TDAH e os limites da comorbidade TDAH+TB, que poderia ser uma extensão dos sintomas do espectro bipolar, uma sobreposição dos dois transtornos ou uma entidade separada com substrato neurobiológico distinto. Impõe-se, assim, a pesquisa de biomarcadores válidos com potencial aplicação na prática clínica. O surgimento recente de técnicas de classificação de padrões morfológicos cerebrais complexos possibilita uma investigação mais direcionada de biomarcadores, buscando em cada indivíduo um conjunto de características que seja capaz de classificá-lo como pertencente a um determinado grupo. OBJETIVOS: Aplicar, de maneira inédita, a técnica de reconhecimento automatizado de padrão aos dados de neuroimagem de pacientes adultos sem tratamento prévio com diagnóstico de TDAH com início na infância, TB, TDAH+TB e controles saudáveis (CS), em busca de assinaturas neuroanatômicas associadas a estes transtornos. MÉTODOS: Três grupos de adultos nunca tratados compostos de 67 sujeitos com TDAH, 30 sujeitos com TB e 16 sujeitos preenchendo critérios diagnósticos para ambos os transtornos; e uma amostra de CS (n=66), foram submetidos ao exame de ressonância magnética (RM) estrutural e de imagem por tensor de difusão (diffusion tensor imaging; DTI). Através de um método automatizado, regiões de interesse foram posicionadas ao longo de todo o cérebro e através destas foram obtidas medidas cerebrais a partir das imagens multimodais. Tais medidas foram usadas como dados de entrada para um classificador não-linear baseado em support vector machine (SVM). Comparações entre todos os pacientes e CS foram feitas através de subgrupos pareados individualmente para gênero e idade e pareados entre os grupos para nível socioeconômico e escolaridade. As medidas de desempenho diagnóstico foram analisadas com o auxílio de curvas receiver operating characteristic (ROC). RESULTADOS: As análises de classificação entre todos os subgrupos apresentaram resultados expressivamente acima do acaso, com exceção da comparação entre os pacientes com TB e os CS (p=0,09). A comparação entre os subgrupos com TDAH e CS apresentou medidas de área sob a curva (AUC) e acurácia diagnóstica de até 0,71 e 66,2% (p=0,003). A comparação entre os subgrupos com TDAH e TB obteve AUC e acurácia diagnóstica de até 0,78 e 70,2% (p=0,01). As análises de classificação entre os pacientes TDAH+TB e todos os outros subgrupos resultaram em valores de até 0,89 e 80,5% (p=0,0009) de AUC e acurácia diagnóstica respectivamente. CONCLUSÃO: Os resultados fornecem endosso neurobiológico para a validade do diagnóstico clinico de TDAH em adultos. As características cerebrais mostraram-se suficientemente fortes para o diagnóstico diferencial entre o TDAH e o TB e também reforçam a hipótese de que a associação TDAH+TB deve ser compreendida como uma entidade neurobiológica distinta. Restam ainda relevantes dificuldades na busca de biomarcadores para a caracterização do TB. As assinaturas neuroanatômicas identificadas neste estudo podem fornecer informações objetivas adicionais e valiosas, servindo como base para estudos futuros que avaliem sua possível influência em decisões terapêuticas dos pacientes apresentando sintomas do espectro TDAH e da comorbidade TDAH+TBINTRODUCTION: Attention-deficit/hyperactivity disorder (ADHD) is a highly prevalent condition in the general adult population. Also important is its high rate of comorbidity with other psychiatric disorders, particularly bipolar disorder (BD). However, not only the definition of ADHD is still a matter of discussion but also the limits of the ADHD+BD comorbidity; such comorbidity may be interpreted as a continuum spectrum of BD, an overlap of symptoms, or a separate diagnostic entity with a distinct neurobiological substrate. Therefore, further search for valid biomarkers with potential application in clinical practice is still required. The recent development of high-dimensional pattern recognition techniques has allowed targeted investigations of biomarkers, searching for sets of characteristics that could be used to classify each patient in a particular group. OBECTIVES: To apply, for the first time in the literature, machine learning-based pattern recognition methods to neuroimaging data obtained in never-treated adults with childhood-onset ADHD, BD, ADHD+BD and healthy controls (HC), searching for different neuroanatomical signatures associated with each disorder. METHODS: Three groups of never treated adults as following: 67 ADHD patients, 30 BD patients, 16 patients fulfilling diagnostic criteria for both disorders; and a sample of HC (n=66) underwent structural magnetic resonance imaging (MRI) and diffusion magnetic resonance imaging (DTI) acquisitions. A support vector machine (SVM) classifier with non-linear kernel was applied on multi-modal image features extracted on regions-of-interest placed across the whole brain. Comparisons among all patients and controls were carried out through subgroups individually matched for gender and age, and group-matched for years of education and socio-economic status. Diagnostic performance measures were evaluated by computing receiver operating characteristic (ROC) curves. RESULTS: All results on classification analyses were clearly significant above chance level, except in the comparison analysis between BD patients and HC (p=0.09). The comparison between ADHD and HC subgroups afforded area under the curve (AUC) measures and diagnostic accuracy of up to 0.71 and 66.2% (p=0.003). Comparison between ADHD and BD subgroups achieved AUC and diagnostic accuracy of up to 0.78 and 70.2% (p=0.01). Classification analysis between ADHD+BD patients and the other subgroups yielded AUC and diagnostic accuracy values of up to 0.89 and 80.5% (p=0.0009). CONCLUSION: The present study provides neurobiological endorsement to the validity of the clinically-based diagnosis of ADHD in adults. Brain features were strong enough to the differential diagnosis between ADHD and BD, as well as to reinforce the hypothesis that ADHD+BD may represent a distinct neurobiological entity. However, relevant challenges persist regarding the search for biomarkers for BD. The neuroanatomical signatures identified herein may provide additional, objective information, paving the way for future studies assessing its influence in treatment decisions in adults with ADHD and ADHD+BD spectrum symptoms
24
Le, Ster Caroline. "Exploration de la moelle osseuse en Imagerie par Résonance Magnétique : quantification de biomarqueurs." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1B009/document.
Full textAbstract:
De récentes études ont démontré la pertinence de la quantification par IRM (Imagerie par Résonance Magnétique) de la fraction de graisse, des temps de relaxation T1 et T2* de l’eau et des lipides, de la diffusion et de la perfusion dans la moelle osseuse, ces paramètres pouvant être utilisés en tant que biomarqueurs dans le cadre de pathologies affectant la moelle osseuse, telles que le myélome ou l'ostéoporose. La quantification de ces paramètres requiert cependant l'application de séquences IRM présentant des artéfacts spécifiques et dont les temps d'acquisition provoquent une immobilisation prolongée des patients. Ce travail de thèse porte sur la quantification de biomarqueurs dans le cadre de l’exploration de la moelle osseuse par IRM. L'objectif de ce travail de thèse était d'optimiser la quantification de ces biomarqueurs (fraction de graisse, T1, T2*, diffusion et perfusion) via l'optimisation de protocoles d'imagerie compatibles avec la pratique clinique, spécifiquement pour l'imagerie eau-graisse et l'imagerie de diffusion. Cette optimisation a consisté à prendre en compte les artéfacts inhérents aux techniques de quantification, les imperfections de l'instrument et à améliorer le rapport signal-sur-bruit par unité de temps des séquences IRM pour une application sur la moelle osseuse. La première partie de ce travail de thèse a porté sur le développement d’un protocole d’imagerie rapide, permettant la quantification simultanée de la fraction de graisse et des temps de relaxation T1 et T2* de l'eau et des lipides à partir de séquences eau-graisse. Dans un premier temps, cette méthode de quantification a été validée cliniquement par application à une population de volontaires, dans le cadre d'une étude réalisée au CHU de Rennes. Au cours d’une seconde étude sur volontaires, cette méthode de quantification a été appliquée à différents sites de moelle osseuse (humérus, sternum, vertèbres lombaires ilium et fémur), ce qui a permis de mettre en évidence des variations régionales de ces paramètres ainsi que la présence d'une corrélation négative entre le T1 de l'eau et la fraction de graisse. L’équation du signal utilisée dans cette méthode de quantification fait intervenir l'angle de basculement appliqué dans la séquence eau-graisse. Dans le but d’estimer l’influence de la variation de l’angle de basculement sur la mesure des paramètres, une méthode de quantification de l'angle de basculement spécialement adaptée à l'imagerie du rachis a également été développée au cours de ce travail.La seconde partie de ce travail de thèse a porté sur la quantification de la diffusion et de la perfusion dans la moelle osseuse, avec notamment l’imagerie des mouvements intra-voxels incohérents (IVIM). Ce travail a tout d’abord consisté à optimiser le protocole d’imagerie de diffusion pour une application au rachis lombaire, puis à étudier l'influence de la présence de graisse sur la quantification des paramètres de diffusion et de perfusion grâce à une étude sur volontaires. La perspective de ce travail est l'application des séquences eau-graisse et des séquences de diffusion optimisées à des populations atteintes de pathologies de la moelle osseuse, ces séquences permettant de réduire la durée d'immobilisation des patients et de détecter les modifications spécifiques à ces pathologiesRecently published studies have shown the relevance of quantifying the bone marrow fat fraction, T1 and T2* relaxation times of water and lipid components, diffusion and perfusion with MRI (Magnetic Resonance Imaging). These parameters have indeed been used as biomarkers for bone marrow related pathologies, such as the myeloma and osteoporosis. The quantification of these parameters however requires the application of MR sequences which show specific artefacts and have long acquisition times that can be tiresome for older patients. The aim of this thesis was to optimise the quantification of the fat fraction, T1 and T2* relaxation times, diffusion and perfusion in the bone marrow. The quantification of these biomarkers was optimised by improving the imaging protocols of water-fat sequences and diffusion sequences for clinical applications. These sequences were optimised by taking into account the imperfections of the MR system and the specific artefacts of these techniques and by improving the signal-to-noise ratio per unit time of the sequences for an application on bone marrow. The first part of this work consisted in developing a fast quantification method that allows for the simultaneous quantification of the fat fraction and of the T1 and T2* relaxation times of water and lipids with water-fat sequences. This method was first clinically validated by applying these sequences in a population of healthy volunteers. In a second study, this method was applied in a population of healthy volunteers to different sites of bone marrow (humerus, sternum, vertebrae, ilium and femur). The results of this study showed local variations of these parameters and a strong negative correlation between the T1 of water and the fat fraction. The signal equation of this quantification method uses the flip angle applied in the water-fat sequence. In order to assess the influence of flip angle variations on the parameters measurement, a flip angle quantification method specially dedicated to spine imaging was also developed during this work. The second part of this work consisted in quantifying diffusion and perfusion in bone marrow, especially with the intra-voxel incoherent motion imaging (IVIM). The imaging protocol of the diffusion sequence was first optimised for a spine application; then the influence of fat on the quantification of diffusion and perfusion parameters was assessed in a study on healthy volunteers. In the future, the optimised water-fat sequences and diffusion sequences will be applied to patients suffering from bone marrow pathologies. These sequences allow a decreased total acquisition time and the detection of pathology-specific modifications
25
Kornaropoulos, Evgenios. "Enregistrement d'Image Déformable en Groupe pour l'Estimation de Mouvement en Imagerie Médicale en 4D." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLC042/document.
Full textAbstract:
La présente thèse propose des méthodes pour l'estimation du mouvement des organes d'un patient autravers de l'imagerie tomographique. Le but est la correction du mouvement spatio-temporel sur les imagesmédicales tomographiques. En tant que paradigme expérimental, nous considérons le problème de l'estimation dumouvement dans l'imagerie IRM de diffusion, une modalité d'imagerie sensible à la diffusion des molécules d'eaudans le corps. Le but de ces travaux de thèse est l'évaluation des patients atteints de lymphome, car l'eau diffusedifféremment dans les tissus biologiques sains et dans les lésions. L'effet de la diffusion de l'eau peut être mieuxreprésenté par une image paramétrique, grâce au coefficient de diffusion apparente (image à ADC), créé sur la based'une série d'images DWI du même patient (séquence d'images 3D), acquises au moment de la numérisation. Unetelle image paramétrique a la possibilité de devenir un biomarqueur d'imagerie d’IRM et de fournir aux médecinsdes informations complémentaires concernantl'image de FDG-PET qui est la méthode d'imagerie de base pour lelymphome et qui montre la quantité de glucose métabolisée.Nos principales contributions sont au nombre de trois. Tout d'abord, nous proposons une méthode de recalaged'image déformable en groupe spécialement conçue pour la correction de mouvement dans l’IRM de diffusion, carelle est guidée par un modèle physiologique décrivant le processus de diffusion qui se déroule lors de l'acquisitionde l'image. Notre méthode détermine une image à ADC de plus grande précision en termes de représentation dugradient de la diffusion des molécules d'eau par rapport à l` image correspondante obtenue par pratique couranteou par d'autres méthodes de recalage d'image non basé sur un modèle. Deuxièmement, nous montrons qu'enimposant des contraintes spatiales sur le calcul de l'image à ADC, les tumeurs de l'image peuvent être encore mieuxcaractérisées en les classant dans les différentes catégories liées à la maladie. Troisièmement, nous montronsqu'une corrélation entre DWI et FDG-PET doit exister en examinant la corrélation entre les caractéristiquesstatistiques extraites par l'image à ADC lisse découlant de notre méthode du recalage d’image déformable et lesscores de recommandation sur la malignité des lésions, donnés par des experts basés sur une évaluation des imagesFDG-PET correspondantes du patientThis doctoral thesis develops methods to estimate patient's motion, voluntary and involuntary (organs'motion), in order to correct for motion in spatiotemporal tomographic medical images. As an experimentalparadigm we consider the problem of motion estimation in Diffusion-Weighted Magnetic Resonance Imaging (DWI),an imaging modality sensitive to the diffusion of water molecules in the body. DWI is used for the evaluation oflymphoma patients, since water diffuses differently in healthy tissues and in lesions. The effect of water diffusioncan be better depicted through a parametric map, the so-called apparent diffusion coefficient (ADC map), createdbased on a series of DW images of the same patient (3D image sequence), acquired in time during scanning. Such aparametric map has the potentiality to become an imaging biomarker in DWI and provide physicians withcomplementary information to current state-of-the-art FDG-PET imaging reflecting quantitatively glycosemetaboslism.Our contributions are three fold. First, we propose a group-wise deformable image registration methodespecially designed for motion correction in DWI, as it is guided by a physiological model describing the diffusionprocess taking place during image acquisition. Our method derives an ADC map of higher accuracy in terms ofdepicting the gradient of the water molecules' diffusion in comparison to the corresponding map derived bycommon practice or by other model-free group-wise image registration methods. Second, we show that by imposingspatial constraints on the computation of the ADC map, the tumours in the image can be even better characterized interms of classifying them into the different types of the disease. Third, we show that a correlation between DWI andFDG-PET should exist by examining the correlation between statistical features extracted by the smooth ADC mapderived by our deformable registration method, and recommendation scores on the malignancy of the lesions, givenby experts based on an evaluation of the corresponding FDG-PET images of the patient
26
de, Waha Suzanne, Ingo Eitel, Steffen Desch, Georg Fuernau, Philipp Lurz, Thomas Stiermaier, Stephan Blazek, Gerhard Schuler, and Holger Thiele. "Prognosis after ST-elevation myocardial infarction." Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-148644.
Full textAbstract:
Background: This study aimed to evaluate the incremental prognostic value of infarct size, microvascular obstruction (MO), myocardial salvage index (MSI), and left ventricular ejection fraction (LV-EFCMR) assessed by cardiac magnetic resonance imaging (CMR) in comparison to traditional outcome markers in patients with ST-elevation myocardial infarction (STEMI) reperfused by primary percutaneous intervention (PCI). Methods: STEMI patients reperfused by primary PCI (n = 278) within 12 hours after symptom onset underwent CMR three days after the index event (interquartile range [IQR] two to four). Infarct size and MO were measured 15 minutes after gadolinium injection. T2-weighted and contrast-enhanced CMR were used to calculate MSI. In addition, traditional outcome markers such as ST-segment resolution, pre- and post-PCI Thrombolysis In Myocardial Infarction (TIMI)-flow, maximum level of creatine kinase-MB, TIMI-risk score, and left ventricular ejection fraction assessed by echocardiography were determined in all patients. Clinical follow-up was conducted after 19 months (IQR 10 to 27). The primary endpoint was defined as a composite of death, myocardial reinfarction, and congestive heart failure (MACE). Results: In multivariable Cox regression analysis, adjusting for all traditional outcome parameters significantly associated with the primary endpoint in univariable analysis, MSI was identified as an independent predictor for the occurrence of MACE (Hazard ratio 0.94, 95% CI 0.92 to 0.96, P <0.001). Further, C-statistics comparing a model including only traditional outcome markers to a model including CMR parameters on top of traditional outcome markers revealed an incremental prognostic value of CMR parameters (0.74 versus 0.94, P <0.001). Conclusions:
CMR parameters such as infarct size, MO, MSI, and LV-EFCMR add incremental prognostic value above traditional outcome markers alone in acute reperfused STEMI.
27
Lee, Kuan Jin. "Fast magnetic resonance imaging." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397487.
Full text
28
O'Neil, Shannon M. "Magnetic resonance imaging centers /." Online version of thesis, 1994. http://hdl.handle.net/1850/11916.
Full text
29
Lu, Wenmiao. "Off-resonance correction in magnetic resonance imaging /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
30
Manners, David Neil. "Magnetic resonance imaging and magnetic resonance spectroscopy of skeletal muscle." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269250.
Full text
31
Zierhut, Matthew Luke. "Improving cancer biomarkers through magnetic resonance technology." Diss., Search in ProQuest Dissertations & Theses. UC Only, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3339210.
Full textAbstract:
Thesis (Ph.D.)--University of California, San Francisco with the University of California, Berkeley, 2008.Source: Dissertation Abstracts International, Volume: 69-12, Section: B, page: 7655. Adviser: Sarah J. Nelson.
32
Petropoulos, Labros Spiridon. "Magnetic field issues in magnetic resonance imaging." Case Western Reserve University School of Graduate Studies / OhioLINK, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=case1060710667.
Full text
33
Campbell, Jennifer 1975. "Magnetic resonance diffusion tensor imaging." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30809.
Full textAbstract:
Magnetic resonance imaging (MRI) can be used to image diffusion in liquids, such as water in brain structures. Molecular diffusion can be isotropic or anisotropic, depending on the fluid's environment, and can therefore be characterized by a scalar, D, or by a tensor, D, in the respective cases. For anisotropic environments, the eigenvector of D corresponding to the largest eigenvalue indicates the preferred direction of diffusion.This thesis describes the design and implementation of diffusion tensor imaging on a clinical MRI system. An acquisition sequence was designed and post-processing software developed to create diffusion trace images, scalar anisotropy maps, and anisotropy vector maps. A number of practical imaging problems were addressed and solved, including optimization of sequence parameters, accounting for flow effects, and dealing with eddy currents, patient motion, and ghosting. Experimental validation of the sequence was performed by calculating the trace of the diffusion tensor measured in various isotropic liquids. The results agreed very well with the quantitative values found in the literature, and the scalar anisotropy index was also found to be correct in isotropic phantoms. Anisotropy maps, showing the preferred direction of diffusion, were generated in human brain in vivo. These showed the expected white matter tracts in the corpus callosum.
34
Lindsay, Alistair. "Magnetic resonance imaging of atherosclerosis." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.526491.
Full text
35
Glover, Paul Martin. "High field magnetic resonance imaging." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335575.
Full text
36
Yoo, Seung-Schik 1970. "Adaptive functional magnetic resonance imaging." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/70893.
Full textAbstract:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2000.Some research performed with the Harvard-M.I.T. Division of Health Sciences and Technology.
Includes bibliographical references (leaves 132-140).
Functional MRI (fMRI) detects the signal associated with neuronal activation, and has been widely used to map brain functions. Locations of neuronal activation are localized and distributed throughout the brain, however, conventional encoding methods based on k-space acquisition have limited spatial selectivity. To improve it, we propose an adaptive fMRI method using non-Fourier, spatially selective RF encoding. This method follows a strategy of zooming into the locations of activation by progressively eliminating the regions that do not show any apparent activation. In this thesis, the conceptual design and implementation of adaptive fMRI are pursued under the hypothesis that the method may provide a more efficient means to localize functional activities with increased spatial or temporal resolution. The difference between functional detection and mapping is defined, and the multi- resolution approach for functional detection is examined using theoretical models simulating variations in both in-plane and through-plane resolution. We justify the multi-resolution approach experimentally using BOLD CNR as a quantitative measure and compare results to those obtained using theoretical models. We conclude that there is an optimal spatial resolution to obtain maximum detection; when the resolution matches the size of the functional activation. We demonstrated on a conventional 1.5-Tesla system that RF encoding provides a simple means for monitoring irregularly distributed slices throughout the brain without encoding the whole volume. We also show the potential for increased signal-to-noise ratio with Hadamard encoding as well as reduction of the in-flow effect with unique design of excitation pulses.
(cont.) RF encoding was further applied in the implementation of real-time adaptive fMRI method, where we can zoom into the user-defined regions interactively. In order to do so, real-time pulse prescription and data processing capabilities were combined with RF encoding. Our specific implementation consisted of five scan stages tailored to identify the volume of interest, and to increase temporal resolution (from 7.2 to 3.2 seconds) and spatial resolution (from 10 mm to 2.5-mm slice thickness). We successfully demonstrated the principle of the multi- resolution adaptive fMRI method in volunteers performing simple sensorimotor paradigms for simultaneous activation of primary motor as well as cerebellar areas.
by Seung-Schik Yoo.
Ph.D.
37
Eichner, Cornelius. "Slice-Accelerated Magnetic Resonance Imaging." Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184944.
Full textAbstract:
This dissertation describes the development and implementation of advanced slice-accelerated (SMS) MRI methods for imaging blood perfusion and water diffusion in the human brain. Since its introduction in 1977, Echo-Planar Imaging (EPI) paved the way toward a detailed assessment of the structural and functional properties of the human brain. Currently, EPI is one of the most important MRI techniques for neuroscientific studies and clinical applications. Despite its high prevalence in modern medical imaging, EPI still suffers from sub-optimal time efficiency - especially when high isotropic resolutions are required to adequately resolve sophisticated structures as the human brain. The utilization of novel slice-acceleration methods can help to overcome issues related to low temporal efficiency of EPI acquisitions.
The aim of the four studies outlining this thesis is to overcome current limitations of EPI by developing methods for slice-accelerated MRI. The first experimental work of this thesis describes the development of a slice-accelerated MRI sequence for dynamic susceptibility contrast imaging. This method for assessing blood perfusion is commonly employed for brain tumor classifications in clinical practice. Following up, the second project of this thesis aims to extend SMS imaging to diffusion MRI at 7 Tesla. Here, a specialized acquisition method was developed employing various methods to overcome problems related to increased energy deposition and strong image distortion. The increased energy depositions for slice-accelerated diffusion MRI are due to specific radiofrequency (RF) excitation pulses. High energy depositions can limit the acquisition speed of SMS imaging, if high slice-acceleration factors are employed. Therefore, the third project of this thesis aimed at developing a specialized RF pulse to reduce the amount of energy deposition. The increased temporal efficiency of SMS imaging can be employed to acquire higher amounts of imaging data for signal averaging and more stable model fits. This is especially true for diffusion MRI measurements, which suffer from intrinsically low signal-to-noise ratios. However, the typically acquired magnitude MRI data introduce a noise bias in diffusion images with low signal-to-noise ratio. Therefore, the last project of this thesis aimed to resolve the pressing issue of noise bias in diffusion MRI. This was achieved by transforming the diffusion magnitude data into a real-valued data representation without noise bias. In combination, the developed methods enable rapid MRI measurements with high temporal efficiency. The diminished noise bias widens the scope of applications of slice- accelerated MRI with high temporal efficiency by enabling true signal averaging and unbiased model fits. Slice-accelerated imaging for the assessment of water diffusion and blood perfusion represents a major step in the field of neuroimaging. It demonstrates that cur- rent limitations regarding temporal efficiency of EPI can be overcome by utilizing modern data acquisition and reconstruction strategies.
38
Harvey, Ian. "Magnetic resonance imaging in schizophrenia." Thesis, University of Edinburgh, 1991. http://hdl.handle.net/1842/19829.
Full text
39
Huber, Adrian Thomas. "Multi-organ non-invasive tissue characterization of fibrosis, adipose tissue, edema and inflammation with magnetic resonance (MR) imaging : applications to myocardium, skeletal muscle and liver interactions Cardiac MR strain: a noninvasive biomarker of fibro-fatty remodeling of the left atrial myocardium Comparison of MR T1 and T2 mapping parameters to characterize myocardial and skeletal muscle involvement in systemic Idiopathic Inflammatory Myopathy (IIM) Non-invasive differentiation of acute viral myocarditis and idiopathic inflammatory myopathy with cardiac involvement using magnetic resonance imaging T1 and T2 mapping CT predicts liver fibrosis: Prospective evaluation of morphology- and attenuationbased quantitative scores in routine portal venous abdominal scans." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS135.
Full textAbstract:
Cette thèse réalise une preuve de concept pour quantifier la déformation de l’oreillette gauche (OG) en IRM, ainsi que la relaxométrie IRM dans le myocarde, dans les muscles squelettiques et dans le foie. Grâce à l’interaction entre radiologues et ingénieurs, deux logiciels différents ont été développés, appliqués et validés pour l'analyse de la déformation myocardique multi-chambre et pour la cartographie quantitative du T1 multi-organes. La première publication a montré une forte corrélation de la déformation de l’OG, avec le degré de remplacement fibro-graisseux en histologie. Ce biomarqueur d'imagerie fonctionnelle est prometteur, puisque le remodelage structurel du myocarde est un substrat morphologique connu du dysfonctionnement électro-physiologique et de la fibrillation atriale. La deuxième publication a démontré l'influence de la composition et de la vascularisation de différents tissus sur les paramètres cartographiques T1. ΔT1 (prise de contraste musculaire relative) et EHF (prise de contraste musculaire normalisée par la prise de contraste dans le sang) ont été introduits comme alternatives simples au volume extracellulaire (ECV). Dans la troisième publication, les paramètres de relaxométrie appliqués aux muscles squelettiques ont permis une discrimination entre patients avec myocardite aiguë et patients avec des myosites systémiques. La quatrième publication a introduit le T1 du foie pour quantifier l’insuffisance cardiaque chez des patients avec des cardiomyopathies idiopathiques dilatées, montrant de meilleures performances que les paramètres fonctionnels établis tels que les volumes, la fraction d'éjection ou la déformation myocardiqueThis thesis provides a proof of concept for MR atrial strain, as well as MR relaxometry in the myocardium, in skeletal muscles and in the liver. Thanks to a close interaction between radiologist and software engineers, two different softwares were developed, applied and validated: one for multiorgan T1 mapping in the myocardium, skeletal muscle and liver, another one for cardiac four-chamber strain analysis and volumetry. The first publication showed a strong correlation of LA strain with the degree of fibro-fatty replacement in histology. Such functional imaging biomarker in combination with LA volumetry could help to guide clinical decisions, since myocardial structural remodeling is a known morphologic substrate of LA dysfunction, atrial fibrillation and adverse outcome. In the second publication, MR relaxometry parameters applied to the myocardium and skeletal muscles in IIM patients and healthy volunteers were used as a model to demonstrate influences of different tissue composition and vascularization on T1 mapping parameters. ΔT1 and EHF were introduced as simple alternatives to ECV in highly vascularized tissues such as the myocardium. In the third publication, MR relaxometry parameters applied to the skeletal muscls allowed for an accurate discrimination of AVM and IIM with cardiac involvement. However, when applied to the myocardium, parametric mapping did not separate between the two groups. The fourth publication introduced native T1 of the liver an easily accessible and accurate non-invasive imaging associate of congestive HF in IDCM patients with better performance than established functional parameters such as LV volumes, ejection fraction or strain
40
Sharkey-Toppen, Travis P. "Imaging Iron and Atherosclerosis by Magnetic Resonance Imaging." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429796182.
Full text
41
Yoshimaru, Eriko Suzanne. "Magnetic Resonance Imaging Techniques for Rodent Pulmonary Imaging." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/293388.
Full textAbstract:
Magnetic Resonance Imaging (MRI) is a safe and widely used diagnostic imaging method that allows in vivo observation of anatomy and characterization of tissues. MRI provides a method to monitor patients without invasive measures, making it suitable for both diagnostics and longitudinal monitoring of various pathologies. A notable example of this is the work carried out by the Alzheimer's Disease Neuroimaging Initiative (ADNI), which utilizes imaging, including multiple MRI techniques, to monitor disease progression in AD patients and evaluates treatment responses and prevention strategies. Similarly, MRI has been extensively used in evaluating diseases in a variety of animal models. In order to detect subtle anatomical changes over time, small differences in MR images must be accurately extracted. Furthermore, to ensure that the extracted differences are due to anatomical changes rather than equipment variance, it becomes essential to monitor and to assess the MRI system stability. In the first chapter of the dissertation, a method for monitoring pre-clinical MRI system performance is discussed. The technique developed during the study provides a fast and simple method to monitor pre-clinical MRI systems but also has applications for all areas of MRI. The second chapter describes the development of a 3D UTE MRI method for pulmonary imaging in freely breathing mice. The development of the 3D UTE sequence for pulmonary MRI has demonstrated its ability to collect images without noticeable motion artifacts and with appreciable signal from the lung parenchyma. Furthermore, images at two distinct respiratory phases were reconstructed from a single data set, providing functional information of the rodents' lungs. Finally, in the third chapter, 3D ¹⁹F UTE MRI is evaluated for imaging in vivo distributions of perfluorocarbon (PFC) nanoemulsions for measuring pulmonary inflammation. Building upon the development of pulmonary imaging, fluorinated contrast agents made from PFCs were used to target immune cells in response to pulmonary pathology. Both 3D ¹H and ¹⁹F UTE MRI were used to acquire pulmonary images of mouse models documented to have pulmonary pathology. Even though the mice had confirmed elevation in alveolar macrophage counts, no visible ¹⁹F signal accumulation within the pulmonary tissue was observed with MRI.
42
Costa, Leandro Menezes Alves da. "Liberação de biomarcadores de necrose miocárdica após revascularização cirúrgica do miocárdio sem circulação extracorpórea, em ausência de infarto do miocárdio manifesto, avaliado pela ressonância magnética cardíaca." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/5/5131/tde-09082017-125122/.
Full textAbstract:
Introdução: A liberação de biomarcadores de necrose miocárdica após revascularização miocárdica cirúrgica (RM) ocorre com frequência. No entanto, a correlação entre a liberação de biomarcadores e o diagnóstico do infarto agudo do miocárdio (IAM) periprocedimento gera controvérsias, especialmente com o aumento da sensibilidade nos ensaios de troponina (Tn). Neste estudo, objetivou-se quantificar a liberação dos biomarcadores cardíacos em pacientes submetidos à RM, sem o uso de circulação extra corpórea (CEC), que não apresentaram evidências de infarto do miocárdio por meio da avaliação do realce tardio pelo gadolínio (RTG) na ressonância magnética cardíaca (RMC). Métodos: Pacientes portadores de doença arterial coronária estável e função ventricular preservada, com indicação eletiva para RM sem CEC, foram incluídos. RMC com RTG foi realizada em todos os pacientes antes e depois do procedimento. Aferições seriadas de Tn e creatinoquinase fração MB (CK-MB) foram realizadas antes do procedimento e até 72h após. Pacientes com RTG na RMC após o procedimento foram excluídos. Resultados: 73 pacientes foram referenciados para a realização eletiva da RM sem CEC e 20 (27%) foram excluídos, 14 (19%) por causa do surgimento de um novo RTG na RMC. Dentre os 53 pacientes sem evidência de IAM periprocedimento pela RMC, 37 (70%) eram do gênero masculino, a média da idade foi 63 (± 10) anos e o escore SYNTAX médio encontrado foi 20 (±7). Após a RM, todos os pacientes apresentaram um pico de elevação de Tn acima do percentil 99; em 48 (91%) pacientes a elevação foi superior a 10 vezes esse limite. Por outro lado, 41 (76%) pacientes apresentaram pico de CK-MB acima do percentil 99 e em apenas 7 (13%) este pico foi superior à10 vezes o percentil 99. A mediana do pico de liberação da Tn foi 2,0 (0,8 - 3,7) ng/mL, valor 50 vezes superior ao percentil 99. Conclusão: Diferente da CK-MB, a liberação da troponina I ocorre, frequentemente, após procedimento de RM sem CEC na ausência de realce tardio pela RMCBackground: The release of myocardial necrosis biomarkers after off-pump coronary artery bypass grafting (OPCAB) frequently occurs. However, the correlation between biomarker release and the diagnosis of procedurerelated myocardial infarction (MI) (type 5) has been controversial. This study aims to evaluate the amount and pattern of cardiac biomarker release after elective OPCAB in patients without the image of a new MI assessed by cardiac magnetic resonance (CMR) with late gadolinium enhancement (LGE). Methods: Patients with normal baseline cardiac biomarkers referred for elective OPCAB were prospectively included. CMR with LGE was performed in all patients before and after interventions. Measurements of troponin I (cTnI) and creatinekinase MB fraction (CK-MB) were systematically performed before and after the procedure. Patients with a new LGE on the post-procedure CMR were excluded. Results: Of the 53 patients without the evidence of a procedure-related MI assessed by the CMR after OPCAB, all patients exhibited cTnI elevation peak above the 99th percentile. In 48 (91%), the peak value was greater than 10 times this threshold. However, 41 (76%) had CK-MB peak above the limit of the 99th percentile, and this peak was greater than 10 times the 99th percentile in only 7 patients (13%). The median peak release of cTnI was 0.20 (0.8 - 3.7) ng/mL, which is 50-fold higher than the 99th percentile. Conclusions: In contrast to CK-MB, cTnI release often occurs after an elective OPCAB procedure, despite the absence of a new LGE on CMR
43
MA, DAN. "Magnetic Resonance Fingerprinting." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1426170542.
Full text
44
Lei, Hao. "Magnetic resonance perfusion imaging and double quantum coherence transfer magnetic resonance spectroscopy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0021/NQ45007.pdf.
Full text
45
Tymofiyeva, Olga. "Magnetic resonance imaging in dental medicine." Göttingen Sierke, 2010. http://d-nb.info/1002094976/04.
Full text
46
McDougall, Mary Preston. "Single echo acquisition magnetic resonance imaging." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3324.
Full textAbstract:
The dramatic improvement in magnetic resonance imaging (MRI) scan time over the past fifteen years through gradient-based methods that sample k-space more efficiently and quickly cannot be sustained, as thresholds regarding hardware and safety limitations are already being approached. Parallel imaging methods (using multiple receiver coils to partially encode k-space) have offered some relief in the efforts and are rapidly becoming the focus of current endeavors to decrease scan time. Ideally, for some applications, phase encoding would be eliminated completely, replaced with array coil encoding instead, and the entire image formed in a single echo.
The primary objective of this work was to explore that acceleration limit  to implement and investigate the methodology of single echo acquisition magnetic resonance imaging (SEA MRI). The initial evaluation of promising array coil designs is described, based on parameters determined by the ability to enable the imaging method. The analyses of field patterns, decoupling, and signal-to-noise ratio (SNR) that led to the final 64-channel array coil design are presented, and the fabrication and testing of coils designed for 4.7T and 1.5T are described. A detailed description of the obtainment of the first SEA images  64xNreadout images, acquired in a single echo  is provided with an evaluation of those images and highly accelerated images (through parallel imaging techniques) based on SNR and artifact power. Finally, the development of methodologies for various MR applications is described: applications that would particularly benefit from the speed of the imaging method, or those to which the method or the tool (array coil) lends itself. These applications include, but are not limited to, 3D imaging (phase encode in the slice select direction), resolution-enhanced imaging, large-scale (field-of-view) microscopy, and conformal surface imaging. Finally, using the primary enablement of the method  the ability to obtain complete MR images at speeds limited only by the time it takes to acquire a single echo  is presented with a discussion of extremely high frame rate imaging.
The contribution to the field of medical imaging is the first implementation, characterization, and demonstration of applications for the acquisition of MR images in a single echo.
47
Brown, David Gerald. "Instrumentation for parallel magnetic resonance imaging." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4784.
Full textAbstract:
Parallel magnetic resonance (MR) imaging may be used to increase either the
throughput or the speed of the MR imaging experiment. As such, parallel imaging may
be accomplished either through a "parallelization" of the MR experiment, or by the use
of arrays of sensors. In parallelization, multiple MR scanners (or multiple sensors) are
used to collect images from different samples simultaneously. This allows for an
increase in the throughput, not the inherent speed, of the MR experiment. Parallel
imaging with arrays of sensor coils, on the other hand, makes use of the spatial
localization properties of the sensors in an imaging array to allow a reduction in the
number of phase encodes required in acquiring an image. This reduced phase-encoding
requirement permits an increase in the overall imaging speed by a factor up to the
number of sensors in the imaging array. The focus of this dissertation has been the
development of cost-effective instrumentation that would enable advances in the state of
the art of parallel MR imaging.
First, a low-cost desktop MR scanner was developed (< $13,000) for imaging small
samples (2.54 cm fields-of view) at low magnetic field strengths (< 0.25 T). The
performance of the prototype was verified through bench-top measurements and
phantom imaging. The prototype transceiver has demonstrated an SNR (signal-to-noise ratio) comparable to that of a commercial MR system. This scanner could make
parallelization of the MR experiment a practical reality, at least in the areas of small
animal research and education.
A 64-channel receiver for parallel MR imaging with arrays of sensors was also
developed. The receiver prototype was characterized through both bench-top tests and
phantom imaging. The parallel receiver is capable of simultaneous reception of up to
sixty-four, 1 MHz bandwidth MR signals, at imaging frequencies from 63 to 200 MHz,
with an SNR performance (on each channel) comparable to that of a single-channel
commercial MR receiver. The prototype should enable investigation into the speed
increases obtainable from imaging with large arrays of sensors and has already been
used to develop a new parallel imaging technique known as single echo acquisition
(SEA) imaging.
48
Hill, Richard J. "Developments in quantitative magnetic resonance imaging." Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/843527/.
Full textAbstract:
Two magnetic resonance imaging studies based on relaxometry are presented. Firstly, various methods of measuring T1, T2, and flip angle are reviewed, along with various applications of relaxometry. After a study of the relevant background and theory, a method of measuring T1, T2, and the flip angle simultaneously using echo planar imaging is described, followed by a study of diffusion in a biological system employing T2 measurements. A series of echo planar images acquired with a repetition time that is short compared with the relaxation times T1 and T2 shows fluctuations in image intensity, which are dependent on these relaxation times and the flip angle. These fluctuations are best modelled using the Kaiser theory of isochromats. The Levenberg-Marquardt non-linear least squares algorithm can then be used to estimate the parameters from the data. This has been shown to work consistently in zero and one dimensions, but inconsistently in two dimensions when high gradient amplitudes affect coherence. Bacterial polysaccharides are known to exhibit a property known as anion exclusion, where the diffusion of cations is permitted, but the diffusion of anions is prevented. According to the theory of permselectivity, negatively-charged functional groups on the surfaces of pores not only block anions, but assist the diffusion of cations. The relationship between T2 and the concentration of paramagnetic species is used to follow the diffusion of Mn2+ ions through several polysaccharides. It is shown that the diffusion coefficients of Mn2+ ions are higher in neutral than in positively-charged polysaccharides, and greater still in negatively charged polysaccharides.
49
Kristoffersen, Wiberg Maria. "Magnetic resonance imaging in breast diagnosis /." Stockholm : Karolinska Univ. Press, 2002. http://diss.kib.ki.se/2002/91-7349-343-0.
Full text
50
Blomqvist, Lennart. "Magnetic resonance imaging of rectal tumours /." Stockholm, 1997. http://diss.kib.ki.se/1997/91-628-2797-9.
Full text