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Dissertations / Theses on the topic 'Diffusion MR Imaging'
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Skare, Stefan. "Optimisation strategies in diffusion tensor MR imaging /." Stockholm, 2002. http://diss.kib.ki.se/2002/91-7349-175-6.
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Candrák, Matúš. "Zpracování difuzně vážených obrazů pořízených MR tomografem." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220983.
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The semester thesis describes the basic principles of MRI, methods for measuring diffusion coefficients and creating DWI and DTI images. As a result a practical implementation of program was implemented in Matlab, based on theoretical knowledge of the problem.
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Bai, Y. "Correcting for motion between acquisitions in diffusion MR imaging." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18690/.
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The diffusion tensor (DT) and other diffusion models assume that each voxel corresponds to the same anatomical location in all the measurements. Movements and distortions violate this assumption and typically the images are realigned before model fitting. We propose a set of model-based methods to improve motion correction and avoid the errors that the traditional method introduces. The new methods are based on a three-step procedure to register DWI datasets, and use different reference images for DWIs with different gradient directions for registration, so the registrations take into account the contrast differences of measurements. Performance of the model-based registration techniques depends critically on outlier rejection. We develop new methods for fitting the diffusion tensor to diffusion MRI measurements in the presence of outliers by drawing on the RANSAC algorithm from computer vision. We compareone popularly used outlier rejection method RESTORE in the diffusion MRI literature with our new method. Then, we combine outlier rejection methods with model-based registration schemes, and compare the performance of motion correction with other methods. After aligning the dataset, we also update diffusion gradients for the registered datasets from both traditional and our methods, according to the transformations used in registrations. We develop and discuss a variety of registration evaluation methods using both synthetic and human-brain diffusion MRI datasets. Experiments demonstrate both quantitative and qualitative improvements using our new model-based methods.
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MacGillivray, Cathy Carleton University Dissertation Physics. "Diffusion-weighted MR imaging of moving structures using a three echo navigator imaging technique." Ottawa, 1996.
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Domenig, Claudia. "Development and evaluation of MR imaging techniques for quantitative diffusion imaging of the human pelvis." Thesis, University of Surrey, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273242.
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Kerttula, L. (Liisa). "Magnetic resonance imaging of the intervertebral disc:post-traumatic findings and the value of diffusion-weighted MR imaging." Doctoral thesis, University of Oulu, 2001. http://urn.fi/urn:isbn:9514264711.
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Abstract
Magnetic resonance imaging (MRI) provides important information about structural and biochemical changes in organs. MRI is also an effective imaging method for the evaluation of spinal disorders. However, many of its potential applications - particularly diffusion imaging - have not yet been thoroughly explored.
The purpose of this study was to determine the MRI-detectable changes in the intervertebral disc after trauma and to test the feasibility of diffusion-weighted MR imaging of the intervertebral discs.
A minipig model was used in the experimental study to determine the MRI changes in the intervertebral disc after peripheral annular lesions in different time frames. Three of eight discs with experimental annular lesions had a normal annular appearance in MRI. Annular lesions, when detectable, were manifested as a bulging of the disc or as a high-intensity zone (HIZ) inside the annulus. Either the signal intensity or the area of bright signal intensity in the nucleus had nearly always decreased after one month, but they were still detectable even in cases where no signs of annular trauma could be seen in the MR images. The histology of HIZ is presented for the first time: clusters of nuclear cells and disorganized granulation tissue with capillaries were detected in the HIZ area.
Fourteen patients 8 to 21 years of age with histories of vertebral fracture at least one year previously and 14 asymptomatic healthy control subjects 8 to 22 years of age were studied by MRI. In these young people a vertebral fracture, especially with end-plate injury, proved to be a notable risk factor for initiating disc degeneration.
The apparent diffusion coefficients (ADCs) of the thoracolumbar intervertebral discs were determined in three orthogonal directions in 18 healthy young volunteers aged 8-22 years. The ADCs were also determined in 10 young patients with previous vertebral fractures, and clear decreases were found in the ADCx and ADCy directions, but in the ADCz direction values had not changed significantly as compared to the values in the controls. The most marked changes were observed in the degenerated discs, followed by those in the discs with a normal signal intensity adjacent to the primary trauma area. Diffusion-weighted MR imaging affords a useful tool for evaluating disc diseases in the early phases.
Additionally, 37 adult volunteers without back symptoms were studied by MRI and by magnetic resonance angiography (MRA) and it was found that the status of the lumbar arteries significantly explained the diffusion values in the lumbar intervertebral discs. The correlation between disc degeneration and diffusion was mostly linear, but not significant.
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Gong, Nanjie, and 龔南杰. "Probing tissue microstructural changes in neurodegenerative processes using non-gaussian diffusion MR imaging." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208583.
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Development of non-invasive imaging biomarkers sensitive to microstructural organization is crucial for deepening our understanding of mechanisms underlying neurodegenerative processes such as aging and further improving early diagnosis and monitoring of neurodegenerative disease such as Alzheimer’s disease (AD) and amnestic mild cognitive impairment (MCI). The diffusional kurtosis imaging (DKI) is an extension of conventional diffusion tensor imaging. It is hypothesized that DKI will provide complementary information to conventional diffusivity metrics in a new dimension that will more comprehensively capture microstructural changes in anisotropic white matter tracts and particularly in relatively isotropic tissues such as gray matter during neurodegenerative processing of aging, MCI and AD and probably improve the early diagnosis of the diseases.
Firstly, DKI method and a white-matter model that provided metrics of explicit neurobiological interpretations were applied on healthy participants. In white matter tracts, age-related degenerations appeared to be broadly driven by axonal loss. Demyelination may also be a major driving mechanism, although confined to the anterior brain. In terms of deep gray matter, higher mean kurtosis (MK) and fractional anisotropy (FA) in the globus pallidus, substantia nigra, and red nucleus reflected higher microstructural complexity and directionality compared with the putamen, caudate nucleus, and thalamus. In particular, unique age-related positive correlations for FA, MK, and radial kurtosis (KR) in the putamen opposite to those in other regions were observed.
Secondly, to verify the speculation that iron deposition could be one probable underlying mechanism driving changes in microstructure, another advance MRI technique of quantitative susceptibility mapping (QSM) was also used in healthy participants. Significant age-related increases of iron were observed in the putamen, red nucleus, substantia nigra, and caudate nucleus. Putamen exhibited the highest rate of iron accumulation with aging, which was nearly twice of the rates in substantia nigra and caudate nucleus. Significant positive correlations between susceptibility value and diffusion measurements were observed for FA and MK in the putamen as well as FA in the red nucleus.
Thirdly, whether DKI metrics could serve as imaging biomarkers to indicate the severity of cognitive deficiency for AD and MCI was investigated. In AD, significantly increased diffusivity and decreased kurtosis parameters were observed in both white and gray matter of the parietal and occipital lobes as compared to MCI. Significantly decreased FA was also observed in the white matter of these lobes in AD. With the exception of FA and KR, all the other five DKI metrics exhibited significant correlations with mini-mental state examination score in both white and gray matter.
Lastly, DKI metrics were compared against volumetry for diagnosis of AD and MCI. In AD vs. aMCI, although no significant difference of either FA or MD was observed in white matter tracts, it is encouraging to note that MK captured loss of microstructural complexity in the superior longitudinal fasciculus and internal capsule. MK in the putamen showed the highest power that outperformed volume of the hippocampus for discriminating AD from normal. Besides, FA in the putamen showed the second highest power for discriminating aMCI from normal.<br>published_or_final_version<br>Diagnostic Radiology<br>Doctoral<br>Doctor of Philosophy
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Coope, David John. "Use of [11C]-methionine PET and diffusion-/perfusion-weighted MR imaging in gliomas." Thesis, University of Manchester, 2010. http://www.manchester.ac.uk/escholar/uk-ac-man-scw:207525.
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Introduction: Low-grade gliomas are a sub-group of primary brain tumours that typically affect young adults and which present specific challenges to conventional diagnostic imaging. They demonstrate a pattern of growth whereby tumour cells infiltrate healthy brain tissue without distortion of the surrounding brain or blood-brain barrier integrity. These features limit the capacity of conventional neuro-imaging strategies to effectively delineate the tumour extent or characterise the degree of 'malignancy'. One solution is to apply multiple imaging modalities to image different aspects of the tumour behaviour, analogous to histological classification based upon changes in mitotic activity, cellular atypia, microvascular proliferation and necrosis. Published information regarding how imaging techniques that address these parameters correlate within the tumour volume is limited. This reflects the technical challenges in acquiring and processing data at an adequate spatial resolution to characterise small but heterogenous tumours. In this thesis, following a series of experiments seeking to optimise the sensitivity and reproducibility of PET analysis in gliomas, a prospective multi-modal neuro-imaging study is presented addressing this need. Methods: Retrospective [11C]-methionine PET (MET PET) data made available through a collaboration with the Max-Planck Institute for Neurological Research in Cologne was carried out first to address the optimal method of analysis of PET data in gliomas. A normal methionine uptake map was created and its use in the analysis of patient scans validated against a conventional approach. Automated methods for delineating the extent of abnormal methionine uptake and identifying the region of peak uptake were developed and evaluated to optimise the reproducibility of the approach. High-resolution MET PET and a comprehensive MRI brain tumour protocol were then acquired prospectively in 20 subjects in Manchester. Detailed analysis of the peak uptake and extent of abnormal tissue defined using PET and MRI modalities including structural, diffusion- and perfusion-weighted techniques was performed. Results: Evaluation of methionine uptake with respect to population normal data, the 'RatioMap' technique, yielded peak uptake measurements that correlated closely with a conventional approach (r = 0.97) but with improved reproducibility. The constrained 3D region-growing algorithm designed to delineate the abnormal region was shown to be reproducible and to generate volumes that correlated with tumour grade. High-resolution multi-modal data in suspected low-grade gliomas demonstrated consistent correlation between peak methionine uptake ratio and peak regional cerebral blood volume (r = 0.85) but with disparity between the location of the maximal uptake regions (mean distance = 11.2mm). Significant correlation was seen between multi-modal MRI and PET ‘tumour’ volumes (r = 0.91) but with substantially larger MRI defined abnormal volumes (ratio = 2.0) including small regions identified as abnormal by multiple MRI parameters but normal on PET imaging. Conclusion: A novel method to enhance the reproducibility of analysis of MET PET images in gliomas has been presented and validated but there remains no single imaging modality capable of fully characterising glioma extent and 'malignancy' non-invasively. Considerable correlation between PET and MRI tumour biomarkers has been demonstrated but there are significant differences between the regions identified as the 'most malignant' for biopsy targeting and the extent of potentially tumour bearing tissue. Combined use of diffusion- and perfusion-weighted MRI parameters can provide results very closely correlated to the PET findings but cannot yet completely replace the use of nuclear medicine techniques. The use of multi-modal approaches to tumour characterisation as demonstrated in this study provides the most effective currently available approach to fully characterise a suspected glioma.
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Tamai, Ken. "The utility of diffusion-weighted MR imaging in the diagnosis of uterine malignancy." Kyoto University, 2008. http://hdl.handle.net/2433/135802.
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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.
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Thuen, Marte. "Manganese-enhanced and diffusion tensor MR imaging of the normal, injured and regenerating rat visual pathway." Doctoral thesis, Norwegian University of Science and Technology, Department of Circulation and Medical Imaging, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2269.
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Ho, Nga-yee. "Longitudinal study of white matter fractional anisotropy in childhood medulloblastoma survivors by diffusion tensor MR imaging." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B39849041.
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Ho, Nga-yee, and 何雅儀. "Longitudinal study of white matter fractional anisotropy in childhood medulloblastoma survivors by diffusion tensor MR imaging." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B39849041.
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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.
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Khong, Pek-Lan. "Diffusion tensor MR imaging in the evaluation of treatment-induced white matter injury in childhood cancer survivors." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B38320666.
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Khong, Pek-Lan, and 孔碧蘭. "Diffusion tensor MR imaging in the evaluation of treatment-induced white matter injury in childhood cancer survivors." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B38320666.
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Wang, Silun. "Diffusion tensor MR imaging as a biomarker for the evaluation of white matter injury in rodent models." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43085416.
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Nazaran, Amin. "Ultra Short MR Relaxometry and Histological Image Processing for Validation of Diffusion MRI." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6348.
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Magnetic Resonance Imaging (MRI) is an imaging modality that acquires an image with little to no damage to the tissue. MRI does not introduce foreign particles or high energy radiation into the body, making it one of the least invasive medical imaging modalities. MRI can achieve excellent soft tissue contrast and is therefore useful for diagnosis of a wide variety of diseases. While there are a wide variety of available techniques for generating contrast in MRI, there are still many open areas for research. For example, many tissues in the human body exhibit such rapid signal decay that they are difficult to image with MRI: they are "MRI invisible". Furthermore, some of the newer MRI imaging techniques have not been fully validated to ensure that they are truly revealing accurate information about the underlying anatomical microstructure that they purport to image. This dissertation focuses on the development of new techniques in two distinct areas. First, a novel method for accurately assessing the MRI signal decay properties of tissues that are normally MRI invisible, such as tendons, ligaments, and certain pathological chemical deposits in the brain, is presented. This is termed "ultrashort MRI relaxometry". Second, two new image processing algorithms that operate on high resolution images of stained histological slices of the ex vivo brain are presented. The first of these image processing algorithms allows the semi-automated extraction of nerve fiber directionality from the histological slice images, a process that is normally done manually, is incredibly time consuming, and is prone to human error. This new technique represents one significant step in the complicated problem of attempting to validate a popular MRI technique, Diffusion Tensor Imaging (DTI), by ensuring that DTI results correlate with the true underlying physiology revealed by histological slicing and staining. The second of these image processing algorithms attempts to extract and segment regions of different "cytoarchitectonic characteristics" from stained histological slices of ex vivo brain. Again, traditional cytoarchitectonic segmentation relies on manual segmentation by an expert neuroanatomist, which is slow and sometimes inconsistent. The new technique is a first step towards automated this process, potentially providing greater accuracy and repeatability of the segmentations in a much shorter time. Together, these contributions represent a significant contribution to the body of MR imaging techniques, and associated image processing techniques for validation of newer MR neuroimaging techniques against the gold standard of stained histological slices of ex vivo brain.
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Kanao, Shotaro. "Differentiating benign and malignant inflammatory breast lesions: Value of T2 weighted and diffusion weighted MR images." Kyoto University, 2019. http://hdl.handle.net/2433/236592.
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Wang, Yanxin. "Hypoxic-ischemic injury in the neonatal rat model prediction of irreversible infarction size by Diffusion Weighted MR Imaging /." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B35757577.
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Thörmer, Gregor. "Diagnostischer Wert von ADC-Parameterkarten in der MR-Diagnostik des Prostatakarzinoms: Einfluss der Wahl verschiedener b-Werte." Doctoral thesis, Universitätsbibliothek Leipzig, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-105124.
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Zielsetzung: Die diffusionsgewichtete Bildgebung ist wesentlicher Bestandteil der Magnetresonanz-tomographie des Prostatakarzinoms (PCa). Aus entsprechenden Rohdaten, aufgenommen bei verschie-denen b-Werten (Diffusionswichtungsfaktoren), kann der Diffusionskoeffizient (apparent diffusion coefficient - ADC) abgeschätzt werden, der ein sensitiver Indikator für maligne Veränderungen der Gewebearchitektur ist. Die absoluten ADC-Werte sind allerdings stark von der Wahl der zugrundeliegenden b-Werte abhängig und darüber hinaus gibt es Hinweise, dass die Wahl der b-Werte einen signifikanten Einfluss auf die visuelle Analyse, insbesondere auf die Abgrenzbarkeit der Läsion von der Umgebung und auf den Kontrast hat. Es wurde daher untersucht, inwieweit die Wahl der b-Werte den diagnostischen Wert des ADC im Hinblick auf die Detektion und Beurteilung des PCa hat.
Methodik: 41 konsekutive Patienten mit gesichertem PCa erhielten eine multiparametrische, endorektale MR-Bildgebung bei 3 Tesla. Die ADC-Karten wurden retrospektiv auf Basis vier verschiedener Kombinationen von b-Werten (0-800 s/mm2) berechnet. Drei Untersucher bestimmten die „führende“ Läsion und beurteilten dann den diagnostischen Wert der jeweiligen ADC-Karten (Visual Score - VS) mit sehr gut (2), befriedigend (1) oder schlecht (0). Für die quantitative Auswertung wurden der mittlere ADC für gesundes und für Tumorgewebe bestimmt. Unterschiede in Abhängigkeit von den gewählten b-Werten wurden mittels statistischer Tests (einseitige ANOVA, Faktor Methode, Signifikanzniveau 5 %) ausgewertet.
Ergebnisse: 85 % der Tumoren wurden von den Auswertern richtig erkannt. Die Wahl der b-Werte hatte hochgradig signifikanten (P<0,001) Einfluss auf die absoluten ADC-Werte in gesundem und verändertem Gewebe. ADC-Karten auf Basis von b=[50, 800] und [0, 800] wurden am besten (VS=1,6±0,3) und zweitbesten (VS=1,1±0,3; P<0,001) bewertet. Insbesondere für niedrig-gradige Karzinome (Gleason Score ≤ 6, 13/41 Patienten), wurde nur die Kombination [50, 800] besser als befriedigend (VS=1,4±0,3) bewertet. Der mittlere Tumor-ADC zeigte eine moderate aber signifikant negative Korrelation (Spearman ρ: -0,38 bis -0,46; P<0,05) mit dem Gleason Score.
Schlussfolgerung: Absolute ADC-Werte sind stark von der Wahl der zugrundeliegenden b-Werte abhängig und eignen sich daher nicht zur allgemeingültigen Charakterisierung von Prostatakarzinomen. Ein minimaler b-Wert > 0 s/mm2 wird für die Berechnung der ADC-Karten im Hinblick auf eine nachweislich verbesserte visuelle Auswertbarkeit empfohlen.
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Stahle, Jessica Anne. "Diffusion Weighted MR Imaging in the Differentiation between Metastatic and Benign Lymph Nodes in Canine Patients with Head and Neck Disease." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/86612.
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In dogs with large primary tumors, regional lymph node involvement or evidence of distant metastasis can have worse prognoses and significantly decreased survival. Lymph node size alone has been shown to be insufficient as a predictor for the accurate clinical staging of some canine neoplasia, including oral malignant melanoma. However, regional lymph nodes of the oral cavity, such as the medial retropharyngeal lymph nodes, are difficult to access for routine sampling. Diffusion weighted magnetic resonance imaging (DWI) has demonstrated the ability to differentiate metastatic from inflammatory/benign lymph nodes in clinical studies with human cancer patients through the calculation of quantitative values of diffusion termed apparent diffusion coefficients (ADC). The objective of this exploratory study was to evaluate DWI and ADC as potential future methods for detecting malignant lymph nodes in dogs with naturally occurring disease. We hypothesized that DWI would identify significantly different ADC values between benign and metastatic lymph nodes in a group of canine patients with head or neck disease.
Our results demonstrated that two of four observers identified a significant difference between the mean ADC values of the benign and metastatic lymph nodes. When data from all four observers were pooled, the difference between the mean ADC values of the benign and metastatic lymph nodes approached but did not reach significance (P-value: 0.0566). Therefore, our hypothesis was not supported. However, DWI does show promise in its ability to differentiate benign from metastatic lymph nodes, and further studies with increased patient numbers are warranted<br>Master of Science
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Okada, Tsutomu. "Diffusion tensor fiber tractography at 3.0-T MR imaging : visualization of eloquent fiber tracts and application to the tractography-guided neurosurgery." Kyoto University, 2007. http://hdl.handle.net/2433/135663.
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Owler, Brian Kenneth. "Pathophysiology of normal pressure hydrocephalus." University of Sydney. Surgery, 2004. http://hdl.handle.net/2123/685.
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Normal pressure hydrocephalus (NPH), a CSF circulation disorder, is important as a reversible cause of gait and cognitive disturbance in an aging population. The inconsistent response to CSF shunting is usually attributed to difficulties in differential diagnosis or co-morbidity. Improving outcome depends on an increased understanding of the pathophysiology of NPH. Specifically, this thesis examines the contribution of, and inter-relationship between, the brain parenchyma and CSF circulation in the pathophysiology of NPH. Of the four core studies of the thesis, the first quantifies the characteristics of the CSF circulation and parenchyma in NPH using CSF infusion studies to measure the resistance to CSF absorption and brain compliance. The second study assesses cerebral blood flow (CBF) was using O15-labelled positron emission tomography (PET) with MR co-registration. By performing CSF infusion studies in the PET scanner, CBF at baseline CSF pressure and at a higher equilibrium pressure is measured. Regional changes and autoregulatory capacity are assessed. The final study examines the microstructural integrity of the parenchyma using MR diffusion tensor imaging. These studies confirm the importance of the inter-relationship of the brain parenchyma and CSF circulation. NPH symptomatology and its relationship to the observed regional CBF reductions in the basal ganglia and thalamus are discussed. Regional CBF reductions with increased CSF pressure and the implications for autoregulatory capacity in NPH are considered. The reduction in CBF when CSF was increased was most striking in the periventricular regions. In addition, periventricular structures demonstrated increased diffusivity and decreased anisotropy. The relationship between these changes and mechanisms such as transependymal CSF passage are reviewed. The findings of this thesis support a role of both the CSF circulation and the brain parenchyma in the pathophysiology of NPH. The results have implications for the approach to the management of patients with NPH.
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Purvis, Nina Louise. "Classification of breast malignancy using optimised advanced diffusion-weighted imaging, and, Surgical planning for breast tumour resection using MR-guided focused ultrasound." Thesis, University of Hull, 2016. http://hydra.hull.ac.uk/resources/hull:15193.
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Intravoxel Incoherent Motion Imaging (IVIM) is a non-invasive MR-imaging technique that enables the measurement of cellularity and vascularity using diffusion-weighted (DW)-imaging. IVIM has been applied to various cancer types including breast cancer, and is becoming more popular but lacks standardisation. The quantitative parameters; diffusion, D, perfusion fraction, f, and pseudo micro capillary diffusion, D* are thought to be correlated with tumour physiognomies such as proliferation, angiogenesis and heterogeneity. In Part 1 of this thesis, an optimised clinical b-value protocol is produced using a robust statistical method. This optimised protocol and various fitting methodologies are investigated in healthy volunteers, and then the most precise approach is applied in a clinical trial in patients following diagnosis of breast cancer, before treatment, to correlate IVIM parameters with breast cancer grade, histological type and molecular subtype with statistically significant results supporting IVIM’s potential as a non-invasive biomarker for malignancy. Monte Carlo simulations support this clinical application, where real data mean squared errors due to SNR limitations lie within simulated errors. A computed DW-imaging program is also presented to produce better quality images than acquired high b-value images as an adjunct to the optimised IVIM protocol. In Part 2 of this thesis, MR-guided Focused Ultrasound (MRgFUS) is explored as a means to create a pre-surgical template of thermally induced palpable markers to enable a surgeon to resect occult lesions and potentially reduce positive tumour margin status and local recurrence after breast conserving surgery. A surrogate animal model with pseudo lesion is presented, as well as a clinical tool to plan spot markers around a lesion as seen on MRI.
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Filipiak, Isabelle. "IRM de diffusion des fibres blanches cérébrales : développement et validation d'un objet-test." Thesis, Tours, 2014. http://www.theses.fr/2014TOUR3311/document.
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L'imagerie en tenseur de diffusion (DTI) est basée sur la mesure de la mobilité des molécules d'eau permettant l'analyse de la microarchitecture du tissu cérébral. Le trajet des fibres blanches peut être alors reconstruit par des méthodes de tractographie déterministes basées sur la direction principale de la diffusion. Toutefois elle repose sur des outils mathématiques complexes donnant un regard indirect sur les structures anatomiques, et sa validation est un enjeu majeur. Notre objectif a été de concevoir un objet-Test (OT) tri-Dimensionnel permettant la validation de la diffusion dans des faisceaux de fibres imitant l'organisation cérébrale. Cet OT se compose de trois modules: BOITE, SOLUTION, FIBRE réalisés en impression 3D. Il se compose de solutions de glucose et de fibres de dyneema orientées dans les trois orientations de l’espace. Nous nous sommes intéressés au développement d'une méthode de contrôle qualité des mesures quantitatives de diffusion dans le module SOLUTION<br>Diffusion Tensor Imaging (DTI) is based on the measurement of water diffusion mobility in order to investigate brain microarchitecture and white fiber connectivity. The trajectory of white fibers bundles can be reconstructed by deterministic tractography methods depending on the principal direction of diffusion in tissu. However, tractography consist to complex mathematical algorithms reflecting an indirect visualization of white fibers. Our goal consisted to design a 3D phantom which imitates brain's diffusion properties, offering different degrees of diffusion mobility and imitating the organization of brain fibers. The phantom consists of three components 3D-Printing: BOX, SOLUTION, FIBER. The phantom was composed of various glucose solutions and dyneema synthetical fibers organized in all 3 directions. We developed a quality control of quantitative measurements for the SOLUTION's component. We have lead a comparison of fibers reconstruction between tractography and ground truth in FIBER's component. Results show that : ADC values were ranged on those brain values with glucose solutions; FA
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Ruoss, Kerstin Andrea. "1. Brain development (sulci and gyri) as assessed by MR imaging in preterm and term newborn infants. 2. Germinal matrix hemorrhage and white matter lesions in neonates; correlation of serial ultrasound and early magnetic resonance imaging findings. 3. Diffusion-weighted MRI of middle cerebral artery stroke in a newborn /." Bern, 2002. http://www.stub.unibe.ch/html/haupt/datenbanken/diss/bestell.html.
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Martens, Corentin. "Patient-Derived Tumour Growth Modelling from Multi-Parametric Analysis of Combined Dynamic PET/MR Data." Doctoral thesis, Universite Libre de Bruxelles, 2021. https://dipot.ulb.ac.be/dspace/bitstream/2013/320127/5/contratCM.pdf.
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Gliomas are the most common primary brain tumours and are associated with poor prognosis. Among them, diffuse gliomas – which include their most aggressive form glioblastoma (GBM) – are known to be highly infiltrative. The diagnosis and follow-up of gliomas rely on positron emission tomography (PET) and magnetic resonance imaging (MRI). However, these imaging techniques do not currently allow to assess the whole extent of such infiltrative tumours nor to anticipate their preferred invasion patterns, leading to sub-optimal treatment planning. Mathematical tumour growth modelling has been proposed to address this problem. Reaction-diffusion tumour growth models, which are probably the most commonly used for diffuse gliomas growth modelling, propose to capture the proliferation and migration of glioma cells by means of a partial differential equation. Although the potential of such models has been shown in many works for patient follow-up and therapy planning, only few limited clinical applications have seemed to emerge from these works. This thesis aims at revisiting reaction-diffusion tumour growth models using state-of-the-art medical imaging and data processing technologies, with the objective of integrating multi-parametric PET/MRI data to further personalise the model. Brain tissue segmentation on MR images is first addressed with the aim of defining a patient-specific domain to solve the model. A previously proposed method to derive a tumour cell diffusion tensor from the water diffusion tensor assessed by diffusion-tensor imaging (DTI) is then implemented to guide the anisotropic migration of tumour cells along white matter tracts. The use of dynamic [S-methyl-11C]methionine ([11C]MET) PET is also investigated to derive patient-specific proliferation potential maps for the model. These investigations lead to the development of a microscopic compartmental model for amino acid PET tracer transport in gliomas. Based on the compartmental model results, a novel methodology is proposed to extract parametric maps from dynamic [11C]MET PET data using principal component analysis (PCA). The problem of estimating the initial conditions of the model from MR images is then addressed by means of a translational MRI/histology study in a case of non-operated GBM. Numerical solving strategies based on the widely used finite difference and finite element methods are finally implemented and compared. All these developments are embedded within a common framework allowing to study glioma growth in silico and providing a solid basis for further research in this field. However, commonly accepted hypothesis relating the outlines of abnormalities visible on MRI to tumour cell density iso-contours have been invalidated by the translational study carried out, leaving opened the questions of the initialisation and the validation of the model. Furthermore, the analysis of the temporal evolution of real multi-treated glioma patients demonstrates the limitations of the formulated model. These latter statements highlight current obstacles to the clinical application of reaction-diffusion tumour growth models and pave the way to further improvements.<br>Les gliomes sont les tumeurs cérébrales primitives les plus communes et sont associés à un mauvais pronostic. Parmi ces derniers, les gliomes diffus – qui incluent la forme la plus agressive, le glioblastome (GBM) – sont connus pour être hautement infiltrants. Le diagnostic et le suivi des gliomes s'appuient sur la tomographie par émission de positons (TEP) ainsi que l'imagerie par résonance magnétique (IRM). Cependant, ces techniques d'imagerie ne permettent actuellement pas d'évaluer l'étendue totale de tumeurs aussi infiltrantes ni d'anticiper leurs schémas d'invasion préférentiels, conduisant à une planification sous-optimale du traitement. La modélisation mathématique de la croissance tumorale a été proposée pour répondre à ce problème. Les modèles de croissance tumorale de type réaction-diffusion, qui sont probablement les plus communément utilisés pour la modélisation de la croissance des gliomes diffus, proposent de capturer la prolifération et la migration des cellules tumorales au moyen d'une équation aux dérivées partielles. Bien que le potentiel de tels modèles ait été démontré dans de nombreux travaux pour le suivi des patients et la planification de thérapies, seules quelques applications cliniques restreintes semblent avoir émergé de ces derniers. Ce travail de thèse a pour but de revisiter les modèles de croissance tumorale de type réaction-diffusion en utilisant des technologies de pointe en imagerie médicale et traitement de données, avec pour objectif d'y intégrer des données TEP/IRM multi-paramétriques pour personnaliser davantage le modèle. Le problème de la segmentation des tissus cérébraux dans les images IRM est d'abord adressé, avec pour but de définir un domaine propre au patient pour la résolution du modèle. Une méthode proposée précédemment permettant de dériver un tenseur de diffusion tumoral à partir du tenseur de diffusion de l'eau évalué par imagerie DTI a ensuite été implémentée afin de guider la migration anisotrope des cellules tumorales le long des fibres de matière blanche. L'utilisation de l'imagerie TEP dynamique à la [S-méthyl-11C]méthionine ([11C]MET) est également investiguée pour la génération de cartes de potentiel prolifératif propre au patient afin de nourrir le modèle. Ces investigations ont mené au développement d'un modèle compartimental pour le transport des traceurs TEP dérivés des acides aminés dans les gliomes. Sur base des résultats du modèle compartimental, une nouvelle méthodologie est proposée utilisant l'analyse en composantes principales pour extraire des cartes paramétriques à partir de données TEP dynamiques à la [11C]MET. Le problème de l'estimation des conditions initiales du modèle à partir d'images IRM est ensuite adressé par le biais d'une étude translationelle combinant IRM et histologie menée sur un cas de GBM non-opéré. Différentes stratégies de résolution numérique basées sur les méthodes des différences et éléments finis sont finalement implémentées et comparées. Tous ces développements sont embarqués dans un framework commun permettant d'étudier in silico la croissance des gliomes et fournissant une base solide pour de futures recherches dans le domaine. Cependant, certaines hypothèses communément admises reliant les délimitations des anormalités visibles en IRM à des iso-contours de densité de cellules tumorales ont été invalidée par l'étude translationelle menée, laissant ouverte les questions de l'initialisation et de la validation du modèle. Par ailleurs, l'analyse de l'évolution temporelle de cas réels de gliomes multi-traités démontre les limitations du modèle. Ces dernières affirmations mettent en évidence les obstacles actuels à l'application clinique de tels modèles et ouvrent la voie à de nouvelles possibilités d'amélioration.<br>Doctorat en Sciences de l'ingénieur et technologie<br>info:eu-repo/semantics/nonPublished
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Varoquaux, Arthur Damien. "Evaluation clinique et expérimentale des nouvelles modalités d'imagerie dans la prise en charge des néoplasies ORL notamment par la TEP/IRM." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM5058.
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En oncologie ORL, l'imagerie multiparamétrique est utilisée par un nombre grandissant d'équipes. Parmi les bio-marqueurs, la captation normalisée du fluoro-désoxyglucose (SUV-FDG) en tomoscintigraphie par émission de positons (TEP) et la restriction de la diffusion en IRM (DWI-MRI) sont les plus utilisées.L'IRM couplée à la TEP (TEP/IRM) est une nouveauté qui permet une diminution très significative des doses d'irradiation délivrées par rapport à la TEP/TDM. Nous adressons notre première expérience concernant l'aspect en diffusion et en TEP/IRM dans la surveillance des patients après radio-chimiothérapie. A la question de l'interchangeabilité du FDG-PET et de la DWI-MRI, nous avons tenté d'identifier un lien en imagerie entre la cellularité tumorale et sa consommation glucidique. La cellularité tumorale est approchée en IRM par la mesure du coefficient apparent de diffusion (ADC) et son métabolisme glucidique est approché en TEP en utilisant le 18F-desoxyglucose (FDG) par la mesure de la valeur de fixation normalisée (SUV). Dans une série appariée de 33 patients, nous avons analysé la reproductibilité des mesures de l'ADC et de SUV. Puis nous avons évalué l'indépendance statistique de ces biomarqueurs. Nous avons ensuite voulu comparer les résultats de la TEP obtenus à partir de la TEP/TDM et de la TEP/IRM. Dans une série prospective appariée chez 32 patients explorés en FDG-TEP, nous avons évalué qualitativement les images obtenues par la fusion des images recalées en TEP/IRM et TEP/TDM. Nous avons ensuite comparé la pertinence clinique des deux techniques. Et enfin nous avons comparé les valeurs quantitatives de SUV obtenues du tissu sain et du tissu pathologique<br>Multiparametric imaging interest and clinical use is rising for head and neck carcinoma (HNC). Among these modalities, FDG in PET and DWI-MRI are the most studied. PET/MRI is a new modality that allows in a single examination of combined various biologic biomarkers.After an optimization process of PET/MRI, we applied our first experience concerning the aspects of DWI-MRI and PET-MRI after radiation therapy. Thereafter we studied the correlation of SUV and ADC in HNC. In this study SUV and ADC values were independent parameters in HNSCC. Measurements of these two biomarkers were reproducible with almost perfect observer agreements for both methods. Neither SUV nor ADC values were able to predict the histologic grade, although a trend towards higher SUV and lower ADC values was observed in poorly differentiated tumours. Secondly, we we studied detection and quantification of focal uptake in head and neck tumours: 18F-FDG PET/MRI versus PET/CT in 32 consecutive HNSCC who underwent 18F-FDG PET/MRI and PET/CT. Attenuation correction sequence for PET/MRI and CT for PET/CT were used to caculate SUV. In results, PET/MRI coregistration and image fusion was feasible in all patients. There was no statistically significant difference between PET/MRI and PET/CT regarding rating scores for image quality, fusion quality, lesion conspicuity or anatomic location, number of detected lesions and number of patients with and without malignant lesions. A high correlation was observed for SUV measured on PET/MRI and PET/CT. SUV measured on PET/MRI were significantly lower than on PET/CT for malignant tumours, metastatic neck nodes, benign lesions, bone marrow, and liver (p <0.05)
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Borges, Renato Callado. "Ferramentas computacionais para a síntese de imagens de difusão por ressonância magnética." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-23042014-120357/.
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Trabalhos anteriores sobre a síntese de imagens de difusão por ressonância magnética se limitaram a estudos sobre estruturas microscópicas, menores que as dimensões típicas de um voxel (e.g., [BF08] [BF13] [LFS + 10] e [BA94]). Isto decorre em parte devido às metodologias utilizadas, que têm como ponto em comum serem simulações de tipo Monte Carlo, nas quais os elementos mínimos da simulação são as partículas de água. Portanto o custo computacional destas simulações é proporcional ao número de partículas a simular, e isto limita os volumes que podem ser simulados a tamanhos microscópicos. Propomos uma metodologia alternativa, que utiliza a imagem T 2 de uma amostra para sintetizar imagens de difusão por ressonância magnética. Os elementos mínimos desta nova metodologia são os pontos da imagem T 2 , e portanto seu custo computacional é proporcional à resolução da imagem T 2 utilizada, o que permite a síntese a partir de amostras de qualquer tamanho físico. Estas sínteses são realizadas por meio da integração numérica da equação do artigo seminal de Stejskal e Tanner [ST65] que relaciona a atenuação do sinal de ressonância magnética devida à difusão com os parâmetros da sequência de pulsos PGSE. Usamos os parâmetros típicos dessa sequência (b, gamma, tau\', g 0, g, delta e Delta), que podem ser configurados explicitamente em máquinas de ressonância magnética, para calcular valores do coeficiente de difusão aparente D em direções arbitrárias. Desenvolvemos software, disponibilizado [Bor] por licença GPL [Fou07], para realizar estas simulações, e para especificar uma máscara de direções, útil para modelar a difusão de uma amostra. Estas ferramentas permitem o estudo sistemático das variações dos parâmetros na síntese de imagens de difusão por ressonância magnética. Apresentamos um estudo de um fantoma de capilares imersos em água, exemplificando como utilizar as ferramentas para investigar a influência destes parâmetros na difusão da água da amostra.<br>Previous work on the synthesis of diffusion-weighted magnetic resonance imaging are limited to microscopic structures, smaller than the typical dimensions of a single voxel (e.g., [BF08] [BF13] [LFS + 10] and [BA94]). This is consequence, in part, of the methodologies used, that have in common the adoption of Monte Carlo simulation strategies, in which the minimal elements of simulation are the water particles. Therefore the computational cost of these simulations is proportional to the number of particles to simulate, and this limits the volume to be simulated to microscopic sizes. We propose a novel methodology, that uses the T 2 image from a sample to synthesize diffusion-weighted magnetic resonance images. The mininal elements of this novel methodology are the points of the T 2 image, and therefore its computational cost is proportional to the resolution of the T 2 image to be used, which allows the synthesis from samples of any physical size. These syntheses are made through numerical integration of the equation from the seminal article by Stejskal and Tanner [ST65] that relates the attenuation of the magnetic resonance signal due to diffusion to the parameters of the PGSE pulse sequence. We use the typical parameters of this sequence (b, gamma, tau\', g 0, g, delta and Delta), that can be explicitly configured in magnetic resonance machines, to calculate apparent diffusion coefficients D in arbitrary directions. We developed software, available [Bor] through GPL license [Fou07], to run these simulations, and to specify a mask of directions useful to model diffusion. These tools allow the systematic study of parameter variation in the synthesis of diffusion-weighted magnetic resonance images. We present a case study of a phantom made of capillary tubes immersed in water, to exemplify the use of these tools and how to investigate the influence of parameter variation on diffusion in the sample.
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Ko, Ching-Chung, and 柯景中. "Applications of Diffusion-Weighted MR Imaging in Brain Tumors." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/tytjh5.
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博士<br>國立中山大學<br>生物醫學研究所<br>106<br>Although magnetic resonance imaging (MRI) had been used to diagnose brain tumors for a long time, the differentiation of brain tumors is still difficult in some situations. In addition, it is difficult to predict recurrence of brain tumors on conventional qualitative MR imaging. Nowadays, the diffusion-weighted MR imaging (DWI) is already being incorporated into daily clinical practice in neuroradiology, and quantitative apparent diffusion coefficient (ADC) value could be acquired in DWI. Among brain tumors, the differentiation between glioblastoma multiforme (GBM) and primary cerebral lymphoma (PCL) is clinically important because treatment strategies of these two different diseases are substantially different. However, the differentiation of GBM and PCL is difficult on conventional MRI. On the other hand, although most meningiomas are benign brain tumors, a subset of benign skull base meningiomas show early progression/recurrence (P/R) in the first years after surgical resection. In this study, we will investigate the preoperative DWI and ADC values for differentiation between GBM and PCL, and for prediction of P/R in skull base meningiomas.
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Fichtner, Nicole Damara. "MR Diffusion Measurements of Apoptotic Changes in Tumour Cells." Thesis, 2013. http://hdl.handle.net/1807/35606.
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Monitoring treatment efficacy is a large area of cancer research as it can increase the effectiveness of therapy regimens. Diffusion weighted Magnetic Resonance imaging (DWI), allows assessment of tissue microstructure without exogenous contrast agents. In this thesis, two different DWI techniques were used to acquire data from acute myeloid leukemia cells undergoing apoptosis, and data was fitted to an analytical model of re- stricted diffusion. Results indicated a decrease in average restriction size from 6.4 to 2.7μm, and an increase in the restricted diffusion coefficient from 0.17 to 0.82μm^2/ms in untreated versus treated cells. The free diffusion coefficient was constant indicating changes in restrictions, rather than any intrinsic changes in the intra-cellular or extra- cellular fluid. This combination of techniques has the potential for use in preclinical and clinical settings as it demonstrates that apoptotic changes may be measured consistently.
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"Diffusion-Weighted MR Imaging: Behaviors of Phenomenological Models and Enhanced PROPELLER Data Acquisition." Doctoral diss., 2012. http://hdl.handle.net/2286/R.I.15836.
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abstract: The aim of this study was to investigate the microstructural sensitivity of the statistical distribution and diffusion kurtosis (DKI) models of non-monoexponential signal attenuation in the brain using diffusion-weighted MRI (DWI). We first developed a simulation of 2-D water diffusion inside simulated tissue consisting of semi-permeable cells and a variable cell size. We simulated a DWI acquisition using a pulsed gradient spin echo (PGSE) pulse sequence, and fitted the models to the simulated DWI signals using b-values up to 2500 s/mm2. For comparison, we calculated the apparent diffusion coefficient (ADC) of the monoexponential model (b-value = 1000 s/mm2). In separate experiments, we varied the cell size (5-10-15 μ), cell volume fraction (0.50-0.65-0.80), and membrane permeability (0.001-0.01-0.1 mm/s) to study how the fitted parameters tracked simulated microstructural changes. The ADC was sensitive to all the simulated microstructural changes except the decrease in membrane permeability. The σstat of the statistical distribution model increased exclusively with a decrease in cell volume fraction. The Kapp of the DKI model increased exclusively with decreased cell size and decreased with increasing membrane permeability. These results suggest that the non-monoexponential models have different, specific microstructural sensitivity, and a combination of the models may give insights into the microstructural underpinning of tissue pathology. Faster PROPELLER DWI acquisitions, such as Turboprop and X-prop, remain subject to phase errors inherent to a gradient echo readout, which ultimately limits the applied turbo factor and thus scan time reductions. This study introduces a new phase correction to Turboprop, called Turboprop+. This technique employs calibration blades, which generate 2-D phase error maps and are rotated in accordance with the data blades, to correct phase errors arising from off-resonance and system imperfections. The results demonstrate that with a small increase in scan time for collecting calibration blades, Turboprop+ had a superior immunity to the off-resonance related artifacts when compared to standard Turboprop and recently proposed X-prop with the high turbo factor (turbo factor = 7). Thus, low specific absorption rate (SAR) and short scan time can be achieved in Turboprop+ using a high turbo factor, while off-resonance related artifacts are minimized.<br>Dissertation/Thesis<br>Ph.D. Electrical Engineering 2012
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Lee, Cheng-Hui, and 李正輝. "The application of SPIO-contrast agent used for liver MR diffusion weighted imaging." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/81526355894511062854.
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碩士<br>中原大學<br>醫學工程研究所<br>97<br>Hepatic tumor was the top of deadly diseases for male and the second deadly diseases for female in Taiwan. Traditional, physical examination, laboratory blood test and medical imaging including computer tomography (CT), ultrasound and magnetic resonance imaging (MRI) were used for hepatic lesions diagnosis. The purpose of this study is to evaluate the accuracy of hepatic lesion detection after Super paramagnetic iron oxide (SPIO) injection followed by diffusion weighted imaging (DWI).
Ten patients with suspected hepatic tumors were recruited for this study. For each patient, conventional MR liver scanning and pre-SPIO diffusion weighted imaging (DWI) were performed before contrast agent administration. Additional, a T1 weight (T1W) imaging series with the same geometric characterizes was performed for images fusion. Then 10min, 20min, 30min after SPIO administration DWI were performed. Five volunteers without any biliary system diseases were chosen to perform conventional MR liver scanning and pre-SPIO diffusion weighted imaging (DWI) to evaluate the specificity in this study. Moreover, an image processing program was used to segmentation and enhances the edge of hepatic tumor; T1W images were fused with these post-processed DWI to archive both anatomic and functional information. Then, these images were elevated independently by two radiologists with blind patient’s clinical information
The primary result shows that all the present lesions of the eight patients could be detected, i.e. the sensitivity is 1; and during the volunteer group test, no any false positive lesion has been detected, therefore the specificity is 1. This technique also has been reviewed by radiologists and the satisfaction level is up to 93.75%.
Therefore, to be an assisted tool, we expect that by combining this technique with SPIO-enhanced MR imaging and DWI, can become a popular method for hepatic lesions detection in MR scanning. Coordinated with SPIO-enhanced MR imaging and DWI, SPIO-enhanced MR imaging, we believe this technique is useful and can increase the ability of lesion detection ratio significantly.
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Yang, Yu-Ting, and 楊玉婷. "Monitoring Brain Neural Development in New Zealand Rabbit Using MR Diffusion Tensor Imaging." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/72319824499474955924.
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碩士<br>義守大學<br>生物醫學工程學系<br>101<br>Diffusion tensor imaging (DTI), a novel non-invasive method of magnetic resonance imaging (MRI), has been wildly used in neurophysiology, neurons anatomy and multiple sclerosis diagnosis and research. Brain white matter tracts’ fractional anisotropy (FA) was significantly higher than gray matter, and sensitive to white matter in diffusion tensor imaging as well. Diffusion anisotropy changes with diseases and also with neural developments. Therefore, diffusion tensor imaging was used to acquire image data and to investigate changes in regional diffusion quantitative indices, mean diffusivity (MD), FA, and white matter fiber tract during rabbit brain developments. The results were evaluated and compared longitudinally. DTI is able to fully document integrity of neural fiber tracks and presents tissue’s microstructure in rabbit brain in vivo. The goal of this study was to study changes in regional diffusion quantitative indices and white matter fiber tract of animal brain development model. In order to present neural fiber tractography and diffusion characteristics in different regions of rabbit’s brain, time course MD, FA and MR tractography of normal New Zealand rabbits were statistically quantified longitudinally. The results showed that the MD values in each part of the New Zealand rabbits’ brain gradually decreased as they became older. On the contrary, the FA values in each part of the brain showed significantly increased as the New Zealand rabbit getting older. DTI tractography also showed that the brain neural fibers became denser and gradually showing integrity as the New Zealand rabbits getting older. Hence, it might be capable of investigating the developmental process of brain neural fiber longitudinally. It is hoped that the achievements of this study can be further applied in clinical diagnosis.
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Yi-Hsin, Nieh, and 聶伊辛. "The Evaluation of Diffusion-Weighted MR Imaging Damage Area Analysis for Patients with Acute Infarction Stroke." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/nug3s4.
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碩士<br>元培科學技術學院<br>影像醫學研究所<br>95<br>Diffusion-weighted MR Imaging is the most important clinical tools for diagnosis of acute brain infraction. This research takes advantage of all sorts of different image analysis technology that direct to brain infraction images of Magnetic Resonance proceed dispose, and automatization technology precise brain tissue damage area to replace artificial manual trouble and not precise. In the study, five different edge detection algorithms ( namely Roberts algorithm, Sobel algorithm, Laplacian algorithm, Marr-Hildreth algorithm and Canny algorithm ) have been applied as preprocessing for brain infraction outlining detection. Among all these algorithms, Canny algorithm result and real brain tissue damage region inosculate highest, and it cans precise trace brain infraction area and normal brain tissue. Canny algorithm with doctors’ artificial manual depiction brain infarction area, Canny algorithm's dependable degree and definition than artificial style to rapidly right again. Therefore, the Canny algorithm eventually achieve the best outline contour.
Brain tissue damage area compare for Canny algorithm and doctor’s manual depiction relationship. The result show Canny algorithm is dependable and precise than artificial style and this algorithm advantage of can debase human factor different result in area. The finally, seriously level classification, two-dimensional sections and three-dimensional image reconstruction technique, these is able to display damage volume and damage area in brain tissue. To inquire into damage area and seriously level classification, it’ll is able to supply clinical medically in infarction stroke consultation and treatment basis.
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Shen, Elise Ting-Hsin, and 沈廷馨. "Diffusion MR Imaging Progression of Structural Connectivity and Therapeutic Potential of Deep Brain Stimulation in Alzheimer’s Disease Model." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/g442hw.
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碩士<br>國立臺灣大學<br>醫學工程學研究所<br>105<br>Alzheimer’s disease (AD) is one of the major causes of death that currently cannot be cured, prevented, or slowed. Due to the rising survival age, the upward trend of the disease prevalence will continue. Deep brain stimulation (DBS) has proven to be a viable therapy for various neurological disorders, by enhancing or interrupting different connections within the brain. Various brain structures have been considered as the target for DBS, including the fornix. DBS of the fornix, a major output tract of the hippocampus, has been shown to be a promising target for DBS therapy in AD patients. Even though these studies and trials are taking place, it is still not well understood what alterations are resulting in positive changes within AD patients. In this study, a triple-transgenic (3xTg) mouse model of AD was used in order to understand the longitudinal changes of white matter over the course of the disease through the use of diffusion tensor imaging (DTI). The 3xTg mouse model showed to have decreased FA values and behavioral performance around the age of 6 months. Through the integration of a MR compatible probe and the 3xTg model, it was observed that the timing of the implantation of DBS stimulation probes and stimulation therapy makes a difference in the effectiveness of the therapy. DBS of the fornix showed improvement in the behavior of 3xTg mice and FA values.
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Thörmer, Gregor. "Diagnostischer Wert von ADC-Parameterkarten in der MR-Diagnostik des Prostatakarzinoms: Einfluss der Wahl verschiedener b-Werte." Doctoral thesis, 2012. https://ul.qucosa.de/id/qucosa%3A11837.
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Zielsetzung: Die diffusionsgewichtete Bildgebung ist wesentlicher Bestandteil der Magnetresonanz-tomographie des Prostatakarzinoms (PCa). Aus entsprechenden Rohdaten, aufgenommen bei verschie-denen b-Werten (Diffusionswichtungsfaktoren), kann der Diffusionskoeffizient (apparent diffusion coefficient - ADC) abgeschätzt werden, der ein sensitiver Indikator für maligne Veränderungen der Gewebearchitektur ist. Die absoluten ADC-Werte sind allerdings stark von der Wahl der zugrundeliegenden b-Werte abhängig und darüber hinaus gibt es Hinweise, dass die Wahl der b-Werte einen signifikanten Einfluss auf die visuelle Analyse, insbesondere auf die Abgrenzbarkeit der Läsion von der Umgebung und auf den Kontrast hat. Es wurde daher untersucht, inwieweit die Wahl der b-Werte den diagnostischen Wert des ADC im Hinblick auf die Detektion und Beurteilung des PCa hat.
Methodik: 41 konsekutive Patienten mit gesichertem PCa erhielten eine multiparametrische, endorektale MR-Bildgebung bei 3 Tesla. Die ADC-Karten wurden retrospektiv auf Basis vier verschiedener Kombinationen von b-Werten (0-800 s/mm2) berechnet. Drei Untersucher bestimmten die „führende“ Läsion und beurteilten dann den diagnostischen Wert der jeweiligen ADC-Karten (Visual Score - VS) mit sehr gut (2), befriedigend (1) oder schlecht (0). Für die quantitative Auswertung wurden der mittlere ADC für gesundes und für Tumorgewebe bestimmt. Unterschiede in Abhängigkeit von den gewählten b-Werten wurden mittels statistischer Tests (einseitige ANOVA, Faktor Methode, Signifikanzniveau 5 %) ausgewertet.
Ergebnisse: 85 % der Tumoren wurden von den Auswertern richtig erkannt. Die Wahl der b-Werte hatte hochgradig signifikanten (P<0,001) Einfluss auf die absoluten ADC-Werte in gesundem und verändertem Gewebe. ADC-Karten auf Basis von b=[50, 800] und [0, 800] wurden am besten (VS=1,6±0,3) und zweitbesten (VS=1,1±0,3; P<0,001) bewertet. Insbesondere für niedrig-gradige Karzinome (Gleason Score ≤ 6, 13/41 Patienten), wurde nur die Kombination [50, 800] besser als befriedigend (VS=1,4±0,3) bewertet. Der mittlere Tumor-ADC zeigte eine moderate aber signifikant negative Korrelation (Spearman ρ: -0,38 bis -0,46; P<0,05) mit dem Gleason Score.
Schlussfolgerung: Absolute ADC-Werte sind stark von der Wahl der zugrundeliegenden b-Werte abhängig und eignen sich daher nicht zur allgemeingültigen Charakterisierung von Prostatakarzinomen. Ein minimaler b-Wert > 0 s/mm2 wird für die Berechnung der ADC-Karten im Hinblick auf eine nachweislich verbesserte visuelle Auswertbarkeit empfohlen.
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Meddour, Miriam. "MR-tomographische Darstellung intracerebraler Blutungen mit und ohne Therapie." Doctoral thesis, 2011. http://hdl.handle.net/11858/00-1735-0000-0006-B180-D.
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