Dissertations / Theses: 'Diffusion tendor imaging'

1

Inano, Rika. "Voxel-based clustered imaging by multiparameter diffusion tensor images for glioma grading." Kyoto University, 2016. http://hdl.handle.net/2433/215442.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Heim, Susanne. "Statistical Diffusion Tensor Imaging." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-72610.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Shen, Litao. "Diffusion tensor imaging application." Thesis, Purdue University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1602902.

Full text

Abstract:

Central nervous system (CNS) related conditions and diseases like mild traumatic brain injury (mTBI) and multiple sclerosis (MS) affect people’s life quality, yet there is no single test for the diagnosis of these diseases or conditions. Patients may need to wait for years until they are diagnosed correctly to get the correct treatment, which is often too late. Thus, there is a strong need to develop some techniques to aid the diagnosis of CNS-related conditions and diseases. The conventional MRI can reveal the structure of the brain but cannot detect the difference between the healthy tissue and the anomalies. Diffusion tensor imaging (DTI) has been used for detecting white matter integrity and demyelination for the past decade in experiments and has been proven to have the ability to depict the problem effectively. In the past decade, many techniques were found based on DTI data, and these techniques improved pre-processing, processing, and post-processing.

Though there are many software and APIs that can provide functions for DTI file input/output (IO), visualization and other DTI related topics, there is no general software or API that is dedicated to covering the whole processing procedure of DTI that at the same time can be extended easily by the user. This thesis is dedicated to developing a software that can be used to aid in the diagnosis of CNS-related conditions and diseases while at the same time trying to cover as many topics as possible. Another purpose is to make the software highly extensible.

This thesis work first introduces the background of CNS-related disease and uses MS as an example to introduce the process of demyelination and the white matter integrity problem, which are involved in these CNS-related diseases and conditions. Then the diffusion process and the technique that can detect the diffusion signal (DTI) is presented. After this, concepts and meaning of the secondary metrics are discussed. Then, current existing software and APIs and their advantages and disadvantages are outlined. After these points, the techniques that are discussed in this thesis as well as their advantages are outlined. This part is followed by the charts and code samples which can illustrate the process and structure of this software. Then different modules and their results are explained.

In this software, the results are represented by images and 3D models. There are color images, pseudo color images with different schemes and gray scale images. Images are mainly included to represent the FA and MD data. In this software, streamlines are generated from the eigenvalue and eigenvector. Then a bundled result for the streamline is also realized in this software. The streamline and bundled results are 3D models. For 3D models, there are mainly two ways to display the real 3D model. One is the naked eye 3D which doesn’t require the user to wear glasses but has less stereoscopic characteristics. As the stereoscopic monitors and glasses are more and more popular and easily accessible, this software also provides stereoscopic views for 3D models, and the user can choose red & blue, interlaced techniques with proper glasses.

This thesis work ends with the discussion of the results and limitations of DTI. Finally, there is a discussion about the future work that can improve the performance of this software and topics that need to be covered.

APA, Harvard, Vancouver, ISO, and other styles

4

Rane, Swati. "Diffusion tensor imaging at long diffusion time." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29708.

Full text

Abstract:

Thesis (Ph.D)--Biomedical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Hu, Xiaoping; Committee Member: Brummer, Marijn; Committee Member: Duong, Tim; Committee Member: Keilholz, Shella; Committee Member: Schumacher, Eric. Part of the SMARTech Electronic Thesis and Dissertation Collection.

APA, Harvard, Vancouver, ISO, and other styles

5

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 text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

6

Prem, Martin [Verfasser], and Dieter [Akademischer Betreuer] Riemann. "Diffusion-Tensor-Imaging bei primärer Insomnie." Freiburg : Universität, 2012. http://d-nb.info/1123469768/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Zhou, Diwei. "Statistical analysis of diffusion tensor imaging." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11430/.

Full text

Abstract:

This thesis considers the statistical analysis of diffusion tensor imaging (DTI). DTI is an advanced magnetic resonance imaging (MRI) method that provides a unique insight into biological microstructure \textit{in vivo} by directionally describing the water molecular diffusion. We firstly develop a Bayesian multi-tensor model with reparameterisation for capturing water diffusion at voxels with one or more distinct fibre orientations. Our model substantially alleviates the non-identifiability issue present in the standard multi-tensor model. A Markov chain Monte Carlo (MCMC) algorithm is then developed to study the uncertainty of the model parameters based on the posterior distribution. We apply the Bayesian method to Monte Carlo (MC) simulated datasets as well as a healthy human brain dataset. A region containing crossing fibre bundles is investigated using our multi-tensor model with automatic model selection. A diffusion tensor, a covariance matrix related to the molecular displacement at a particular voxel in the brain, is in the non-Euclidean space of 3x3 positive semidefinite symmetric matrices. We define the sample mean of tensor data to be the Fréchet mean. We carry out the non-Euclidean statistical analysis of diffusion tensor data. The primary focus is on the use of Procrustes size-and-shape space. Comparisons are made with other non-Euclidean techniques, including the log-Euclidean, Riemannian, Cholesky, root Euclidean and power Euclidean methods. The weighted generalised Procrustes analysis has been developed to efficiently interpolate and smooth an arbitrary number of tensors with the flexibility of controlling individual contributions. A new anisotropy measure, Procrustes Anisotropy is defined and compared with other widely used anisotropy measures. All methods are illustrated through synthetic examples as well as white matter tractography of a healthy human brain. Finally, we use Giné’s statistic to design uniformly distributed diffusion gradient direction schemes with different numbers of directions. MC simulation studies are carried out to compare effects of Giné’s and widely used Jones' schemes on tensor estimation. We conclude by discussing potential areas for further research.

APA, Harvard, Vancouver, ISO, and other styles

8

Errangi, Bhargav Kumar. "A diffusion tensor imaging study of." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28156.

Full text

Abstract:

Thesis (M. S.)--Biomedical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: James K. Rilling; Committee Chair: Xiaoping Hu; Committee Member: Shella Keilholz; Committee Member: Todd M. Preuss.

APA, Harvard, Vancouver, ISO, and other styles

9

Edalati, Ahmadsaraei Masoud. "Diffusion Tensor Imaging: Application to Cardiovascular Magnetic Resonance Imaging." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1470754609.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Wang, Zhizhou. "Diffusion tensor field restoration and segmentation." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0006046.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Skare, Stefan. "Optimisation strategies in diffusion tensor MR imaging /." Stockholm, 2002. http://diss.kib.ki.se/2002/91-7349-175-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Pandurangi, Sindhu. "Diffusion Tensor Imaging Investigation of Kibra Genotypes." Thesis, The University of Arizona, 2012. http://hdl.handle.net/10150/244485.

Full text

Abstract:

A sample of 130 adults over the age of 50 underwent diffusion tensor imaging and KIBRA genotyping. The relations between KIBRA genotype and white matter integrity were investigated through measures of Fractional Anisotropy and Apparent Diffusion Coefficient. No statistically significant findings were obtained.

APA, Harvard, Vancouver, ISO, and other styles

13

Maximov, Ivan I., Farida Grinberg, and Nadim Jon Shah. "Robust estimator framework in diffusion tensor imaging." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184368.

Full text

Abstract:

Diffusion of water molecules in the human brain tissue has strong similarities with diffusion in porous media. It is affected by different factors such as restrictions and compartmentalization, interaction with membrane walls, strong anisotropy imposed by cellular microstructure, etc. However, multiple artefacts abound in in vivo measurements either from subject motions, such as cardiac pulsation, bulk head motion, respiratory motion, and involuntary tics and tremor, or hardware related problems, such as table vibrations, etc. All these artefacts can substantially degrade the resulting images and render postprocessing diffusion analysis difficult or even impossible. In order to overcome these problems, we have developed a robust and efficient approach based on the least trimmed squares algorithm that works well with severely degraded datasets with low signal-to-noise ratio. This approach has been compared with other diffusion imaging post-processing algorithms using simulations and in vivo experiments. We demonstrate that the least trimmed squares algorithm can be easily adopted for multiple non-Gaussian diffusion models such as the biexponential model. The developed approach is shown to exhibit a high efficiency and accuracy and can, in principle, be exploited in other diffusion studies where artefact/outlier suppression is demanded.

APA, Harvard, Vancouver, ISO, and other styles

14

Clement, Meagan E. Couper David J. "Analysis techniques for diffusion tensor imaging data." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2008. http://dc.lib.unc.edu/u?/etd,2010.

Full text

Abstract:

Thesis (DrPH)--University of North Carolina at Chapel Hill, 2008.
Title from electronic title page (viewed Feb. 17, 2009). "... in partial fulfillment of the requirements for the degree of Doctorate of Public Health in the School of Public Health Department of Biostatistics." Discipline: Biostatistics; Department/School: Public Health.

APA, Harvard, Vancouver, ISO, and other styles

15

Maximov, Ivan I., Farida Grinberg, and Nadim Jon Shah. "Robust estimator framework in diffusion tensor imaging." Diffusion fundamentals 18 (2013) 10, S. 1-6, 2013. https://ul.qucosa.de/id/qucosa%3A13717.

Full text

Abstract:

Diffusion of water molecules in the human brain tissue has strong similarities with diffusion in porous media. It is affected by different factors such as restrictions and compartmentalization, interaction with membrane walls, strong anisotropy imposed by cellular microstructure, etc. However, multiple artefacts abound in in vivo measurements either from subject motions, such as cardiac pulsation, bulk head motion, respiratory motion, and involuntary tics and tremor, or hardware related problems, such as table vibrations, etc. All these artefacts can substantially degrade the resulting images and render postprocessing diffusion analysis difficult or even impossible. In order to overcome these problems, we have developed a robust and efficient approach based on the least trimmed squares algorithm that works well with severely degraded datasets with low signal-to-noise ratio. This approach has been compared with other diffusion imaging post-processing algorithms using simulations and in vivo experiments. We demonstrate that the least trimmed squares algorithm can be easily adopted for multiple non-Gaussian diffusion models such as the biexponential model. The developed approach is shown to exhibit a high efficiency and accuracy and can, in principle, be exploited in other diffusion studies where artefact/outlier suppression is demanded.

APA, Harvard, Vancouver, ISO, and other styles

16

Irfanoglu, Mustafa O. "Robust Variability Analysis Using Diffusion Tensor Imaging." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306946868.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Song, Xin. "Path reconstruction in diffusion tensor magnetic resonance imaging." Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00694403.

Full text

Abstract:

The complicated underwater environment and the poor underwater vision make super-mini underwater cable robot hardly to be controlled. Traditionally, the manual control method by operators is adopted by this kind of robots. Unfortunately, the robots can hardly work normally in these practical circumstances. Therefore, to overcome these shortcomings and improve the abilities of these underwater cable robots, this paper proposes several improvements, including the system design, the motion controller design, three dimensional obstacle recognition and three dimensional path reconstruction technologies etc. The details are displayed as follow: (1) Super-mini underwater robot system design: several improvement schemes and important design ideas are investigated for the super-mini underwater robot.(2) Super-mini robot motion controller design: The motion controller design of underwater robot in complicated circumstance is investigated. A new adaptive neural network sliding mode controller with balanced parameter controller (ANNSMB) is proposed. Based on the theory of adaptive fuzzy sliding mode controller (AFSMC), an improved algorithm is also proposed and applied to the underwater robot. (3)Research of three dimensional underwater environment reconstructions: The algorithms and the experiments of underwater environment reconstructions are investigated. DT-MRI image processing algorithm and the theory of three dimensional obstacle reconstructions are adopted and improved for the application of the underwater robot. (4) The super-mini underwater robot path planning algorithms are investigated.

APA, Harvard, Vancouver, ISO, and other styles

18

Jordaan, Johannes Petrus. "Noise reduction during diffusion tensor imaging of infants." Master's thesis, Faculty of Health Sciences, 2019. https://hdl.handle.net/11427/31610.

Full text

Abstract:

Acoustic noise produced during echo planar imaging (EPI) has been known to reach excessive levels. In addition to causing general patient discomfort and anxiety, this level of noise makes the scanning of young children and infants particularly difficult. Infants are typically scanned while sleeping to minimise motion as they cannot ethically be sedated for research purposes. The extreme noise during MRI acquisitions often cause them to wake before the end of the scanning session. This problem is exacerbated by particularly noisy acquisitions, such as the single shot echo planar diffusion tensor imaging sequence. The main aim of this project was to reduce the noise of this particular acquisition specifically for the scanning of newborn infants. Acoustic noise during MRI acquisitions mainly originates from mechanical vibrations in the gradient coil assemblies due to interactions between the rapidly changing currents applied to the coils and the main static field. A transfer function relating the output acoustic noise spectrum to the gradient excitation input spectrum was developed and used to identify resonant peaks which would amplify coinciding gradient waveform harmonics. In addition to resonant peaks, the transfer function showed significant amplification of frequencies above 1 kHz. In this work, noise reduction was achieved by implementing digital low-pass filters to reduce high-frequency harmonics of the standard trapezoidal gradient waveforms, focusing on the EPI readout portion of a diffusion tensor imaging (DTI) sequence. For comparison purposes, an EPI readout using sinusoidal frequency encoding waveforms and a constant phase encoding blip was also implemented. In addition to reducing produced noise, a passive noise reduction enclosure was built from open cell polyurethane foam mounted in a PVC frame to surround the sleeping infant and act as an acoustic insulation box. Lastly, the effectiveness of introducing pink noise from an external source to mask the abrupt changes in scanner noise, was also investigated. The altered k-space trajectories due to the modifications made to the EPI readout gradient waveforms were corrected through a custom one-dimensional regridding procedure applied along the frequency encoding axis in k-space. Noise reduction was measured with an Optimic 1155 optical microphone from Optoacoustics, attached on top of a cylindrical water phantom inside a 16 channel infant head coil in the isocenter along the Z-direction, facing the bore in the rightleft direction (similar to the orientation that the ears of a sleeping infant would be). Signal-to-noise ratio (SNR) and fractional anisotropy (FA) within the corpus callosum (CC) were compared for images acquired using the standard and modified (filtered and sinusoidal readouts) DTI sequences, the latter each for regridding kernel window sizes of 2 and 4, respectively. The acoustic noise spectra of the filtered and sinusoidal EPI sequences demonstrated a significant reduction in EPI harmonics compared to the standard sequence, but very little difference between each other. Without the foam enclosure, the filtered acquisition with filtered crushers reduced peak sound pressure levels (SPL) by 3.4 and 4 dBA for strong and no fat suppression, respectively, and A-weighted equivalent continuous sound levels (LA,eq) by 2.5 and 2.8 dBA, respectively. Adding the foam enclosure increased peak SPL reduction to 4.8 dBA with fat suppression and 7 dBA without. The sinusoidal sequence performing similarly or marginally (no more than 0.5%) worse than the filtered on all outcomes. SNR measurements in the CC were higher for all volumes of the filtered acquisition compared to the standard, while those of the sinusoidal were similar or slightly lower compared to the standard acquisition. FA values in the CC of the sinusoidal and filtered acquisitions did not differ from those of the standard acquisition (pairwise student’s t-test, all p’s >0.2). For the 16 channel head coil, image reconstruction time increased by only 45 seconds for a regridding kernel width W = 2. Filtering gradient waveforms is an effective technique to reduce acoustic noise during DTI without increasing acquisition time, reducing image quality, or altering FA measures. The proposed method has the potential to be generalized to most gradient waveforms across a variety of sequences. With the addition of the passive noise reduction enclosure, the combined noise reduction could greatly reduce infant anxiety and startling, leading to an increase in the number of infants in whom the acquisition protocol is completed. Acoustic noise produced during echo planar imaging (EPI) has been known to reach excessive levels. In addition to causing general patient discomfort and anxiety, this level of noise makes the scanning of young children and infants particularly difficult. Infants are typically scanned while sleeping to minimise motion as they cannot ethically be sedated for research purposes. The extreme noise during MRI acquisitions often cause them to wake before the end of the scanning session. This problem is exacerbated by particularly noisy acquisitions, such as the single shot echo planar diffusion tensor imaging sequence. The main aim of this project was to reduce the noise of this particular acquisition specifically for the scanning of newborn infants. Acoustic noise during MRI acquisitions mainly originates from mechanical vibrations in the gradient coil assemblies due to interactions between the rapidly changing currents applied to the coils and the main static field. A transfer function relating the output acoustic noise spectrum to the gradient excitation input spectrum was developed and used to identify resonant peaks which would amplify coinciding gradient waveform harmonics. In addition to resonant peaks, the transfer function showed significant amplification of frequencies above 1 kHz. In this work, noise reduction was achieved by implementing digital low-pass filters to reduce high-frequency harmonics of the standard trapezoidal gradient waveforms, focusing on the EPI readout portion of a diffusion tensor imaging (DTI) sequence. For comparison purposes, an EPI readout using sinusoidal frequency encoding waveforms and a constant phase encoding blip was also implemented. In addition to reducing produced noise, a passive noise reduction enclosure was built from open cell polyurethane foam mounted in a PVC frame to surround the sleeping infant and act as an acoustic insulation box. Lastly, the effectiveness of introducing pink noise from an external source to mask the abrupt changes in scanner noise, was also investigated. The altered k-space trajectories due to the modifications made to the EPI readout gradient waveforms were corrected through a custom one-dimensional regridding procedure applied along the frequency encoding axis in k-space. Noise reduction was measured with an Optimic 1155 optical microphone from Optoacoustics, attached on top of a cylindrical water phantom inside a 16 channel iv infant head coil in the isocenter along the Z-direction, facing the bore in the rightleft direction (similar to the orientation that the ears of a sleeping infant would be). Signal-to-noise ratio (SNR) and fractional anisotropy (FA) within the corpus callosum (CC) were compared for images acquired using the standard and modified (filtered and sinusoidal readouts) DTI sequences, the latter each for regridding kernel window sizes of 2 and 4, respectively. The acoustic noise spectra of the filtered and sinusoidal EPI sequences demonstrated a significant reduction in EPI harmonics compared to the standard sequence, but very little difference between each other. Without the foam enclosure, the filtered acquisition with filtered crushers reduced peak sound pressure levels (SPL) by 3.4 and 4 dBA for strong and no fat suppression, respectively, and A-weighted equivalent continuous sound levels (LA,eq) by 2.5 and 2.8 dBA, respectively. Adding the foam enclosure increased peak SPL reduction to 4.8 dBA with fat suppression and 7 dBA without. The sinusoidal sequence performing similarly or marginally (no more than 0.5%) worse than the filtered on all outcomes. SNR measurements in the CC were higher for all volumes of the filtered acquisition compared to the standard, while those of the sinusoidal were similar or slightly lower compared to the standard acquisition. FA values in the CC of the sinusoidal and filtered acquisitions did not differ from those of the standard acquisition (pairwise student’s t-test, all p’s >0.2). For the 16 channel head coil, image reconstruction time increased by only 45 seconds for a regridding kernel width W = 2. Filtering gradient waveforms is an effective technique to reduce acoustic noise during DTI without increasing acquisition time, reducing image quality, or altering FA measures. The proposed method has the potential to be generalized to most gradient waveforms across a variety of sequences. With the addition of the passive noise reduction enclosure, the combined noise reduction could greatly reduce infant anxiety and startling, leading to an increase in the number of infants in whom the acquisition protocol is completed.

APA, Harvard, Vancouver, ISO, and other styles

19

Hui, Sai-kam, and 許世鑫. "Magnetic resonance diffusion tensor imaging for neural tissue characterization." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42841306.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Ingalhalikar, Madhura Aditya Magnotta Vincent A. "Spatial normalization of diffusion models and tensor analysis." Iowa City : University of Iowa, 2009. http://ir.uiowa.edu/etd/299.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Dean, Ryan J., Timothy Stait-Gardner, Simon J. Clarke, Suzy Y. Rogiers, and William S. Pricea. "Diffusion Tensor Imaging (DTI) studies of the grape berry." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-184852.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

丁莹 and Ying Ding. "Magnetic resonance diffusion characterization of brain diseases." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B4961762X.

Full text

Abstract:

Magnetic resonance imaging (MRI) is a valuable imaging technique. It provides excellent soft tissue contrast and multi-parametric non-invasive imaging protocols. Among those various techniques, diffusion MRI measures the water diffusion properties of biological tissue. It is a useful tool in characterizing various brain tissue microstructures quantitatively. With its rapid development, it is emerging that subtle changes can be probed by diffusion tensor imaging (DTI) quantitation. The objectives of this doctoral work are to access the subtle microstructural alterations in rodent brains due to hemodynamic changes, fear conditioning and sleep deprivation using in vivo DTI. With the improved reproducibility and specificity achieved by using advanced post-processing and animal preparation procedures, in vivo DTI is expected to be useful to explore the underlying biological mechanisms for posttraumatic stress disorder and memory deficit following sleep loss in human. Firstly, as DTI could be influenced by the presence of water molecules in brain vasculature, for better understand the reproducibility and sensitivity of in vivo DTI measurements, conventional DTI protocol was applied to a well-controlled rat model of hypercapnia. Our data demonstrated that diffusivities increased in whole brain, gray and white matter regions in response to hypercapnia. These results indicate that in vivo DTI quantitation in brain can be interfered by vascular factors on the order of few percents. Cautions should be taken in designing and interpreting quantitative DTI studies as all DTI indices can be potentially confounded by physiologic conditions, cerebrovascular and hemodynamic characteristics. Secondly, recent DTI studies have shown detection of long-term neural plasticity weeks to months following relatively extensive periods of training in animals. However, rapid plasticity within a short period (24 hours) after learning is important for observing the time course of training-evoked changes and narrow down candidate mechanisms. Fear conditioning (FC), which typically occurs over a short timescale (in minutes), was selected as a paradigm for investigation. Using voxel-wise repeated measures analysis, FA was found to increase in amygdala and decrease in hippocampus 1-hour post-FC, and it reversed in both regions 1-day post-FC. Results indicate that DTI can detect rapid microstructural changes in brain regions known to mediate fear conditioning in vivo. DTI indices could be explored as a translational tool to capture potential early biological changes in individuals at risk for developing post-traumatic stress disorder. Thirdly, in vivo DTI was employed to access regional specific microstructural changes following rapid eye movement sleep deprivation (SD), and explore possible temporal differentiation of these changes. With voxel-base analysis, MD is found to decrease in post-SD time points in bilateral hippocampi and cerebral cortex. The distributions of these clusters exhibited differentiable layer specific patterns, which were pointing to dentate gyrus and CA1 layer in hippocampus, and parietal cortex and barrel field layers in cerebral cortex. Results indicate that in vivo DTI is capable to detect microstructural changes in specific layers and reveal temporal distinction between them. These specific layers are possibly more susceptible to sleep loss, and the temporal distinction of changes between these layers might underlie learning and memory decline after SD.
published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy

APA, Harvard, Vancouver, ISO, and other styles

23

Nilsson, Daniel. "Diffusion tensor imaging and tractography in epilepsy surgery candidates /." Göteborg : University of Gothenburg, Institute of Neuroscience and Physiology, Epilepsy Research Group, Sahlgrenska Academy, 2008. http://hdl.handle.net/2077/10030.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Wang, Jiun-Jie. "High spatial resolution diffusion tensor imaging and its applications." Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272166.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Unrath, Alexander. "Richtungsabhängige Farbcodierung des menschlichen Thalamus mittels Diffusion Tensor Imaging." [S.l. : s.n.], 2007. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-59832.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Hui, Sai-kam. "Magnetic resonance diffusion tensor imaging for neural tissue characterization." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42841306.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Solomon, Daniel L. "Evaluation of normal pressure hydrocephalus with diffusion tensor imaging." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12226.

Full text

Abstract:

Thesis (M.A.)--Boston University
Purpose: Normal Pressure Hydrocephalus (NPH) is a clinical diagnosis with no formal definition. Textbooks describe NPH as a clinical triad of gait abnormality, dementia, and urinary incontinence. Few patients present with all three symptoms, forcing the clinician to rely on a “preponderance of evidence” approach, which involves weighing triad symptoms with radiological findings, Cerebrospinal Fluid (CSF) opening pressure, response to Tap Test, external lumbar CSF drainage, lumbar infusion, and finally shunting. Radiological findings in NPH are limited to enlarged ventricles out of proportion to sulcal atrophy, callosal angles greater than 40 degrees, and ventricles with Evan’s ratios greater than 0.3. When radiologists evaluate suspected NPH patients they are limited to excluding disease, as opposed to searching for any particular finding. In this study we used Diffusion Tensor Imaging (DTI) to determine if differences can be identified on a group basis between NPH and normal groups to see if DTI (including tractography) can be a useful tool for understanding disease morphology and laying the groundwork for future clinical use of DTI for identification of NPH. Materials and Methods: A retrospective study of patients who underwent brain MRI imaging with a Philips 3T magnet. NPH patients were classified as “definite” or “probable NPH” by their referring physicians. Normal subjects were patients found to have no anatomical brain abnormality. DTI and tractography data were acquired using Philips Fibertrak software, and post-processing was done using Tract Based Spacial Statistics (TBSS). Conclusion: NPH patients were found to have higher Fractional Anisotropy (FA) values in the upper corticospinal tract, lower FA values in the Corpus Callosum and mixed results in the internal capsule, to p ≤ 0.05 levels, consistent with previous reports. NPH tractography was also characterized with a distinct “heart-shaped” sign. Possible uses for tractography for patients under suspicion of NPH will be discussed.

APA, Harvard, Vancouver, ISO, and other styles

28

Dean, Ryan J., Timothy Stait-Gardner, Simon J. Clarke, Suzy Y. Rogiers, and William S. Pricea. "Diffusion Tensor Imaging (DTI) studies of the grape berry." Diffusion fundamentals 16 (2011) 29, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13762.

Full text

APA, Harvard, Vancouver, ISO, and other styles

29

Shereen, Ahmed D. "Diffusion Tensor Magnetic Resonance Imaging Applications to Neurological Disease." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1300393032.

Full text

APA, Harvard, Vancouver, ISO, and other styles

30

Barakat, Nadia. "Diffusion Tensor Imaging (DTI) of the Pediatric Spinal Cord." Diss., Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/190288.

Full text

Abstract:

Bioengineering
Ph.D.
Diffusion Tensor Imaging (DTI) is a technique for noninvasively examining diffusion of water molecules in each voxel of an image in directions parallel and transverse to the plane of neuronal axons. The quantitative characteristic of DTI allows for the characterization of physical properties of tissues. The unique characteristic architecture of the spinal cord allows DTI to characterize cord white matter, separate white from gray matter and assess structural damage of the cord. While studies on diffusion imaging of the spinal cord in adults, as well as in animal models have been reported, a comprehensive study of the pediatric spinal cord examining the accuracy and reproducibility of DTI measures has not yet been reported. The purpose of this study is to (a) evaluate the accuracy of cervical spinal cord DTI in children using a newly developed inner-Field-of-View (iFoV) sequence with spatially selective 2D RF excitations, (b) investigate reproducibility of the DTI measures and (c) examine correlation of DTI with standardized clinical exams. Twenty-five pediatric control subjects and ten pediatric patients with Spinal Cord Injuries (SCI) were recruited. The iFoV DTI pulse sequence was implemented on a 3 Tesla MRI scanner. The protocol was optimized for imaging the pediatric spinal cord and tested on phantom models, human cadaveric spine and adult subjects. All thirty-five pediatric subjects underwent two DTI scans of the spinal cord. Imaging results were compared between controls and patients with SCI. Statistical analysis was performed to examine reproducibility of DTI parameters and their correlation with standard clinical examinations. Results showed reduced FA and increased diffusivity values (AD, RD and MD) in patients compared to controls. Reproducibility of the different DTI parameters showed moderate to strong agreement between the repeated-measurements scans. Correlations between clinical examinations (ISNCSCI and MRI scores) and DTI values showed that DTI predicts sacral sparing outcomes, motor and MRI levels in the injured spinal cord with good to strong accuracy. Results also revealed that DTI values differ between children with and without cervical SCI and between children with SCI who have incomplete injuries and complete injuries. Finally, the study showed DTI to have relatively low specificity values for AC and DAP, compared with specificity for S4-5 sensation, and that the combination of the three DTI parameters FA, AD and RD was the strongest predictor of both motor level and MRI level of injury. This study was the first to demonstrate the feasibility of pediatric spinal cord DTI and produced accurate and reliable DTI measures.
Temple University--Theses

APA, Harvard, Vancouver, ISO, and other styles

31

Cui, Jiaolong, and 崔蛟龍. "Region-specific analysis of diffusion tensor imaging for cervical spondylotic myelopathy." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/197098.

Full text

Abstract:

Cervical Spondylotic Myelopathy (CSM) is a common type of spinal cord dysfunction in the elderly. The natural history of CSM is associated with disc degeneration and spondylosis, leading to the static and dynamic compression of the spinal cord, tissue ischemia, tissue damage, and ultimately neurological function deficit. However, the severity of the spinal cord compression does not necessarily correlate with the signs and symptoms of CSM in patients. Until now, the pathomechanism of CSM was not well understood. Establishing an evaluation technique is, therefore, criticalfor the pathophysiological investigation of CSM. Magnetic resonance imaging (MRI) has been widely used for evaluating the spinal cord parenchyma. However, conventional MRI is limited in detecting macroscopic changes, e.g. spinal cord compression, edema or hemorrhage etc. Recently, there has been increasing interest in diffusion tensor imaging (DTI), which permitting detects tissue water molecule diffusion at the microscopic level. The conventional DTI analysis for CSM relies on hand-drawn regions of interest (ROIs), so called ROI-based measurements. The ROIs are drawn on the sagittal image or on the axial image to cover the whole cord, which are insufficient to describe the precise diffusion pattern. In particular, the deformation and degeneration of the myelopathic cord poses a big challenge for the ROI-based analysis. The most commonly used parameter, fractional anisotropy (FA) has difficulty in determining the level diagnosis due to its relatively large variance along the cord. Furthermore, the functional activation following microstructural damage remains underexplored. In this dissertation, several novel methods for region-specific analysis were proposed for the investigation of microstructural changes in the CSM. In Chapter 2, ROI-based analysis was employed to detect the regional diffusion characteristics in CSM. In Chapter 3, an auto-template was developed that segments the cord and measures the DTI parameters automatically. We found that our auto-template outperforms hand-drawn ROI-based methods in terms of efficiency and reproducibility. In Chapter 4, entropy-based analysis was proposed to characterize the loss of complexity of microstructure in the myelopathic cord. It was demonstrated that FA entropy was an objective and quantitative evaluation parameter that was superior to conventional methods for separating CSM patients from healthy subjects. In Chapter 5, orientation entropy was used to detect the disordered orientational distribution of the nerve tracts in CSM, which could be used as a good index for the pathogenic level estimation. In Chapter 6, a diffusion tensor tractography-based method was proposed to overcome the difficulties in column-specific ROI drawing on the deformed and degenerated spinal cords. In Chapter 7, the structure-function relationship in the cervical spinal cord was explored by a combination of DTI and functional MRI. A significant correlation was found between enhanced functional responses and the loss of microstructural integrity in CSM. In this study, several novel post-processing methods were proposed and demonstrated, which were shown to have extraordinary capabilitiesfor the investigation and assessment of CSM. It is expected that these methods can be used as valuable tools for clinical diagnosis and for the selection of the most appropriate treatment strategy for CSM.
published_or_final_version
Orthopaedics and Traumatology
Doctoral
Doctor of Philosophy

APA, Harvard, Vancouver, ISO, and other styles

32

Fitzpatrick, Atiba Omari. "Automated Quality Assurance for Magnetic Resonance Imaging with Extensions to Diffusion Tensor Imaging." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33832.

Full text

Abstract:

Since its inception, Magnetic Resonance Imaging (MRI) has largely been used for qualitative diagnosis. Radiologists and physicians are increasingly becoming interested in quantitative assessments. The American College of Radiology (ACR) developed an accreditation program that incorporates tests pertaining to quantitative and qualitative analyses. As a result, sites often use the ACR procedure for daily quality assurance (QA) testing. The ACR accreditation program uses information obtained from clinical and phantom images to assess overall image quality of a scanner. For the phantom assessment, a human observer performs manual tests on T1 and T2-weighted volumes of the provided phantom. As these tests are tedious and time consuming, the primary goal of this research was to fully automate the procedure for QA purposes. The performance of the automated procedure was assessed by comparing the test results with the decisions made by human observers. The test results of the automated ACR QA procedure were well correlated with that of human observers. The automated ACR QA procedure takes approximately 5 minutes to complete. Upon program completion, the test results are logged in multiple text files. To this date, no QA procedure has been reported for Diffusion Tensor Imaging (DTI). Therefore, the secondary goal of this thesis was to develop a DTI QA procedure that assess two of the associated features used most in diagnosis, namely, diffusion anisotropy and the direction of primary diffusion. To this end, a physical phantom was constructed to model restricted diffusion, relative to axon size, using water-filled polytetrafluoroethylene (PTFE) microbore capillary tubes. Automated procedures were developed to test fractional anisotropy (FA) map contrast and capillary bundle (axon) orientation accuracy.
Master of Science

APA, Harvard, Vancouver, ISO, and other styles

33

Järmann, Thomas. "Diffusion Tensor Imaging and fiber tractography in the human brain /." Zürich, 2005. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15994.

Full text

APA, Harvard, Vancouver, ISO, and other styles

34

Byrnes, Tiernan James Dermot. "Diffusion tensor imaging and tractography : An investigation of neurosurgical applications." Thesis, St George's, University of London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511896.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Jones, Derek K. "Diffusion tensor magnetic resonance imaging in the central nervous system." Thesis, University of Leicester, 1998. http://hdl.handle.net/2381/34117.

Full text

Abstract:

This thesis begins by describing the effect of diffusion on the nuclear magnetic resonance (NMR) signal, discusses quantitative assessment of diffusion using NMR and introduces the concepts of qualitative and quantitative diffusion imaging in isotropic and anisotropic systems. The first study of subcortical ischaemia using diffusion tensor imaging (DTI) is described and a characteristic pattern of increased diffusivity and reduced diffusion anisotropy in white matter is demonstrated. These findings are highly consistent with post-mortem pathological data, suggesting that DTI can be used to monitor tissue change in vivo and improve understanding of the disease progression. Next, optimal strategies are developed for diffusion measurement in anisotropic systems. Marked improvements in the precision of estimates of diffusion in both phantom and human studies are demonstrated. For example, in a water phantom the standard deviation in the estimate of mean diffusivity is reduced by more than 30% and the artefactual anisotropy is reduced by more than 55% when using the optimal schemes. These improvements have important implications including reduced scan times, improved resolution and increased sensitivity to pathological change. A novel method for displaying the three dimensional orientation of anisotropic structures in one image, and an algorithm for the non-invasive assessment and display of axonal fibre connectivity are then described. Results from healthy human brains are presented demonstrating fibre orientation and connections in the major white-matter tracts. These techniques have important potential applications in the study of a wide range of neurological, psychiatric and developmental disorders. Finally, techniques are described for the characterisation of tissue change in human traumatic brain injury using DTI, and for the detection of cortical spreading depression (CSD) using dynamic diffusion imaging. Static imaging revealed a region of reduced diffusivity and normal T2 bordering the injury site which may represent a reversible state. No candidate CSD events were observed in this initial study.

APA, Harvard, Vancouver, ISO, and other styles

36

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.

Full text

Abstract:

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.

APA, Harvard, Vancouver, ISO, and other styles

37

Zhang, Zhongping, and 张忠平. "Quantitative in vivo assessment of tissue microstructure using diffusion tensor and kurtosis imaging." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B4694395X.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Smale, Peter Rich. "Diffusion Tensor Imaging of Motor Connectivity in Selected Subjects with Stroke." Thesis, University of Canterbury. Physics and Astronomy, 2007. http://hdl.handle.net/10092/1446.

Full text

Abstract:

Diffusion Tensor Magnetic Resonance Imaging (DTI) is a recently-developed technique that can image in vivo the white matter pathways of the central nervous system. This study used 12-direction diffusion-weighted MRI data from nine stroke patients acquired as part of a three-year stroke rehabilitation study coordinated by the Movement Neuroscience Laboratory at the University of Auckland. DTI was used to investigate corticospinal connectivity. From the FA maps, it is found that in those patients whose motor connectivity has been compromised by the stroke to the extent that no motor evoked potential (MEP) can be elicited from a selected affected muscle group, the asymmetry in mean FA values in the posterior limbs of the internal capsules (PLICs) is correlated with functional recovery as measured by the Fugl-Meyer clinical score. Using probabilistic tractography in the contralesional hemisphere produced CST location and somatotopy results that were consistent with those of previous studies. However, in the ipsilesional hemisphere, connectivity results were highly variable. A measure of change in symmetry of mean connectivity is found to correlate with functional recovery as measured by change in FM score. This supports previous work which has correlated CST integrity and functional improvement and it supports the theory that functional recovery after stroke depends on the extent to which motor CNS symmetry can be regained in the new post-stroke architecture. It also suggests that the movement of the fMRI activations occurs in such a way as to make the most of the preserved white matter connectivity.

APA, Harvard, Vancouver, ISO, and other styles

39

Heckenberg, Gregory Duan Ye. "Shape reconstruction from volumetric images." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5787.

Full text

Abstract:

Thesis (M.S.)--University of Missouri-Columbia, 2008.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 12, 2009) Includes bibliographical references.

APA, Harvard, Vancouver, ISO, and other styles

40

Petzold, Friederike. "In-vivo Darstellung hypothalamischer Substrukturen mit Hilfe von Diffusions-Tensor-Bildgebung." Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-153207.

Full text

Abstract:

In der vorliegenden Arbeit wird der Hypothalamus, eine kleine, aber bedeutsame Struktur des Zwischenhirns untersucht. Er spielt unter anderem eine Rolle bei der Regulation des Schlaf-Wach-Rhythmus, des Sexualverhaltens, der Stimmungslage, autonomer und Stoffwechsel-Funktionen. Veränderungen einzelner oder mehrerer spezifischer Kerngruppen sind bei neuropsychiatrischen bzw. -endokrinologischen Erkrankungen, wie Narkolepsie, Schizophrenie, affektiver Störung, Demenz, Borderline-Persönlichkeitsstörung, Pädophilie oder Adipositas zu beobachten. Die Substrukturierung und Darstellung der einzelnen Kerngruppen gelang bisher nur in Postmortem-Studien. Im Rahmen dieser Studie konnte mit Hilfe der Diffusions-Tensor-Bildgebung erstmals eine in-vivo Substrukturierung des Hypothalamus konsistent bei zehn gesunden Probanden vorgenommen werden. Dabei wurden nach einem Algorithmus zunächst die Segmentierung und anschließend die Parzellierung durchgeführt, woraus sich drei konsistente Cluster ergaben. Der topografische Vergleich der erhaltenen Cluster mit Postmortem-Studien der Literatur ergab vergleichbare und anatomisch plausible Korrelate. Mit der von uns entwickelten Methode könnten anhand einer größeren Patientengruppe pathophysiologische Zusammenhänge neuropsychiatrischer und –endokrinologischer Störungen genauer eruiert werden und zu einem besseren Verständnis des Krankheitsverlaufs und der Therapie beitragen.

APA, Harvard, Vancouver, ISO, and other styles

41

Filho, Antonio Carlos da Silva Senra. "Otimização da segmentação e processamento de imagens do encéfalo com ênfase para lesões da substância branca." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/59/59135/tde-10102017-153226/.

Full text

Abstract:

Esclerose Múltipla (MS) é uma doença neurodegenerativa que tem ganhado grande atenção nas últimas décadas, sendo o diagnóstico por imagens de ressonância magnética (MRI) um grande aliado para a avaliação da doença.Porém, um dos principais desafios é garantir uma maior sensibilidade e especificidade para detecção de diferentes lesões no sistema nervoso central (CNS) e assim classificar as diferentes variantes da MS, auxiliando na tomada de decisão para o tratamento farmacológico. Nas últimas décadas, a técnica de imagens ponderadas por difusão (DWI), em especial a técnica de imagem por tensor de difusão (DTI), têm sido evidenciada com grande potencial para o estudo da MS, apresentando uma melhora significativa para a detecção de lesões sutis, ainda em estágios iniciais da MS. Desta forma, as técnicas de processamento de imagens estão em constante aprimoramento para que sejam adaptados às novas modalidades de aquisição de imagens. Neste estudo focamos o desenvolvimento de uma técnica de processamento digital de imagens multimodais a fim de proporcionar uma solução viável para a rotina de diagnóstico por imagem em MS. Um conjunto de 25 pacientes de uma variante de MS foi selecionado aleatoriamente do banco de imagens do HCFMRP. Três modalidades de imagens foram coletadas para a avaliação da segmentação automatica (T1, T2-FLAIR e DTI), assim como a segmentação manual do especialista para cada paciente. Três métodos de segmentação multimodal automática de lesões foram analisados (Bayesiano, Frequentista e Agrupamento) afim de analisar a sensibilidade e especificidade de detecção de lesões na substância branca aparentemente normal (NAWM). Os resultados sugerem que o método de segmentação Bayesiano apresenta maior robustes e precisão na definição tanto de lesões visivelmente contrastantes em T1 e T2-FLAIR (i.e. lesões hipo e hiperintensas) assim como lesões da NAWM evidentes nos mapas quantitativos de DTI (FA e ADC). O erro associado à técninca automática de segmentação ficou em torno de 1.51 +- 0.51 % do volume total de lesões marcadas pelo especialista. Concluímos que o uso de ferramentas multimodais de segmentação de imagens MRI alcançou patamares razoáveis de detecção de lesões de MS, tornando assim uma ferramenta computacional hábil para uso no diagnóstico clínico.
Multiple sclerosis (MS) is a neurodegenerative disease that has gained great attention in the last decades, which magnetic resonance imaging (MRI) have shown as an important tool for the disease evaluation. However, one of the main challenges is guaranteeing greater lesion detection sensitivity and specificity in the whole central nervous system (CNS) and thus classify the different variants of MS, which aids in decision making for pharmacological treatment. In the last decades, the diffusion-weighted imaging (DWI) technique, especially the diffusion tensor imaging approach (DTI), has been evidenced with great potential for the study of MS, presenting a significant improvement for the detection of lesions even in early stages of MS. Hence, the techniques of image processing are constantly improving in order to be adapted on a multimodal image evaluation. In this study, the development of a multimodal digital image processing technique to provide a viable solution to the MS imaging routine was focused. A set of 25 patients from a MS variant was randomly selected from the HCFMRP imaging database. Three MR imaging modalities were collected for the evaluation of our automatic segmentation (T1, T2-FLAIR and DTI), as well as manual segmentation of the specialist for each patient. Three methods of automatic multimodal segmentation of MS lesions were analyzed (Bayesian, Frequentist and Clustering) in order to analyze the sensitivity and specificity of lesion detection in the apparently normal white matter (NAWM). The results suggest that the Bayesian segmentation method presented greater robustness and precision in the definition of visibly contrasting lesions in T1 and T2-FLAIR (i.e. hypo and hyperintense lesions) as well as NAWM lesions that are evident in quantitative DTI (FA and ADC). The error associated with the automatic segmentation technique was around 1.51 +- 0.51 % of the total lesion volume being evaluated by the a specialist. We conclude that the use of multimodal MRI images can be used in an automatic segmentation tools, reaching reasonable levels of MS lesion detection, thus making it a useful tool for clinical diagnosis.

APA, Harvard, Vancouver, ISO, and other styles

42

Neji, Radhouène. "Diffusion Tensor Imaging of the Human Skeletal Muscle : Contributions and Applications." Phd thesis, Ecole Centrale Paris, 2010. http://tel.archives-ouvertes.fr/tel-00504678.

Full text

Abstract:

Cette thèse propose des techniques pour le traitement d'images IRM de diffusion. Les méthodes proposées concernent l'estimation et la régularisation, le groupement et la segmentation ainsi que le recalage. Le cadre variationnel proposé dans cette thèse pour l'estimation d'un champ de tenseurs de diffusion à partir d'observations bruitées exploite le fait que les données de diffusion représentent des populations de fibres et que chaque tenseur peut être reconstruit à partir d'une combinaison pondérée de tenseurs dans son voisinage. La méthode de segmentation traite aussi bien les voxels que les fibres. Elle est basée sur l'utilisation de noyaux défini-positifs sur des probabilités gaussiennes de diffusion afin de modéliser la similarité entre tenseurs et les interactions spatiales. Ceci permet de définir des métriques entre fibres qui combinent les informations de localisation spatiale et de tenseurs de diffusion. Plusieurs approches de groupement peuvent être appliquées par la suite pour segmenter des champs de tenseurs et des trajectoires de fibres. Un cadre de groupement supervisé est proposé pour étendre cette technique. L'algorithme de recalage utilise les noyaux sur probabilités pour recaler une image source et une image cible. La régularité de la déformation est évaluée en utilisant la distortion induite sur les distances entre probabilités spatialement voisines. La minimisation de la fonctionnelle de recalage est faite dans un cadre discret. La validation expérimentale est faite sur des images du muscle du mollet pour des sujets sains et pour des patients atteints de myopathies. Les résultats des techniques développées dans cette thèse sont encourageants.

APA, Harvard, Vancouver, ISO, and other styles

43

Cheung, Charlton. "Diffusion tensor imaging pre-processing methods and application in autism research." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B39793916.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Kellerer, Andreas. "Diffusion-Tensor-Imaging des retropatellaren Gelenkknorpels im Vergleich mit der Anatomie." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-172574.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Tournier, Jacques-Donald. "Diffusion tensor magnetic resonance imaging and fibre tractography in the brain." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408020.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Prucka, William R. "Wavelet-based regression and classification for longitudinal diffusion tensor imaging data." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2008p/prucka.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Padgett, Kyle Robert. "Optimizing high field T₁ and diffusion tensor structural magnetic resonance imaging." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010053.

Full text

APA, Harvard, Vancouver, ISO, and other styles

48

Anjari, Mustafa. "Exploring the developing preterm brain with diffusion tensor magnetic resonance imaging." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/11238.

Full text

APA, Harvard, Vancouver, ISO, and other styles

49

Qiu, Deqiang, and 邱德強. "Diffusion tensor imaging in evaluating normal and abnormal white matter development in childhood." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41508324.

Full text

APA, Harvard, Vancouver, ISO, and other styles

50

Diehl, B. "Imaging correlates of the epileptogenic zone and functional deficit zone using diffusion tensor imaging (DTI)." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1135641/.

Full text

Abstract:

Focal epilepsy is a common serious neurologic disorder. One out of three patients is medication refractory and epilepsy surgery may be the best treatment option. Neuroimaging and electroencephalography (EEG) techniques are critical tools to localise the ictal onset zone and for performing functional mapping to identify the eloquent cortex in order to minimise functional deficits following resection. Diffusion tensor magnetic resonance imaging (DTI) informs about amplitude (diffusivity) and directionality (anisotropy) of diffusional motion of water molecules in tissue.This allows inferring information of microstructure within the brain and reconstructing major white matter tracts (diffusion tensor tractography, DTT), providing in vivo insights into connectivity. The contribution of DTI to the evaluation of candidates for epilepsy surgery was examined: 1. Structure function relationships were explored particularly correlates of memory and language dysfunction often associated with intractable temporal lobe epilepsy (TLE; chapters 3 and 4). Abnormal diffusion measures were found in both the left and right uncinate fasciculus (UF), correlating in the expected directions in the left UF with auditory memory and in the right UF with delayed visual memory performance. Examining the arcuate fasciculus (AF), bilateral diffusion changes were found with correlations between left AF DTI measures and language scores. 2. The second aim of this thesis was to validate DTT results and test the hypothesis that cortical language areas determined by cortical stimulation serve as anchor points for the tractography defined AF (chapter 5). Subdural grid contacts overlying anterior language cortex co-localised in 84.2% with the AF, and in 55.8% in posterior language areas. This provides some validation that the AF reconstructed using DTT subserves language function, but further study is needed. 3. Lastly, seizure propagation was investigated in a case series of patients with cortical dysplasia (chapter 6). Reduced connectivity with reduced arborization and thinning of the fibre bundles between subcortical WM and the dysplastic cortex was demonstrated. Fibre tracts reconstructed from regions underlying the ictal onset zone showed abnormal connectivity.

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Diffusion tendor imaging'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles