Cardiovascular Disease (CVD) continues to be the leading cause of death in western countries according to the statistics update by the American Heart Association. Atherosclerosis is estimated to be responsible for a large portion of CVD and affects 60 million people in the United States. Accurate diagnosis is crucial for proper treatment planning. Currently, the clinical standard screening technique for diagnosing atherosclerosis is x-ray angiography, which reveals the residual lumen size. X-ray angiographic images possess good resolution and contrast, however, lumen size is not always a proper criterion given the positive remodeling nature of atherosclerotic plaques. In the past decade, it has been shown that most plaques responsible for a fatal or nonfatal myocardial infarction are less than 70% stenosed. Clinical data support the idea that plaques producing non-flow-limiting stenoses account for more cases of plaque rupture and thrombosis than plaques producing a more severe stenosis. Due to this fact, plaque itself must be imaged in order to assess its vulnerability. A wealth of literature suggests that multicontrast MRI has the potential of characterizing plaque constituents, and thus is a promising technique for plaque imaging. Because of the technical difficulties associated with in-vivo plaque imaging and the fact that our research was aimed at developing new methodologies, our approaches was to image excised coronary arteries under simulated in-vivo conditions in a tissue culture chamber. It is shown by this research that automatic plaque characterization techniques developed under ex-vivo conditions still apply for in-vivo studies. Based on this finding, an automatic plaque characterization technique using multicontrast MRI was developed. Furthermore, "shared k-space" reconstruction techniques were interrogated to assess their feasibility in accelerating multicontrast MRI acquisition. Results show that these techniques are promising in accelerating multicontrast MRI acquisitions.

Using Graphic Processor Unit (GPU) to process the parallel operation via Compute Unified Device Architecture (CUDA) is a new technology in recent years. In the past, the GPU has been used in parallel operation but it was not easy for programming so that it couldn¡¦t be widely used in applications. CUDA is the newly-developed environment based on C language mainly for improving the complexity in programming with CUDA. The applications of GPU with CUDA has been expending to various fields gradually due to support of IEEE floating point as well as its lower cost in hardware while comparing to the super computers. Magnetic Resonance Spectroscopy (MRS) has the feature of non-invasive to probe the concentration distributed of metabolites in vivo. It can assist doctor in clinical diagnosis. The Magnetic Resonance Spectroscopy Imaging (MRSI) is imaging by many Signal Voxel Spectroscopy (SVS) to become multi-dimension MRS image. In MRSI, it can offer more information than SVS. CUDA are applied to MR image widely such as accelerating the image reconstruction and promoting the image quality, but in MRS it is seldom for the related application. In this paper, we using the CUDA to applied in MRS, the MRSI data pre-processing, to accelerate the spatial location in MRSI. In this work, we firstly use random data with different dimensions: 1D (one-dimension), 2D and 3D to evaluate the performance of Fourier transformation by using CUDA. We also finally apply some GE 2D/3D MRSI data to see how the acceleration of using CUDA works. Our results show that the acceleration rate of Fastest Fourier Transform (FFT) with CUDA in 1D, 2D and 3D random data largely increases as the data size increases. In the experiment of 2D/3D MRSI data, we find that using CUDA for accelerating the MRSI RAW-file generating procedure would avoid the data moving times, and it is not good for CUDA 1D FFT with parallel architecture while too small data amount processing in kernel. Therefore, how to solve the relationship between MRSI data format with CUDA FFT library and how to decrease the data moving time will discuss in the study.

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Recently functional magnetic resonance imaging has become popular in the studies of human brain functions. As the area of auditory cortex has been proven and defined, we consider music cognition as the next step. In this study, we focus on the response of rhythm. Professional musicians and amateurs were involved in our experiments. Our preliminary result revealed that three of professional musicians have distinguished activation on left cerebrum Inferior Frontal Gyrus BA45/BA47 (language areas). However, since the subjects¡¦ background is difficult to be strictly controlled, further discussion is necessary to define meaning and brain functions of our experiments.

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The dramatic improvement in magnetic resonance imaging (MRI) scan time over the past fifteen years through gradient-based methods that sample k-space more efficiently and quickly cannot be sustained, as thresholds regarding hardware and safety limitations are already being approached. Parallel imaging methods (using multiple receiver coils to partially encode k-space) have offered some relief in the efforts and are rapidly becoming the focus of current endeavors to decrease scan time. Ideally, for some applications, phase encoding would be eliminated completely, replaced with array coil encoding instead, and the entire image formed in a single echo. The primary objective of this work was to explore that acceleration limit – to implement and investigate the methodology of single echo acquisition magnetic resonance imaging (SEA MRI). The initial evaluation of promising array coil designs is described, based on parameters determined by the ability to enable the imaging method. The analyses of field patterns, decoupling, and signal-to-noise ratio (SNR) that led to the final 64-channel array coil design are presented, and the fabrication and testing of coils designed for 4.7T and 1.5T are described. A detailed description of the obtainment of the first SEA images – 64xNreadout images, acquired in a single echo – is provided with an evaluation of those images and highly accelerated images (through parallel imaging techniques) based on SNR and artifact power. Finally, the development of methodologies for various MR applications is described: applications that would particularly benefit from the speed of the imaging method, or those to which the method or the tool (array coil) lends itself. These applications include, but are not limited to, 3D imaging (phase encode in the slice select direction), resolution-enhanced imaging, large-scale (field-of-view) microscopy, and conformal surface imaging. Finally, using the primary enablement of the method – the ability to obtain complete MR images at speeds limited only by the time it takes to acquire a single echo – is presented with a discussion of extremely high frame rate imaging. The contribution to the field of medical imaging is the first implementation, characterization, and demonstration of applications for the acquisition of MR images in a single echo.

<p>There is an increasing interest for nanomaterials in biomedical applications and in this work, nanoparticles of gadolinium oxide (Gd₂O₃) have been investigated as a novel contrast agent for Magnetic Resonance Imaging (MRI). Relaxation properties have been studied in aqueous solutions as well as in cell culture medium and the nanoparticles have been explored as cell labeling agents. The fluorescent properties of the particles were used to visualize the internalization in cells and doped particles were also investigated as a multimodal agent that could work as a fluorescent marker for microscopy and as a contrast enhancer for MRI.</p><p>Results show that in aqueous solutions, there is a twofold increase in relaxivity for Gd₂O₃ compared to commercial agent Gd-DTPA. In cell culture medium as well as in cells, there is a clear T₁ effect and a distinct increase in signal intensity in T₁-mapped images. Fluorescent studies show that the Gd₂O₃ nanoparticles doped with 5% terbium have interesting fluorescent properties and that these particles could work as a multimodal contrast agent.</p><p>This study shows that Gd₂O₃ nanoparticles possess excellent relaxation properties that are retained in more biological environments. Gd₂O₃ particles are suitable as a T₁ contrast agent, but seem also be adequate for T₂ enhancement in for instance cell labeling experiments.</p>

Absence seizures in Childhood Absence Epilepsy (CAE) are 5 10 second episodes of impaired consciousness that are characterized on electroencephalography (EEG) by frontally-predominant, 3 4 Hz spike and wave discharges (SWD). The aims of this study were to use simultaneous EEG, functional magnetic resonance imaging (fMRI), and behavioral testing to identify the neural networks involved in absence seizures as well as to examine the timecourse of those ictal fMRI changes. It was hypothesized that absence seizures involve wide-reaching neural networks including the areas traditionally associated with normal attention processing and that absence seizures produce fMRI signal changes not only during the seizure, but before and after it as well. In this study, we recorded 88 absence seizures from a cohort of 42 children with pure CAE. These seizures were recorded as subjects participated in simultaneous EEG-fMRI scanning while engaged in a continuous performance task (CPT) of attentional vigilance or a repetitive tapping task (RTT) requiring repetitive motor activity. Using a novel, voxel-based percent fMRI change analysis combined with a volume of interest analysis, the second-by-second fMRI signal timecourse of the absence seizures were examined across numerous brain regions of interest, from 20 seconds before seizure onset through 40 seconds after seizure onset. EEG frequency analysis revealed seizures with a mean duration of 6.6 seconds and an abrupt onset and ending that were comprised of frontally-predominant, 3 4 Hz SWD. Ictal behavioral testing demonstrated abrupt onset of impairments during periods of SWD. These behavioral impairments were typical of CAE absence seizures in that impairments were greater in the CPT of attentional vigilance (omission error rate, OER = 81%) than in RTT testing (OER = 39 %) (p < 0.003). The ictal fMRI changes we observed varied depending upon the method of fMRI signal analysis used. Using the traditional general liner model, and assuming the standard hemodynamic response (HRF) function, this study replicated results consistent with previous ictal absence fMRI studies showing ictal activations primarily in the thalamus and ictal deactivations in traditional default mode areas. Using a more data-driven, novel voxel-based fMRI percentage change analysis to examine the ictal fMRI timecourse on a second-by-second basis, both ictally as well as pre- and post- ictally, this study, however, demonstrated ictal involvement of diverse brain regions before, during, and after the seizure. Activation was demonstrated up to 16 seconds before seizure onset, starting first in the parietal and orbital-medial frontal cortices and progressing to lateral frontal and lateral temporal cortices followed by the occipital and Rolandic cortices and finally the thalamus. Deactivation followed a similar anatomic progression and lasted up to 17 seconds after the end of SWD. These findings reveal a complex and long-lasting sequence of fMRI changes in CAE absence seizures that are not detectable by conventional HRF modeling and are important in the understanding and eventual treatment of absence seizures associated with CAE.

Recent studies in the field of dyslexia have used magnetic resonance spectroscopy (MRS) to explore neurochemical manifestations of neurobiological differences in the brains of dyslexic adults compared to controls. This study examines the potential relationship between functional magnetic resonance imaging (fMRI) BOLD (blood oxygen level demand) activation scores in response to cognitive tasks and MRS-measured levels of a metabolite and a neurotransmitter, N-acetylaspartate (NAA) and gamma-aminobutyric acid (GABA) respectively, in the occipital region of brains of seven-year old children. Preliminary results from this multi-arm, longitudinal study indicate a significant positive correlation between fMRI BOLD signal elicited in response to picture-cues in the occipital region of interest bilaterally, and both GABA (R2=0.477 p=0.05, 2-tailed) and NAA (R2=0.587 p=0.01, 2-tailed) levels. The results suggest that the functional neuroanatomical circuitry involved in a cognitive task also has neurochemical indicators.

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references. Also available in print.