Computer vision encompasses a host of computational techniques to process visual information. Medical imagery is one particular area of application where data comes in various forms: X-rays, ultrasound probes, MRI volumes, EEG recordings, NMR spectroscopy, etc. This dissertation is concerned with techniques for accurate reconstruction of neural pathways from diffusion magnetic resonance imagery (dMRI). This dissertation describes a filtered approach to neural tractography. Existing methods independently estimate the diffusion model at each voxel so there is no running knowledge of confidence in the estimation process. We propose using tractography to drive estimation of the local diffusion model. Toward this end, we formulate fiber tracking as recursive estimation: at each step of tracing the fiber, the current estimate is guided by those previous. We argue that this approach is more accurate than conventional techniques. Experiments demonstrate that this filtered approach significantly improves the angular resolution at crossings and branchings. Further, we confirm its ability to trace through regions known to contain such crossing and branching while providing inherent path regularization. We also argue that this approach is flexible. Experiments demonstrate using various models in the estimation process, specifically combinations of Watson directional functions and rank-2 tensors. Further, this dissertation includes an extension of the technique to weighted mixtures using a constrained filter.

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.

published_or_final_version / Diagnostic Radiology / Doctoral / Doctor of Philosophy

Manganese-Enhanced Magnetic Resonance Imaging (MEMRI) has proven itself to be a beneficial technique in the field of Neuroscience. This thesis applies MEMRI to studies in neuroscience by first establishing the limitations concerning the use of MEMRI in live rats. Experiment 1 used an osmotic pump for manganese (Mn) delivery to the lateral ventricles for acquisition of anatomical images using MEMRI. From my knowledge, this was the first method demonstrating slow infusion of Mn to the lateral ventricles. In Experiment 2, MEMRI was used for volumetric analysis the whole brain and hippocampus of prenatally stressed rats. To my knowledge, this study was the first to investigate the effect of generational prenatal stress on the structure of a rat’s brain using MEMRI and histology. Additionally, Experiment 2 investigated the use of a subcutaneous osmotic pump to deliver Mn for MEMRI. A summary on the use of MEMRI in Neuroscience concludes this thesis, with a discussion on the methods used and related technical considerations. / xi, 84 leaves ; 29 cm

There remains a high degree of scepticism about acupuncture since its theoretical basis has no clear reference in Western medical and scientific terms, making any associations between neurophysiology and specific acupuncture concepts difficult to determine. Using neuroimaging and engineering approaches to understand its physiological basis may engender greater acceptance of and improvement in the clinical application of acupuncture. Research into the efficacy of acupuncture has raised a number of difficult methodological issues, particularly in relation to the selection of appropriate controls. Separating specific effects from non-specific effects is complex because acupuncture is a physical, invasive, manual procedure involving time and ritual. Sham acupuncture results show only the difference between sham and real acupuncture not the real affect of acupuncture, and other controls may produce distinct subjective and objective effects. Point injection (the injection of a small amount of a substance at an acupoint), a recent innovation of traditional acupuncture, aims to enhance and prolong the stimulation effect in a standardised, reproducible manner. By providing precise, measurable acupoint stimulation applied incrementally in a specifically designed paradigm, an acupoint could act as its own control. This firstly requires injection to be validated against traditional needling. Aims 1. To develop an instrument for reproducible saline delivery at an acupoint. 2. To cross-validate saline acupoint injection (PI) with traditional needle acupuncture (TA). 3. To demonstrate central nervous system (CNS) effects of acupuncture both in health and chronic pain. Hypothesis The primary hypothesis is that stimulation of specific acupoints with linearly incremental saline injection produces differential effects within the CNS observable with functional magnetic resonance imaging (fMRI) allowing investigation of acupuncture in health and chronic pain. Novelty As neuroimaging has not yet clearly defined the brain structures that may be modulated by acupuncture, this project is exploratory in nature. It is expected that acupuncture effects can be robustly imaged with fMRI in healthy subjects and those suffering chronic pain. The demonstrated effects will result from the acupuncture process of progressive point stimulation by tissue distension rather than needle insertion or biological noise. It is proposed to examine the putative modulation of pain by acupuncture within the extensively mapped neuromatrix of cortical and subcortical regions, including the somatic, insula, and limbic cortices, and thalamus. Detailed information regarding differences in brain response between acupuncture in normal and diseased states will expand understanding of acupuncture as a clinical tool. The dilemma of sham stimulation or arbitrary controls will be addressed by confirming PI as a valid, reproducible stimulation method. Methods and Results A series of empirical experiments was designed and conducted to determine the effects of stimulation of different acupoints. 1. Chapters 1 and 3 outline the current understanding of acupuncture in the Western milieu and a review of the neuroimaging literature respectively. 2. In Chapter 2, the report of PI tested against TA in healthy volunteers to determine equivalence of physiological effect demonstrates no statistically significant differences between the methodologies. 3. Chapter 4 reports the design and validation of a task specific microprocessor controlled syringe driver. 4. Four differing acupoints were tested during an fMRI experiment described in Chapter 5; different activation areas were demonstrated across the acupoints providing early support for the hypothesis that different acupoints may have different effects. A subset of brain areas recognised within the pain neuromatrix was delineated, congruent spatially and directionally with those reported in pharmacological analgesia studies. 5. As outlined in Chapter 6, heart rate variability can be measured rapidly in a stressful environment to provide meaningful data on the response of the autonomic nervous system to acupuncture stimulation. 6. The hypothesis of different acupoints having different effects was tested in subjects suffering chronic pain by contrasting an accepted and a neutral acupoint, the results being reported in Chapter 7. Conclusion Despite a long history of clinical usage, appropriate scientific studies have not yet addressed the basic effectiveness and efficacy of acupuncture. This thesis presents a series of empirical studies designed to address a number of the questions arising in the literature and provides converging evidence of the manner in which different acupoints modulate the CNS, specifically within the pain neuromatrix.

There remains a high degree of scepticism about acupuncture since its theoretical basis has no clear reference in Western medical and scientific terms, making any associations between neurophysiology and specific acupuncture concepts difficult to determine. Using neuroimaging and engineering approaches to understand its physiological basis may engender greater acceptance of and improvement in the clinical application of acupuncture. Research into the efficacy of acupuncture has raised a number of difficult methodological issues, particularly in relation to the selection of appropriate controls. Separating specific effects from non-specific effects is complex because acupuncture is a physical, invasive, manual procedure involving time and ritual. Sham acupuncture results show only the difference between sham and real acupuncture not the real affect of acupuncture, and other controls may produce distinct subjective and objective effects. Point injection (the injection of a small amount of a substance at an acupoint), a recent innovation of traditional acupuncture, aims to enhance and prolong the stimulation effect in a standardised, reproducible manner. By providing precise, measurable acupoint stimulation applied incrementally in a specifically designed paradigm, an acupoint could act as its own control. This firstly requires injection to be validated against traditional needling. Aims 1. To develop an instrument for reproducible saline delivery at an acupoint. 2. To cross-validate saline acupoint injection (PI) with traditional needle acupuncture (TA). 3. To demonstrate central nervous system (CNS) effects of acupuncture both in health and chronic pain. Hypothesis The primary hypothesis is that stimulation of specific acupoints with linearly incremental saline injection produces differential effects within the CNS observable with functional magnetic resonance imaging (fMRI) allowing investigation of acupuncture in health and chronic pain. Novelty As neuroimaging has not yet clearly defined the brain structures that may be modulated by acupuncture, this project is exploratory in nature. It is expected that acupuncture effects can be robustly imaged with fMRI in healthy subjects and those suffering chronic pain. The demonstrated effects will result from the acupuncture process of progressive point stimulation by tissue distension rather than needle insertion or biological noise. It is proposed to examine the putative modulation of pain by acupuncture within the extensively mapped neuromatrix of cortical and subcortical regions, including the somatic, insula, and limbic cortices, and thalamus. Detailed information regarding differences in brain response between acupuncture in normal and diseased states will expand understanding of acupuncture as a clinical tool. The dilemma of sham stimulation or arbitrary controls will be addressed by confirming PI as a valid, reproducible stimulation method. Methods and Results A series of empirical experiments was designed and conducted to determine the effects of stimulation of different acupoints. 1. Chapters 1 and 3 outline the current understanding of acupuncture in the Western milieu and a review of the neuroimaging literature respectively. 2. In Chapter 2, the report of PI tested against TA in healthy volunteers to determine equivalence of physiological effect demonstrates no statistically significant differences between the methodologies. 3. Chapter 4 reports the design and validation of a task specific microprocessor controlled syringe driver. 4. Four differing acupoints were tested during an fMRI experiment described in Chapter 5; different activation areas were demonstrated across the acupoints providing early support for the hypothesis that different acupoints may have different effects. A subset of brain areas recognised within the pain neuromatrix was delineated, congruent spatially and directionally with those reported in pharmacological analgesia studies. 5. As outlined in Chapter 6, heart rate variability can be measured rapidly in a stressful environment to provide meaningful data on the response of the autonomic nervous system to acupuncture stimulation. 6. The hypothesis of different acupoints having different effects was tested in subjects suffering chronic pain by contrasting an accepted and a neutral acupoint, the results being reported in Chapter 7. Conclusion Despite a long history of clinical usage, appropriate scientific studies have not yet addressed the basic effectiveness and efficacy of acupuncture. This thesis presents a series of empirical studies designed to address a number of the questions arising in the literature and provides converging evidence of the manner in which different acupoints modulate the CNS, specifically within the pain neuromatrix.

Thesis (Ph. D.)--Carleton University, 2004. / Includes bibliographical references (p. 107-116). Also available in electronic format on the Internet.

Thesis (doctoral)--Lund University, 1998. / Added t.p. with thesis statement inserted. Includes bibliographical references.

This study was conducted to determine if specialty areas are emerging in the magnetic resonance imaging (MRI) profession due to advancements made in the medical sciences, imaging technology, and clinical applications used in MRI that would require new developments in education/training programs and national registry examinations. In this exploratory study, statistical analysis incorporated the use of factor analysis and chi square. Factor analysis was used to group tasks performed by MRI technologists into factors to better identify emerging specialty areas within the MRI profession. Chi square was used to analyze the association between the tasks performed in (a) the employment setting, and (b) hospital size. Factor analysis identified four meaningful factors. The four named factors were: (a) Routine Imaging non-Central Nervous System Imaging; (b) Advanced Imaging; (c) Routine Imaging with Central Nervous System Imaging; and (d) Musculoskeletal and Spine Imaging. From the four named factors, three emerging specialty areas were identified: (a) central nervous system imaging; (b) vascular/cardiovascular imaging; and (c) musculoskeletal imaging. Chi square analysis identified 47 of the 78 tasks as being significant when finding an association between the employment setting and the frequency of tasks performed. Cramer's V was used to measure the strength of their association. The more complicated the procedure the more likely this procedure is performed in either a university or private hospital. Further, chi square analysis identified 42 of the 78 tasks as being significant when finding the association between the hospital size and the frequency of tasks performed. Gamma was used to measure the strength of their association. This means the larger the hospital, the more frequent the tasks were performed.

This thesis addresses the problem of analysing clinical MRI using modern computer vision methods for a variety of clinical and research-related tasks. We use automated machine learning algorithms to develop a spinal MRI analysis framework for a number of tasks such as vertebrae detection, labelling; disc and vertebrae segmentation, and radiological grading, and we validate the framework on a large, heterogeneous dataset of 300 symptomatic back pain patients from multiple clinical sites and scanners. Our framework has a number of back pain research and other spine-related clinical applications and could hopefully find application in a clinical workflow in the future. Our framework has five steps -- detection, labelling, segmentation, support regions and features, and machine learning for radiological measurements. The framework works in full 3D and has currently been implemented on sagittal T2 slices. We use Deformable Part Models along with a chain model to detect and label vertebrae, and a powerful graph cuts based method for vertebrae and disc segmentation. The labelled detections and segmentations are used to place support regions for feature extraction, which are mapped into a number of radiological measurements -- namely Pfirrmann grade, disc space narrowing, and herniation/bulge. The radiological ground truth was provided by a clinical radiologist with 25 years experience. We demonstrate a high performance in the measurement in each. The measurements are performed using support vector machines and support vector regressors learned on training data. We next investigate the problem of what is the best method of obtaining support regions. We first used pixel intensity features to predict the Pfirrmann grade, narrowing and bulge/herniation, with vertebrae segmentation to localise their support regions. Since segmentation of spine images, especially intervertebral discs is an unsolved problem and algorithms are prone to failure, we then ask the question, to segment or not to segment. To answer the question, we compare results on Pfirrmann grade prediction with three different points on the no segmentation to full disc segmentation involving no segmentation, vertebrae segmentation, or disc segmentation and find that vertebrae segmentation suffices. We finally show preliminary results in distinguishing between different radiological conditions related to the posterior side of the disc more finely than before in literature, taking information from both sagittal and axial slices to attempt to distinguish between herniated and bulged discs.