Techn. Universiẗat, Diss., 2003--Berlin.

BACKGROUND: Migraine is a primary headache disorder that has a high prevalence and burden of disease throughout the world. Migraine symptoms include throbbing head pain, nausea, hypersensitivity to light, sound, and smell, and autonomic, cognitive, emotional, and motor disturbances. About a third of migraineurs have aura symptoms which are transient neurological symptoms with gradual onset before the migraine attack, visual disturbances, sensory loss, and/or communication impairment. The trigeminovascular system, central descending modulation, and brainstem descending modulation have been implicated in the pathophysiology of migraine. However, the exact neurovascular mechanism for migraine has not been determined. Several imaging techniques have been used to find structural and functional brain changes in migraineurs. OBJECTIVE: In order to further existing knowledge of migraine pathophysiology, structural brain differences were investigated using imaging between migraineurs and healthy individuals and differences within migraineurs. METHODS: Thirty-two patients with migraine (25 females) and 32 healthy control subjects (25 females) age-, ethnicity-, and gender-matched participated in our study. Magnetic resonance imaging (MRI) scans were collected from each participant. Then, voxel-based morphometry (VBM) was utilized to find any gray matter (GM) volume differences between migraine patients and controls. Also, VBM was performed in specific regions-of-interest (ROIs) to compare 11 migraine patients with aura (MA) and 11 migraine patients without aura (MO). RESULTS: A significant increase in regional gray matter volume difference was observed for migraine patients compared to control subjects in the intracalcarine gyrus of the visual cortex (corrected, p<0.05). In the VBM analysis of ROIs, the similarities between the MO and MA subjects included increases in the anterior cingulate cortex (ACC), hippocampus, insula, and intracalcarine cortex, along with decreases in the ACC and insula (uncorrected, p<0.05). MO subjects had decreases in the amygdala, hippocampus, intracalcarine cortex, and thalamus, but not in the MA subjects (uncorrected, p<0.05). The MA patients had increases in the amygdala and thalamus, but not in the MO patients (uncorrected, p<0.05). DISCUSSION: It can be concluded that the visual cortex is involved in the migraine mechanism since a large increase in GM volume difference was found in migraine, MO, and MA cohorts, as well as results from previous studies. Numerous GM volume changes in MO and MA cohorts reinforce evidence that particular brain regions are a part of migraine pathophysiology, but there were some regions that do not. Further research using imaging analysis and with larger study populations should be conducted to enhance our understanding of the migraine mechanism and differences that arise between migraine groups, so that diagnosis and treatment administration can be improved.

We aimed to assess whether frontal cortex-striatum-thalamus (FCST) pathway or other grey matter (GM) structures are associated with longitudinal patterns of fatigue, namely reversible (RF) versus sustained fatigue (SF). MS patients enrolled in our prospective cohort were grouped based on their longitudinal Modified Fatigue Impact Scale (MFIS) scores: 1. SF: MFIS≥38 at the two most recent yearly assessments; 2. RF: MFIS<38 at last assessment, but presence of at least one previous MFIS≥38; 3. Never Fatigued (NF): at least five MFIS<38. Accordingly, we selected 98 patients (30 SF, 31 RF, 37 NF; age-range:29-66, female/male:76/22, Extended Disability Status Scale (EDSS)6; 13 patients with secondary progressive (SP) MS and 85 with relapsing remitting (RR) MS in remission). Disability and depression were assessed using the EDSS and CES-D, respectively. 3T T1-weighted MRI was used for voxel based morphometry (VBM) to survey for GM atrophy associated with fatigue, controlling for age, sex and EDSS. Group-wise volumetric comparison was performed on deep GM structures identified by VBM, controlling for age, sex, EDSS and CES-D score. VBM showed significant inverse relation between the MFIS cognitive subscale score and areas within the bilateral fronto-medial and fronto-orbital cortices, anterior striata, thalami, temporal poles, insulae and left lateral occipital cortex (peak FWE-p value of 0.021), and between the MFIS physical subscale and areas within the bilateral frontal poles, and frontal medial cortices (peak FWE-p value of 0.043). Volumetric analysis showed significant atrophy in the putamen (RF<NF p<0.0004; SF<NF p<0.0085) and thalamus (RF<NF p<0.00048).

Computer-aided generation of virtual worlds is vital in modern content production. To manuallycreate all the details which todays computers can visualize would be too daunting atask for any number of artists. Procedural algorithms can quickly generate content, but thecontent suffers from being repetitive. Simulation of geological processes produce good resultsbut require a lot of resources. In this report a solution is presented which combines procedural algorithms with geologicalsimulation in the form of erosion. A pre-processing stage generates a heightfield using proceduralnoise which is then eroded. The erosion is accelerated by being performed on the GPU.A road network is generated by connecting points scattered in the world. The pre-processedworld is then used to define a field function. The function is sampled in a grid as neededto produce voxels with different materials. Roads are added to the world by changing thematerial of the voxels. The voxels are then rendered as textured tiles depending on material. The generated worlds are varied and interesting, much more so than worlds created purelyby procedural methods. A world can be pre-processed within a few minutes and explored inrealtime.

Det finns flera olika metoder och tekniker för tredimensionell rendering, alla med olika för- och nackdelar som lämpar sig för olika applikationer. Voxelbaserad rendering har använts flitigt inom vetenskapliga områden, främst inom det medicinska för visualisering av volymetrisk data. Tekniken används nu inom flera olika områden för tredimensionell rendering, t.ex. i datorspel, i matematiska applikationer och vid geologisk rekonstruktion. I den här rapporten kommer voxelbaserad rendering med Marching Cubes-algoritmen undersökas för att se hur den lämpar sig för realtidsapplikationer. Området behandlas dels teoretiskt, men även praktiskt då en implementering av Marching Cubes gjordes för att genomföra några tester för att se hur prestandan påverkades. Av testerna framkom det tydligt att algoritmen lämpar sig väl för realtidsapplikationer och dagens grafikkort. Viss optimering krävs dock för att kunna utnyttjas på bästa sätt. / There are lots of different methods and techniques for three-dimensional rendering, everyone with different advantages and disadvantages that suits different applications. Voxel-based rendering has been used frequently within the scientific area, mainly within medicin for visualization of volumetric data. The technique is now used within many different areas for three-dimensional rendering, e.g. in computer games, in mathematical applications and in geological reconstruction. In this report voxel-based rendering with Marching Cubes algorithm will be researched to see how it suits for real-time applications. The area will partly be dealt with theoretically, but also practically as an implementation of Marching Cubes was done to run some tests to see how the performance was affected. From the tests it appeared cleary that the algorithm is well suited for real-time applications and today&apos;s graphics card. Though some optimization is needed to fully take advantage of it.

To characterize the relationship between dispersion-based intra-individual variability (IIVd) in neuropsychological test performance and brain volume among HIV seropositive and seronegative men and to determine the effects of cardiovascular risk and HIV infection on this relationship. Magnetic Resonance Imaging (MRI) was used to acquire high-resolution neuroanatomic data from 147 men age 50 and over, including 80 HIV seropositive (HIV+) and 67 seronegative controls (HIV-) in this cross-sectional cohort study. Voxel Based Morphometry was used to derive volumetric measurements at the level of the individual voxel. These brain structure maps were analyzed using Statistical Parametric Mapping (SPM2). IIVd was measured by computing intra-individual standard deviations (ISD’s) from the standardized performance scores of five neuropsychological tests: Wechsler Memory Scale-III Visual Reproduction I and II, Logical Memory I and II, Wechsler Adult Intelligence Scale-III Letter Number Sequencing. Total gray matter (GM) volume was inversely associated with IIVd. Among all subjects, IIVd -related GM atrophy was observed primarily in: 1) the inferior frontal gyrus bilaterally, the left inferior temporal gyrus extending to the supramarginal gyrus, spanning the lateral sulcus; 2) the right superior parietal lobule and intraparietal sulcus; and, 3) dorsal/ventral regions of the posterior section of the transverse temporal gyrus. HIV status, biological, and cardiovascular disease (CVD) variables were not linked to IIVd -related GM atrophy. IIVd in neuropsychological test performance may be a sensitive marker of cortical integrity in older adults, regardless of HIV infection status or CVD risk factors, and degree of intra-individual variability links with volume loss in specific cortical regions; independent of mean-level performance on neuropsychological tests.

京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第13231号 / 論医博第2171号 / 新制||医||1036(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 高橋 淳, 教授 宮本 享, 教授 富樫 かおり / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

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Haptics is a field of robotics that involves many aspects of engineering, requiring the collaboration of different disciplines like mechanics, electronics, control theory and computer science. Although multi-disciplinarity is an element in common with other robotic application, haptic system has the additional requirement of high performance because of the human perception requirement of 1KHz feedback rate. Such high computing requirement impacts the design of the whole haptic system but it is has particular effects in the design and implementation of haptic rendering algorithms. In the chain of software and hardware components that describe a haptic system the haptic rendering is the element that has the objective of computing the force feedback given the interaction of the user with the device.A variety of haptic rendering algorithms have been proposed in the past for the simulation of three degree of freedom (3DoF) interactions in which a single point touches a complex object as well as 6DoF interactions in which two complex objects interact in multiple points. The use of 3DoF or 6DoF algorithms depends mostly from the type of application and consequently the type of device. For example applications like virtual prototype require 6DoF interaction while many simulation applications have less stringent requirements. Apart the number of degree of freedom haptic rendering algorithms are characterized by the geometrical representation of the objects, by the use of rigid or deformable objects and by the introduction of physical properties of the object surface like friction and texture properties. Given this variety of possibilities and the presence of the human factor in the computation of haptic feedback it is hard to compare different algorithms to asses whether one specific solution performs better than any other previously proposed.The goal of the proposed work is two-fold. First this thesis proposes a framework allowing for more objective comparison of haptic rendering algorithms. Such comparison take into account the perceptual aspect of haptic interaction but tries to remove it from the comparison with the aim of obtaining an objective comparison between algorithms. Second, this thesis proposes a new haptic rendering algorithm for 3DoF interaction and one for 6DoF interaction. The first algorithm for 3DoF interaction provides interaction with rotational friction based on a simulation of the soft finger contact model. The new 6DoF interaction algorithm allows the computation of the haptic feedback of interaction between voxel models.