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Labeling of ambiguous subvoxel fibre bundle configurations in high angular resolution diffusion MRI

NEUROimage 2008年第1期41卷 58-68页

作者： Savadjiev, Peter Campbell, Jennifer S. W. Descoteaux, Maxime Deriche, Rachid Pike, G. Bruce Siddiqi, Kaleem McGill Univ Ctr Intelligent Machines Montreal PQ Canada McGill Univ Sch Comp Sci Montreal PQ Canada McGill Univ McConnell Brain Imaging Ctr Montreal Neurol Inst Montreal PQ Canada INRIA Sophia Antipolis Project Team Odyssee Sophia Antipolis France

Whereas high angular resolution reconstruction methods for diffusion MRI can estimate multiple dominant fibre orientations within a single imaging voxel, they are fundamentally limited in certain cases of complex subvoxel fibre structures, resulting in ambiguous local orientation distribution functions. In this article we address the important problem of disambiguating such complex subvoxel fibre tract configurations, with the purpose of improving the performance of fibre tractography. We do so by extending a curve inference method to distinguish between the cases of curving and fanning fibre bundles using differential geometric estimates in a local neighbourhood. The key benefit of this method is the inference of curves, instead of only fibre orientations, to model the underlying fibre bundles. This in turn allows distinct fibre geometries that contain nearly identical sets of fibre orientations at a voxel, to be distinguished from one another. Experimental results demonstrate the ability of the method to successfully label voxels into one of the above categories and improve the performance of a fibre-tracking algorithm. (c) 2008 Elsevier Inc. All rights reserved.

关键词： Adult Algorithms Brain/anatomy & histology Brain/cytology Diffusion Magnetic Resonance Imaging/methods Diffusion Magnetic Resonance Imaging/statistics & numerical data Humans image processing, computer-assisted/methods image processing, computer-assisted/statistics & numerical data Motor Cortex/cytology Motor Cortex/physiology Nerve Fibers/physiology Neural Pathways/anatomy & histology Neural Pathways/cytology Neural Pathways/physiology

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Investigation of spatial resolution, partial volume effects and smoothing in functional MRI using artificial 3D time series

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NEUROimage 2008年第2期41卷 346-353页

作者： Weibull, A. Gustavsson, H. Mattsson, S. Svensson, J. Lund Univ Dept Med Radiat Phys SE-20502 Malmo Sweden Siemens Med Solut Malmo Sweden

This work addresses the balance between temporal signal-to-noise ratio (tSNR) and partial volume effects (PVE) in functional magnetic resonance imaging (fMRI) and investigates the impact of the choice of spatial resolution and smoothing. In fMRI, since physiological time courses are monitored, tSNR is of greater importance than image SNR. Improving SNR by an increase in voxel volume may be of negligible benefit when physiological fluctuations dominate the noise. Furthermore, at large voxel volumes, PVE are more pronounced, leading to an overall loss in performance. Artificial fMRI time series, based on high-resolution anatomical data, were used to simulate BOLD activation in a controlled manner. The performance was subsequently quantified as a measure of how well the resulted activation matched the simulated activation. The performance was highly dependent on the spatial resolution. At high contrast-to-noise ratio (CNR), the optimal voxel volume was small, i.e. in the region of 2(3) mm(3). It was also shown that using a substantially larger voxel volume in this case could potentially negate the CNR benefits. The optimal smoothing kernel width was dependent on the CNR, being larger at poor CNR. At CNR > 1, little or no smoothing proved advantageous. The use of artificial time series gave an opportunity to quantitatively investigate the effects of partial volume and smoothing in single subject fMRI. It was shown that a proper choice of spatial resolution and smoothing kernel width is important for fMRI performance. (c) 2008 Elsevier Inc. All rights reserved.

关键词： Artifacts Brain/physiology Female Humans image processing, computer-assisted/methods Magnetic Resonance Imaging Models, Neurological

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The Retinal Vasculature as a Fractal: Methodology, Reliability, and Relationship to Blood Pressure

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OPHTHALMOLOGY 2008年第11期115卷 1951-1956页

作者： Liew, Gerald Wang, Jie Jin Cheung, Ning Zhang, Yong Ping Hsu, Wynne Lee, Mong Li Mitchell, Paul Tikellis, Gabriella Taylor, Bronwen Wong, Tien Yin Univ Sydney Ctr Vis Sci Sydney NSW 2006 Australia Univ Melbourne Royal Victorian Eye & Ear Hosp Ctr Eye Res Australia Melbourne Vic Australia Ningbo Univ Technol Sch Elect & Informat Engn Ningbo Peoples R China Natl Univ Singapore Yong Loo Lin Sch Med Singapore Eye Res Inst Singapore 117595 Singapore Natl Univ Singapore Sch Comp Singapore 117548 Singapore

Objective: Fractals represent a type of derived geometric pattern that permits the characterization of the branching pattern of retinal vessels. We examined a new semiautomated method to measure retinal vessel fractals. Design: Methodology study. Participants: Three hundred randomly selected participants from the population-based Blue Mountains Eye Study. methods: We developed a semiautomated computer program to measure the fractal dimension (D-f) of the retinal vessels from digitized images of disk-centered retinal photographs. Two trained graders masked to participant characteristics measured D-f of right eye images of participants. Reliability was determined by repeat grading of the images from 60 participants, and association with systolic and diastolic blood pressure was examined in all 300 participants. Main Outcome Measure: D-f of the retinal vessels. Results: Mean D-f was 1.437 with a standard deviation of 0.025. Intragrader and intergrader reliability estimates were high with intraclass correlation ranging from 0.93 to 0.95. D-f was inversely correlated with age (r = -0.42, P = 0.001) and systolic blood pressure (r = -0.29, P<0.0001). After adjustment for age and sex, mean Df was significantly lower in participants with than without hypertension (D-f difference 0.01, P = 0.02). Conclusions: The D-f of the retinal vessels can be reliably measured from photographs and shows a strong inverse correlation with blood pressure. These data suggest that the D-f may be a measure of early microvascular alterations from elevated blood pressure. Further studies to examine the systemic and ocular correlates of the D-f of the retinal vessels are needed. Financial Disclosure(s). The authors have no proprietary or commercial interest in any materials discussed in this article. Ophthalmology 2008;115:1951-1956 (C) 2008 by the American Academy of Ophthalmology.

关键词： Aged Aged, 80 and over Aging/physiology Blood Pressure/physiology Female Fractals Humans image processing, computer-assisted/methods Male Middle Aged Photography Reproducibility of Results Retinal Vessels/anatomy & histology

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Complementary information from multi-exponential T₂ relaxation and diffusion tensor imaging reveals differences between multiple sclerosis lesions

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NEUROimage 2008年第1期40卷 77-85页

作者： Kolind, Shannon H. Laule, Comelia Vavasour, Irene M. Li, David K. B. Traboulsee, Anthony L. Maedler, Burkhard Moore, G. R. Wayne MacKay, Alex L. Univ British Columbia MRI Res Ctr Vancouver BC V6T 2B5 Canada Univ British Columbia Dept Radiol Vancouver BC V5Z 1M9 Canada Univ British Columbia Dept Med Vancouver BC V5Z 1M9 Canada Univ British Columbia Dept Pathol & Lab Med Vancouver BC V5Z 1M9 Canada

While conventional magnetic resonance imaging (MRI) has long been used to study multiple sclerosis (MS), more sensitive and specific approaches to studying both MS lesions and normal appearing white matter (NAWM) are needed to gain a better understanding of the pathogenesis of the disease. Two MRI techniques thought to offer insight regarding myelin and axonal integrity are T-2 relaxation and diffusion tensor imaging (DTI). In this study, metrics obtained from T-2 relaxation (specifically myclin water content (MWC) and long-T-2 fraction) and DTI experiments (in particular the fractional anisotropy, mean diffusivity < D >, parallel diffusivity lambda(parallel to) and perpendicular diffusivity lambda(perpendicular to)) were compared for 19 MS patients within both lesion and contralateral NAWM with the goal of better understanding how each of the measures are affected by pathology. In particular, it was successfully determined that the detection of a long-T-2 signal within an MS lesion is indicative of a different underlying pathology than is present in lesions without long-T-2 signal. All of the diffusion metrics were significantly different in lesions with a long-T-2 signal than in those without. While no significant correlations were found between MWC and < D >, lambda(parallel to) or lambda(perpendicular to) in NAWM (R-2 = 0.02-0.04, p > 0.07), and only weak correlations were found in lesions without long-T-2 Signal (R-2=0.05-0. 14, p < 0.04), strong correlations were observed in lesions exhibiting long-T-2 signal (R-2 =0.54-0.61, p < 0.0001). (c) 2007 Elsevier Inc. All rights reserved.

关键词： Adult Algorithms Brain/pathology Data Interpretation, Statistical Diffusion Magnetic Resonance Imaging Female Humans image processing, computer-assisted/methods Male Middle Aged Multiple Sclerosis/pathology

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The impact of skull-stripping and radio-frequency bins correction on grey-matter segmentation for voxel-based morphometry

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NEUROimage 2008年第4期39卷 1654-1665页

作者： Acosta-Cabronero, Julio Williams, Guy B. Pereira, Joao M. S. Pengas, George Nestor, Peter J. Univ Cambridge Addenbrookes Hosp Sch Clin Med Dept Clin NeurosciWolfson Brain Imaging Ctr Cambridge CB2 0QQ England Univ Cambridge Addenbrookes Hosp Sch Clin Med Dept Clin NeurosciNeurol Unit Cambridge CB2 0QQ England

This study evaluates the application of (i) skull-stripping methods (hybrid watershed algorithm (HWA), brain surface extractor (BSE) and brain-extraction tool (BET2)) and (ii) bias correction algorithms (nonparametric nonuniform intensity normalisation (N3), bias field corrector (BFC) and FMRIB's automated segmentation tool (FAST)) as pre-processing pipelines for the technique of voxel-based morphometry (VBM) using statistical parametric mapping v.5 (SPM5). The pipelines were evaluated using a BrainWeb phantom, and those that performed consistently were further assessed using artificial-lesion masks applied to 10 healthy controls compared to the original unlesioned scans, and finally, 20 Alzheimer's disease (AD) patients versus 23 controls. In each case, pipelines were compared to each other and to those from default SPM5 methodology. The BET2 + N3 pipeline was found to produce the least miswarping to template induced by real abnormalities, and performed consistently better than the other methods for the above experiments. Occasionally, the clusters of significant differences located close to the boundary were dragged out of the glass-brain projections-this could be corrected by adding background noise to low-probability voxels in the grey matter segments. This method was confirmed in a one-dimensional simulation and was preferable to threshold and explicit (simple) masking which excluded true abnormalities. (C) 2007 Elsevier Inc. All rights reserved.

关键词： Adult Aged Algorithms Alzheimer Disease/pathology Brain/anatomy & histology Brain Mapping/methods Brain Mapping/methods Echo-Planar Imaging Female Humans image processing, computer-assisted/methods Male Middle Aged Models, Statistical Skull/anatomy & histology

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Enhanced intersubject correlations during movie viewing correlate with successful episodic encoding

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NEURON 2008年第3期57卷 452-462页

作者： Hasson, Uri Furman, Orit Clark, Dav Dudai, Yadin Davachi, Lila NYU Ctr Neural Sci New York NY 10003 USA NYU Dept Psychol New York NY 10003 USA Weizmann Inst Sci Dept Neurobiol IL-76100 Rehovot Israel

While much has been learned regarding the neural substrates supporting episodic encoding using highly controlled experimental protocols, relatively little is known regarding the neural bases of episodic encoding of real-world events. In an effort to examine this issue, we measured fMRI activity while observers viewed a novel TV sitcom. Three weeks later, subsequent memory (SM) for the narrative content of movie events was assessed. We analyzed the encoding data for intersubject correlations (ISC) based on subjects' subsequent memory (ISC-SM) performance to identify brain regions whose BOLD response is significantly more correlated across subjects during portions of the movie that are successfully as compared to unsuccessfully encoded. These regions include the parahippocampal gyrus, superior temporal gyrus, anterior temporal poles, and the temporal-parietal junction. Further analyses reveal (1) that these correlated regions can display distinct activation profiles and (2) that the results seen with the ISC-SM analysis are complementary to more traditional linear models and allow analysis of complex time course data. Thus, the ISC-SM analysis extends traditional subsequent memory findings to a rich, dynamic and more ecologically valid situation.

关键词： Adult Brain/blood supply Brain/physiology Brain Mapping Brain Mapping Cues Female Humans image processing, computer-assisted/methods Learning/physiology Magnetic Resonance Imaging/methods Male Mental Recall/physiology Neuropsychological Tests Oxygen/blood Photic Stimulation/methods Recognition (Psychology)/physiology Statistics, Nonparametric

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Comparing surface-based and volume-based analyses of functional neuroimaging data in patients with schizophrenia

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NEUROimage 2008年第3期41卷 835-848页

作者： Anticevic, Alan Dierker, Donna L. Gillespie, Sarah K. Repovs, Grega Csernansky, John G. Van Essen, David C. Barch, Deanna M. Washington Univ Dept Psychol St Louis MO 63130 USA Washington Univ Sch Med Dept Anat & Neurobiol St Louis MO 63110 USA Washington Univ Sch Med Dept Psychiat St Louis MO 63110 USA

A major challenge in functional neuroimaging is to cope with individual variability in cortical structure and function. Most analyses of cortical function compensate for variability using affine or low-dimensional nonlinear volume-based registration (VBR) of individual subjects to an atlas, which does not explicitly take into account the geometry of cortical convolutions. A promising alternative is to use surface-based registration (SBR), which capitalizes on explicit surface representations of cortical folding patterns in individual subjects. In this study, we directly compare results from SBR and affine VBR in a study of working memory in healthy controls and patients with schizophrenia (SCZ). Each subject's structural scan was used for cortical surface reconstruction using the SureFit method. fMRI data were mapped directly onto individual cortical surface models, and each hemisphere was registered to the population-average PALS-B12 atlas using landmark-constrained SBR. The precision with which cortical sulci were aligned was much greater for SBR than VBR. SBR produced superior alignment precision across the entire cortex, and this benefit was greater in patients with schizophrenia. We demonstrate that spatial smoothing on the surface provides better resolution and signal preservation than a comparable degree of smoothing in the volume domain. Lastly, the statistical power of functional activation in the working memory task was greater for SBR than for VBR. These results indicate that SBR provides significant advantages over affine VBR when analyzing cortical fMRI activations. Furthermore, these improvements can be even greater in disorders that have associated structural abnormalities. (C) 2008 Elsevier Inc. All rights reserved.

关键词： Adult Brain/anatomy & histology Brain/physiology Brain Mapping/methods Brain Mapping/methods Female Humans image processing, computer-assisted/methods Magnetic Resonance Imaging Male Memory/physiology Schizophrenia/pathology Schizophrenia/physiopathology

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Self responses along cingulate cortex reveal quantitative neural phenotype for high-functioning autism

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NEURON 2008年第3期57卷 463-473页

作者： Chiu, Pearl H. Kayali, M. Amin Kishida, Kenneth T. Tomlin, Damon Klinger, Laura G. Klinger, Mark R. Montague, P. Read Baylor Coll Med Comp Psychiat Unit Houston TX 77030 USA Baylor Coll Med Div Neurosci Houston TX 77030 USA Baylor Coll Med Menninger Dept Psychiat & Behav Sci Houston TX 77030 USA Univ Alabama Dept Psychol Tuscaloosa AL 35487 USA

Attributing behavioral outcomes correctly to oneself or to other agents is essential for all productive social exchange. We approach this issue in high-functioning males with autism spectrum disorder (ASD) using two separate fMRI paradigms. First, using a visual imagery task, we extract a basis set for responses along the cingulate cortex of control subjects that reveals an agent-specific eigenvector (self eigenmode) associated with imagining oneself executing a specific motor act. Second, we show that the same self eigenmode arises during one's own decision (the self phase) in an interpersonal exchange game (iterated trust game). Third, using this exchange game, we show that ASD males exhibit a severely diminished cingulate self response when playing the game with a human partner. This diminishment covaries parametrically with their behaviorally assessed symptom severity, suggesting its value as an objective endophenotype. These findings may provide a quantitative assessment tool for high-functioning ASD.

关键词： Adolescent Adult Autistic Disorder/pathology Autistic Disorder/physiopathology Autistic Disorder/psychology Brain Mapping Brain Mapping Case-Control Studies Gyrus Cinguli/blood supply Gyrus Cinguli/physiopathology Humans image processing, computer-assisted/methods Imitative Behavior/physiology Magnetic Resonance Imaging/methods Male Mental Processes/physiology Neuropsychological Tests Oxygen/blood Phenotype Photic Stimulation/methods Principal Component Analysis Self Concept

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Morphometry of the human cerebral cortex microcirculation: General characteristics and space-related profiles

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NEUROimage 2008年第3期39卷 936-948页

作者： Lauwers, Frederic Cassot, Francis Lauviers-Cances, Valerie Puwanarajah, Prasanna Duvernoy, Henri Fac Med Toulouse Dept Anat F-31062 Toulouse France CHU Purpan INSERM U825 Funct Neuroimaging Lab F-31059 Toulouse 3 France Fac Med Dept Epidemiol & Publ Hlth F-31073 Toulouse France John Radcliffe Hosp Nuffield Dept Surg Oxford OX3 9DU England 12 Chimin Relancons F-25000 Besancon France

Studies on human brain microcirculation have thus far yielded few quantitative data, preventing the closest possible interpretation of functional imaging methods such as fMRI and PET that necessarily rely on robustly delineated morphology of haemodynamic systems. Inadequate data in this area can lead to severe underestimation of the spatial specificity of the BOLD response. We took thick sections of Indian ink injected human brain and, using confocal laser microscopy and a novel three-dimensional computer-assisted method we extracted and analyzed hundreds of thousands of vascular segments within a large area of cortex. From this database the global densities, the statistical distributions of diameters and lengths were analysed, separating the tree-like and the net-like parts of the microcirculation. Furthermore, our analysis included variations in volume density along the cortical depth and along vectors parallel to the cortical surface. These morphometric parameters are all key requirements for a sound model of cerebral microcirculation. (c) 2007 Elsevier Inc. All rights reserved.

关键词： Cerebral Cortex/anatomy & histology Cerebral Cortex/blood supply Cerebrovascular Circulation/physiology Hippocampus/anatomy & histology Hippocampus/blood supply Humans image processing, computer-assisted/methods Microcirculation/anatomy & histology Microcirculation/physiology Microscopy, Confocal

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Achalasia: A New Clinically Relevant Classification by High-Resolution Manometry

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GASTROENTEROLOGY 2008年第5期135卷 1526-1533页

作者： Pandolfino, John E. Kwiatek, Monika A. Nealis, Thomas Bulsiewicz, William Post, Jennifer Kahrilas, Peter J. Northwestern Univ Feinberg Sch Med Dept Med Div Gastroenterol Chicago IL 60611 USA

Background & Aims: Although the diagnosis of achalasia. hinges on demonstrating impaired esophagogastric junction (EGJ) relaxation and aperistalsis, 3 distinct patterns of aperistalsis are discernable with high-resolution manometry (HRM). This study aimed to compare the clinical characteristics and treatment response of these 3 subtypes. methods: One thousand clinical HRM studies were reviewed, and 213 patients with impaired EGJ relaxation were identified. These were categorized into 4 groups: achalasia with minimal esophageal pressurization (type 1, classic), achalasia with esophageal compression (type II), achalasia. with spasm (type III), and functional obstruction with some preserved peristalsis. Clinical and manometric variables including treatment response were compared among the 3 achalasia subtypes. Logistic regression analysis was performed using treatment success as the dichotomous dependent variable controlling for independent manometric and clinical variables. Results: Ninety-\nine patients were newly diagnosed with achalasia (21 type 1, 49 type II, 29 type III), and 83 of these had sufficient follow-up to analyze treatment response. Type II patients were significantly more likely to respond to any therapy (BoTox [71%], pneumatic dilation [91%], or Heller myotomy [100%]) than type 1 (56% overall) or type III (29% overall) patients. Logistic regression analysis found type II to be a predictor of positive treatment response, whereas type III and pretreatment esophageal dilatation were predictive of negative treatment response. Conclusions: Achalasia. can be categorized into 3 subtypes that are distinct in terms of their responsiveness to medical or surgical therapies. Utilizing these subclassifications would likely strengthen future prospective studies of treatment efficacy in achalasia.

关键词： Adolescent Adult Aged Aged, 80 and over Diagnosis, Differential Esophageal Achalasia/classification Esophageal Achalasia/diagnosis Esophageal Achalasia/physiopathology Esophagus/physiopathology Female Follow-Up Studies Humans image processing, computer-assisted/methods Male Manometry/methods Middle Aged Peristalsis/physiology Pressure Prognosis Reproducibility of Results Retrospective Studies Retrospective Studies Severity of Illness Index Severity of Illness Index Young Adult

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