检索结果-内蒙古大学图书馆

A robust method for extraction and automatic segmentation of brain images

NEUROimage 2002年第3期17卷 1087-1100页

作者： Kovacevic, N Lobaugh, NJ Bronskill, MJ Levine, B Feinstein, A Black, SE Sunnybrook & Womens Coll Hlth Sci Ctr Toronto ON Canada Univ Toronto Toronto ON Canada Rotman Res Inst Baycrest Ctr Geriatr Care Toronto ON Canada

A new protocol is introduced for brain extraction and automatic tissue segmentation of MR images. For the brain extraction algorithm, proton density and T2-weighted images are used to generate a brain mask encompassing the full intracranial cavity. Segmentation of brain tissues into gray matter (GM), white matter (WM), and cerebral spinal fluid (CSF) is accomplished on a T1-weighted image after applying the brain mask. The fully automatic segmentation algorithm is histogram-based and uses the Expectation Maximization algorithm to model a four-Gaussian mixture for both global and local histograms. The means of the local Gaussians for GM, WM, and CSF are used to set local thresholds for tissue classification. Reproducibility of the extraction procedure was excellent, with average variation in intracranial. capacity (TIC) of 0.13 and 0.66% TIC in 12 healthy normal and 33 Alzheimer brains, respectively. Repeatability of the segmentation algorithm, tested on healthy normal images, indicated scan-rescan differences in global tissue volumes of less than 0.30% TIC. Reproducibility at the regional level was established by comparing segmentation results within the 12 major Talairach subdivisions. Accuracy of the algorithm was tested on a digital brain phantom, and errors were less than 1% of the phantom volume. Maximal Type I and Type II classification errors were low, ranging between 2.2 and 4.3% of phantom volume. The algorithm was also insensitive to variation in parameter initialization values. The protocol is robust, fast, and its success in segmenting normal as well as diseased brains makes it an attractive clinical application. (C) 2002 Elsevier Science (USA).

关键词： Adult Aged Algorithms Alzheimer Disease/diagnosis Brain/pathology Humans image processing, computer-assisted/methods Magnetic Resonance Imaging/methods Normal Distribution Phantoms, Imaging Reference Values

来源：评论

学校读者我要写书评

暂无评论

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

引用

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

来源：评论

学校读者我要写书评

暂无评论

Factors underlying prefrontal and insula structural alterations in smokers

引用

NEUROimage 2011年第1期54卷 42-48页

作者： Zhang, Xiaochu Salmeron, Betty Jo Ross, Thomas J. Geng, Xiujuan Yang, Yihong Stein, Elliot A. Natl Inst Drug Abuse Neuroimaging Res Branch Intramural Res Program NIH Baltimore MD 21224 USA

Based upon previous reports of alterations in white matter integrity and gray matter density in smokers, we examined these markers in a large, well-matched sample of smokers and non-smokers. We further investigated the effect of heavy cigarette exposure by using pack-years and the effects of two relatively stable, highly heritable traits in smokers (Fagerstrom Test of Nicotine Dependence (FIND), a measure of severity of nicotine dependence and Toronto Alexithymia Scale (TAS-20), a stable personality trait related to smoking). Forty-eight nicotine-dependent subjects and 48 matched controls were included in the analyses, with smokers also subdivided into high/low dependence and high/low pack-years smokers. White matter integrity (fractional anisotropy (FA)) and gray matter density (voxel-based morphometry (VBM)) were measured and compared across groups. Gray matter density was lower in left prefrontal cortex (PFC) in high pack-years smokers and was inversely related to pack-years. In contrast, left insular cortex gray matter density was higher in smokers and associated with TAS-20 total score and with difficulty-identifying-feelings factor. Further, the most highly dependent smokers showed lower prefrontal FA, which was negatively correlated with FEND. There was no correlation between pack-years and FIND in our smoker population. These data suggest chronic tobacco use is correlated with prefrontal gray matter damage, while differences in insula gray matter and PFC white matter appear to reflect stable and heritable differences between smokers and non-smokers. Published by Elsevier Inc.

关键词： Brain Damage, Chronic/etiology Cerebral Cortex/pathology Emotions Humans image processing, computer-assisted/methods Magnetic Resonance Imaging/methods Nerve Degeneration/pathology Prefrontal Cortex/pathology Smoke/adverse effects Smoking/genetics Smoking/genetics Smoking/pathology Smoking/pathology Smoking/psychology Smoking/psychology Thinking

来源：评论

学校读者我要写书评

暂无评论

Improving reliability of subject-level resting-state fMRI parcellation with shrinkage estimators

引用

NEUROimage 2015年 112卷 14-29页

作者： Mejia, Amanda F. Nebel, Mary Beth Shou, Haochang Crainiceanu, Ciprian M. Pekar, James J. Mostofsky, Stewart Caffo, Brian Lindquist, Martin A. Johns Hopkins Univ Dept Biostat Baltimore MD 21205 USA Kennedy Krieger Inst Ctr Neurodev & Imaging Res Baltimore MD 21205 USA Johns Hopkins Sch Med Dept Radiol Baltimore MD USA Kennedy Krieger Inst FM Kirby Res Ctr Funct Brain Imaging Baltimore MD USA Johns Hopkins Sch Med Dept Neurol Baltimore MD USA Johns Hopkins Sch Med Dept Psychiat & Behav Sci Baltimore MD USA Univ Penn Dept Biostat & Epidemiol Philadelphia PA 19104 USA

A recent interest in resting state functional magnetic resonance imaging (rsfMRI) lies in subdividing the human brain into anatomically and functionally distinct regions of interest. For example, brain parcellation is often a necessary step for defining the network nodes used in connectivity studies. While inference has traditionally been performed on group-level data, there is a growing interest in parcellating single subject data. However, this is difficult due to the inherent low signal-to-noise ratio of rsfMRI data, combined with typically short scan lengths. A large number of brain parcellation approaches employ clustering, which begins with a measure of similarity or distance between voxels. The goal of this work is to improve the reproducibility of single-subject parcellation using shrinkage-based estimators of such measures, allowing the noisy subject-specific estimator to "borrow strength" in a principled manner from a larger population of subjects. We present several empirical Bayes shrinkage estimators and outline methods for shrinkage when multiple scans are not available for each subject. We perform shrinkage on raw inter-voxel correlation estimates and use both raw and shrinkage estimates to produce parcellations by performing clustering on the voxels. While we employ a standard spectral clustering approach, our proposed method is agnostic to the choice of clustering method and can be used as a pre-processing step for any clustering algorithm. Using two datasets - a simulated dataset where the true parcellation is known and is subject-specific and a test-retest dataset consisting of two 7-minute resting-state fMRI scans from 20 subjects - we show that parcellations produced from shrinkage correlation estimates have higher reliability and validity than those produced from raw correlation estimates. Application to test-retest data shows that using shrinkage estimators increases the reproducibility of subject-specific parcellations of the motor cortex by

关键词： Algorithms Bayes Theorem Brain/anatomy & histology Brain/physiology Brain Mapping Brain Mapping Cluster Analysis Humans image processing, computer-assisted/methods image processing, computer-assisted/statistics & numerical data Magnetic Resonance Imaging/methods Models, Statistical Motor Cortex/anatomy & histology Motor Cortex/physiology Neural Pathways/physiology Reproducibility of Results Rest/physiology Signal-To-Noise Ratio

来源：评论

学校读者我要写书评

暂无评论

Spatial extent of pigment epithelial detachments in age-related macular degeneration

引用

OPHTHALMOLOGY 1999年第9期106卷 1830-1840页

作者： Kunze, C Elsner, AE Beausencourt, E Moraes, L Hartnett, ME Trempe, CL Schepens Eye Res Inst Boston MA 02114 USA Schepens Retina Assoc Boston MA USA Harvard Univ Sch Med Boston MA USA Univ Klin Augenheilkunde & Optometrie Innsbruck Austria Augenklin Univ Regensburg Germany Univ Estadual Campinas Campinas Brazil

Objective: To quantify the spatial extent of pigment epithelial detachment (PED) associated with age-related macular degeneration (AMD) using a rapid, noninvasive method. Design: Prospective, cross-sectional study. Participants: The authors tested 32 eyes of 21 patients (13 women and 8 men) with AMD 56 to 91 years of age (mean = 72.8 years). The authors retested seven eyes of six patients. Intervention: Three-dimensional imaging and quantification of FED were performed in each subject using confocal infrared imaging (790 nm) with a Topographic Scanning System (TopSS), The data consisted of a series of 32 images within a 3-mm-depth range requiring 0.9 second. Three-dimensional calculations were made from the series. Main Outcome Measure: Height, diameter, area, volume, and slope of each FED were obtained with two calculation methods. The Ellipse Method used a graphics tool to draw elliptical borders circumscribing the region of interest in the image. The software automatically calculated the values for all parameters for the region inside the ellipse, with the retinal reference plane adjusted to match the height of the surrounding retina. The User-Defined Region Method differed in that the region of interest was drawn manually. Results: PEDs were easily detected in all patients using the TopSS. Maximum height of all PEDs above the reference plane ranged from 0.204 to 1.818 mm (mean = 0.57 mm). The diameter was 0.501 to 5.151 mm (mean = 2.711 mm), area was 0.179 to 20.402 mm(2) (mean = 6.585 mm2), and volume was 0.012 to 13.981 mm(3) (mean = 2.173 mm(3)). Intraobserver variability was low, with correlations between first and second measurements for the first visit ranging from r = 0.906 to 0.997 for slope and diameter, respectively. Conclusions: Three-dimensional analysis with the TopSS provides objective outcome measures not obtainable with typical clinical methods such as fundus photography and angiography. Height and volume are crucial in determining whether neovas

关键词： Aged Aged, 80 and over Cross-Sectional Studies Diagnostic Techniques, Ophthalmological Female Fluorescein Angiography Fundus Oculi Humans image processing, computer-assisted/methods Macular Degeneration/complications Male Middle Aged Pigment Epithelium of Eye/pathology Prospective Studies Retinal Detachment/diagnosis Retinal Detachment/etiology Tomography/methods

来源：评论

学校读者我要写书评

暂无评论

Single-trial coupling of the gamma-band response and the corresponding BOLD signal

引用

NEUROimage 2010年第3期49卷 2238-2247页

作者： Mulert, C. Leicht, G. Hepp, P. Kirsch, V. Karch, S. Pogarell, O. Reiser, M. Hegerl, U. Jaeger, L. Moller, H. J. McCarley, R. W. Univ Munich Dept Psychiat & Psychotherapy D-80336 Munich Germany Harvard Univ Dept Psychiat Sch Med Brockton MA 02401 USA VA Boston Healthcare Syst Brockton MA USA Univ Med Ctr Hamburg Eppendorf Ctr Psychosocial Med Dept Psychiat & Psychotherapy Hamburg Germany Univ Munich Inst Clin Radiol D-80336 Munich Germany Univ Leipzig Dept Psychiat & Psychotherapy Leipzig Germany

Oscillations in the gamma-band frequency range have been described to be more closely connected to hemodynamic changes as assessed with functional magnetic resonance imaging (fMRI) than other aspects of neuronal activity. In addition. gamma-band oscillations have attracted much interest during the last few years since they are thought to play a Crucial role in many aspects of brain function related to perception and cognition. It was the aim of the present simultaneous EEG-fMRI Study to identify brain regions specifically involved in the generation of the auditory gamma-band response (GBR) using single-trial coupling of EEG and fMRI. Ten healthy Subjects participated in this study Three different runs of an auditory choice reaction task with increasing difficulty were performed Brain activity was recorded simultaneously with high density FEG (61 channels) and fMRI (1.5 T). BOLD correlates of the GBR have been predicted using the sing-le-trial amplitude of the GBR Reaction times (p<0.001). error rates (p<005) and self-ratings of task difficulty and effort demands (p<0.001) were related to the level of difficulty in the task In addition,we found a significant influence of task difficulty oil the amplitude of the GBR at Cz (p<0.05). Using single-trial Coupling of EEG and fMRI GBR-specific activations were found only in the auditory cortex, the thalamus and the anterior cingulate cortex (ACC) in the most difficult run. Single-trial coupling might be a useful method in order to increase our knowledge about the functional neuroanatomy of "neural ensembles" coupled by 40 Hz oscillations (C) 2009 Elsevier Inc. All rights reserved

关键词： Acoustic Stimulation Adult Brain/anatomy & histology Brain/physiology Brain Mapping/methods Brain Mapping/methods Electroencephalography Evoked Potentials, Auditory/physiology Female Humans image processing, computer-assisted/methods Magnetic Resonance Imaging Male Neural Pathways/anatomy & histology Neural Pathways/physiology Reaction Time/physiology Signal processing, computer-assisted Young Adult

来源：评论

学校读者我要写书评

暂无评论

Automatic segmentation of thalamic nuclei from diffusion tensor magnetic resonance imaging

引用

NEUROimage 2003年第2期19卷 391-401页

作者： Wiegell, MR Tuch, DS Larsson, HBW Wedeen, VJ Massachusetts Gen Hosp Athinoula A Martinos Ctr Biomed Imaging Charlestown MA 02129 USA Hvidovre Univ Hosp Danish Res Ctr Magnet Resonance DK-2650 Hvidovre Denmark Harvard Univ MIT Div Hlth Sci & Technol Cambridge MA 02139 USA

The nuclei of the thalamus have traditionally been delineated by their distinct cyto/myeloarchitectural appearance on histology. Here, we show that diffusion tensor magnetic resonance imaging (DTI) can noninvasively resolve the major thalamic nuclei based on the characteristic fiber orientation of the corticothalamic/thalamocortical striations within each nucleus. Using an automatic clustering algorithm, we extracted the Talairach coordinates for the individual thalamic nuclei. The center-of-mass coordinates for the segmented nuclei were found to agree strongly with those obtained from a histological atlas. The ability to resolve thalamic nuclei with DTI will allow for morphometric analysis of specific nuclei and improved anatomical localization of functional activation in the thalamus. (C) 2003 Elsevier Science (USA). All rights reserved.

关键词： Algorithms Brain Mapping/methods Brain Mapping/methods Cerebral Cortex/anatomy & histology Diffusion Magnetic Resonance Imaging/methods Dominance, Cerebral/physiology Humans image processing, computer-assisted/methods Neural Pathways/anatomy & histology Sensitivity and Specificity Synaptic Transmission/physiology Thalamic Nuclei/anatomy & histology

来源：评论

学校读者我要写书评

暂无评论

Reducing the unwanted draining vein BOLD contribution in fMRI with statistical post-processing methods

引用

NEUROimage 2007年第1期37卷 177-188页

作者： Nencka, Andrew S. Rowe, Daniel B. Med Coll Wisconsin Dept Biophys Milwaukee WI 53226 USA

Recent BOLD fMRI data analysis methods show promise in reducing contributions from draining veins. The phase regressor method developed by [Menon, R.S., 2002. Post-acquisition suppression of large-vessel BOLD signals in high-resolution fMRI. Magn. Reson. Med., 47, 1-9] creates phase and magnitude images, regresses magnitude as a function of phase, and subtracts phase-estimated magnitudes from the observed magnitudes. The corrected magnitude images are used to compute cortical activations. The complex constant phase method, developed by [Rowe, D.B., Logan, B.R., 2004. A complex way to compute fMRI activation. Neuroimage, 23, 1078-1092], uses complex-valued reconstructed images and a nonlinear regressor model to compute magnitude cortical activations assuming temporally constant phase. In both methods, the usage of the phase information is claimed to bias against voxels with task-related phase changes caused by some draining veins. The behavior of the statistical methods in data with several task-related magnitude and phase changes is compared. The power of the statistical methods for determining voxels with specific task-related magnitude and phase change combinations are determined in ideal simulated data. The phase regressor and complex constant phase activation determination techniques are examined to characterize the responses of the models to select task-related phase and magnitude change combinations in representative simulated time series. Possible draining veins in human preliminary data are discussed and analyzed with the models and the current challenges which prevent these methods from being reliably implemented are discussed. (c) 2007 Elsevier Inc. All rights reserved.

关键词： Algorithms Artifacts Cerebral Angiography Cerebral Angiography Cerebral Cortex/blood supply Cerebral Cortex/physiology Cerebral Veins Evoked Potentials, Motor/physiology Fourier Analysis Fourier Analysis Humans image processing, computer-assisted/methods Magnetic Resonance Imaging/methods Models, Statistical Motor Activity/physiology Motor Cortex/blood supply Motor Cortex/physiology Nonlinear Dynamics Oxygen/blood Software

来源：评论

学校读者我要写书评

暂无评论

INITIAL REACTION-KINETICS OF SUCCINATE-DEHYDROGENASE IN MOUSE-LIVER STUDIED WITH A REAL-TIME image ANALYZER SYSTEM

引用

HISTOCHEMISTRY 1992年第1期98卷 7-12页

作者： NAKAE, Y STOWARD, PJ UNIV DUNDEE DEPT ANAT & PHYSIOLDUNDEE DD1 4HNSCOTLAND

The initial reaction kinetics of succinate dehydrogenase in situ were investigated in sections of mouse unfixed liver using an ARGUS-100 image analyser system. The sections were incubated on substrate-containing agarose gel films. images of a section, illuminated with monochromatic light (584 nm), were captured with the image analyser in real time at intervals of 10 s during the incubation. The absorbances of selected hepatocytes in the successive images were determined as a function of time. In every cell, the absorbance increased nonlinearly after the first minute of incubation. The initial velocity of the dehydrogenase was calculated from the linear activities during the first 20 s of incubation. Hanes plots of the initial velocities and succinate concentration yielded the following mean kinetic constants. For periportal hepatocytes, the apparent K(m) = 1.2 +/- 0.8 mM and V(max) = 29 +/- 2-mu-mol hydrogen equivalents formed/cm3 hepatocyte cytoplasm per min. For pericentral hepatocytes, K(m) = 1.4 +/- 1.0 mM and V(max) = 21 +/- 2-mu-mol hydrogen equivalents/cm3 per min. The K(m) values are very similar to those determined previously from biochemical assays. These results, and the observed dependence of the initial velocity on the enzyme concentration, suggest that the technique reported here is valid for the histochemical assay of succinate dehydrogenase.

关键词： Animals Calibration image processing, computer-assisted/methods Kinetics Liver/enzymology Male Mice Mice, Inbred Strains Microtomy Microtomy Sepharose Succinate Dehydrogenase/metabolism Succinate Dehydrogenase/metabolism

来源：评论

学校读者我要写书评

暂无评论

Dual-Core Beamformer for obtaining highly correlated neuronal networks in MEG

引用

NEUROimage 2011年第1期54卷 253-263页

作者： Diwakar, Mithun Huang, Ming-Xiong Srinivasan, Ramesh Harrington, Deborah L. Robb, Ashley Angeles, Annemarie Muzzatti, Laura Pakdaman, Reza Song, Tao Theilmann, Rebecca J. Lee, Roland R. Univ Calif San Diego Radiol Imaging Lab Dept Radiol San Diego CA 92121 USA Univ Calif San Diego Dept Bioengn San Diego CA 92121 USA VA San Diego Healthcare Syst Res Serv San Diego CA USA VA San Diego Healthcare Syst Serv Radiol San Diego CA USA Univ Calif Irvine Dept Cognit Sci Irvine CA 92717 USA Univ Calif Irvine Dept Biomed Engn Irvine CA USA

The "Dual-Core Beamformer" (DCBF) is a new lead-field based MEG inverse-modeling technique designed for localizing highly correlated networks from noisy MEG data. Conventional beamformer techniques are successful in localizing neuronal sources that are uncorrelated under poor signal-to-noise ratio (SNR) conditions. However, they fail to reconstruct multiple highly correlated sources. Though previously published dual-beamformer techniques can successfully localize multiple correlated sources, they are computationally expensive and impractical, requiring a priori information. The DCBF is able to automatically calculate optimal amplitude-weighting and dipole orientation for reconstruction, greatly reducing the computational cost of the dual-beamformer technique. Paired with a modified Powell algorithm, the DCBF can quickly identify multiple sets of correlated sources contributing to the MEG signal. Through computer simulations, we show that the DCBF quickly and accurately reconstructs source locations and their time-courses under widely varying SNR, degrees of correlation, and source strengths. Simulations also show that the DCBF identifies multiple simultaneously active correlated networks. Additionally, DCBF performance was tested using MEG data in humans. In an auditory task, the DCBF localized and reconstructed highly correlated left and right auditory responses. In a median-nerve stimulation task, the DCBF identified multiple meaningful networks of activation without any a priori information. Altogether, our results indicate that the DCBF is an effective and valuable tool for reconstructing correlated networks of neural activity from MEG recordings. Published by Elsevier Inc.

关键词： Algorithms Brain/physiology computer Simulation Electric Stimulation Evoked Potentials, Somatosensory/physiology Humans image processing, computer-assisted/methods Magnetoencephalography/methods Magnetoencephalography/methods Median Nerve/physiology Models, Neurological Nerve Net/physiology Neurons/physiology Signal Transduction

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：