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Volume Differences (volume + difference)
Selected AbstractsCerebral Atrophy Measurement in Clinically Isolated Syndromes and Relapsing Remitting Multiple Sclerosis: A Comparison of Registration-Based MethodsJOURNAL OF NEUROIMAGING, Issue 1 2007Valerie M. Anderson BSc ABSTRACT Background and Purpose. Brain atrophy is a proposed marker of disease progression in multiple sclerosis (MS). Many magnetic resonance imaging-based methods of atrophy quantification exist, but their relative sensitivity and precision is unclear. Our aim was to compare atrophy rates from the brain boundary shift integral (BBSI), structural image evaluation, using normalization of atrophy (SIENA) (both registration-based methods) and segmented brain volume difference, in patients with clinically isolated syndromes (CIS), relapsing remitting MS (RRMS), and controls. Methods. Thirty-seven CIS patients, 30 with early RRMS and 16 controls had T1-weighted volumetric imaging at baseline and 1 year. Brain atrophy rates were determined using segmented brain volume difference, BBSI, and SIENA. Results. BBSI and SIENA were more precise than subtraction of segmented brain volumes and were more sensitive distinguishing RRMS subjects from controls. A strong correlation was observed between BBSI and SIENA. Atrophy rates were greater in CIS and RRMS subjects than controls (RRMS P < .001). With all methods, significantly greater atrophy rates were observed in CIS patients who developed clinically definite MS relative to subjects who did not. Conclusion. Registration-based techniques are more precise and sensitive than segmentation-based methods in measuring brain atrophy, with BBSI and SIENA providing comparable results. [source] In-situ high-pressure study of the ordered phase of ethyl propionateACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2007Roman Gajda Ethyl propionate, C5H10O2 (m.p. 199,K), has been in-situ pressure-frozen and its structure determined at 1.34, 1.98 and 2.45,GPa. The crystal structure of the new high-pressure phase (denoted ,) is different from phase , obtained by lowering the temperature. The freezing pressure of ethyl propionate at 296,K is 1.03,GPa. The molecule assumes an extended chain s-trans,trans,trans conformation, only slightly distorted from planarity. The closest intermolecular contacts in both phases are formed between carbonyl O and methyl H atoms; however, the ethyl-group H atoms in phase , form no contacts shorter than 2.58,Å. A considerable molecular volume difference of 24.2,Å3 between phases , and , can be rationalized in terms of degrees of freedom of molecules arranged into closely packed structures: the three degrees of freedom allowed for rearrangements of molecules confined to planar sheets in phase ,, but are not sufficient for obtaining a densely packed pattern. [source] Effects of brain-derived neurotrophic factor Val66Met polymorphism on hippocampal volume change in schizophreniaHIPPOCAMPUS, Issue 9 2010P. Cédric M.P. Koolschijn Abstract A functional polymorphism of the brain-derived neurotrophic factor (BDNF) gene (Val66Met) has been associated with the risk for schizophrenia and volume differences in the hippocampus. However, little is known about the association between progressive brain volume change in schizophrenia and BDNF genotype. The aim of this study was to investigate the relationship between hippocampal volume change in patients with schizophrenia and healthy control subjects and BDNF genotype. Two structural magnetic resonance imaging brain scans were acquired of 68 patients with schizophrenia and 83 healthy subjects with an interval of approximately 5 yrs. Hippocampal volume change was measured and related to BDNF genotype in patients and healthy controls. BDNF genotype was not associated with hippocampal volume change over time in patients or healthy controls, nor could we replicate earlier findings on smaller hippocampal volume in Met-carriers. However, we did find a genotype-by-diagnosis interaction at baseline demonstrating smaller hippocampal volumes in patients homozygous for the Val-allele relative to healthy Val-homozygotes. In addition, irrespective of genotype, patients showed smaller hippocampal volumes compared with healthy controls at baseline. In summary, our results suggest that the BDNF Val66Met polymorphism is not associated with hippocampal volume change over time. Nevertheless, our findings may support the possibility that BDNF affects brain morphology differently in schizophrenia patients and healthy subjects. © 2009 Wiley-Liss, Inc. [source] Non-spatial expertise and hippocampal gray matter volume in humansHIPPOCAMPUS, Issue 10 2008Katherine Woollett Abstract Previous work suggests that spatial expertise in licensed London taxi drivers is associated with differences in hippocampal gray matter volume relative to IQ-matched control subjects. Here we examined whether non-spatial expertise is associated with similar hippocampal gray matter effects. We compared medical doctors who, like taxi drivers, acquire a vast amount of knowledge over many years, with IQ-matched control subjects who had no tertiary education. Whole brain analysis of structural magnetic resonance imaging (MRI) scans using voxel-based morphometry (VBM) failed to identify any differences in gray matter volume between the groups, including in the hippocampus. Moreover, amount of medical experience that ranged from 0.5 to 22.5 yr did not correlate with gray matter volume in the hippocampus or elsewhere in the brain. We conclude that intensively acquiring a large amount of knowledge over many years is not invariably associated with hippocampal gray matter volume differences. Instead it would seem that hippocampal gray matter volume effects are more likely to be observed when the knowledge acquired concerns a complex and detailed large-scale spatial layout. © 2008 Wiley-Liss, Inc. [source] Brain structure and obesityHUMAN BRAIN MAPPING, Issue 3 2010Cyrus A. Raji Abstract Obesity is associated with increased risk for cardiovascular health problems including diabetes, hypertension, and stroke. These cardiovascular afflictions increase risk for cognitive decline and dementia, but it is unknown whether these factors, specifically obesity and Type II diabetes, are associated with specific patterns of brain atrophy. We used tensor-based morphometry (TBM) to examine gray matter (GM) and white matter (WM) volume differences in 94 elderly subjects who remained cognitively normal for at least 5 years after their scan. Bivariate analyses with corrections for multiple comparisons strongly linked body mass index (BMI), fasting plasma insulin (FPI) levels, and Type II Diabetes Mellitus (DM2) with atrophy in frontal, temporal, and subcortical brain regions. A multiple regression model, also correcting for multiple comparisons, revealed that BMI was still negatively correlated with brain atrophy (FDR <5%), while DM2 and FPI were no longer associated with any volume differences. In an Analysis of Covariance (ANCOVA) model controlling for age, gender, and race, obese subjects with a high BMI (BMI > 30) showed atrophy in the frontal lobes, anterior cingulate gyrus, hippocampus, and thalamus compared with individuals with a normal BMI (18.5,25). Overweight subjects (BMI: 25,30) had atrophy in the basal ganglia and corona radiata of the WM. Overall brain volume did not differ between overweight and obese persons. Higher BMI was associated with lower brain volumes in overweight and obese elderly subjects. Obesity is therefore associated with detectable brain volume deficits in cognitively normal elderly subjects. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Evaluation of automated brain MR image segmentation and volumetry methodsHUMAN BRAIN MAPPING, Issue 4 2009Frederick Klauschen Abstract We compare three widely used brain volumetry methods available in the software packages FSL, SPM5, and FreeSurfer and evaluate their performance using simulated and real MR brain data sets. We analyze the accuracy of gray and white matter volume measurements and their robustness against changes of image quality using the BrainWeb MRI database. These images are based on "gold-standard" reference brain templates. This allows us to assess between- (same data set, different method) and also within-segmenter (same method, variation of image quality) comparability, for both of which we find pronounced variations in segmentation results for gray and white matter volumes. The calculated volumes deviate up to >10% from the reference values for gray and white matter depending on method and image quality. Sensitivity is best for SPM5, volumetric accuracy for gray and white matter was similar in SPM5 and FSL and better than in FreeSurfer. FSL showed the highest stability for white (<5%), FreeSurfer (6.2%) for gray matter for constant image quality BrainWeb data. Between-segmenter comparisons show discrepancies of up to >20% for the simulated data and 24% on average for the real data sets, whereas within-method performance analysis uncovered volume differences of up to >15%. Since the discrepancies between results reach the same order of magnitude as volume changes observed in disease, these effects limit the usability of the segmentation methods for following volume changes in individual patients over time and should be taken into account during the planning and analysis of brain volume studies. Hum Brain Mapp, 2009. © 2008 Wiley-Liss, Inc. [source] The Impact of Foreign Equity Ownership on Emerging Market Share Price VolatilityINTERNATIONAL FINANCE, Issue 1 2000Mark Coppejans We ask whether foreign equity ownership affects the stability of share prices in an emerging economy. We address the effect of ownership restrictions exogenously imposed on stock ownership and the impact of introducing or widening foreign ownership through cross-listing. A methodology for variance ratio analysis is introduced that corrects for liquidity and volume differences across stock series experiencing different degrees of foreign ownership. We find that foreign ownership does not affect volatility in the absence of cross-listing. Foreign ownership introduced or accompanied by cross-listing of a stock series raises the variance of returns. This effect is found to operate in part through increases in volume traded on the domestic market following the listing, and through an identifiable increase in the volatility of information net of volume effects. [source] Hippocampal volume and antidepressant response in geriatric depressionINTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 6 2002Ming-Hong Hsieh Abstract Background Biological markers of treatment response may include structural brain changes seen on neuroimaging. While most imaging studies have focused on cerebrovascular disease, evidence is growing that the hippocampus may play a role in depression, particularly geriatric depression. Method We studied 60 depressed elderly patients enrolled in a longitudinal study who were treated with antidepressant medications using a treatment guideline-based approach. Baseline and 12-week Montgomery-Asberg Depression Rating Scale (MADRS) scores were obtained via interview with a geriatric psychiatrist. All subjects had a baseline magnetic resonance imaging (MRI) brain scan. MRI scans were processed using standard protocols to determine total cerebral volume and right and left hippocampal volumes. Hippocampal volumes were standardized for total cerebral volume. MADRS scores less than 10 were used to define remission. Results When the group with the lowest quartile of standardized hippocampal volumes was compared to those above the first quartile, those with small right and total hippocampal volumes were less likely to achieve remission. In a subsequent logistic regression model controlling for age small standardized right hippocampal volumes remained significantly associated with remission. Conclusion Further studies with larger sample are needed to determine if left-right hippocampal volume differences do exist in depression, and basic neuroscience studies will need to elucidate the role of the hippocampus in geriatric depression. Copyright © 2002 John Wiley & Sons, Ltd. [source] Intratesticular arterial resistance and testicular volume in infertile men with subclinical varicoceleJOURNAL OF CLINICAL ULTRASOUND, Issue 8 2004Nevbahar Akcar MD Abstract Purpose The aim of this study was to evaluate whether intratesticular arterial resistance and testicular volume differed between infertile men with subclinical varicoceles and infertile men without varicoceles. Materials and Methods Fifty-eight infertile men were examined by gray-scale and color Doppler sonography for presence of varicocele, testicular volume, and arterial resistance. For men in the study group, mean testicular volume and resistance index (RI) in testes with varicoceles were compared with those in the contralateral testis by the paired t-test; statistical analyses between the study and control groups were performed by independent t-tests. Results Twenty-seven men had left-sided varicoceles (96% of which were subclinical), and 31 infertile men without varicoceles served as controls. Mean volumes of the right and left testes of study subjects were 14.8 ml and 14.6 ml, respectively, and in controls were 14.2 ml and 13.6 ml, respectively. Mean RI values for the right and left testes of study subjects were 0.61 and 0.58, respectively, and in controls were 0.61 and 0.58, respectively. There were no statistically significant differences in volume or RI, either between the right and left testes within patient groups or between the control and study groups' combined mean values. While the mean intertesticular volume differences for the study and control groups were 2.2 ml and 3.4 ml, respectively, the mean intertesticular RI differences were 0.04 and 0.07, respectively. These values also did not differ significantly between the 2 groups. Conclusions Subclinical varicocele is not associated with ipsilateral testicular atrophy, and does not affect the intratesticular arterial RI. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:389,393, 2004 [source] | |||||||||||||