Reliability of in vivo volume measures of hippocampus and other brain structures using MRI

Intersite brain MRI volumetric biases persist even in a harmonized multisubject study of multiple sclerosis

BACKGROUND AND PURPOSE

Multicenter study designs involving a variety of MRI scanners have become increasingly common. However, these present the issue of biases in image-based measures due to scanner or site differences. To assess these biases, we imaged 11 volunteers with multiple sclerosis (MS) with scan and rescan data at four sites.

METHODS

Images were acquired on Siemens or Philips scanners at 3 Tesla. Automated white matter lesion detection and whole-brain, gray and white matter, and thalamic volumetry were performed, as well as expert manual delineations of T1 magnetization-prepared rapid acquisition gradient echo and T2 fluid-attenuated inversion recovery lesions. Random-effect and permutation-based nonparametric modeling was performed to assess differences in estimated volumes within and across sites.

RESULTS

Random-effect modeling demonstrated model assumption violations for most comparisons of interest. Nonparametric modeling indicated that site explained >50% of the variation for most estimated volumes. This expanded to >75% when data from both Siemens and Philips scanners were included. Permutation tests revealed significant differences between average inter- and intrasite differences in most estimated brain volumes (P < .05). The automatic activation of spine coil elements during some acquisitions resulted in a shading artifact in these images. Permutation tests revealed significant differences between thalamic volume measurements from acquisitions with and without this artifact.

CONCLUSION

Differences in brain volumetry persisted across MR scanners despite protocol harmonization. These differences were not well explained by variance component modeling; however, statistical innovations for mitigating intersite differences show promise in reducing biases in multicenter studies of MS.

Machine Learning for Brain MRI Data Harmonisation: A Systematic Review

BACKGROUND

Magnetic Resonance Imaging (MRI) data collected from multiple centres can be heterogeneous due to factors such as the scanner used and the site location. To reduce this heterogeneity, the data needs to be harmonised. In recent years, machine learning (ML) has been used to solve different types of problems related to MRI data, showing great promise.

OBJECTIVE

This study explores how well various ML algorithms perform in harmonising MRI data, both implicitly and explicitly, by summarising the findings in relevant peer-reviewed articles. Furthermore, it provides guidelines for the use of current methods and identifies potential future research directions.

METHOD

This review covers articles published through PubMed, Web of Science, and IEEE databases through June 2022. Data from studies were analysed based on the criteria of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Quality assessment questions were derived to assess the quality of the included publications.

RESULTS

a total of 41 articles published between 2015 and 2022 were identified and analysed. In the review, MRI data has been found to be harmonised either in an implicit (n = 21) or an explicit (n = 20) way. Three MRI modalities were identified: structural MRI (n = 28), diffusion MRI (n = 7) and functional MRI (n = 6).

CONCLUSION

Various ML techniques have been employed to harmonise different types of MRI data. There is currently a lack of consistent evaluation methods and metrics used across studies, and it is recommended that the issue be addressed in future studies. Harmonisation of MRI data using ML shows promises in improving performance for ML downstream tasks, while caution should be exercised when using ML-harmonised data for direct interpretation.

Degeneration of the Suprachiasmatic Nucleus in an Alzheimer's Disease Mouse Model Monitored by in vivo Magnetic Resonance Relaxation Measurements and Immunohistochemistry

In Alzheimer's disease (AD), disturbances in the circadian rhythm and sleep-wake cycle are frequently observed. Both are controlled by the master clock: the suprachiasmatic nucleus (SCN), which was reported in postmortem studies of AD subjects to be compromised. However, the influence of age and gender on the biophysical integrity and subtle microstructural changes of SCN and mechanistic connections between SCN dysfunction and AD progression in vivo remain to be explored. In the present study, we utilized state-of-the-art in vivo magnetic resonance relaxation measurements in combination with immunohistochemistry to follow microstructural changes in SCN of the Tg2576 mouse model of AD. Longitudinal monitoring of in vivo T2 relaxation with age shows significant shortening of T2 values in the SCN of transgenic mice and more substantially in female transgenic than aged-matched controls. Multiexponential T2 analysis detected a unique long T2 component in SCN of transgenic mice which was absent in wild-type mice. Immunohistochemical examination revealed significantly elevated numbers of activated astrocytes and an increase in the astrocyte to neuron ratio in SCN of transgenic compared to wild-type mice. This increase was more substantial in female than in male transgenic mice. In addition, low GABA production in SCN of transgenic mice was detected. Our results offer a brief appraisal of SCN dysfunction in AD and demonstrate that inflammatory responses may be an underlying perpetrator for the changes in circadian rhythmicity and sleep disturbance in AD and could also be at the root of marked sex disparities observed in AD subjects.

MRI imaging and histopathological study of brain iron overload of β-thalassemic mice

Brain iron overload is chronic and slow progressing and plays an important role in the pathogenesis of neurodegenerative disorders. Magnetic resonance imaging (MRI) is a useful noninvasive tool for determining liver iron content, but it has not been proven to be adequate for evaluating brain iron overload. We evaluated the usefulness of MRI-derived parameters to determine brain iron concentration in β-thalassemic mice and the effects of the membrane permeable iron chelator, deferiprone. Sixteen β-thalassemic mice underwent 1.5T MRI of the brain that included a multiecho T2*-weighted sequence. Brain T2* values ranged from 28 to 31ms for thalassemic mice. For the iron overloaded thalassemic mice, brain T2* values decreased, ranging from 8 to 12ms, which correlated with the iron overload status of the animals. In addition, brain T2* values increased in the group with the treatment of deferiprone, ranging from 18 to 24ms. Our results may be useful to understand brain pathology in iron overload. Moreover, data could lead to an earlier diagnosis, assist in following disease progression, and demonstrate the benefits of iron chelation therapy.

Neural responses to children's faces: Test-retest reliability of structural and functional MRI

INTRODUCTION

Functional MRI (fMRI) is commonly used to investigate the neural mechanisms underlying psychological processes and behavioral responses. However, to draw well-founded conclusions from fMRI studies, more research on the reliability of fMRI is needed.

METHODS

We invited a sample of 41 female students to participate in two identical fMRI sessions, separated by 5 weeks on average. To investigate the potential effect of left-handedness on the stability of neural activity, we oversampled left-handed participants (N = 20). Inside the scanner, we presented photographs of familiar and unfamiliar children's faces preceded by neutral and threatening primes to the participants. We calculated intraclass correlations (ICCs) to investigate the test-retest reliability of peak activity in areas that showed significant activity during the first session (primary visual cortex, fusiform face area, inferior frontal gyrus, and superior temporal gyrus). In addition, we examined how many trials were needed to reliably measure the effects.

RESULTS

Across all participants, only fusiform face area activity in response to faces showed good test-retest reliability (ICC = 0.71). All other test-retest reliabilities were low (0.01 ≤ ICC ≤ 0.35). Reliabilities varied only slightly with increasing numbers of trials, with no consistent increase in ICCs. Test-retest reliabilities for left-handed participants (0.28 ≤ ICC ≤0.66) were generally somewhat higher than for right-handed participants (-0.13 ≤ ICC ≤0.75), but not statistically significant.

CONCLUSION

Our study shows good test-retest reliability for fusiform facer area activity in response to faces, but low test-retest reliability for other contrasts and areas.

Coronal Plane Magnetic Resonance Imaging Measurement of Hippocampal Formation Volume of Healthy Chinese Adults

The aim of this study was to provide hippocampal formation volume data for the clinic and diagnoses of the related diseases for healthy Chinese adult. Three-dimensional fast-spoiled gradient echo magnetic resonance imaging sequence scanning was used in 68 cases of healthy adult brain to gain the image between lateral border of bilateral fourth ventricle and vitreous body. The image then was divided into 10 equal parts in the sagittal plane. We draw the outline and then obtain the area and volume of the hippocampal formation in each part, and the data were analyzed using SPSS 17.0 software. Results of the research showed that the volume of the hippocampal in healthy Chinese adult left side is ∼2319.87 to 2602.47 mm, right side is ∼2443.96 to 2755.89 mm; male left side is ∼2135.00 to 2494.29 mm, right side is -2350.21 to 2745.61 mm; female left side is ∼2328.13 to 2748.41 mm, right side is ∼2398.41 to 2909.48 mm. The volume of hippocampal absence correlated with age (P > 0.05), youth group. The volume of hippocampal has significant sexual difference (t = 2.500, P < 0.05). The volumes of the left and right sides have significant difference (t = 2.571, P < 0.05). For the female group (middle-age and youth), the volumes of right side hippocampal have significant difference (P < 0.05).

Volumetric Analysis from a Harmonized Multisite Brain MRI Study of a Single Subject with Multiple Sclerosis

BACKGROUND AND PURPOSE

MR imaging can be used to measure structural changes in the brains of individuals with multiple sclerosis and is essential for diagnosis, longitudinal monitoring, and therapy evaluation. The North American Imaging in Multiple Sclerosis Cooperative steering committee developed a uniform high-resolution 3T MR imaging protocol relevant to the quantification of cerebral lesions and atrophy and implemented it at 7 sites across the United States. To assess intersite variability in scan data, we imaged a volunteer with relapsing-remitting MS with a scan-rescan at each site.

MATERIALS AND METHODS

All imaging was acquired on Siemens scanners (4 Skyra, 2 Tim Trio, and 1 Verio). Expert segmentations were manually obtained for T1-hypointense and T2 (FLAIR) hyperintense lesions. Several automated lesion-detection and whole-brain, cortical, and deep gray matter volumetric pipelines were applied. Statistical analyses were conducted to assess variability across sites, as well as systematic biases in the volumetric measurements that were site-related.

RESULTS

Systematic biases due to site differences in expert-traced lesion measurements were significant (P < .01 for both T1 and T2 lesion volumes), with site explaining >90% of the variation (range, 13.0-16.4 mL in T1 and 15.9-20.1 mL in T2) in lesion volumes. Site also explained >80% of the variation in most automated volumetric measurements. Output measures clustered according to scanner models, with similar results from the Skyra versus the other 2 units.

CONCLUSIONS

Even in multicenter studies with consistent scanner field strength and manufacturer after protocol harmonization, systematic differences can lead to severe biases in volumetric analyses.

In vivo visualization of the locus coeruleus in humans: quantifying the test-retest reliability

The locus coeruleus (LC) is a brainstem nucleus involved in important cognitive functions. Recent developments in neuroimaging methods and scanning protocols have made it possible to visualize the human LC in vivo by utilizing a T₁-weighted turbo spin echo (TSE) scan. Despite its frequent use and its application as a biomarker for tracking the progress of monoaminergic-related neurodegenerative diseases, no study to date has investigated the reproducibility and inter-observer variability of LC identification using this TSE scan sequence. In this paper, we aim to quantify the test-retest reliability of LC imaging by assessing stability of the TSE contrast of the LC across two independent scan sessions and by quantifying the intra- and inter-rater reliability of the TSE scan. Additionally, we created a probabilistic LC atlas which can facilitate the spatial localization of the LC in standardized (MNI) space. Seventeen healthy volunteers participated in two scanning sessions with a mean intersession interval of 2.8 months. We found that for intra-rater reliability the mean Dice coefficient ranged between 0.65 and 0.74, and inter-rater reliability ranged between 0.54 and 0.64, showing moderate reproducibility. The mean LC contrast was 13.9% (SD 3.8) and showed scan-rescan stability (ROI approach: ICC = 0.63; maximum intensity approach: ICC = 0.53). We conclude that localization and segmentation of the LC in vivo are a challenging but reliable enterprise although clinical or longitudinal studies should be carried out carefully.

Test-retest reliability of brain morphology estimates

Metrics of brain morphology are increasingly being used to examine inter-individual differences, making it important to evaluate the reliability of these structural measures. Here we used two open-access datasets to assess the intersession reliability of three cortical measures (thickness, gyrification, and fractal dimensionality) and two subcortical measures (volume and fractal dimensionality). Reliability was generally good, particularly with the gyrification and fractal dimensionality measures. One dataset used a sequence previously optimized for brain morphology analyses and had particularly high reliability. Examining the reliability of morphological measures is critical before the measures can be validly used to investigate inter-individual differences.

Genetic Moderation of Stress Effects on Corticolimbic Circuitry

Stress exposure is associated with individual differences in corticolimbic structure and function that often mirror patterns observed in psychopathology. Gene x environment interaction research suggests that genetic variation moderates the impact of stress on risk for psychopathology. On the basis of these findings, imaging genetics, which attempts to link variability in DNA sequence and structure to neural phenotypes, has begun to incorporate measures of the environment. This research paradigm, known as imaging gene x environment interaction (iGxE), is beginning to contribute to our understanding of the neural mechanisms through which genetic variation and stress increase psychopathology risk. Although awaiting replication, evidence suggests that genetic variation within the canonical neuroendocrine stress hormone system, the hypothalamic-pituitary-adrenal axis, contributes to variability in stress-related corticolimbic structure and function, which, in turn, confers risk for psychopathology. For iGxE research to reach its full potential it will have to address many challenges, of which we discuss: (i) small effects, (ii) measuring the environment and neural phenotypes, (iii) the absence of detailed mechanisms, and (iv) incorporating development. By actively addressing these challenges, iGxE research is poised to help identify the neural mechanisms underlying genetic and environmental associations with psychopathology.

The coronal plane magnetic resonance imaging measurement of hippocampal formation volume

The aim of this study was to provide healthy Chinese adult hippocampal formation volume data for the clinic and diagnoses of the related diseases. Three-dimensional fast spoiled gradient echo magnetic resonance imaging sequence scanning was used in 68 cases of healthy adult brain to gain the image between lateral border of bilateral fourth ventricle and vitreous body. The image then was divided into 10 equal parts in the sagittal plane. We draw the outline and then obtain the area and volume of the hippocampal formation in each part, and the data were analyzed by SPSS 17.0 software. Results of the research showed that the volume of the hippocampal in healthy Chinese adult left side is ≈ 2319.87 to 2602.47 mm3, right side is ≈ 2443.96 to 2755.89 mm3; male left side is ≈ 2135.00 to 2494.29 mm3, right side is ≈ 2350.21 to 2745.61 mm3; female left side is ≈ 2328.13 to 2748.41 mm3, right side is ≈ 2398.41 to 2909.48 mm3. The volume of hippocampal absence correlated with age (P > 0.05), youth group. The volume of hippocampal has significant sexual difference (t = 2.500, P < 0.05). The volumes of the left and right sides have significant difference (t = 2.571, P < 0.05). The female group (middle-age and youth) which the volumes of right-side hippocampal have significant difference (P < 0.05).

Three-dimensional mapping of hippocampal and amygdalar structure in euthymic adults with bipolar disorder not treated with lithium

Structural neuroimaging studies of the amygdala and hippocampus in bipolar disorder have been largely inconsistent. This may be due in part to differences in the proportion of subjects taking lithium or experiencing an acute mood state, as both factors have recently been shown to influence gray matter structure. To avoid these problems, we evaluated euthymic subjects not currently taking lithium. Thirty-two subjects with bipolar type I disorder and 32 healthy subjects were scanned using magnetic resonance imaging. Subcortical regions were manually traced, and converted to three-dimensional meshes to evaluate the main effect of bipolar illness on radial distance. Statistical analyses found no evidence for a main effect of bipolar illness in either region, although exploratory analyses found a significant age by diagnosis interaction in the right amygdala, as well as positive associations between radial distance of the left amygdala and both prior hospitalizations for mania and current medication status. These findings suggest that, when not treated with lithium or in an acute mood state, patients with bipolar disorder exhibit no structural abnormalities of the amygdala or hippocampus. Future studies, nevertheless, that further elucidate the impact of age, course of illness, and medication on amygdala structure in bipolar disorder are warranted.

In vivo measurement of transverse relaxation time in the mouse brain at 17.6 T

PURPOSE

To establish regional T1 and T2 values of the healthy mouse brain at ultra-high magnetic field strength of 17.6 T and to follow regional brain T1 and T2 changes with age.

METHODS

In vivo T1 and T2 values in the C57BL/6J mouse brain were followed with age using multislice-multiecho sequence and multiple spin echo saturation recovery with variable repetition time sequence, respectively, at 9.4 and 17.6 T. Gadolinium-tetra-azacyclo-dodecane-tetra-acetic acid phantoms were used to validate in vivo T2 measurements. Student's t-test was used to compare mean relaxation values.

RESULTS

A field-dependent decrease in T2 is shown and validated with phantom measurements. T2 values at 17.6 T typically increased with age in multiple brain regions except in the hypothalamus and the caudate-putamen, where a slight decrease was observed. Furthermore, T1 values in various brain regions of young and old mice are presented at 17.6 T. A large gain in signal-to-noise ratio was observed at 17.6 T.

CONCLUSIONS

This study establishes for the first time the normative T1 and T2 values at 17.6 T over different mouse brain regions with age. The estimates of in vivo T1 and T2 will be useful to optimize pulse sequences for optimal image contrast at 17.6 T and will serve as baseline values against which disease-related relaxation changes can be assessed in mice.

Long acting injection versus oral risperidone in first-episode schizophrenia: differential impact on white matter myelination trajectory

CONTEXT

Imaging and post-mortem studies provide converging evidence that subjects with schizophrenia (SZ) have a dysregulated trajectory of frontal lobe myelination. Prior MRI studies suggested that early in treatment of SZ, antipsychotic medications initially increase frontal lobe white matter (WM) volume, which subsequently declines prematurely in chronic stages of the disease. Insofar as the trajectory of WM decline associated with chronic disease may be due to medication non-adherence, it may be modifiable by long acting injection (LAI) formulations.

OBJECTIVES

Examine the impact of antipsychotic formulation on the myelination trajectory during a randomized six-month trial of LAI risperidone (RLAI) versus oral risperidone (RisO) in first-episode SZ subjects.

DESIGN

Two groups of SZ subjects (RLAI, N=11; and RisO, N=13) that were matched in pre-randomization oral medication exposure and 14 healthy controls (HCs) were prospectively examined. Frontal lobe WM volume was estimated using inversion recovery (IR) MRI images. A brief neuropsychological battery that focused on reaction times was performed at the end of the study.

MAIN OUTCOME MEASURE

WM volume change scores.

RESULTS

WM volume remained stable in the RLAI and decreased significantly in the RisO groups resulting in a significant differential treatment effect, while the HC had a WM change intermediate and not significantly different from the two SZ groups. WM increase was associated with faster reaction times in tests involving frontal lobe function.

CONCLUSIONS

The results suggest that RLAI may improve the trajectory of myelination in first-episode patients and have a beneficial impact on cognitive performance. Better adherence provided by LAI may underlie the modified trajectory of myelin development. In vivo MRI biomarkers of myelination can help clarify mechanisms of action of treatment interventions.

Normal amygdala activation but deficient ventrolateral prefrontal activation in adults with bipolar disorder during euthymia

Functional neuroimaging studies have implicated the involvement of the amygdala and ventrolateral prefrontal cortex (vlPFC) in the pathophysiology of bipolar disorder. Hyperactivity in the amygdala and hypoactivity in the vlPFC have been reported in manic bipolar patients scanned during the performance of an affective faces task. Whether this pattern of dysfunction persists during euthymia is unclear. Using functional magnetic resonance imaging (fMRI), 24 euthymic bipolar and 26 demographically matched healthy control subjects were scanned while performing an affective task paradigm involving the matching and labeling of emotional facial expressions. Neuroimaging results showed that, while amygdala activation did not differ significantly between groups, euthymic patients showed a significant decrease in activation of the right vlPFC (BA47) compared to healthy controls during emotion labeling. Additionally, significant decreases in activation of the right insula, putamen, thalamus and lingual gyrus were observed in euthymic bipolar relative to healthy control subjects during the emotion labeling condition. These data, taken in context with prior studies of bipolar mania using the same emotion recognition task, could suggest that amygdala dysfunction may be a state-related abnormality in bipolar disorder, whereas vlPFC dysfunction may represent a trait-related abnormality of the illness. Characterizing these patterns of activation is likely to help in understanding the neural changes related to the different mood states in bipolar disorder, as well as changes that represent more sustained abnormalities. Future studies that assess mood-state related changes in brain activation in longitudinal bipolar samples would be of interest.

Scan-rescan reliability of subcortical brain volumes derived from automated segmentation

Large-scale longitudinal studies of regional brain volume require reliable quantification using automated segmentation and labeling. However, repeated MR scanning of the same subject, even if using the same scanner and acquisition parameters, does not result in identical images due to small changes in image orientation, changes in prescan parameters, and magnetic field instability. These differences may lead to appreciable changes in estimates of volume for different structures. This study examined scan-rescan reliability of automated segmentation algorithms for measuring several subcortical regions, using both within-day and across-day comparison sessions in a group of 23 normal participants. We found that the reliability of volume measures including percent volume difference, percent volume overlap (Dice's coefficient), and intraclass correlation coefficient (ICC), varied substantially across brain regions. Low reliability was observed in some structures such as the amygdala (ICC = 0.6), with higher reliability (ICC = 0.9) for other structures such as the thalamus and caudate. Patterns of reliability across regions were similar for automated segmentation with FSL/FIRST and FreeSurfer (longitudinal stream). Reliability was associated with the volume of the structure, the ratio of volume to surface area for the structure, the magnitude of the interscan interval, and the method of segmentation. Sample size estimates for detecting changes in brain volume for a range of likely effect sizes also differed by region. Thus, longitudinal research requires a careful analysis of sample size and choice of segmentation method combined with a consideration of the brain structure(s) of interest and the magnitude of the anticipated effects.

Amygdala reactivity in healthy adults is correlated with prefrontal cortical thickness

Recent evidence suggests that putting feelings into words activates the prefrontal cortex (PFC) and suppresses the response of the amygdala, potentially helping to alleviate emotional distress. To further elucidate the relationship between brain structure and function in these regions, structural and functional magnetic resonance imaging (MRI) data were collected from a sample of 20 healthy human subjects. Structural MRI data were processed using cortical pattern-matching algorithms to produce spatially normalized maps of cortical thickness. During functional scanning, subjects cognitively assessed an emotional target face by choosing one of two linguistic labels (label emotion condition) or matched geometric forms (control condition). Manually prescribed regions of interest for the left amygdala were used to extract percentage signal change in this region occurring during the contrast of label emotion versus match forms. A correlation analysis between left amygdala activation and cortical thickness was then performed along each point of the cortical surface, resulting in a color-coded r value at each cortical point. Correlation analyses revealed that gray matter thickness in left ventromedial PFC was inversely correlated with task-related activation in the amygdala. These data add support to a general role of the ventromedial PFC in regulating activity of the amygdala.

Hippocampal and striatal gray matter volume are associated with a smoking cessation treatment outcome: results of an exploratory voxel-based morphometric analysis

RATIONALE

Compared to nonsmokers, smokers exhibit a number of potentially important differences in regional brain structure including reduced gray matter (GM) volume and/or density in areas including frontal and cingulate cortices, thalamus, and insula. However, associations between brain structure and smoking cessation treatment outcomes have not been reported.

OBJECTIVES

In the present analysis we sought to identify associations between regional GM volume--as measured by voxel-based morphometry (VBM)--and a smoking cessation treatment outcome (point prevalence abstinence at 4 weeks).

METHODS

Adult smokers underwent high-resolution anatomical MRI scanning prior to an open label smoking cessation treatment trial. VBM was conducted in SPM5 using the DARTEL algorithm and relapser vs. quitter groups were compared using independent sample t tests (p < 0.001, uncorrected). Analyses controlled for potentially confounding factors including years smoked, cigarettes per day, total intracranial volume (TIV), and sex.

RESULTS

Of 18 smokers, 8 achieved a 4-week point prevalence abstinence, confirmed by CO level (<or=8 ppm). After controlling for all covariates, compared to relapsers, quitters had significantly higher GM volume in the left putamen and right occipital lobe, while also significantly lower GM volume in bilateral hippocampus and right cuneus.

CONCLUSIONS

These preliminary results suggest that maintaining smoking abstinence is associated with higher pre-quit brain volume in regions that subserve habit learning and visual processing, and lower brain volume in regions that subserve long-term memory processes and visual information processing. Future, large-scale studies can determine whether brain structure variables can serve as clinically useful predictors of smoking cessation treatment outcome.

Hippocampal volumes in youth with type 1 diabetes

OBJECTIVE

Hippocampal neurons in adult animals and humans are vulnerable to severe hypoglycemia and hyperglycemia. Effects are hypothesized to be exacerbated during development, but existing studies on developing human brains are limited. We examined whether hypoglycemia or hyperglycemia experienced during brain development in humans affects hippocampal volumes.

RESEARCH DESIGN AND METHODS

We analyzed T1-weighted magnetic resonance images in 95 youth with type 1 diabetes and 49 sibling control subjects aged 7-17 years. Youth with diabetes were categorized as having 0 (n = 37), 1-2 (n = 41), or 3 or more (3+; n = 17) prior severe hypoglycemic episodes. Hyperglycemia exposure was estimated from median lifetime A1C, weighted for duration of diabetes. Stereologic measurements of hippocampal volumes were performed in atlas-registered space to correct for whole brain volume.

RESULTS

Greater exposure to severe hypoglycemia was associated with larger hippocampal volumes (F [3,138] = 3.6, P = 0.016; 3+ larger than all other groups, P < 0.05). Hyperglycemia exposure was not associated with hippocampal volumes (R(2) change = 0.003, F [1,89] = 0.31, P = 0.58, semipartial r = 0.06; one outlier removed for high median A1C), and the 3+ severe hypoglycemia group still had larger hippocampal volumes after controlling for age of onset and hyperglycemia exposure (main effect of hypoglycemia category, F [2,88] = 6.4, P = 0.002; 3+ larger than all other groups, P < 0.01).

CONCLUSIONS

Enlargement of the hippocampus may reflect a pathological reaction to hypoglycemia during brain development, such as gliosis, reactive neurogenesis, or disruption of normal developmental pruning.

Amygdala volumes in childhood absence epilepsy

Abnormal amygdala volumes in pediatric mood-anxiety disorders and attention deficit hyperactivity disorder (ADHD), as well as high rates of these diagnoses in childhood absence epilepsy (CAE), prompted this study of amygdala volume in CAE. Twenty-six children with CAE and 23 normal children, aged 6.6-15.8 years, underwent MRI at 1.5 T. The tissue imaged with MRI was segmented, and amygdala volumes were obtained by manual tracings. There were no significant amygdala volume differences between the CAE and normal groups. Within the CAE group, however, the children with ADHD had significantly smaller amygdala volumes than the subjects with CAE with no psychopathology and those with mood/anxiety diagnoses. There was also a significant relationship between higher seizure frequency and greater amygdala asymmetry in the epilepsy group. Given ongoing development of the amygdala during late childhood and adolescence, despite the lack of significant group differences in amygdala volumes, the association of amygdala volume abnormalities with ADHD and seizure frequency implies a possible impact of the disorder on amygdala development and CAE-associated comorbidities, such as ADHD.

Regional corpus callosum morphometry: effect of field strength and pulse sequence

PURPOSE

To investigate whether scanning at different field strengths and pulse sequences would influence reproducibility of corpus callosum (CC) morphometric measurements as variations in scanning parameters may result in differences in contrast properties between resulting images that are independent of the underlying tissue but rather reflect the physics of the imaging process.

MATERIALS AND METHODS

Ten subjects were scanned twice at 3T using magnetization-prepared rapid gradient-echo imaging (MPRAGE) and modified driven equilibrium Fourier transform (MDEFT) sequences and once at 1.5T using MPRAGE. Cross-sectional area measurements of four callosal regions were performed on midsagittal magnetic resonance imaging (MRI) sections.

RESULTS

Repeated measures analysis of variance with four regions as dependent variables and three scanning protocols (1.5T MPRAGE, 3T MPRAGE and 3T MDEFT) as independent variables revealed no significant region by protocol interaction: F(6,54) = 0.69, P = 0.52. Reliability measures for (3T MPRAGE/3T MDEFT) and (1.5T MPRAGE/3T MPRAGE; 1.5T MPRAGE/3T MDEFT) comparisons were high, ranging between 0.90 and 0.97.

CONCLUSION

Based on our results, combining and comparing CC morphometric data obtained at different field strengths and/or with different pulse sequences appears possible.

Localization of deformations within the amygdala in individuals with psychopathy

CONTEXT

Despite the repeated findings of impaired fear conditioning and affective recognition in psychopathic individuals, there has been a paucity of brain imaging research on the amygdala and no evidence suggesting which regions within the amygdala may be structurally compromised in individuals with psychopathy.

OBJECTIVE

To detect global and regional anatomical abnormalities in the amygdala in individuals with psychopathy.

DESIGN

Cross-sectional design using structural magnetic resonance imaging.

SETTING

Participants were recruited from high-risk communities (temporary employment agencies) in the Los Angeles, California, area and underwent imaging at a hospital research facility at the University of Southern California.

PARTICIPANTS

Twenty-seven psychopathic individuals as defined by the Hare Psychopathy Checklist-Revised and 32 normal controls matched on age, sex, and ethnicity.

MAIN OUTCOME MEASURES

Amygdala volumes were examined using traditional volumetric analyses and surface-based mesh modeling methods were used to localize regional surface deformations.

RESULTS

Individuals with psychopathy showed significant bilateral volume reductions in the amygdala compared with controls (left, 17.1%; right, 18.9%). Surface deformations were localized in regions in the approximate vicinity of the basolateral, lateral, cortical, and central nuclei of the amygdala. Significant correlations were found between reduced amygdala volumes and increased total and facet psychopathy scores, with correlations strongest for the affective and interpersonal facets of psychopathy.

CONCLUSIONS

Results provide the first evidence, to our knowledge, of focal amygdala abnormalities in psychopathic individuals and corroborate findings from previous lesion studies. Findings support prior hypotheses of amygdala deficits in individuals with psychopathy and indicate that amygdala abnormalities contribute to emotional and behavioral symptoms of psychopathy.

In vivo evidence of differential impact of typical and atypical antipsychotics on intracortical myelin in adults with schizophrenia

CONTEXT

Imaging and post-mortem studies provide converging evidence that patients with schizophrenia have a dysregulated developmental trajectory of frontal lobe myelination. The hypothesis that typical and atypical medications may differentially impact brain myelination in adults with schizophrenia was previously assessed with inversion recovery (IR) images. Increased white matter (WM) volume suggestive of increased myelination was detected in the patient group treated with an atypical antipsychotic compared to a typical one.

OBJECTIVE

In a follow-up reanalysis of MRI images from the original study, we used a novel method to assess whether the difference in WM volumes could be caused by a differential effect of medications on the intracortical myelination process.

DESIGN, SETTING, AND PARTICIPANTS

Two different male cohorts of healthy controls ranging in age from 18-35 years were compared to cohorts of subjects with schizophrenia who were treated with either oral risperidone (Ris) or fluphenazine decanoate (Fd).

MAIN OUTCOME MEASURE

A novel MRI method that combines the distinct tissue contrasts provided by IR and proton density (PD) images was used to estimate intracortical myelin (ICM) volume.

RESULTS

When compared with their pooled healthy control comparison group, the two groups of schizophrenic patients differed in the frontal lobe ICM measure with the Ris group having significantly higher volume.

CONCLUSIONS

The data suggest that in adults with schizophrenia antipsychotic treatment choice may be specifically and differentially impacting later-myelinating intracortical circuitry. In vivo MRI can be used to dissect subtle differences in brain tissue characteristics and thus help clarify the effect of pharmacologic treatments on developmental and pathologic processes.

Sodium MR imaging detection of mild Alzheimer disease: preliminary study

BACKGROUND AND PURPOSE

There is significant interest in the development of novel noninvasive techniques for the diagnosis of Alzheimer disease (AD) and tracking its progression. Because MR imaging has detected alterations in sodium levels that correlate with cell death in stroke, we hypothesized that there would be alterations of sodium levels in the brains of patients with AD, related to AD cell death.

MATERIALS AND METHODS

A total of 10 volunteers (5 with mild AD and 5 healthy control subjects) were scanned with a 20-minute sodium (23Na) MR imaging protocol on a 3T clinical scanner.

RESULTS

After normalizing the signal intensity from the medial temporal lobes corresponding to the hippocampus with the ventricular signal intensity, we were able to detect a 7.5% signal intensity increase in the brains of patients with AD (AD group, 68.25% +/- 3.4% vs control group, 60.75% +/- 2.9%; P < .01). This signal intensity enhancement inversely correlated with hippocampal volume (AD group, 3.22 +/- 0.50 cm3 vs control group, 3.91 +/- 0.45 cm3; r2 = 0.50).

CONCLUSIONS

This finding suggests that sodium imaging may be a clinically useful tool to detect the neuropathologic changes associated with AD.

Volume determination of amygdala and hippocampus at 1.5 and 3.0T MRI in temporal lobe epilepsy

Since magnetic resonance imaging (MRI) technique is constantly evolving with higher field strength scanners, the question arises whether images from different field strength scanners can be used interchangeably for scientific and clinical purposes. We address this issue in a study group of patients with temporal lobe epilepsy (TLE). Two different quantification methods for analysing structural (MRI) were used. Conventional volumetry was performed by manually tracing amygdala and hippocampus volumes on both 1.5 and 3T scans of 10 TLE patients. Additionally a voxel-based morphometry (VBM)-based extraction of those structures was conducted. As an answer to the main question, it was determined that the volumetrically derived volumes of amygdala and hippocampus from 1.5 and 3.0T images did not differ. Our findings concerning the volumetry are consistent with findings in healthy controls, thus offering the possibility to use volumetry of the different scanners interchangeably. The results of the VBM-analyses show satisfying inter-scanner volume quantification but not consistent enough to be deemed interchangeable. Further investigations analysing the outcomes of conventional VBM of different field strength scanners are necessary.

Amygdala volume and psychopathology in childhood complex partial seizures

OBJECTIVE

The purpose of this study was to compare amygdala volume in children with cryptogenic epilepsy who have complex partial seizures (CPS) with that of age- and gender-matched normal children. The relationship of amygdala volume to seizure variables and presence of psychopathology was also examined in these patients.

METHODS

Twenty-eight children with cryptogenic epilepsy, all of whom had CPS, and gender-matched normal children, all aged 6-16 years, underwent magnetic resonance imaging (MRI) at 1.5T. Tissue was segmented, and total brain volume and amygdala volumes obtained from manual tracings were computed.

RESULTS

There were no significant differences in amygdala volume between the CPS and normal groups. Within the CPS group, the children with an affective/anxiety disorder had significantly larger left amygdala volumes, as well as greater amygdala asymmetry, compared with those with no psychopathology. Exploring the association between seizure variables and amygdala volume yielded no significant predictors.

CONCLUSIONS

In pediatric CPS, left amygdala involvement may reflect effects of the neuropathology underlying comorbid affective or anxiety disorders on amygdala development rather than effects of ongoing seizures.

Childhood adversity predicts earlier onset of major depression but not reduced hippocampal volume

Childhood adversity may influence severity and age of onset of depression, potentially mediated by greater vulnerability to an existing biochemical or neural mechanism. Prior studies have suggested that reduced hippocampal volume is a result of childhood adversity. This study examined the relationship between childhood adversity, hippocampal volumes and clinical characteristics in women who were recruited for depression history rather than abuse experiences. Thirty-one women with remitted unipolar depression and 24 psychiatrically healthy women completed the Childhood Experience of Care and Abuse interview [Bifulco, A., Brown, G.W., Harris, T.O., 1994. Childhood Experience of Care and Abuse (CECA): A retrospective interview measure. Journal of Child Psychology and Psychiatry 55, 1419-1435]. High resolution MRI scans and hippocampal volumetric determination by stereological assessment were obtained. We found that childhood adversity was associated with a history of recurrent depression and with earlier age of depression onset. We did not find a relationship between childhood adversity and hippocampal volumes in this sample with mild childhood adversity. Our results suggest that the decreased hippocampal volume seen in Major Depressive Disorder may be mediated by additional factors. Further research is needed to more fully understand the interrelationships among childhood adversity, hippocampal morphology, neuroendocrine regulation, and other genetic and environmental factors influencing vulnerability to depression.

[Stereology as a tool to estimate brain volume and cortical atrophy in elders with dementia]

INTRODUCTION

stereology is a body of methods that allow unbiased and efficient estimation of geometric quantities defined in arbitrary physical structures. In particular, stereology is a valuable tool to assist neuroimaging in the estimation of morphometric parameters in the brain. Therefore, stereology may confer objectivity in the complementary and diagnostic evaluation of dementia by adding disease by adding quantitative data to clinical evaluation.

OBJECTIVES AND METHODS

our purpose was to illustrate estimation of brain volume and pial surface area by means of quantitative, computer-assisted stereological methods. Both parameters were estimated by means of a vertical design with a single series of parallel Cavalieri sections at a random orientation and perpendicular to a fixed horizontal plane. The sections were obtained by magnetic resonance imaging. Suitable test systems (of test points for volume, and of cycloids for surface area) were superimposed on these sections with the aid of special software.

RESULTS

to explore the statistical error of the volume estimator due to stereological sampling, 5 or 10 systematic sections were used in combination with two test point densities in a ratio of 1:4, so that the workload varied in the proportions 1:2:4:8. The four resulting estimators varied between 986 and 1120 cm(3). The surface area estimators varied between 1947 and 2096 cm(2), with workloads varying in the proportions of 1:2:2.3:4.6.

CONCLUSIONS

stereology is a simple and efficient tool to obtain objective brain volume and surface area estimators that are unbiased by design and accurate at a modest cost. Thus the corresponding methods can effectively assist in diagnostic and follow-up evaluation of elders with dementia.

Differential effects of typical and atypical antipsychotics on brain myelination in schizophrenia

CONTEXT

Imaging and post-mortem studies provide converging evidence that patients with schizophrenia have a dysregulated developmental trajectory of frontal lobe myelination even in adulthood. Atypical antipsychotics have been shown to have a wide spectrum of efficacy across multiple psychiatric diseases and to be particularly efficacious in treatment resistant cases of disorders such as schizophrenia.

OBJECTIVE

To test the a priori hypothesis that antipsychotic medications may differentially impact frontal lobe myelination in patients with schizophrenia.

DESIGN, SETTING, AND PARTICIPANTS

Participants ranged in age from 18-35 years, were all male, and were recruited by a single group of investigators using the same criteria. Two cohorts of subjects with schizophrenia early in their disease who were treated either with oral risperidone (Ris) or fluphenazine decanoate (Fd) were imaged in conjunction with cohorts of healthy controls. Each cohort was imaged using a different MRI instrument using identical imaging sequences.

MAIN OUTCOME MEASURE

MRI measures of frontal lobe white matter volume.

RESULTS

We estimated differences due to differences in the MRI instruments used in the two studies in the two healthy control groups matched to the patient samples, adjusting for age and other covariates. We then statistically removed those differences (which we assumed were due to instrument effects) from the data in the schizophrenia samples by subtraction. Relative to the differences seen in controls, the two groups of schizophrenic patients differed in their pattern of frontal lobe structure with the Ris-treated group having significantly larger white matter volume than the Fd group.

CONCLUSIONS

The results suggest that the choice of antipsychotic treatment may differentially impact brain myelination in adults with schizophrenia. Prospective studies are needed to confirm this finding. MRI can be used to dissect subtle differences in brain tissue characteristics and thus could help clarify the effect of pharmacologic treatments on neurodevelopmental and pathologic processes in vivo.

Hippocampal volume in childhood complex partial seizures

PURPOSE

This study compared hippocampal volume in children with cryptogenic epilepsy, all of whom had complex partial seizures (CPS), and age and gender matched normal children controlling for between group differences in IQ and demographic variables (e.g., age, gender, ethnicity, socioeconomic status). It also examined the relationship between hippocampal volumes and seizure variables in the patients.

METHODS

Using quantitative magnetic resonance imaging (MRI), we compared the hippocampal volumes of 19 medically treated children with CPS, aged 6-14 years, to 21 age and gender matched normal children.

RESULTS

The children with CPS had significantly smaller total hippocampal volumes than the normal children. This finding was accounted for primarily by significantly smaller anterior hippocampal volumes. Within the CPS group, smaller total and posterior hippocampus volumes were significantly associated with longer duration of illness. Anterior hippocampal volumes, however, were unrelated to seizure variables.

CONCLUSIONS

These findings imply impaired development of the hippocampus, particularly the anterior hippocampus, and a differential effect of the underlying illness and on-going seizures on hippocampal development in medically controlled pediatric CPS.

Brain ferritin iron may influence age- and gender-related risks of neurodegeneration

BACKGROUND

Brain iron promotes oxidative damage and protein oligomerization that result in highly prevalent age-related proteinopathies such as Alzheimer's disease (AD), Parkinson's disease (PD), and Dementia with Lewy Bodies (DLB). Men are more likely to develop such diseases at earlier ages than women but brain iron levels increase with age in both genders. We hypothesized that brain iron may influence both the age- and gender-related risks of developing these diseases.

METHODS

The amount of iron in ferritin molecules (ferritin iron) was measured in vivo with MRI by utilizing the field dependent relaxation rate increase (FDRI) method. Ferritin iron was measured in four subcortical nuclei [caudate (C), putamen (P), globus pallidus (G), thalamus (T)], three white matter regions [frontal lobe (Fwm), genu and splenium of the corpus callosum (Gwm, Swm)] and hippocampus (Hipp) in 165 healthy adults aged 19-82.

RESULTS

There was a high correlation (r>0.99) between published post-mortem brain iron levels and FDRI. There were significant age-related changes in ferritin iron (increases in Hipp, C, P, G, and decreases in Fwm). Women had significantly lower ferritin iron than men in five regions (C, T, Fwm, Gwm, Swm).

CONCLUSIONS

This is the first demonstration of gender differences in brain ferritin iron levels. It is possible that brain iron accumulation is a risk factor that can be modified. MRI provides the opportunity to assess brain iron levels in vivo and may be useful in targeting individuals or groups for preventive therapeutic interventions.

Segmenting magnetic resonance images via hierarchical mixture modelling

We present a statistically innovative as well as scientifically and practically relevant method for automatically segmenting magnetic resonance images using hierarchical mixture models. Our method is a general tool for automated cortical analysis which promises to contribute substantially to the science of neuropsychiatry. We demonstrate that our method has advantages over competing approaches on a magnetic resonance brain imagery segmentation task.

MR-based in vivo hippocampal volumetrics: 1. Review of methodologies currently employed

The advance of neuroimaging techniques has resulted in a burgeoning of studies reporting abnormalities in brain structure and function in a number of neuropsychiatric disorders. Measurement of hippocampal volume has developed as a useful tool in the study of neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. From this database, the methodology of all original manual tracing protocols were studied. These protocols differed in a number of important factors for accurate hippocampal volume determination including magnetic field strength, the number of slices assessed and the thickness of slices, hippocampal orientation correction, volumetric correction, software used, inter-rater reliability, and anatomical boundaries of the hippocampus. The findings are discussed in relation to optimizing determination of hippocampal volume.

MR-based in vivo hippocampal volumetrics: 2. Findings in neuropsychiatric disorders

Magnetic resonance imaging (MRI) has opened a new window to the brain. Measuring hippocampal volume with MRI has provided important information about several neuropsychiatric disorders. We reviewed the literature and selected all English-language, human subject, data-driven papers on hippocampal volumetry, yielding a database of 423 records. Smaller hippocampal volumes have been reported in epilepsy, Alzheimer's disease, dementia, mild cognitive impairment, the aged, traumatic brain injury, cardiac arrest, Parkinson's disease, Huntington's disease, Cushing's disease, herpes simplex encephalitis, Turner's syndrome, Down's syndrome, survivors of low birth weight, schizophrenia, major depression, posttraumatic stress disorder, chronic alcoholism, borderline personality disorder, obsessive-compulsive disorder, and antisocial personality disorder. Significantly larger hippocampal volumes have been correlated with autism and children with fragile X syndrome. Preservation of hippocampal volume has been reported in congenital hyperplasia, children with fetal alcohol syndrome, anorexia nervosa, attention-deficit and hyperactivity disorder, bipolar disorder, and panic disorder. Possible mechanisms of hippocampal volume loss in neuropsychiatric disorders are discussed.

Volumetric analysis of the prefrontal cortex, amygdala, and hippocampus in major depression

Magnetic resonance imaging (MRI) studies in depressed subjects report smaller volumes of amygdala, hippocampus, inferior anterior cingulate, and the orbital prefrontal cortex (OPFC), components of the limbic-cortico-thalamic circuit. Major depression occurs more commonly in women, raising the possibility of an additional psychopathological process affecting women and not men. We sought to determine whether volumetric differences related to mood disorders are dependent on sex. Eight male and 10 female depressed subjects, meeting DSM III R criteria for a major depressive episode, and eight male and 10 female healthy volunteers had MRI scans on a 1.5 T GE Signa Advantage scanner. The regions of interest included amygdala, hippocampus, inferior anterior cingulate, and OPFC. In all analyses, regional volumes were normalized for total cerebral volume. Volumetric changes in the ROIs showed a significant sex by diagnosis interaction, indicating a different pattern of volumetric changes in depressed males compared with females relative to controls. Relative to sex-matched controls, the left inferior anterior cingulate was smaller in depressed males (23%) compared with depressed females (11%). Depressed females but not depressed males had smaller amygdala compared with controls (F-value = 4.946, p = 0.033). No significant volumetric differences were noted in the hippocampus or OPFC. No volumetric correlations were noted with clinical variables, depression subtypes, or a reported history of sexual or physical abuse. Sex may affect volumetric deficits in amygdala and anterior cingulate cortex in mood disorders, but no effects were found in the hippocampus or OPFC. The biology of mood disorders in females may differ in some aspects from males, and may contribute to the higher rate of depression in women.

Decreased hippocampal 5-HT2A receptor binding in major depressive disorder: in vivo measurement with [18F]altanserin positron emission tomography

BACKGROUND

Serotonin 5-HT(2A) receptors play an important role in the regulation of many functions that are disturbed in patients with major depressive disorder. Postmortem and positron emission tomography studies have reported both increased and decreased 5-HT(2A) receptor binding in different limbic and paralimbic regions.

METHODS

We conducted a quantitative 5-HT(2A) receptor binding study using positron emission tomography and [(18)F]altanserin of four regions hypothesized to have altered levels of 5-HT(2A) receptors in major depressive disorder. Using a four-compartment model, the 5-HT(2A) receptor distribution was estimated by calculating the regional [(18)F]altanserin k(3)/k(4) ratio in which k(3) is the rate of binding to the receptor and k(4) is the rate of dissociation from the receptor. Forty-six antidepressant-free patients with major depressive disorder and 29 healthy control subjects were enrolled.

RESULTS

5-HT(2A) receptor binding in the hippocampus was reduced by 29% in depressed subjects (p =.004). In other regions, 5-HT(2A) receptor binding was decreased (averaging 15%) but not significantly. Both groups had similar age-dependent decreases in 5-HT(2A) receptors throughout all brain regions.

CONCLUSIONS

Altered serotoninergic function in the hippocampus is likely involved in the disturbances of mood regulation in major depressive disorder, although the specific role of the 5-HT(2A) receptor changes is still unclear.

Neuroanatomical correlates of formal thought disorder in schizophrenia

INTRODUCTION

We attempted to extend findings of a relationship between formal thought disorder and left superior temporal gyrus (STG) volume in schizophrenia by examining two indices of formal thought disorder.

METHODS

Three brain regions of interest were selected from magnetic resonance imaging slices in 15 young, right-handed, male schizophrenia patients: the STG, the anterior hippocampus, and the amygdala. Thought disorder was assessed using the Bizarre-Idiosyncratic Thinking (BIZ) scale, a sensitive measure of formal thought disorder based on responses to a standard set of stimuli, and the BPRS Conceptual Disorganization item, a global rating based on a clinical interview.

RESULTS

BIZ ratings of thought disorder were significantly correlated with the left STG volume (Spearman r = -.73) and with the right STG volume (Spearman r = -.58). BIZ ratings were not significantly correlated with either the left or right anterior hippocampus or amygdala volumes. The BPRS Conceptual Disorganisation rating was not significantly related to the STG, anterior hippocampus, or amygdala volumes.

CONCLUSIONS

This study confirms the previously reported association between the left STG and formal thought disorder, and suggests that detection of this relationship may be facilitated by use of highly sensitive formal thought disorder assessments.

Dysregulated brain development in adult men with schizophrenia: a magnetic resonance imaging study

BACKGROUND

Recent imaging evidence suggests that normal brain development/maturation of the frontal lobes and association areas is a well-regulated process consisting of continued myelination and expansion of white matter volumes into the late 40s accompanied by complementary reductions in gray matter volumes. The possibility that a dysregulation of this process may contribute to the syndrome of schizophrenia was investigated using magnetic resonance imaging.

METHODS

Fifty-two normal adult males and 35 males with schizophrenia underwent magnetic resonance imaging. Coronal images were acquired using pulse sequences that maximized myelin signal. The age-related change in the gray to white matter ratio was used as a measure of developmental dysregulation in the schizophrenic subjects and contrasted to the age-related changes of the normal control group.

RESULTS

Regression analyses on frontal and temporal gray to white matter ratio yielded highly significant interactions of diagnosis and age for both regions (p =.0003 and p =.01, respectively). In the normal group, both frontal and temporal gray to white matter ratios decreased significantly and linearly across the age range. In contrast, neither ratio showed meaningful age-related change in the schizophrenia group. Thus, differences in gray to white matter ratio between the groups increased markedly with age, driven primarily by the absence of a white matter volume expansion in the patient group.

CONCLUSIONS

The absence of the normal complementary volume changes in the gray and white matter with age in the schizophrenic sample suggests that this dynamic developmental process is dysregulated in adult schizophrenic subjects. The importance of myelination to the continued maturation and normal functioning of the brain has implications for the diagnosis, treatment, and prognosis of schizophrenia.

Seizure-associated hippocampal volume loss: a longitudinal magnetic resonance study of temporal lobe epilepsy

This longitudinal quantitative magnetic resonance imaging study of 24 patients with mild temporal lobe epilepsy shows an ipsilateral hippocampal volume decrease of 9% (range, -30 to +0.5%; p = 0.002, paired t test) over a period of 3.5 +/- 0.7 years. The hippocampal volume loss was correlated to the number of generalized seizures between the scans (p = 0.0007, r = 0.6), suggesting seizure-associated hippocampal damage.

Brain maturation may be arrested in chronic cocaine addicts

BACKGROUND

Animal and human newborn studies suggest that exposure to cocaine in utero delays glial maturation and white matter myelination. Postmortem data show that in the frontal and temporal lobes, white matter myelination continues into middle age. Recent magnetic resonance imaging (MRI) data have confirmed continued white matter volume increase in these regions, reaching a maximum at age 47.

METHODS

Thirty-seven male cocaine dependent (CD) and 52 normal control subjects between ages 19 and 47 were evaluated with MRI. Coronal images focused on the frontal and temporal lobes were acquired using pulse sequences that maximized gray/white matter contrast.

RESULTS

Highly significant positive correlations between white matter volume and age were observed in both the frontal and temporal lobes of the control group (r =.52, p =.0001 and r =.54, p =.0001, respectively); however, CD subjects did not demonstrate any age-related increase in white matter volume of the frontal (r = -.001; p =.99) and temporal (r = -.07; p =.67) lobes in this age range.

CONCLUSIONS

The age-related expansion in white matter volume occurring in normal control subjects was absent in CD subjects. The findings suggest that in adults, cocaine dependence may arrest normal white matter maturation in the frontal and temporal lobes of addicts who continue using cocaine.

Hippocampal pathology in refractory temporal lobe epilepsy: T2-weighted signal change reflects dentate gliosis

BACKGROUND

The MR and pathologic features of hippocampal sclerosis (HS) are well described and include volume decrease and T2-weighted signal increase for MRI, and neuron cell loss and gliosis for pathology.

OBJECTIVE

To confirm the established correlation between hippocampal volumes and neuron cell counts, and to study the still controversial association between signal change and gliosis.

METHODS

The authors studied 44 patients (22 men and 22 women; mean age at surgery, 37 years) with refractory temporal lobe epilepsy. Quantitative assessment of hippocampal volumes and T2 relaxometry, and neuron and glial cell count in the region CA1 and molecular layer of the dentate gyrus was performed. The proportion of glial fibrillary acidic protein (GFAP)-positive glial cells (reactive astrocytes) was indicated.

RESULTS

In a stepwise regression, the ipsilateral hippocampal volume was predicted best by the neuron cell count in the dentate gyrus (p = 0.005, r = 0.4). Hippocampal T2 time, however, was predicted best by the glial cell count in the dentate gyrus (p = 0.01, r = 0.4). None of the other cell counts contributed to either model. In the dentate, 31% of the glial cells were reactive astrocytes, whereas in CA1, 5% were reactive.

CONCLUSION

The results confirmed the correlation between hippocampal volumes and neuron cell counts. T2-weighted signal increase in the hippocampus was mainly influenced by gliosis in the dentate gyrus, where a high proportion of glial cells show abnormal activity. This activity may reflect changes important in the development of hippocampal epileptogenicity.

Medial temporal lobe in childhood-onset schizophrenia

The majority of anatomic and neuroimaging studies in adult-onset schizophrenia demonstrate decreased volumes of the medial temporal lobe when compared with findings in normal individuals. The goal of this study was to investigate the hypothesis that subjects with childhood-onset schizophrenia would show decreased volumes of the medial temporal lobe when compared to normal children. Thirteen children meeting DSM-III-R criteria for schizophrenia (mean age 14.2+/-3.8 years) and 20 normal children (mean age 12.0+/-2.8 years) were investigated. MRI scans were performed on a 1.5-T GE Signa MR scanner using a coronal plane SPGR at 1.4-mm slice thickness. Volumes were assessed by manually tracing bilateral hippocampus, amygdala and temporal lobes. After adjustment for age and total brain volume, the amygdala was significantly larger in the schizophrenics than in the control subjects, and this volume increase was more pronounced on the left side. Hippocampus volumes did not differ significantly across groups. There was a nearly significant left-greater-than-right asymmetry of the amygdala in the schizophrenic group but not in the normal group. A nearly significant right-greater-than-left asymmetry was found in the anterior hippocampus for both schizophrenic and control groups. These findings are consistent with previous reports of at least initial sparing of temporal lobe regions in childhood-onset schizophrenia.

Comparison of hippocampal volumetry at 1.5 tesla and at 3 tesla

PURPOSE

Hippocampal volumetry using magnetic resonance imaging (MRI) is a common clinical study in epilepsy patients. Most clinical MR scans operate at 1.5 tesla (T); however, there is increasing use of scanners of a higher field strength. We analyzed whether control data of hippocampal volumes can be used across different field-strength scanners.

METHODS

We studied eight adult healthy controls twice at both 1.5 and 3 T. Bilateral hippocampal volumes were measured by manual outlining. Measurement error was analyzed based on the variability between two measurements at the same field strength, and intrascanner variability was analyzed based on the difference between measurements obtained at 1.5 and at 3 T.

RESULTS

The measurement error was 4.0% (+/-3.1) at 1.5 T, and 3.4% (+/-2.5) at 3 T. The intrascanner variability between measurements at 1.5 and at 3 T was 6% (+/-3.9). The intrascanner variability was not different from the measurement error.

CONCLUSIONS

Control hippocampal volume measurements obtained at 1.5 and at 3 T were not different.

Three-dimensional mapping of temporo-limbic regions and the lateral ventricles in schizophrenia: gender effects

BACKGROUND

Local alterations in morphological parameters are poorly characterized in several brain regions widely implicated in schizophrenia neuropathology.

METHODS

Surface-based anatomical modeling was applied to magnetic resonance data to obtain three-dimensional (3D) average anatomical maps and measures of location, shape, asymmetry, and volume for the lateral ventricles, hippocampus, amygdala, and superior temporal gyrus in schizophrenic (n = 25; 15 male) and normal subjects (n = 28; 15 male) matched for demographic variables. For all regions, intra-group variability was visualized and group differences assessed statistically to discriminate local alterations in anatomy across sex and diagnosis.

RESULTS

Posterior hippocampal volumes, lengths, and widths were reduced in patients. The right amygdala showed volume increases in schizophrenia patients versus controls. Ventricular enlargements, pronounced in the left hemisphere, occurred in the superior and lateral dimensions in patients, and these effects interacted with gender. Superior horn anterior extremes, inferior horn volumes, and hippocampal asymmetries exhibited gender effects. Significant group differences were absent in superior temporal gyrus parameters. Finally, regional variability profiles differed across groups.

CONCLUSIONS

Clear morphometric differences of the lateral ventricles, hippocampus, and amygdala indicate regional displacements and shape distortions in several functional systems in schizophrenia. Alterations in these structures as mapped in 3D may provide the foundation for establishing brain abnormalities not previously defined at such a local level.

Tumor volume measurements of acoustic neuromas with three-dimensional constructive interference in steady state and conventional spin-echo MR imaging

The purpose was to compare three-dimensional (3D) constructive interference in steady state (CISS) and conventional spin-echo (SE) MR imaging in tumor volume measurements of acoustic neuromas. Twenty-two patients with acoustic neuromas were examined using high-resolution 3D-CISS and SE imaging at a 1.5-T system. Tumor volume determined by SE imaging with the ellipsoid formula was overestimated by 692 mm(3)(35%) on average as compared with that at 3D-CISS with the voxel-count method (the reference standard). Intra- and interobserver variations in SE imaging were poor as compared with 3D-CISS imaging. However, tumor volume results with SE imaging showed a high correlation with those using 3D-CISS imaging (P <. 0001). On the basis of diameters shown on SE images, the tumor volume could be assessed using the following equation (P <.0001): (Tumor volume) = -26.407 + 0.387 x (maximum diameter along the pyramid) x(maximum diameter perpendicular to the pyramid) x (maximum height). J. Magn. Reson. Imaging 2000;12:826-832.

Quantitative magnetic resonance imaging in consecutive patients evaluated for surgical treatment of temporal lobe epilepsy

We present the results of quantitative Magnetic Resonance Imaging (MRI) in 55 consecutively referred patients with clinical evidence of temporal lobe epilepsy (TLE). The Cavalieri method was used in combination with point counting to provide unbiased estimates of the volume of the left and right hippocampus, amygdala, temporal lobe, lateral ventricles and cerebral hemisphere, and pixel by pixel maps of the T2 relaxation time were computed for both central and anterior sections of the hippocampus. The 99th centiles of hippocampal volume, hippocampal volume asymmetry and T2 relaxation times in 20 control subjects provided limits which identified the presence of MTS. The results of the quantitative MRI were compared with the results of conventional diagnostic MRI, foramen ovale (FO) recording and the WADA test. Thirty-one patients were found to have unilateral MTS (17 left and 14 right) and 7 bilateral MTS. No evidence of MTS was detected in 16 patients. Of the 31 patients diagnosed with unilateral MTS on the basis of hippocampal volume and T2 measurement, 74% and 77% would respectively have received the same diagnosis on the basis of hippocampal volume and T2 measurements alone. In comparison to FO recording, quantitative MRI has a sensitivity of 55% and a specificity of 86%, while conventional diagnostic MRI has a sensitivity of 42% and a specificity of 80% for detection of MTS. Unilateral abnormalities were detected by FO recording in 30% cent of patients who appeared normal on quantitative MRI. WADA test results were available for 40 patients. The findings were consistent with quantitative MRI showing reduced memory function ipsilateral to unilateral MTS in 18 patients, but reduced memory function contralateral to unilateral MTS in two patients, and reduced memory function without MR abnormality in seven patients. WADA testing revealed unilateral memory impairments where MRI found bilateral pathology in 4 patients and in 4 patients in whom quantitative MRI detected unilateral MTS there was no evidence of reduced memory during WADA testing of the corresponding cerebral hemisphere. In the patients with unilateral right MTS a highly significant negative correlation (p = 0.0003) was observed between age of onset and the volume of the contralateral temporal lobe. Quantitative MR imaging of the hippocampus (i.e. volume and T2 measurement) is preferable to conventional radiological reporting for providing objective evidence of the presence of MTS on which to base the referral of patients for surgery, and since it has associated morbidity FO recording is now only being used in selected patients. Furthermore, stereology provides a convenient method for estimating the volume of other brain structures, which is relevant to obtaining a better understanding of the effects of laterality and age of onset of TLE.