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Results for “structural magnetic resonance imaging”

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At least 19 recordsLinked to original sources

PubMed2004

Semiautomatic brain region extraction: a method of parcellating brain regions from structural magnetic resonance images.

Structural MR imaging has become essential to the evaluation of regional brain changes in both healthy aging and disease-related processes. Several methods have been developed to measure structure size and regional brain volumes, but many of these methods involve substantial manual tracing and/or landmark identification. We present a new technique, semiautomatic brain region extraction (SABRE), for the rapid and reliable parcellation of cortical and subcortical brain regions. We combine the SABRE parcellation with tissue compartment segmentation [NeuroImage 17 (2002) 1087] to produce measures of gray matter (GM), white matter (WM), ventricular CSF, and sulcal CSF for 26 brain regions. Because SABRE restricts user input to a few easily identified landmarks, inter-rater reliability is high for all volumes, with all coefficients between 0.91 and 0.99. To assess construct validity, we contrasted SABRE-derived volumetric data from healthy young and older adults. Results from the SABRE parcellation and tissue segmentation showed significant differences in multiple brain regions in keeping with regional atrophy described in the literature by researchers using lengthy manual tracing methods. Our findings show that SABRE is a reliable semiautomatic method for assessing regional tissue volumes that provides significant timesavings over purely manual methods, yet maintains information about individual cortical landmarks.

Adult↗

PubMed1998

Structural magnetic resonance image averaging in schizophrenia.

OBJECTIVE: Intersubject averaging of structural magnetic resonance (MR) images has been infrequently used as a means to study group differences in cerebral structure throughout the brain. In the present study, the authors used linear intersubject averaging of structural MR images to evaluate the validity and utility of this technique and to extend previous research, conducted using a different approach to image averaging, in which reduction in thalamic size and abnormalities in perithalamic white matter tracts in the brains of schizophrenic patients were reported by Andreasen et al. METHOD: A 1.5-T MR scanner was used to obtain high-resolution, whole brain T1-weighted structural MR images for an age-matched sample of 25 schizophrenic patients and 25 normal control subjects. A "bounding box" procedure was used to create a single "averaged" brain for the schizophrenic group and for the control group. Differences in signal intensity between the two average brains were examined on a pixel-wise basis through use of one-tailed effect size maps. RESULTS: Effect size maps revealed widespread patchy signal intensity differences between the two groups in both cortical and periventricular areas, including major white matter tracts. The signal intensity differences were consistent with cortical thinning/sulcal widening and ventricular enlargement. No differences were found within thalamus or in immediately surrounding white matter. Effect size maps for differences (schizophrenic minus normal subjects) had only small values. CONCLUSIONS: These results are consistent with diffuse structural brain abnormalities of both gray and white matter in schizophrenic populations such as the one in this study.

Adult↗

PubMed2004

The entorhinal cortex in first-episode psychotic disorders: a structural magnetic resonance imaging study.

OBJECTIVE: Neuropathological findings regarding the entorhinal cortex in schizophrenia are conflicting. The authors used structural magnetic resonance imaging to examine the entorhinal cortex volumes of healthy subjects and medication-naive patients experiencing their first episode of psychotic illness. METHOD: The study included 33 patients with schizophrenia and related disorders, 11 patients with nonschizophrenic disorders, and 43 matched healthy subjects. All subjects were rated on the Scale for the Assessment of Positive Symptoms and the Scale for the Assessment of Negative Symptoms, and volumetric measurements of the entorhinal cortex were obtained for all subjects. The authors examined differences across the groups as well as clinical correlations of entorhinal cortex volumes adjusted for intracranial volume. RESULTS: A significant diagnosis effect was seen in the left entorhinal cortex: patients with schizophrenia and related disorders and patients with nonschizophrenic psychotic disorders had smaller left entorhinal cortex volumes than healthy subjects. The mean entorhinal cortex volume of patients with schizophrenic disorders did not differ from that of patients with nonschizophrenic psychotic disorders. In patients with schizophrenic disorders, the entorhinal cortex volume positively correlated with severity of delusions. The mean entorhinal cortex volume of patients with nondelusional psychotic disorders was significantly smaller than that of patients with delusional psychotic disorders and healthy subjects. CONCLUSIONS: Smaller entorhinal cortex volume in first-episode, neuroleptic-naive psychotic disorders may not be a confound of the effects of illness chronicity or antipsychotic treatment. Entorhinal cortex pathology appears to have a significant association with positive symptoms, specifically delusions. The impairment of functions in which the entorhinal cortex participates-such as novelty detection, associative learning, and processing episodic, recognition, and autobiographical memory-could be responsible for its association with psychotic disorders and delusions.

Adult↗

PubMed1985

Gated cardiac magnetic resonance structural imaging: optimization by electronic axial rotation.

Most magnetic resonance imaging has used body orthogonal axes with the Z axis placed along the length of the body and the X and Y axes at right angles to the body. This orientation is not optimum for the heart; visualization of sections along the short and long cardiac axes would best define cardiac structural detail and functional status. The new orientation was accomplished by selection of electronic angulation of the magnetic fields for each subject rather than by attempting to approximate the cardiac axes by altering the position of the patient. This technique improved visualization of comparative wall segments, valvular structures, and the true four-chamber view of the heart, and also gave the best visualization of the pericardium. In addition, more accurate estimates of chamber size and myocardial mass can be made from the short-axis orientation, since the sections are orthogonal to the myocardium.

Cardiomegaly↗

PubMed2005

Handedness, dichotic-listening ear advantage, and gender effects on planum temporale asymmetry--a volumetric investigation using structural magnetic resonance imaging.

Previous research has often examined whether the asymmetrical structure of the planum temporale (PT) represents an anatomical correlate of lateralized language-processing functions, gathering diverging empirical evidence by comparing PT asymmetry in subjects with differing handedness, gender, or speech lateralization. Apart from other methodological problems, direct comparisons between studies are hampered by insufficient assessment and consideration of all three potential determinants of structural cerebral asymmetry. Based on volumetric assessment of structural Magnetic Resonance Imaging (MRI) scans of 104 healthy subjects, the present study replicated earlier observations of an overall leftward PT asymmetry, which was found to prevail irrespective of handedness, gender, or dichotic-listening ear advantage. However, the mean magnitude of this leftward asymmetry was not determined by either one of these factors in itself, but varied depending on their specific combination. A clear correspondence between structural and functional asymmetry was only observed among right-handed males. In this particular subgroup, more pronounced structural asymmetry was associated with an enlarged PT on the left side, while the enhanced leftward asymmetry of female sinistrals resulted from smaller adjusted volumes of their right PT. The existence of such complex interactions suggests that future research in this area can only be expected to overcome past inconsistencies by adequately considering handedness, gender, and speech lateralization.

Auditory Cortex↗

PubMed2000

Supporting evidence for the model of cognitive dysmetria in schizophrenia--a structural magnetic resonance imaging study using deformation-based morphometry.

The aim of the study was to investigate whether there is any structural evidence for the model of 'cognitive dysmetria' in schizophrenia if an automatic whole-brain analysis method is used. High-resolution magnetic resonance scans were obtained for 75 schizophrenic patients and 75 controls. These data were analysed using the recently developed deformation-based morphometry allowing the assessment of volumetric differences without a priori definition of regions of interest. When compared with controls, we found reduced volumes in patients with schizophrenia in the frontal lobe (gyrus frontalis superior, medius and medialis), the temporal lobe (gyrus temporalis superior and inferior), the thalamus, the left cerebellar hemisphere and the right cerebellar vermis. There was an increase in volume in the right putamen. To date, this is the first structural magnetic resonance imaging study to demonstrate that the three key-elements of the model of cognitive dysmetria--frontal lobe, thalamus, and cerebellum--are reduced in volume in schizophrenic patients. This highlights the importance of this concept for future investigations.

Adult↗

PubMed2005

Anatomical analysis of an aye-aye brain (Daubentonia madagascariensis, primates: Prosimii) combining histology, structural magnetic resonance imaging, and diffusion-tensor imaging.

This report presents initial results of a multimodal analysis of tissue volume and microstructure in the brain of an aye-aye (Daubentonia madagascariensis). The left hemisphere of an aye-aye brain was scanned using T2-weighted structural magnetic resonance imaging (MRI) and diffusion-tensor imaging (DTI) prior to histological processing and staining for Nissl substance and myelinated fibers. The objectives of the experiment were to estimate the volume of gross brain regions for comparison with published data on other prosimians and to validate DTI data on fiber anisotropy with histological measurements of fiber spread. Measurements of brain structure volumes in the specimen are consistent with those reported in the literature: the aye-aye has a very large brain for its body size, a reduced volume of visual structures (V1 and LGN), and an increased volume of the olfactory lobe. This trade-off between visual and olfactory reliance is likely a reflection of the nocturnal extractive foraging behavior practiced by Daubentonia. Additionally, frontal cortex volume is large in the aye-aye, a feature that may also be related to its complex foraging behavior and sensorimotor demands. Analysis of DTI data in the anterior cingulum bundle demonstrates a strong correlation between fiber spread as measured from histological sections and fiber spread as measured from DTI. These results represent the first quantitative comparison of DTI data and fiber-stained histology in the brain.

Animals↗

PubMed1997

Grey matter correlates of syndromes in schizophrenia. A semi-automated analysis of structural magnetic resonance images.

BACKGROUND: Symptoms in schizophrenia cluster into syndromes, each of which may be associated with a particular pattern of cerebral blood flow. We sought to investigate whether these syndromes are also related to neuroanatomical changes. METHOD: A semi-automated method was used to examine structural magnetic resonance images in 12 patients with schizophrenia. The relationship between the relative regional grey matter volume and ratings of the syndromes of psychomotor poverty, disorganisation and reality distortion was investigated. RESULTS: There was a significant negative correlation between psychomotor poverty score and the relative volume of the left ventro-medial prefrontal grey matter, and a significant positive correlation between disorganisation and the relative volumes of the hippocampus, and the parahippocampal/fusiform gyrus bilaterally. CONCLUSION: The correlation between psychomotor poverty and left prefrontal grey matter volume resembles that previously seen with prefrontal blood flow in the same patient, suggesting that this functional abnormality is related to an underlying anatomical change.

Adult↗

PubMed2004

Brain anatomy in adults with velocardiofacial syndrome with and without schizophrenia: preliminary results of a structural magnetic resonance imaging study.

CONTEXT: Velocardiofacial syndrome is associated with interstitial deletions of chromosome 22q11, mild to borderline learning disability, characteristic dysmorphology, and a high prevalence of schizophrenia. The biological basis for this increased risk for schizophrenia is unknown, but people with velocardiofacial syndrome may have genetically determined differences in brain anatomy that predispose to the development of schizophrenia. OBJECTIVE: To determine whether there are differences in brain structure between subjects with velocardiofacial syndrome with and without schizophrenia. DESIGN: A cross-sectional quantitative structural magnetic resonance imaging study in 39 adult subjects. SETTING: Referrals were made through medical genetics clinics and psychiatric services throughout the United Kingdom. PARTICIPANTS: Thirteen subjects with velocardiofacial syndrome and schizophrenia, 12 with velocardiofacial syndrome without history of a psychosis, and 14 healthy controls volunteered to participate after screening for eligibility. MAIN OUTCOME MEASURES: Total and regional brain volumes were analyzed by means of manual tracing, and gray- and white-matter densities were obtained by computerized voxel-based methods. RESULTS: People with velocardiofacial syndrome and schizophrenia, compared with both controls and nonschizophrenic patients with velocardiofacial syndrome, had a significant (P<.05) reduction in volume of whole-brain (white + gray) matter and whole-brain white matter, and an increase in total and sulcal cerebrospinal fluid volume. Both velocardiofacial syndrome groups had a reduced cerebellar volume compared with controls. CONCLUSIONS: Within velocardiofacial syndrome, schizophrenia is associated with generalized differences in brain anatomy, but white matter may be particularly implicated. Studies with larger samples are needed to replicate our findings.

Adult↗

PubMed2000

Brain abnormalities in early-onset schizophrenia spectrum disorder observed with statistical parametric mapping of structural magnetic resonance images.

OBJECTIVE: The purpose of this study was to assess neuroanatomic abnormalities in children and adolescents with childhood-onset schizophrenia by using whole-brain voxel-based morphometric analyses. Previous volumetric studies of brain abnormalities in childhood-onset schizophrenia have revealed anomalies similar to those in subjects with adult-onset schizophrenia. Specifically, low cerebral volume, high ventricular volume, and thalamic, basal ganglia, callosal, and temporal lobe abnormalities have been observed in childhood-onset schizophrenia. Relatively few anatomical structures have been delineated and measured in this rare population, partly because of the labor involved in the slice-by-slice region definition required of conventional volumetric image analyses. METHOD: The subjects were 10 normal children and adolescents and nine children and adolescents with early-onset schizophrenia (mean age at diagnosis, 11.0 years; range, 7-16 years). The authors conducted voxel-by-voxel and volumetric statistical analyses of high-resolution structural magnetic resonance images. RESULTS: Statistical parametric maps of gray matter, white matter, and CSF differences between the groups revealed that the subjects with early-onset schizophrenia had larger ventricles, predominantly in the posterior horns of the lateral ventricles, and midcallosal, posterior cingulate, caudate, and thalamic abnormalities. Volumetric analyses of the lateral ventricles in native image data space confirmed significantly higher volume in posterior, but not anterior, regions. Randomization tests confirmed the overall statistical significance of the group differences and validity of the parametric maps. CONCLUSIONS: These findings are generally consistent with the findings of other research groups, but localization of enlarged ventricles specific to the posterior region may be a new finding in the literature on childhood-onset schizophrenia.

Adolescent↗

PubMed2004

Relationship of structural magnetic resonance imaging, magnetic resonance perfusion, and other disease factors to neuropsychological outcome in sickle cell disease.

OBJECTIVE: To investigate the relationship between neuropsychological functioning and radiographic findings in children with sickle cell disease (SCD) with no history of clinical neurological events. METHODS: Thirty-one patients with SCD randomly selected from a regional treatment center underwent neuropsychological and disease severity assessments. Of these, 22 also had structural magnetic resonance imaging and magnetic resonance perfusion studies performed. RESULTS: Forty-five percent of the imaged subgroup showed imaging abnormalities that were found to be correlated with disease severity but not neuropsychological level of performance indices. A significant relationship, however, was found between imaging abnormalities and increased variability in neuropsychological performance. CONCLUSIONS: These results corroborate the high rate of rheologic and vascular pathology in SCD and underscore the importance of representing neuropsychological functioning in multiple ways.

Adolescent↗

PubMed2003

[Structural magnetic resonance imaging (MRI) studies in bipolar disorder].

To review structural MRI studies in bipolar disorder. A computer-assisted literature search of the Medline Ovid files for the period 1966 to November 2002 was performed, augmented by the use of articles meeting the criteria of this study from recent reviews. The studies included in this review show that there are abnormalities in the regions playing a role in the prefrontal-subcortical circuits that have been implicated in the pathophysiology of bipolar disorder, rather than generalized abnormalities like cerebral volume reduction or ventricular enlargement. The most widely studied and frequently reported finding of T2 signal hyperintensities is not considered to be specific to bipolar disorder. The findings of dorsolateral and subgenual prefrontal cortical volumetric reductions are in agreement with the findings of few neuropathological studies of bipolar disorder and suggest that prefrontal cortex plays an important role in the pathophysiology of the disorder. Among the medial temporal structures, the increase in amygdala volume seems to be specific to bipolar disorder. The findings in structures like the striatum and thalamus are conflicting, due to difficulties in the detailed measuring of the volumes of these structures with current techniques. Bipolar disorder is associated with brain abnormalities detected with structural MRI. Studies integrating structural neuroimaging methods with functional neuroimaging are needed to specifically determine how these abnormalities affect the function of these brain regions.

Bipolar Disorder↗

PubMed2000

Brain abnormalities observed in childhood-onset schizophrenia: a review of the structural magnetic resonance imaging literature.

Childhood-onset schizophrenia (COS) is a rare, severe form of schizophrenia in which there are structural brain abnormalities that may be related to the psychotic symptomatology and neurocognitive deficits found in these patients. While there are numerous structural imaging studies of the adult-onset variant of schizophrenia (with many conflicting findings), relatively few brain imaging studies of COS have been conducted. This paper summarizes the extant literature of magnetic resonance imaging (MRI) studies of structural brain abnormalities in COS, and compares findings to similar studies of adult-onset patients. Volumetric MRI studies of COS patients have consistently shown evidence for increased ventricular volume, reduced cerebral gray matter, and increased caudate volume, consistent with findings from adult-onset studies. Other volumetric brain abnormalities are observed in COS patients, such as reduced total brain volume, but not consistently across all studies. Voxel-based morphometric analyses have revealed abnormalities in the shape and spatial location of structures in COS such as the corpus callosum, caudate, and thalamus that could not be observed in the more traditional volumetric assessments. Similar findings also are observed in adult-onset patients. Progressive degenerative changes, such as ventricular enlargement, appear to occur in COS only until young adulthood where there is an apparent asymptote with no further degenerative changes. This is consistent with the lack of progressive changes noted in most longitudinal studies of adult-onset schizophrenia.

Age of Onset↗

PubMed2002

Cortical and subcortical gray matter abnormalities in schizophrenia determined through structural magnetic resonance imaging with optimized volumetric voxel-based morphometry.

OBJECTIVE: Structural neuroimaging studies have suggested an association between schizophrenia and abnormalities in brain morphology such as ventricular enlargement and differences in gray matter distribution. Less consistently reported are findings of regional abnormalities such as selective differences in thalamic volume. The authors applied an unbiased technique to test for differences in cerebral morphometry between patients with schizophrenia and matched comparison subjects. METHOD: T(1)-weighted images from 20 schizophrenic patients and matched comparison subjects were processed by using optimized automated voxel-based morphometry within multiple linear regression analyses. RESULTS: Global differences in gray matter volume were seen between the schizophrenic and comparison subjects, with selective regional gray matter differences noted in the mediodorsal thalamus and across cortical regions, including the ventral and medial prefrontal cortices. Within the schizophrenic subjects, a relationship was observed between gray matter volume loss in the medial prefrontal cortex and a positive family history of schizophrenia. There was no significant difference between patients and comparison subjects in rates of proportional gray matter reduction with age. CONCLUSIONS: These observations confirm an association between thalamocortical morphometric abnormalities and schizophrenia, consistent with theoretical models of primary pathoetiological dysfunction in filtering, integration, and information transfer processes in patients with schizophrenia.

Adult↗

PubMed2002

Structural magnetic resonance imaging in the practical assessment of dementia: beyond exclusion.

Neuroimaging is increasingly used to aid diagnosis in dementia. The traditional view that imaging is important solely as means of excluding treatable causes of dementia is maintained by many guidelines. These conditions however, account for a tiny proportion (<1%) of all causes of dementia. Over the past few years it has been recognised that a more accurate diagnosis and prognosis is important for patients and their families. The different pathological processes that produce cerebral dysfunction at a cellular level also produce macroscopic effects that can be detected in vivo with imaging. Clinically useful measures that distinguish between neurodegenerative disorders at an early stage are still awaited. The most likely future use of structural imaging will be the identification of patients at risk for Alzheimer's disease or with preclinical Alzheimer's disease. For magnetic resonance imaging (MRI) this will mean focusing on those areas that are affected earliest in the disease; ie, entorhinal cortex and hippocampus, using high resolution structural MRI or sophisticated brain mapping techniques. Imaging research is also likely to focus on measuring progression and detecting therapeutic effect. As such, MRI is already become an indispensable tool in clinical trials in dementia.

Brain↗

PubMed2002

Structural magnetic resonance imaging in patients with first-episode schizophrenia, psychotic and severe non-psychotic depression and healthy controls. Results of the schizophrenia and affective psychoses (SAP) project.

BACKGROUND: Structural brain abnormalities are prevalent in patients with schizophrenia and affective disorders. AIMS: To study how regional brain volumes and their ratios differ between patients with schizophrenia, psychotic depression, severe non-psychotic depression and healthy controls. METHOD: Magnetic resonance imaging scans of the brain on first-episode patients and on healthy controls. RESULTS: Patients with schizophrenia had a smaller left frontal grey matter volume than the other three groups. Patients with psychotic depression had larger ventricular and posterior sulcal cerebrospinal fluid (CSF) volumes than controls. Patients with depression had larger white matter volumes than the other patients. CONCLUSIONS: Left frontal lobe, especially its grey matter volume, seems to be specifically reduced in first-episode schizophrenia. Enlarged cerebral ventricles and sulcal CSF volumes are prevalent in psychotic depression. Preserved or expanded white matter is typical of non-psychotic depression.

Adult↗

PubMed2004

Parahippocampal gyrus in first episode psychotic disorders: a structural magnetic resonance imaging study.

Neuropathological abnormalities in schizophrenia have been demonstrated in the parahippocampal gyrus (PHG). Only a few studies on first-episode neuroleptic-naive schizophrenia patients have been done using in vivo neuroimaging techniques. The authors examined the PHG morphology using structural MRI in neuroleptic-naive subjects with first episode psychoses. Volumetric measurements of PHG and intracranial volume (ICV) were obtained on subjects with schizophrenia and schizoaffective disorders (SCZ; n = 33), nonschizophrenia psychotic disorders (NSCZ; n = 11) and matched healthy subjects (HS; n = 43). The subjects were rated on the Brief Psychiatric Rating Scale (BPRS). Group differences and clinical correlations of ICV-adjusted PHG volumes were examined. Left PHG was significantly different across the groups consisting of SCZ, NSCZ and HS. PHG was larger in NSCZ compared to SCZ but not relative to HS. Bilaterally, PHG was no different between SCZ and HS. In pooled psychotic patients, the PHG volume negatively correlated with total positive symptom, delusion and conceptual disorganization scores on BPRS. Patients with delusions had relatively smaller PHG compared to nondelusional subjects. Observed differences in PHG volume in first-episode neuroleptic-naive patients suggest that these observations are not confounded by illness chronicity or medication effects. Significant association of PHG volume with psychotic symptoms suggests that PHG pathology plays an important role in the etiopathology of psychosis and its symptoms.

Adult↗

PubMed1998

Neuroanatomical correlates of cognitive aging: evidence from structural magnetic resonance imaging.

To examine putative brain substrates of cognitive functions differentially affected by age the authors measured the volume of cortical regions and performance on tests of executive functions, working memory, explicit memory, and priming in healthy adults (18-77 years old). The results indicate that shrinkage of the prefrontal cortex mediates age-related increases in perseveration. The volume of visual processing areas predicted performance on nonverbal working memory tasks. Contrary to the hypotheses, in the examined age range, the volume of limbic structures was unrelated to any of the cognitive functions; verbal working memory, verbal explicit memory, and verbal priming were independent of cortical volumes. Nevertheless, among the participants aged above 60, reduction in the volume of limbic structures predicted declines in explicit memory. Chronological age adversely influenced all cognitive indices, although its effects on priming were only indirect, mediated by declines in verbal working memory.

Adolescent↗