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At least 541 records · Page 30Linked to original sources
PubMed2001

Detailed ultrasonographic mapping of the pelvis in clinically normal horses and ponies.

OBJECTIVE: To map the equine pelvis using ultrasonography, validated by use of computed tomography (CT), magnetic resonance imaging (MRI), and measurements of frozen cadaver slices. ANIMALS: 6 ponies and 6 horses. PROCEDURE: Ultrasonographic examination of the pelvis was performed on 6 clinically normal ponies. Measurements were obtained for imaged structures. Computed tomography, MRI, and measurements of frozen sections were performed after death and used to verify measurements. Linear regression determined the degree of correlation between measurements obtained ultrasonographically and the other modalities. Six clinically normal horses were then examined by use of ultrasonography. For each structure measured mean, SD, and range were calculated. RESULTS: Data obtained from ponies revealed high correlations between ultrasonographic findings and those of CT, MRI, and frozen section measurements (r2 = 0.97, r2 = 0.99, and r2 = 0.99, respectively). Differences between structures measured on each side of the pelvis were not significant. Variation in size of structures was not associated with weight of horses. A correlation was not found between weight of horses and ponies and size of structure. CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasonography can be used to accurately measure and evaluate the musculoskeletal structures of the pelvis of horses. The use of CT, MRI, and measurements of frozen sections provided a means of validating the ultrasonographic measurements. Reference range values determined in our study can be used to evaluate horses with suspected pelvic disease.

Animals↗
PubMed2003

Noninvasive identification of human central sulcus: a comparison of gyral morphology, functional MRI, dipole localization, and direct cortical mapping.

The locations of the human primary hand cortical somatosensory and motor areas were estimated using structural and functional MRI, scalp-recorded somatosensory-evoked potential dipole localization, expert judgments based on cortical anatomy, and direct cortical stimulation and recording studies. The within-subject reliability of localization (across 3 separate days) was studied for eight normal subjects. Intraoperative validation was obtained from five neurosurgical patients. The mean discrepancy between the different noninvasive functional imaging methods ranged from 6 to 26 mm. Quantitative comparison of the noninvasive methods with direct intraoperative stimulation and recording studies did not reveal a significant mean difference in accuracy. However, the expert judgments of the location of the sensory hand areas were significantly more variable (maximum error, 39 mm) than the dipole or functional MRI techniques. It is concluded that because expert judgments are less reliable for identifying the cortical hand area, consideration of the findings of noninvasive functional MRI and dipole localization studies is desirable for preoperative surgical planning.

Adult↗
PubMed2005

Retrospective cross-evaluation of an histological and deformable 3D atlas of the basal ganglia on series of Parkinsonian patients treated by deep brain stimulation.

In functional neurosurgery, there is a growing need for accurate localization of the functional targets. Since deep brain stimulation (DBS) of the Vim thalamic nucleus has been proposed for the treatment of Parkinson's disease, the target has evolved toward the globus pallidus and subthalamic nucleus (STN) and the therapeutic indications have enlarged to include psychiatric disorders such as Tourette syndrome or obsessive compulsive disorders. In these pathologies, the target has been restrained to smaller functional subterritories of the basal ganglia, requiring more refined techniques to localize smaller and smallerbrain regions, often invisible in routine clinical MRI. Different strategies have been developed to identify such deep brain targets. Direct methods can identify structures in the MRI itself, but only the larger ones. Indirect methods are based on the use of anatomical atlases. The present strategy comprised a 3D histological atlas and the MRI of the same brain specimen, and deformation methodology developped to fit the atlas toward the brain of any given patient. In this paper, this method is evaluated in the aim of being applied to further studies of anatomo-clinical correlation. The accuracy of the method is first discussed, followed by the study of short series of Parkinsonian patients treated by DBS, allowing to compare the deformed atlas with various per- and post-operative data.

Basal Ganglia↗
PubMedDate not supplied

Clinical significance of brain white matter hyperintensities in young adults with psychiatric illness.

Magnetic resonance imaging (MRI) provides detailed images of brain anatomy, with especially clear definition of gray and white matter structures. Several brain MRI studies have suggested that adults with bipolar disorder (BD) are more likely to have "white matter hyperintensities" (WMH) than adults without BD. The disproportionately greater frequency of these lesions in otherwise physically healthy patients suggests that the illness itself, or treatments used to control the illness, may be risk factors for the development of white matter changes. Similarly, WMH may be an etiological factor for some types of BD. In addition to reviewing the relevant literature, this research study attempted to determine whether lithium treatment is associated with an increased prevalence of WMH in young adults with psychiatric illness. To test this hypothesis, we evaluated over 600 brain MRI scans from inpatients at McLean Hospital, Belmont, Massachusetts. We controlled for possible confounding variables such as age, vascular disease, substance abuse, and markers of illness severity. We found that individuals with BD were no more likely to have WMH than other psychiatric patients. Lithium use was nonsignificantly associated with the presence of WMH. A multivariate regression model for the presence of WMH showed that heart disease, female gender, and multiple psychiatric admissions were significant predictors of WMH. This study does not support previous findings that BD, compared to other psychiatric illnesses, was associated with increased risk of WMH. Lithium use may be subtly associated with WMH. Our results are consistent with previous research that found an association between cardiovascular disease, advanced age, and the presence of WMH, though our analysis appears to be unique in its inclusion of cardiovascular disease as a risk factor in young adults with psychiatric illness.

Adolescent↗
PubMed1997

Association between striatal reduction and poor Wisconsin card sorting test performance in patients with schizophrenia.

Several findings support the hypothesis that the striatum is implicated in executive functions and in the modulation of goal-directed behavior, and could play a key role in the pathophysiology and in the production of symptoms and signs in schizophrenia. We have studied the relationship between the objective measures of the striatal structures, as evaluated by magnetic resonance imaging (MRI), and the Wisconsin Card Sorting Test (WCST) performance in a schizophrenic sample. Thirty-five schizophrenic patients underwent MRI scans of striatal structure and neuropsychological evaluation of executive functions by WCST. Poor WCST performers had a reduction of the left caudate nucleus and putamen, and right total striatum when compared to 24 healthy controls. Significant correlation coefficients were also observed between neuropsychological indexes and left striatal measures. The findings suggest the existence of a relationship between abnormalities of striatal structure and abnormal executive-type or organizational cognitive functions.

Adult↗
PubMed2005

Pallidal index on MRI as a target organ dose of manganese: structural equation model analysis.

We have used a structural equation model (SEM) to analyze the interrelationships among exposure markers, magnetic resonance imaging (MRI) signal index, and neurobehavioral effects. Based on exposure groups, we assessed blood manganese, MRI measurements of pallidal index (PI), and neurobehavioral core test battery (WHO-NCTB) on 111 male workers occupationally exposed to manganese, including welders, smelter workers, and welding rod manufacturing workers. Latent variables were constructed to represent the neurobehavioral effects in an integrated way. The structural equation model revealed that airborne manganese and blood manganese contribute to PI significantly. Manganese exposure in the ambient air may lead to an increase in the internal dose, not only indirectly, by increasing blood manganese level, but also directly, independent of blood concentration. PI significantly contributed to a decrease in neurobehavioral test scores. We found that airborne manganese contributed to PI, and that PI is the most effective predictor of neurobehavioral performance, after adjusting for age and level of education. In conclusion, PI on MRI reflects target organ dose of occupational manganese exposure.

Accidents, Occupational↗
PubMed2005

Functional approximation and optimal specification of the mechanical risk index.

The mechanical risk index (MRI) is a numerical measure that quantifies the complexity of drilling a well. The purpose of this article is to examine the role of the component factors of the MRI and its structural and parametric assumptions. A meta-modeling methodology is applied to derive functional expressions of the MRI, and it is shown that the MRI can be approximated in terms of a linear functional. The variation between the MRI measure and its functional specification is determined empirically, and for a reasonable design space, the functional specification is shown to a good approximating representation. A drilling risk index is introduced to quantify the uncertainty in the time and cost associated with drilling a well. A general methodology is outlined to create an optimal MRI specification.

Journal Article↗
PubMed2005

Separating functional and structural damage in persistent vegetative state using combined voxel-based analysis of 3-D MRI and FDG-PET.

Functional and structural damage in postanoxic persistent vegetative state (PVS) was analysed using 18fluorodeoxyglucose PET (FDG-PET) coregistered to 3-D MRI in combination with morphometric 3-D MRI analysis (voxel-based morphometry, VBM). In five patients in late stages of non-traumatic PVS, combined analysis using statistical parametric mapping (SPM2) was performed to compare metabolic impairment and structural loss. FDG-PET showed widespread hypometabolism at p<0.001 (corrected) in the parietal, parietooccipital and frontotemporal cortices, cingulum, frontal medial and precentral gyrus, and within the bilateral thalamus. VBM revealed multilocal structural loss at p<0.001 (corrected) in the inferior parietal and superior/medial frontal cortices, insula and operculum, superior and medial temporal lobes, cingulum and fusiform gyrus, caudate, midbrain, dorsal pons, and the cerebellum, but to a lesser extent in the thalamus. The selective vulnerability of the brain in a sample of PVS patients could be mapped in vivo, indicating that a complex structural and functional lesion pattern of the cerebral networks seems to be associated with this condition.

Adult↗
PubMed2001

A new method to investigate brain stem structural-functional correlations using digital post-processing MRI--reliability in ischemic internuclear ophthalmoplegia.

We investigated the reliability of a new digital post-processing magnetic resonance imaging (MRI) technique in ischemic brain stem lesions to identify relations of the lesion to anatomical brain stem structures. The target was a medial longitudinal fasciculus (MLF) lesion, which was evident from ipsilateral internuclear ophthalmoplegia (INO). Sixteen patients with acute unilateral INO and an isolated acute brain stem lesion in T2- and EPI-diffusion weighted MRI within 2 days after the onset of symptoms were studied. The MRI slice direction was parallel and perpendicular to a slice selection of a stereotactic anatomical atlas. The individual slices were normalized and projected in the digitalized atlas. The eye movement disorder was monitored by electro-oculography. In all patients with clinical or subclinical electro-oculographically documented INO and MRI proven brain stem infarction the lesion covered or at least partially overlapped the ipsilateral MLF at one or more atlas levels. We conclude that digital post-processing MRI with normalizing and projecting brain stem lesions in an anatomical atlas is a reliable method to demonstrate the anatomical structures involved by the lesion. Combined with electrophysiological brain stem testing, this method may be a useful tool to identify incompletely understood pathways mediating brain stem reflexes or the generators of evoked potentials.

Adult↗
PubMed2000

Memory and MRI-based hippocampal volumes in aging and AD.

OBJECTIVE: To demonstrate structural-functional relationships between MRI-based volumetric measurements of medial temporal lobe structures and cognitive function. BACKGROUND: Previous work has documented the ability of MRI-based measurements of the hippocampus to discriminate between age-matched control subjects and patients with very mild AD. Relatively less is known about the correlation between medial temporal lobe structures and cognitive functions. METHOD: We evaluated structural-functional relationships among the hippocampal formation, parahippocampal gyrus, and amygdala, and measures of memory, language, and general cognitive performance in 220 probable AD patients and normal control subjects. Standardized instruments of memory and general cognitive function were used to assess subjects enrolled in a longitudinal study of aging and dementia. RESULTS: The volume of the hippocampal formation predicted performance on most acquisition and recall measures across the spectrum of normal aging and AD. If the groups were segregated, most of the expected associations between medial temporal lobe structures and memory measures were observed in the AD patients. CONCLUSION: MRI-based hippocampal volumetry accurately depicts the structural-functional relationships between memory loss and hippocampal damage across the spectrum from normal aging to dementia.

Aged↗
PubMed2001

MR perfusion imaging in Moyamoya Syndrome: potential implications for clinical evaluation of occlusive cerebrovascular disease.

BACKGROUND AND PURPOSE: Ischemic symptoms in patients with moyamoya syndrome (MMS) are usually due to hemodynamically mediated perfusion failure, and identification of abnormal tissue perfusion in these patients is therefore clinically important. Although dynamic susceptibility contrast (DSC) MRI can be used to study tissue perfusion, there are potential technical problems in MMS. This study investigates the scope and limitations of perfusion MRI in the clinical evaluation of such patients. METHODS: Thirteen patients with bilateral MMS were studied with the use of structural, diffusion, and perfusion MRI. The DSC MRI data were analyzed both visually and by a quantitative regional analysis, and the relationship between perfusion status and clinical symptoms was investigated. RESULTS: Extensive bilateral DSC MRI abnormalities were observed in all the patients. There was a very heterogeneous distribution of bolus arrival time. The areas of abnormality included the major arterial border zones in all cases, although these usually appeared normal on structural and diffusion MRI. Only the most clinically unstable patients had peak width (defined as time to peak minus bolus arrival time) >5 seconds on the quantitative regional analysis. Several technical limitations of perfusion quantification in MMS are described, as well as the implications of these limitations in patients with other forms of occlusive large-vessel disease. CONCLUSIONS: The technical limitations of DSC MRI described in this study are important for the accurate interpretation of perfusion MRI in MMS. Despite these limitations, these preliminary findings suggest that the use of quantitative regional analysis of summary parameters may provide clinically useful information in patients with MMS.

Adolescent↗
PubMed1997

Cortical grey matter and benzodiazepine receptors in malformations of cortical development. A voxel-based comparison of structural and functional imaging data.

Using [11C]flumazenil-PET and statistical parametric mapping (SPM), we have shown recently that regions of increased and decreased benzodiazepine receptor density may be seen in patients with localization-related epilepsy due to malformations of cortical development. These abnormalities were seen both within and beyond lesions visually apparent on high-resolution MRI. We have also shown, using an interactive anatomical segmentation technique and volume-of-interest measurements, that subtle and unsuspected abnormalities of cortical grey matter volume were found in the same group of patients on high-resolution MRI, beyond the lesions visually apparent. In 10 patients with localization-related epilepsy and malformations of cortical development, we have now applied the automated and objective technique of SPM to the analysis of high-resolution structural MRI. Each individual patient was compared with 16 normal control subjects. We have then simultaneously compared the structural and functional data obtained for each individual patient with normal control high-resolution MRI and [11C]flumazenil-PET image using a novel technique. This comparison allowed the detection of functional abnormalities that were not accounted for by either visible or unsuspected structural abnormalities, in an automated and statistically rigorous manner. Five patients had abnormalities of cortical grey matter volume detected using SPM; only these five patients had been found abnormal using the previous volume-of-interest technique. Six of the 10 patients showed regions of cerebral cortex with disproportionate flumazenil binding compared with local grey matter volume. This included regions not found to have abnormal flumazenil binding on analysis of the PET data alone. Furthermore, regions found to have abnormal binding on examination of the PET data alone were, in some instances, shown to be accounted for by abnormalities of cortical grey matter volume. We conclude that the analysis of ligand PET data should always include a comparison with structural MRI; such comparisons are greatly facilitated by the novel approach described.

Adolescent↗
PubMed2002

Structure analysis of high resolution magnetic resonance imaging of the proximal femur: in vitro correlation with biomechanical strength and BMD.

The purpose of this study was to use high resolution magnetic resonance imaging (HR-MRI) combined with structure analysis to investigate the trabecular structure of the human proximal femur and to compare this technique with bone mineral density (BMD) using dual energy X-ray absorptiometry (DXA) in the prediction of bone strength in vitro. Thirty-one fresh human proximal femur specimens were examined with HR-MRI using a T1-weighted 3D spinecho-sequence in a coronal plane (voxel size: 0.195 x 0.195 x 0.9 mm and 0.195 x 0.195 x 0.3 mm). In these images structure parameters analogous to standard bone histomorphometry were obtained in a femoral head, neck, and trochanteric region of interest (ROI). In addition, BMD measurements were obtained using DXA and finally, all specimens were tested biomechanically in a materials testing machine, and maximum compressive strength (MCS) was determined. Correlations between BMD and MCS were significant (p <0.01) with R-values up to 0.74. Correlating structure parameters and MCS R-values up to 0.69 (P <0.01) were obtained. Using multivariate regression analysis, combining structure parameters and BMD, improved correlations versus MCS substantially (up to R = 0.93; P <0.01). In conclusion, this study showed that in an experimental setting, structure parameters determined in high resolution MR images of the proximal femur correlated significantly with bone strength. The highest correlations, however, were obtained combining BMD and structure measures.

Aged↗
PubMed2005

Visualization of intraarticular structures of the acromioclavicular joint in an ex vivo model using a dedicated MRI protocol.

OBJECTIVE: The purpose of this study was to develop an MRI protocol that could visualize the intraarticular structures of the acromioclavicular (AC) joint. MATERIALS AND METHODS: Using six fresh specimens from cadaveric shoulders, several MRI sequences were performed on 1.0-T scanners with a superficial coil (the temporomandibular joint coil). After the radiologic examination, the specimens were prepared for histology and 300-microm-thick, toluidine blue-stained sections were prepared that corresponded to the MR images. In each series of sections, immunohistochemistry using a type II collagen antibody was performed to further characterize the intraarticular structures. RESULTS: The coronal 3D T1-weighted fast-field echo water-selective sequence allowed the identification of the intraarticular disk in all cases. Determination on MRI of other intraarticular structures--adipose tissue, synovial fluid, and the borders between neighboring tissues of different types--that corresponded to the histologic sections was possible. The use of a second plane in the 1.0-T sequences did not reveal additional information. CONCLUSION: The described MRI protocol allows the visualization of the intraarticular fibrocartilaginous disk and the border between articular cartilage and the disk. Future clinical studies will indicate the diagnostic value of this protocol. We assume that this MRI protocol could help us to better understand AC joint disorders, in particular those located intraarticularly, and dislocations.

Acromioclavicular Joint↗
PubMed2026

Treatment-related associations of nucleus accumbens connectivity within mesocorticolimbic circuits in depression.

Pharmacological treatment remains a mainstay in managing depression, yet the neural correlates associated with treatment response remain incompletely understood. This study used multimodal neuroimaging to examine nucleus accumbens (NAc)-centered structural and functional alterations associated with fluoxetine and Shugan Jieyu Capsule (SG), a traditional Chinese medicine, in patients with mild-to-moderate depression (MMD). Sixty patients were randomized to an 8-week course of fluoxetine or SG. Depression severity was assessed using the 24-item Hamilton Depression Rating Scale (HAMD-24), and structural and functional MRI scans were acquired at baseline and endpoint. Both treatments were associated with significant symptom improvement. Neuroimaging analyses revealed structural and functional alterations involving the NAc. Changes in NAc-amygdala connectivity showed an exploratory association with symptom improvement in the SG group, whereas changes in NAc-rostral anterior cingulate cortex connectivity were associated with symptom improvement in the fluoxetine group and remained significant after correction for multiple comparisons. In addition, remitters exhibited stronger baseline connectivity between the NAc and ventral tegmental area and between the NAc and middle frontal gyrus compared with non-remitters. These findings suggest that NAc-centered connectivity may be relevant to treatment-related neural changes in depression and may inform future research on imaging-based candidate markers of treatment response and personalized treatment approaches. TRIAL REGISTRATION: The study is registered in https://www.chictr.org.cn/ with a registration number ChiCTR1900024988 (date: 08.06.2019).

Humans↗
PubMed1991

[Nuclear magnetic resonance tomography and ultrasound imaging of anatomic structures of the shoulder joint].

The possibilities of MRI and ultrasound in visualizing the structures of the shoulder joint are compared. Both methods have a good accuracy in detecting changes of the soft tissue of the shoulder. Changes of the cartilage and the bony structures are better seen in the MRI. The MRI gives a static and clear view of the shoulder joint, meanwhile the ultrasound depends on the dynamic examination. Ultrasound and MRI are both reproducible and non-invasive methods, who seem to complete one another at the examination of the shoulder.

Acromioclavicular Joint↗
PubMed2003

Functional MRI in neonates using neonatal head coil and MR compatible incubator.

Structural and functional magnetic resonance imaging of the newborn brain is a complex and challenging task. Term and preterm neonates require a controlled microenvironment and close monitoring during the MRI study to maintain respiratory and cardiovascular functions, body temperature, and fluid and electrolyte homeostasis. In addition, to minimize motion artifacts, most neonates also need to be sedated, which carries the risk of respiratory depression compromising the neonate's ability to maintain appropriate ventilation and oxygenation during the procedure. Finally, because of their small head size, the use of the standard MR head coils results in suboptimal picture quality in the neonate. Thus, these limitations affect our ability to obtain both high quality structural and functional MRI studies. To overcome these difficulties, we have utilized an MR compatible incubator with a built-in radiofrequency head coil optimized for the neonatal brain volume. In this study we demonstrate that functional MRI and high-resolution structural MRI of the newborn brain can be achieved with this novel design. The use of this equipment offers potential for studying the development of the preterm and term neonatal brain and obtaining state-of-the-art, high-resolution structural and functional imaging in this most vulnerable patient population.

Chloral Hydrate↗
PubMed1992

Nuclear magnetic resonance and the brain.

The first successful demonstrations of nuclear magnetic resonance (NMR) in bulk matter were reported in 1946 (Bloch, Hansen and Packard 1946; Purcell, Torrey and Pound 1946). Since then NMR has become a widespread technique for investigating matter of all kinds. In the 1970's NMR was applied to living systems, including man, in 2 distinct approaches. One application was in the production of images (Lauterbur 1973), called Magnetic Resonance Imaging or MRI, and the other in the production of NMR spectra (Moon and Richards 1973; Hoult et al. 1974), called Magnetic Resonance Spectroscopy or MRS. By appropriate manipulation of the NMR signal an NMR image may be generated. This can be a 2D image of a single slice, or a set of 2D images of parallel slices, or a 3D image. 2D images may be obtained directly in any orientation, axial, coronal, sagittal. The method uses no ionizing radiation and is inherently safe. It is non-invasive, although paramagnetic solutions may be injected intravenously to improve contrast. MRI images observed in normal clinical practice are maps of the NMR signals from water and fat in the tissues; they depend on proton density, but also significantly on the relaxation times T1 and T2. Images can be provided of flow (MR angiography) and diffusion (free, restricted or anisotropic). Images are typically 512 x 512 pixels with spatial resolution of about 0.5 mm. The images can be correlated with anatomical structures and indeed MRI is a primary source of such structures with localization precision of 0.5 mm as in CT.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗