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Results for “Structural MRI”

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PubMed2004

MRI of the brainstem in patients with major depression, bipolar affective disorder and normal controls.

Structural imaging studies of bipolar affective disorder or major depression have shown a spectrum of abnormal findings. However, a characteristic pattern of abnormality for either disease has not yet emerged. While the majority of studies focused on brain atrophy and the volumes of supratentorial cerebral structures, little attention has been paid to infratentorial structures. This MRI study focused on the pontomesencephalic area including the region of the raphe nuclei. The raphe nuclei are of special interest in affective disorders as they are the origin of the major serotonergic projections in this region. MRI scans of 10 bipolar I patients, 10 patients with major depression and 10 age-matched healthy control subjects were studied. The brain stem and the fourth ventricle areas as well as T2-relaxation times in the area of the raphe nuclei were evaluated. A difference between patients with major depression and control subjects for T(2)-relaxation times was found in a region of interest located along the midline of the pons. No difference was found between patients with bipolar disorder and control subjects. This finding needs to be replicated in a larger sample with more elaborated MRI techniques (multi-echo sequences) for the determination of T2-relaxation times.

Adult↗
PubMed2003

Investigation of the microstructure of the isolated rat heart: a comparison between T*2- and diffusion-weighted MRI.

Myocardial fiber structure can be determined with diffusion-weighted (DW) MRI as well as with high-resolution T*(2) imaging. The purpose of the present study was twofold: to provide a more quantitative description of T*(2)-based myocardial fiber contrast, and to compare the T*(2)-based fiber structure with high-resolution (78 microm in-plane, 1-mm slice thickness) DW images of the isolated rat heart at 11.75 T. This study demonstrates that the static dephasing regime is responsible for visualization of myocardial microstructure, and that the dynamic dephasing regime can be neglected. In comparison with DW experiments, T*(2) mapping and DW images yield almost equivalent information on myocardial fiber structure.

Animals↗
PubMed2002

Correlations between structural CNS damage and functional MRI changes in primary progressive MS.

In patients with primary progressive multiple sclerosis (PPMS), we investigated whether brain and cervical cord structural changes in lesions and normal-appearing brain tissue (NABT), measured using conventional, magnetization transfer (MT), and diffusion tensor (DT) MRI, are correlated with movement-associated cortical activations measured using functional magnetic resonance imaging (fMRI). From 26 right-handed PPMS patients and 15 right-handed, sex- and age-matched healthy controls, we obtained: (a) brain and cervical cord dual-echo scans and MT ratio (MTR) maps; (b) brain mean diffusivity (D(-)) maps, and (c) f-MRI (flexion-extension of the last four fingers of the right hand). All PPMS patients had no previous symptoms affecting their right upper limbs, which were functionally normal. Healthy volunteers showed more significant activation in the ipsilateral cerebellar hemisphere than PPMS patients. PPMS patients showed greater activation bilaterally in the superior temporal gyrus, ipsilaterally in the middle frontal gyrus, and, contralaterally in the insula/claustrum. In PPMS patients, moderate to strong correlations (r values ranging from 0.59 to 0.68) were found between relative activations of cortical areas located in a widespread network for sensory-motor and multimodal integration and the severity of structural changes of the NABT (as measured using MT and DT MRI) and the severity of cervical cord damage (as measured using MT MRI). This study shows that the pattern of cortical activation of PPMS patients is different from that of normal controls even when performing a motor task with clinically unaffected limbs. It also suggests that cortical reorganization might be able to limit the consequences of MS injury in the brain and cervical cord.

Adult↗
PubMed1992

The clinical utility of magnetic resonance imaging in 3-dimensional treatment planning of brain neoplasms.

Results of the clinical experience gained since 1986 in the treatment planning of patients with brain neoplasms through integration of magnetic resonance imaging (MRI) into computerized tomography (CT)-based, three-dimensional treatment planning are presented. Data from MRI can now be fully registered with CT data using appropriate three-dimensional coordinate transformations allowing: (a) display of MRI defined structures on CT images; (b) treatment planning of composite CT-MRI volumes; (c) dose display on either CT or MRI images. Treatment planning with non-coplanar beam arrangements is also facilitated by MRI because of direct acquisition of information in multiple, orthogonal planes. The advantages of this integration of information are especially evident in certain situations, for example, low grade astrocytomas with indistinct CT margins, tumors with margins obscured by bone artifact on CT scan. Target definitions have repeatedly been altered based on MRI detected abnormalities not visualized on CT scans. Regions of gadolinium enhancement on MRI T1-weighted scans can be compared to the contrast-enhancing CT tumor volumes, while abnormalities detected on MRI T2-weighted scans are the counterpart of CT-defined edema. Generally, MRI markedly increased the apparent macroscopic tumor volume from that seen on contrast-CT alone. However, CT tumor information was also necessary as it defined abnormalities not always perceptible with MRI (on average, 19% of composite CT-MRI volume seen on CT only). In all, the integration of MRI data with CT information has been found to be practical, and often necessary, for the three-dimensional treatment of brain neoplasms.

Astrocytoma↗
PubMedDate not supplied

Structural and functional magnetic resonance imaging of autism.

Magnetic resonance imaging (MRI) of brain structures and function is uniquely suited to characterize the range of neuroanatomical and physiological changes that characterize the autism phenotype as it develops over time. In this review, we examine the scientific literature in MRI as applied to autism and related areas, over approximately the last decade, discussing findings which have emerged, methodological stumbling blocks which have been identified, and potential future directions. Structural MRI studies have recently begun to elucidate the neurodevelopmental underpinnings and brain-behavior relationships in autism while fMRI studies, building on the wealth of data in normal individuals, are beginning to characterize the underlying neuropsychological deficits of the disorder. Together, these two methods combine to contribute to a better understanding of the neural basis and brain phenotype of this disorder.

Autistic Disorder↗
PubMed2001

Magnetic resonance imaging in the evaluation of congenital anomalies of the external genitalia.

OBJECTIVES: To assess the value of magnetic resonance imaging (MRI) in the anatomic evaluation and management planning of complex congenital genitourinary anomalies. METHODS: Multiplanar T(1) and T(2)-weighted MR images were obtained in 6 pediatric patients with congenital genitourinary anomalies, including aphallia, diphallia, ectopic scrotum, and epispadias. The imaging studies were read by experienced radiologists and discussed with the urologic surgeons in a multidisciplinary conference. RESULTS: Each congenital anomaly was demonstrated in detail by MRI. The MR images of penile agenesis showed hypoplastic corpora cavernosa and a vestigial bulb. In patients with penile duplication, MRI was able to delineate the course of each corporal body and the varying degree of thickness of the tunica albuginea. For the patient with scrotal ectopia, detailed MR images excluded both the possibility of urethral and corporal duplications and the presence of viable testes in the ectopic scrotum. In the case of epispadias, MRI illustrated the precise spatial relationship between the erectile bodies and urethra. Additionally, MRI identified related aberrant pelvic organs and provided images of the external genital structures. CONCLUSIONS: MRI, by rendering excellent anatomic interpretation of complex genital anomalies and associated abnormal pelvic tissues, assists surgeons in conceptualizing the anomalous structures and contributes to their formulation of management approaches.

Adult↗
PubMed1989

Marchiafava-Bignami disease with recovery diagnosed by CT and MRI: demyelination affects several CNS structures.

Marchiafava-Bignami disease (MBD) is a rare complication of chronic alcoholism. Most reported cases have been diagnosed at autopsy. With CT and, especially, MRI it is possible to diagnose MBD in its early stages. Lesions of CNS structures other than the typical demyelination of the corpus callosum are described ante mortem in a patient with MBD. The more frequent use of CT and MRI in sudden onset encephalopathies of alcoholics could reveal the real incidence of MBD, and the consequent detection of other involved CNS systems might improve our knowledge about the aetiology, pathogenesis, prognosis and therapy of MBD.

Alcoholism↗
PubMed2002

Anomalous muscle of the wrist.

A case of an anomalous muscle found in the right wrist of a 52-year-old man during routine carpal tunnel decompression surgery is reported. The muscle was observed lying transversely across the carpal tunnel superficial and parallel to the flexor retinaculum. Its further definition was subsequently demonstrated by postoperative magnetic resonance imaging (MRI). No similar structure was detectable on MRI of the left wrist.

Carpal Tunnel Syndrome↗
PubMed2003

Gender and age effects in structural brain asymmetry as measured by MRI texture analysis.

Effects of gender and age on structural brain asymmetry were studied by 3D texture analysis in 380 adults. Asymmetry is detected by comparing the complex 3D gray-scale image patterns in the left and right cerebral hemispheres as revealed by anatomical T1-weighted MRI datasets. The Talairach and Tournoux parcellation system was applied to study the asymmetry on five levels: the whole cerebrum, nine coronal sections, 12 axial sections, boxes resulting from both coronal and axial subdivisions, and by a sliding spherical window of 9 mm diameter. The analysis revealed that the brain asymmetry increases in the anterior-posterior direction starting from the central region onward. Male brains were found to be more asymmetric than female. This gender-related effect is noticeable in all brain areas but is most significant in the superior temporal gyrus, Heschl's gyrus, the adjacent white matter regions in the temporal stem and the knee of the optic radiation, the thalamus, and the posterior cingulate. The brain asymmetry increases significantly with age in the inferior frontal gyrus, anterior insula, anterior cingulate, parahippocampal gyrus, retrosplenial cortex, coronal radiata, and knee region of the internal capsule. Asymmetry decreases with age in the optic radiation, precentral gyrus, and angular gyrus. The texture-based method reported here is based on extended multisort cooccurrence matrices that employ intensity, gradient, and anisotropy features in a uniform way. It is sensitive, simple to reproduce, robust, and unbiased in the sense that segmentation of brain compartments and spatial transformations are not necessary. Thus, it should be considered as another tool for digital morphometry in neuroscience.

Adolescent↗
PubMed2006

Controlling diffusion of 3He by buffer gases: a structural contrast agent in lung MRI.

PURPOSE: To study the influence of admixing inert buffer gases to laser-polarized (3)He in terms of resulting diffusion coefficients and the consequences for image contrast and resolution. MATERIALS AND METHODS: The diffusion coefficient of (3)He was altered by admixing buffer gases of various molecular weights ((4)He, N(2), and SF(6)). The influence of the pulse sequence and the diffusion coefficient on the appearance of MRI of (laser-polarized) gases was analyzed by comparison of basic theoretical concepts with demonstrative experiments. RESULTS: Excellent agreement between theoretical description and observed signal in simple gradient echoes was observed. A maximum signal gain can be predicted and was experimentally validated. Images acquired under such conditions revealed improved resolution. The nature and concentration of the admixed gas defines a structural threshold for the observed apparent diffusion coefficient (ADC) as demonstrated with diffusion-weighted MRI on a pig's lung flooded with suitable gas mixtures. CONCLUSION: A novel procedure is proposed to control the diffusion coefficient of gases in MRI by admixture of inert buffer gases. Their molecular mass and concentration enter as additional parameters into the equations that describe structural contrast. This allows for setting a structural threshold up to which structures contribute to the image. For MRI of the lung this enables images of very small structural elements (alveoli) only, or in the other extreme, all airways can be displayed with minimal signal loss due to diffusion.

Contrast Media↗
PubMed2005

Gadolinium meets medicinal chemistry: MRI contrast agent development.

Magnetic resonance imaging (MRI) contrast agents are utilized adjunctively to enhance the contrast between normal and abnormal structures on MRI scans. Along with the rapid evolution of the field has come a new appreciation for the medicinal chemistry of this unique class of metallopharmaceuticals. The efficacy of MRI agents is a complex function of chemical, biophysical, and pharmacological properties, which must be married in a package of exquisite safety. This report illustrates the wide range of medicinal chemistry relevant to existing agents that are either approved or in clinical development, as well as concepts, which may result in exciting new pharmaceuticals in the future.

Chelating Agents↗
PubMed2007

[Imaging in ankylosing spondylitis].

In addition to the typical clinical symptoms, conventional x-rays and magnetic resonance imaging (MRI) are important for the diagnosis and management of ankylosing spondylitis (AS). While radiography is mainly useful for detecting chronic structural changes, MRI is, in addition, able to detect active inflammation. The detection of structural changes in the sacroiliac joints and, in part, the spine, remains the gold standard for the diagnosis of AS. The detection of active sacroiliitis or spondylitis in early disease stages is only possible using MR techniques such as STIR and T1 post-gadolinium sequences. Lateral radiographs of the spine are useful for detecting shiny corners and the characteristic syndesmophytes and ankylosis. The modified Stoke Anklyosing Spondylitis Spine Score (SASSS) is the best scoring method for quantifying such changes, allthough only the cervical and the lumber spine are evaluated with this method. MRI changes can also be quantified. New scoring methods are sensitive to change only 3 months after initiation of therapy with anti-TNF agents.

Humans↗
PubMed2000

A functional MRI case study of acquired cerebral dyschromatopsia.

Evidence from imaging studies suggests that primary visual cortex and multiple areas in ventral occipitotemporal cortex subserve color perception in humans. To learn more about the organization of these areas, we used structural and functional MRI (fMRI) to examine a patient with damage to ventral cortex. An art professor, KG, suffered a cerebrovascular accident during heart surgery that impaired his ability to perceive color. The Farnsworth-Munsell 100-Hue test was used to assess the extent of his deficit. When tested 12 months after the lesion, KG performed worse than 95% of age-matched normals on the 100-Hue test, but well above chance. Structural and functional MRI studies were conducted 3 years after the lesion to investigate the neuroanatomical correlates of KG'ss remaining color ability. Structural MRI revealed bilateral damage to ventral occipitotemporal cortex. In young and age-matched normal controls, an fMRI version of the 100-Hue reliably activated bilateral, color-selective regions in primary visual cortex and anterior and posterior ventral cortex. In subject KG, color-selective cortex was found in bilateral primary visual cortex. In ventral cortex, no color-selective activity was observed in right ventral cortex, and only a small area of activity was observed in left anterior ventral cortex. However, significant color-selective activity was observed in posterior left ventral cortex spared by the lesion. This posterior left ventral activation was similar in extent, position, and degree of color-selectivity to the posterior left posterior activation observed in normal controls, suggesting that this focus may be the cortical substrate underlying KG's remaining color perception.

Adult↗
PubMed2006

Posterior longitudinal ligament status in cervical spine bilateral facet dislocations.

OBJECTIVE: It is generally accepted that cervical spine bilateral facet dislocation results in complete disruption of the posterior longitudinal ligament. The goal of this study was to evaluate the integrity of numerous spine-stabilizing structures by MRI, and to determine if any associations between injury patterns exist with respect to the posterior longitudinal ligament status. DESIGN: Retrospective case series. PATIENTS: A retrospective review was performed of 30 cervical spine injury subjects with bilateral facet dislocation. Assessment of 1.5T MRI images was carried out for: intervertebral disc disruption, facet fracture, and ligamentous disruption. Statistical analyses were performed to evaluate for associations between various injury patterns and posterior longitudinal ligament status. RESULTS: The frequency of MRI abnormalities was: anterior longitudinal ligament disruption (26.7%), disc herniation or disruption (90%), posterior longitudinal ligament disruption (40%), facet fracture (63.3%) and disruption of the posterior column ligament complex (97%). There were no significant associations between injury to the posterior longitudinal ligament and other structures. Compared to surgical reports, MRI was accurate for determining the status for 24 of 26 ligaments (three of three anterior longitudinal ligament, seven of nine posterior longitudinal ligament, and 14 of 14 posterior column ligament complex) but generated false negatives in two instances (in both MRI showed an intact posterior longitudinal ligament that was torn at surgery). CONCLUSIONS: In contradistinction to the existing concept, the posterior longitudinal ligament can remain intact in a substantial proportion of hyperflexion injuries that produce bilateral cervical facet dislocation. Posterior longitudinal ligament integrity is not associated with any other injury pattern related to the anterior longitudinal ligament, intervertebral disc or facet fracture.

Adult↗
PubMed1985

X-ray and magnetic resonance stereotaxy for functional and nonfunctional neurosurgery.

By means of new plastic stereotactic ring and head fixers, stereotactic procedures can be combined with MRI, with stereotactic coordinates obtained from the MRI images. The method was rechecked against CT stereotaxy and shows a good correspondence of the target coordinates. With MRI stereotaxy, structures near bony regions will be more accessible than with CT stereotaxy. Moreover, the MRI procedure seems to have advantages for functional therapy without the necessity of contrast ventriculography.

Brain Neoplasms↗
PubMedDate not supplied

MRI of right atrial pseudomass: is it really a diagnostic problem?

OBJECTIVE: To determine whether the high proportion of patients reported to have prominence of normal right atrial structures by MRI may lead to inappropriate diagnosis of intracardiac tumors. MATERIALS AND METHODS: One hundred forty-nine subjects were examined by spin-echo MRI: patients with cardiac (no. 40), pericardial (no. 30), or thoracic aortic disease (no. 40) and mediastinal tumor (no. 15), and normal volunteers (no. 24). Imaging was reviewed to determine the frequency of a prominent crista terminalis/Chiari network and the likelihood of misdiagnosis of cardiac tumor. RESULTS: Prominent intraatrial structures were seen in 59% of subjects, a single prominent nodule in 36%, an intraatrial strand in 13%, and both in 10%. In no case were these findings originally or on review thought to represent a pathological mass or was it felt likely that they could reasonably be misinterpreted as such. CONCLUSION: Normal structures within the right atrium, such as the crista terminalis and Chiari network, may be seen more commonly with MRI than with other imaging modalities. An appreciation of the frequency with which these findings are seen should prevent inappropriate misdiagnosis of pathological masses when none is present.

Diagnostic Errors↗
PubMed2004

Influence of age and osteoporosis on calcaneus trabecular bone structure: a preliminary in vivo MRI study by quantitative texture analysis.

Recent developments in high-resolution MR imaging techniques have opened up new perspectives for structural characterization of trabecular bone by non-invasive methods. In this study, 3-D MR imaging was performed on 17 healthy volunteers and 6 osteoporotic patients. Two different MR sequences were used to evaluate the impact on MR acquisition on texture analysis results. Images were analyzed with four automated methods of texture analysis (grey level histogram, cooccurrence, runlength and gradient matrices) enabling quantitative analysis of grey level intensity and distribution within three different regions of interest (ROI). Texture analysis is not very frequently used since the interpretation of the large number of calculated parameters is difficult. We applied multiparametric data analyses such as principal component analysis (CFA) and hierarchical ascending classification (HAC) to determine the relevant parameters to differentiate between three sets of images (healthy young volunteers, healthy postmenopaused and osteoporotic patients). The results suggest that relevant texture information (depending on the ROI localization in the calcaneus) can be extracted from calcaneus MR images to evaluate osteoporosis and age effects on trabecular bone structure if strictly the same acquisition sequences are used for all patients' examination.

Adult↗
PubMed2004

Diagnostic value of magnetic resonance imaging and computed tomography for oral masses in dogs.

The purpose of this study was to determine the diagnostic value of magnetic resonance imaging (MRI) and computed tomography (CT) in oral masses of dogs. Nineteen dogs underwent clinical, MR and CT examinations. Eleven malignant and ten non-malignant masses were evaluated. Osteosarcoma was the most commonly found malignant oral mass and gingival hyperplasia was the most commonly found benign mass. The results showed that MRI provided more accurate information regarding the size of the masses and invasion of adjacent structures although MRI and CT show similar accuracy in assessment of bone invasion. Calcification and cortical bone erosion was better seen on CT images. Whereas contrast-MRI provided useful additional information, contrast-CT had no added benefit. In general, oral masses located in the caudal mandible, oropharynx and maxilla are better evaluated using MRI, once the histological type has been verified.

Animals↗