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At least 1,153 records · Page 64Linked to original sources
PubMed1996

Neuroepithelial cyst of the posterior fossa: two case reports with radiologic-pathologic correlation.

The clinical, radiologic and pathological findings in two cases of neuroepithelial cyst of the posterior fossa are described. The first patient was a 43-year-old woman who presented with clumsiness of the hands, gait disturbance and slurring of speech. Magnetic resonance imaging (MRI) revealed a large cystic structure between the cerebellum and the brain stem on the left side, accompanied by compression of the medulla oblongata and displacement of the forth ventricle to the right. The second patient was an 11-month-old boy who presented with progressive bulbar dysfunction. He had previously undergone surgery for myelomeningocele and hydrocephalus associated with Arnold-Chiari type 2 malformation. MRI revealed a large cystic mass isointense with cerebrospinal fluid between the cerebellum and the midbrain, compressing the fourth ventricle and displacing the brain stem to the right. The cases were pathologically similar, the cyst containing a single layer of cuboidal epithelium and rims of neuroglial cells. Immunohistochemical staining was consistent with neuroepithelial cyst. It is important to distinguish this type of cyst from a malignant mass to ensure appropriate treatment and determine the prognosis. In addition, even though neuroepithelial cysts of the posterior fossa are benign, they are often symptomatic because of their mass effect. The second case was unusual because the cyst developed over a period of 2 months, which shows that this type of cyst can develop rapidly. To the authors' knowledge, the association with Arnold-Chiari type 2 malformation has not previously been reported.

Adult↗
PubMed1991

Computer-assisted superimposition of magnetic resonance and high-resolution technetium-99m-HMPAO and thallium-201 SPECT images of the brain.

A method for registering three-dimensional CT, MR, and PET data sets that require no special patient immobilization or other precise positioning measures was adapted to high-resolution SPECT and MRI and was applied in 14 subjects (five normal volunteers, four patients with dementia (Alzheimer's disease), two patients with recurrent glioblastoma, and three patients with focal lesions (stroke, arachnoid cyst and head trauma]. T2-weighted axial magnetic resonance images and transaxial 99mTc-HMPAO and 201Tl images acquired with an annular gamma camera were merged using an objective registration (translation, rotation and rescaling) program. In the normal subjects and patients with dementia and focal lesions, focal areas of high uptake corresponded to gray matter structures. Focal lesions observed on MRI corresponded to perfusion defects on SPECT. In the patients who had undergone surgical resection of glioblastoma followed by interstitial brachytherapy, increased 201Tl corresponding to recurrent tumor could be localized from the superimposed images. The method was evaluated by measuring the residuals in all subjects and translational errors due to superimposition of deep structures in the 12 subjects with normal thalamic anatomy and 99mTc-HMPAO uptake. This method for superimposing magnetic resonance and high-resolution SPECT images of the brain is a useful technique for correlating regional function with brain anatomy.

Alzheimer Disease↗
PubMed2005

Comparison of voxel-based 3-D MRI analysis and subtraction ictal SPECT coregistered to MRI in focal epilepsy.

While voxel-based 3-D MRI analysis methods as well as assessment of subtracted ictal versus interictal perfusion studies (SISCOM) have proven their potential in the detection of lesions in focal epilepsy, a combined approach has not yet been reported. The present study investigates if individual automated voxel-based 3-D MRI analyses combined with SISCOM studies contribute to an enhanced detection of mesiotemporal epileptogenic foci. Seven consecutive patients with refractory complex partial epilepsy were prospectively evaluated by SISCOM and voxel-based 3-D MRI analysis. The functional perfusion maps and voxel-based statistical maps were coregistered in 3-D space. In five patients with temporal lobe epilepsy (TLE), the area of ictal hyperperfusion and corresponding structural abnormalities detected by 3-D MRI analysis were identified within the same temporal lobe. In two patients, additional structural and functional abnormalities were detected beyond the mesial temporal lobe. Five patients with TLE underwent epileptic surgery with favourable postoperative outcome (Engel class Ia and Ib) after 3-5 years of follow-up, while two patients remained on conservative treatment. In summary, multimodal assessment of structural abnormalities by voxel-based analysis and SISCOM may contribute to advanced observer-independent preoperative assessment of seizure origin.

Adult↗
PubMed1993

Comparison of anatomically-defined versus physiologically-based regional localization: effects on PET-FDG quantitation.

The potential of anatomic imaging to improve the quantitative accuracy of functional brain imaging through refined regional definition is widely accepted. However, there are little data addressing the impact of approach to regional localization on quantitation of metabolic images in the absence of gross structural pathology. We compared MRI-based versus PET-based approaches to the analysis of PET 18F-fluorodeoxyglucose (FDG) images using a standard adjustable template based on simple geometric regions. For the MRI-based approach, templates and individual regions were adjusted to each individual's anatomy, whereas the PET-based definition involved only global proportional adjustment of the standard templates. Metabolic rates for glucose and volume-to-whole brain ratios were determined by two operators for 78 volumes of interest in five subjects. Pairwise correlations indicated high interoperator agreement for each approach and high intraoperator agreement for MRI-based versus PET-based metabolic values. The stability of the metabolic rates and ratios among operators and analysis approaches was supported by low coefficients of variation across measurements and small average differences in paired comparisons. Thus, within the current spatial resolution of PET imaging, quantitation of metabolic images is relatively robust to image analysis approach in the absence of gross structural abnormality. To take advantage of the greater quantitative accuracy promised by high-resolution anatomic and functional imaging, more refined delineation of anatomic images will be necessary.

Brain↗
PubMed1995

[Magnetic resonance arthrography. Preliminary experience in study technic and main diagnostic applications].

In the study of osteoarticular conditions, MRI makes a definite diagnostic improvement, even though some problems are still to be solved. Thus, on the basis of their arthrographic experience, the authors experimentally applied this technique to MRI, to assess the actual feasibility of MR arthrography. Forty-three patients were selected to undergo MR examinations after the intraarticular injection of 15-20 ml paramagnetic contrast agent (Gd-DTPA), with 0.25% saline solution. Before MR arthrography every patient underwent a baseline MR arthrography exam. Normal anatomy was better depicted with MR arthrography. In all cases, even small lesions and other structural changes missed at baseline MRI were demonstrated. Therefore, in agreement with previous arthrographic and CT arthrographic reports, we believe MR arthrography to be a simple technique improving MR diagnostic capabilities in selected cases.

Ankle Joint↗
PubMed2005

Volumetric magnetic resonance imaging of functionally relevant structural alterations in chronic epilepsy after pilocarpine-induced status epilepticus in rats.

PURPOSE: After pilocarpine-induced epilepsy in rats, volumetric magnetic resonance imaging (MRI) reveals significant morphologic changes in functionally relevant structures of the brain. To relate structural changes to functional alteration, we studied the correlation of regional brain atrophy (e.g., of the hippocampus) with lesion-induced learning deficits in the Morris water maze. METHODS: MRI experiments were performed on an MR scanner at 4.7 Tesla. For volumetric analysis, various cerebral structures were segmented in horizontal and coronal T(2)-weighted MR images. Before the MRI investigations, animals were trained for 10 days in a Morris water maze. RESULTS: Volumetric MRI revealed a significant loss in hippocampal size in both the dorsal and ventral parts, correlated with an increase in ventricular size. Furthermore, significant losses were found in the relative size of thalamus, putamen, cortex, and the combined areas of perirhinal, entorhinal, and piriform cortices adjacent to the hippocampus. A significant correlation of learning performance in the Morris water maze with the relative hippocampal area and not with other areas tested was observed in pilocarpine-treated animals. CONCLUSIONS: The data provide a quantitative analysis of functionally relevant structural alterations in rats with chronic epilepsy. Water maze performance of pilocarpine-treated animals correlates with the degree of hippocampal but not with the degree of cortical damage, demonstrating the potential of this method for the investigation of cognitive impairments in relation to cerebral changes. In addition, the data point to an important role of even the residual hippocampus in memory formation.

Animals↗
PubMed2005

Quantification of trabecular bone structure using magnetic resonance imaging at 3 Tesla--calibration studies using microcomputed tomography as a standard of reference.

The purpose of this study is to use high-resolution magnetic resonance (MR) imaging at 3 Tesla (3T) to quantify trabecular bone structure in vitro using femoral head specimens, and to correlate the calculated structure measures with those that were determined using microcomputed tomography (microCT), the standard of reference. Fifteen cylindrical cores were obtained from fresh femoral heads after total hip arthroplasty. MR images were obtained at 3T using a transmit-receive wrist coil. High-resolution coronal images were acquired using a modified three-dimensional (3D) fast-gradient echo sequence. From these data sets two-dimensional (2D) structural parameters analogous to bone histomorphometry were derived by using both mean intercept length (MIL) methods based on the plate model and the more recent model-assumption free 3D distance-transformation (DT) methods. The parameters measured by the 2D plate model-based MIL method and the DT method included apparent (App). BV/TV (bone volume/total volume), App. Tb.Th (trabecular thickness), App. Tb.Sp (trabecular separation), and App. Tb.N (trabecular number). Identical regions of interest were analyzed in the MR images and the microCT data sets, and similar structure measures were derived. The means and standard deviations of the parameters over all slices were calculated and MR-derived measures were correlated with those derived from the microCT data sets using linear regression analyses. Structure measures were overestimated with MRI, for example, the mean App. BV/TV was 0.45 for MRI and 0.20 for microT, and the slope of the graph was 1.45. App. Tb.Th was overestimated by a factor of 1.9, whereas App. Tb.Sp was underestimated; Tb.N showed the smallest effect. Correlations between the individual parameters were excellent (App. BV/TV, r2 = 0.82; App. Tb.Sp, r2 = 0.84; App. Tb.N, r2 = 0.81), except for App.Tb.Th (r2 = 0.67). The results of this study show that trabecular bone structure measures may be obtained using 3T MR imaging. These measures, although higher than the standard of reference, show a highly significant correlation with true structure measures obtained by microCT.

Aged↗
PubMed2005

Progressive gray matter damage in patients with relapsing-remitting multiple sclerosis: a longitudinal diffusion tensor magnetic resonance imaging study.

BACKGROUND: Diffusion tensor magnetic resonance imaging (DT MRI) has the potential to provide in vivo information about tissue microstructure. In multiple sclerosis (MS), DT MRI has disclosed the presence of occult structural damage in the normal-appearing brain tissues. OBJECTIVE: To investigate whether DT MRI is sensitive to longitudinal changes of brain damage that may occur beyond the resolution of T2-weighted images in patients with relapsing-remitting MS. DESIGN: Twenty-six untreated patients with relapsing-remitting MS were followed up for 18 months. Dual-echo, DT and postcontrast T1-weighted MRIs of the brain were obtained at baseline and then every 3 months. Mean diffusivity (D) histograms of normal-appearing gray (GM) and white matter were produced. Total T2-hyperintense and T1-hypointense lesion volumes; normalized whole brain tissue, GM, and white matter volumes; percentage brain volume change between the study entry and exit images; average lesion D; and fractional anisotropy were also calculated. RESULTS: During the study period, a significant decrease of normalized whole brain tissue, average lesion fractional anisotropy and normal-appearing GM D histogram peak height, and a significant increase of average normal-appearing GM D and T2-hyperintense lesion volumes were observed. Changes of normal-appearing GM diffusivity were independent of the concomitant changes of normalized whole brain tissue and GM volumes. CONCLUSIONS: The DT MRI findings show progressive microstructural changes in the normal-appearing GM of patients with untreated relapsing-remitting MS. Such changes do not reflect a concomitant development of brain atrophy and confirm the importance of GM pathology in MS.

Adult↗
PubMed1988

MRI of hypothalamic hamartomas in children.

Eight cases of hypothalamic hamartomas (HH) diagnosed in children by clinical, biological and CT studies have been explored by MRI and compared with a control group of twenty children without hypothalamohypophyseal signs. MRI revealed the hamartoma in all cases. Its location and position relative to the floor of the third ventricle was precisely determined. The signal intensity of the lesion was identical to that of normal grey matter on T1-weighted images (300/600.28), but an hyperintense signal was observed over T2-weighted images (1800.60/120) in seven of the eight cases. These data suggest that HH are somewhat different in structure from normal brain tissue. MRI variations in signal intensity should be taken into account in the diagnostic work-up of these lesions.

Child↗
PubMed2004

[Imaging modalities in the preoperative staging of rectal carcinoma].

Thorough clinical examination, endorectal ultrasound, and magnetic resonance tomography (MRI) are decisive tools in the pretherapeutic work-up of patients with rectal cancer. Depth of infiltration to the rectal wall as well as involvement of perirectal lymph nodes by the tumor are the key questions to be answered. To receive adequate information from imaging procedures, the right questions need to be asked. The extent of invasion of the rectal wall and exact location of tumor infiltration to neighboring structures can be demonstrated by MRI very well, particularly if imaging planes are acquired at 90 degrees to the position of the rectum. Recent developments in computed tomography (CT) using isotrope voxels allow three-dimensional reconstructions of tumors without loss of imaging quality. Assessment of the primary tumor and its nodal metastases after preoperative radio-(chemo-)therapy is still seriously limited. Fusion of positron emission tomography and CT could be a step towards solving the problem of response assessment in the near future.

Contrast Media↗
PubMedDate not supplied

Magnetic resonance imaging of systemic venous anomalies.

Seven cases of anomalous development of the systemic great veins were found in the first 18 months of adult body imaging with a 0.15 T resistive magnetic resonance unit. Comparison was made with CT. In most cases, CT and MRI were equivalent in demonstrating the abnormality. In one case, MRI was superior to a drip-infusion CT. MRI was less successful when the low signal abnormal vein was adjacent to normal structures of low signal. Awareness of the MRI appearance of venous anomalies will aid their recognition as incidental findings.

Adult↗
PubMed1991

MRI of the temporal lobe: normal variations, with special reference toward epilepsy.

Recent investigations of epilepsy, Alzheimer's disease, amnesia, and schizophrenia have used magnetic resonance imaging (MRI) to evaluate changes in temporal lobe structures. Normal variations in these structures need to be defined before one can use these structures to describe abnormal conditions. Twenty-nine normal volunteers were studied by coronal MRI. Frequent findings include notching of the uncus by the tentorium or adjacent vessels (22/29) and asymmetry of the temporal horns (20/29). This finding of uncal notching strengthens the evidence against "incisural sclerosis" as the basis for hippocampal sclerosis. Temporal horn dilatation occurred in four. However, mild asymmetry of the temporal horn was seen frequently at its anterior tip (16/29) and may be related to head rotation. Asymmetry of the choroidal fissure was never marked. Mild asymmetry was common at the hippocampal head (pes). Mild enlargement of the right temporal lobe by visual inspection is not uncommon. Subtle asymmetry of the white matter between the hippocampus and the collateral sulcus occurred in six. The collateral sulcus does not always point to the temporal horn. The occipitotemporal sulcus may point to the temporal horn. Asymmetric uncal protrusion (0/29) and Sylvian fissure dilatation (4/29) occur rarely.

Cerebral Ventricles↗
PubMed2004

Distortion-free single point imaging of multi-layered composite sandwich panel structures.

The results of a magnetic resonance imaging (MRI) investigation concerning the effects of an aluminum honeycomb sandwich panel on the B1 and B0 fields and on subsequent image quality are presented. Although the sandwich panel structure, representative of an aircraft composite material, distorts B0 and attenuates B1, distortion-free imaging is possible using single point (constant time) imaging techniques. A new expression is derived for the error caused by gradient field distortion due to the heterogeneous magnetic susceptibility within a sample and this error is shown not to cause geometric distortion in the image. The origin of the B0 distortion in the sample under investigation was also examined. The graphite-epoxy 'skin' of the panel is the principal source of the B0 distortion. Successful imaging of these structures sets the stage for the development of methods for detecting moisture ingress and degradation within composite sandwich structures.

Journal Article↗
PubMed2004

Altered functioning of the cingulate gyrus in two cases of chromosome 22q11 deletion syndrome.

The 22q11 microdeletion syndrome (22q11-DS) is strongly associated with schizophreniform disorders and, in turn, the 22q11 deletion region harbours several candidate genes for schizophrenia. Here, we present the case of an adolescent female patient with 22q11-DS associated with impaired cognitive abilities and behavioural abnormalities. The patient was studied with magnetic resonance imaging (MRI) and positron emission tomography (PET) as well as extensive neurophysiological investigations. Although no structural or functional abnormalities were found in MRI and PET, assessment of event-related potentials elicited during the Continuous Performance Test revealed a lack of NoGo anteriorisation. The latter was replicated in a second case of 22q11-DS with schizoaffective disorder but devoid of a severe somatic syndrome. This electrophysiological finding, which indicates modified functioning of the cingulate gyrus, has previously been demonstrated only in patients suffering from schizophrenia and attention deficit/hyperactivity disorder, two psychopathological conditions frequently associated with 22q11-DS. We conclude that more extensive study of NoGo anteriorisation as a potential endophenotype of 22q11-DS patients at risk for 22q11-associated psychiatric conditions is warranted.

Adolescent↗
PubMed1996

A serial CT scan and MRI verification of diffuse cerebrospinal gliomatosis: a case report with stereotactic diagnosis and radiological confirmation.

Gliomatosis cerebri is an infrequent tumor of neuroepithelial origin presenting with deterioration of cognitive functions, behavioral and mental changes, motor weakness, headache, and seizures. Laboratory data are unconclusive. MRI appears to be the imaging modality of choice and mainly reveals a bilateral and diffuse infiltration of midline adjacent brain structures whose anatomical configuration remain intact. MRI- or CT-guided stereotactic biopsy is advised as the diagnostic procedure in suspected cases. A 9-year-old girl with diffuse cerebrospinal gliomatosis, investigated with sequential cranial CT scans, and MRI-verified spinal cord involvement is reported, and the corresponding literature is reviewed.

Biopsy↗
PubMed2002

[Craniopharyngioma in children: MRI study of 43 cases].

BACKGROUND AND PURPOSE: Craniopharyngiomas are intra-cranial tumors, relatively frequent in children, expanding in the pituitary stalk axis, from the third ventricle to the sphenoid body. Plain films and CT scan generally show a calcified lesion, deforming the sella turcica. MRI improves tumor description and topographic and structural analysis of the lesion. The aim of this study is to analyze the MRI aspect of craniopharyngiomas in a pediatric population and to correlate findings with surgical data. METHODS: MR and CT studies of 43 pediatric cases of histology-proven craniopharyngiomas were reviewed retrospectively. Tumor emergence, extensions and signal on different sequences were recorded. We searched for radio-surgical correlations. RESULTS: Craniopharyngiomas can be classified into two groups: intra-sellar tumors and third ventricle floor tumors (infundibulum and tuber cinereum). Preferential routes of extension are observed in each group correlated with consistency (cystic and/or solid). Surgical data confirmed these results. CONCLUSIONS: MRI is crucial for the pre-therapeutic evaluation of craniopharyngiomas allowing not only a detailed description of the tumor but also guiding therapeutic decisions. This series demonstrated that craniopharyngiomas exhibit two different types of localization and behavior. Embryonic development of the tumor explains the topographical differences.

Adolescent↗
PubMed1988

Magnetic resonance imaging of the cardiovascular system. Present state of the art and future potential. Council on Scientific Affairs. Report of the Magnetic Resonance Imaging Panel.

State-of-the-art magnetic resonance imaging (MRI) generates high-resolution images of the cardiovascular system. Conventional MRI techniques provide images in six to ten minutes per tomographic slice. New strategies have substantially improved the speed of imaging. The technology is relatively expensive, and its cost-effectiveness remains to be defined in relation to other effective, less expensive, and noninvasive technologies, such as echocardiography and nuclear medicine. The ultimate role of MRI will depend on several factors, including the development of specific applications such as (1) noninvasive angiography, especially of the coronary arteries; (2) noninvasive, high-resolution assessment of regional myocardial blood flow distribution (eg, using paramagnetic contrast agents); (3) characterization of myocardial diseases using proton-relaxation property changes; and (4) evaluation of in vivo myocardial biochemistry. The three-dimensional imaging capability and the ability to image cardiovascular structures without contrast material give MRI a potential advantage over existing noninvasive diagnostic imaging techniques. This report analyzes current applications of MRI to the cardiovascular system and speculates on their future.

Angina Pectoris↗
PubMed1995

Bradykinin antagonism inhibits the antigrowth effect of converting enzyme inhibition in the dog myocardium after discrete transmural myocardial necrosis.

BACKGROUND: Converting enzyme inhibitor (CEI) therapy, but not angiotensin II subtype I receptor blockade, has been shown to attenuate left ventricular remodeling in the dog after transmyocardial direct current (DC) shock. The purpose of this study was to address the importance of preservation of bradykinin to the antiremodeling effect of CEI treatment in this model. METHODS AND RESULTS: Twenty-four hours after DC shock, adult mongrel dogs were assigned to one of three groups: a control group; a group treated with ramipril 10 mg BID; and a group treated with ramipril 10 mg BID along with a continuous subcutaneous infusion of HOE 140, a bradykinin antagonist. To assess change in left and right ventricular structure, a magnetic resonance imaging (MRI) study was performed 4 weeks after DC shock and compared with a baseline MRI study performed before DC shock. The increase in left ventricular mass (mean +/- SEM) in the control group was similar to that observed in the CEI-HOE 140 group (+0.73 +/- 0.19 versus +0.75 +/- 0.18 g/kg, P = NS), but both were greater than the change in mass in the ramipril group (-0.48 +/- 0.13 g/kg, P = .004 and P = .0005, respectively). No significant change occurred in left ventricular volume or right ventricular structure in any group. Mean arterial pressure was reduced by ramipril compared with the control group (-8 +/- 2 versus +7 +/- 2 mm Hg, P = .03), and this effect was not blunted by the addition of HOE 140 (-7 +/- 3 mm Hg). CONCLUSIONS: Prevention by ramipril of the early increase in left ventricular mass in the DC shock model appears to be related to the preservation of bradykinin.

Angiotensin-Converting Enzyme Inhibitors↗