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At least 1,117 records · Page 62Linked to original sources
PubMed2003

MRI-guided SPECT perfusion measures and volumetric MRI in prodromal Alzheimer disease.

OBJECTIVE: To identify group differences in the prodromal phase of Alzheimer disease (AD) using quantitative single-photon emission computed tomography (SPECT) perfusion and magnetic resonance imaging (MRI) volume measures within specific volumes of interest. SETTING: Gerontology research unit. PARTICIPANTS: There were 17 healthy controls, 56 nondemented patients with memory problems who did not develop AD during 3 to 5 years of follow-up (questionables), and 27 nondemented patients with memory problems who developed AD during follow-up (converters). METHODS: A Tc 99m hexamethylpropyleneamine oxime SPECT study and an MRI were performed in each participant at baseline. Mean SPECT activity concentration and MRI volume were estimated within 9 structures: rostral anterior cingulate, caudal anterior cingulate, posterior cingulate, hippocampus, entorhinal cortex, basal forebrain, temporal horn, amygdala, and the banks of the superior temporal sulcus. Data were analyzed using overall and pairwise discriminant analysis, and performance in pairwise group discrimination was measured using correlated receiver operating characteristic curve analysis. RESULTS: The overall (3-group) discriminant function was significant for SPECT (F test, P<.001) and MRI (F test, P<.0001). For the SPECT analysis, the ranking of structures for discriminating among the 3 groups was, in order of decreasing discriminating power, caudal anterior cingulate, temporal horn, superior temporal sulcus, entorhinal cortex, hippocampus, rostral anterior cingulate, amygdala, basal forebrain, and posterior cingulate. For the MRI analysis, this ranking was entorhinal cortex, superior temporal sulcus, temporal horn, hippocampus, amygdala, caudal anterior cingulate, rostral anterior cingulate, basal forebrain, and posterior cingulate. Combining the 2 modalities yielded significantly better discrimination performance than did either alone. Furthermore, the correlation between SPECT and MRI measures was low. CONCLUSION: Measures of structure activity concentration and volume carry independent information; both reveal group differences in prodromal AD.

Aged↗
PubMed2001

Investigating the pathogenesis of posttraumatic stress disorder with neuroimaging.

Rapidly evolving brain neuroimaging techniques such as magnetic resonance imaging (MRI) and positron emission tomography (PET) are proving fruitful in exploring the pathogenesis and pathophysiology of posttraumatic stress disorder (PTSD). Structural abnormalities in PTSD found with MRI include nonspecific white matter lesions and decreased hippocampal volume. These abnormalities may reflect pretrauma vulnerability to develop PTSD, or they may be a consequence of traumatic exposure, PTSD, and/or PTSD sequelae. Functional neuroimaging symptom provocation and cognitive activation paradigms using PET measurement of regional cerebral blood flow have revealed greater activation of the amygdala and anterior paralimbic structures (which are known to be involved in processing negative emotions such as fear), greater deactivation of Broca's region (motor speech) and other nonlimbic cortical regions, and failure of activation of the cingulate cortex (which possibly plays an inhibitory role) in response to trauma-related stimuli in individuals with PTSD. Functional MRI research has shown the amygdala to be hyperresponsive to fear-related stimuli in this disorder. Research with PET suggests that cortical, notably hippocampal, metabolism is suppressed to a greater extent by pharmacologic stimulation of the noradrenergic system in persons with PTSD. The growth of knowledge concerning the anatomical and neurochemical basis of this important mental disorder will hopefully eventually lead to rational psychological and pharmacologic treatments.

Brain↗
PubMed2005

Fetal magnetic resonance imaging enhances detection of spinal cord anomalies in patients with sonographically detected bony anomalies of the spine.

OBJECTIVE: Although fetal magnetic resonance imaging (MRI) is being increasingly used to evaluate sonographically suspected abnormalities, its utility in the evaluation of the spinal canal is not well studied. Because it is not susceptible to the limitations of fetal position, oligohydramnios, and shadowing from bony structures, we hypothesize that fetal MRI is better suited to assess the contents of the spinal canal compared with prenatal sonography. The purpose of this investigation was to determine whether fetal MRI could detect spinal abnormalities in cases in which they had not been originally suspected on prenatal sonography. METHODS: Fetal spine MR images were retrospectively reviewed over a 42-month period. Corresponding sonographic images were then rereviewed to determine whether there were findings in retrospect that might have suggested the cord abnormalities. Cases of myelomeningocele were counted as a spinal cord abnormality only if fetal MRI showed a cord anomaly other than the myelomeningocele. RESULTS: Of 33 cases referred for bony anomalies of the spine, fetal MRI showed additional abnormalities involving the spinal cord in 3 patients. These included diastematomyelia in 2 cases and segmental spinal dysgenesis in the third case. One case of diastematomyelia occurred in association with a lumbosacral myelomeningocele. The spinal cord anomalies were not visible on any of the prenatal sonograms, even in retrospect. CONCLUSIONS: Additional spinal cord anomalies were detected in 10% of cases reviewed. Fetal MRI can be useful in assessing the spinal cord in fetuses with bony spinal anomalies. Our findings suggest that fetuses with sonographically diagnosed bony abnormalities of the spine may benefit from further evaluation with fetal MRI.

Female↗
PubMed2005

Magnetic resonance techniques in the assessment of myelin and myelination.

Leukodystrophy is a common central nervous system manifestation of inborn errors of metabolism. Until magnetic resonance imaging (MRI) emerged as a clinical tool, the diagnosis of leukodystrophy was difficult and imprecise; MRI has allowed new understandings and classifications of leukodystrophies that have greatly enhanced both our diagnostic ability and our understanding of these complex disorders. However, optimal use of MRI in this setting requires a fundamental understanding of myelin structure, myelin development, and the changes seen on MRI with myelination and demyelination. The purpose of this review is to provide the reader with the necessary tools for the use of MRI to diagnose and follow patients with leukodystrophies.

Diffusion Magnetic Resonance Imaging↗
PubMed1999

Silent meniscal abnormalities in athletes: magnetic resonance imaging of asymptomatic competitive gymnasts.

BACKGROUND: Magnetic resonance imaging (MRI) produces exceptionally detailed images of the intra-articular structures of the knee. Recognising the range of MRI appearances within a normal population is therefore necessary in order to avoid attributing a greater significance to these than is clinically justified. OBJECTIVE: To compare MRI appearances in asymptomatic gymnasts with those in a less active population in order to identify findings that may be seen in the absence of significant pathology and thereby aid the clinical management of this athletic group. METHODS: MR images were obtained from 24 knees of asymptomatic competitive American collegiate gymnasts aged 18-22. The menisci were evaluated according to established grading criteria, and compared with a group of controls matched for age and sex. RESULTS: Grade 3 intrameniscal signal abnormalities are considered to be highly correlated with meniscal tears. When compared with control group, the experimental group of gymnasts had a significantly different distribution (p<0.001) of grade 3 intrameniscal signal changes, preferentially involving the lateral meniscus. The overall incidence of grade 3 changes (13%) in gymnasts was not, however, significantly different from the incidence in the controls. CONCLUSIONS: A knowledge of these MRI appearances is important when evaluating the lateral menisci within this group of athletes to prevent unnecessary treatment or intervention. This is particularly pertinent when the imaging findings do not closely correlate with the site of symptoms.

Adolescent↗
PubMed1986

Magnetic resonance imaging of experimental cerebral oedema.

Triethyl tin(TET)-induced cerebral oedema has been studied in cats by magnetic resonance imaging (MRI), and the findings correlated with the histology and fine structure of the cerebrum following perfusion-fixation. MRI is a sensitive technique for detecting cerebral oedema, and the distribution and severity of the changes correlate closely with the morphological abnormalities. The relaxation times, T1 and T2 increase progressively as the oedema develops, and the proportional increase in T2 is approximately twice that in T1. Analysis of the magnetisation decay curves reveals slowly-relaxing and rapidly-relaxing components which probably correspond to oedema fluid and intracellular water respectively. The image appearances taken in conjunction with relaxation data provide a basis for determining the nature of the oedema in vivo.

Animals↗
PubMed1993

[Meniscal lesions].

The polymorphism and richness of arthrographic imaging and MRI of meniscal lesions require a perfect understanding of the anatomy of the menisci and the mechanisms of production of the lesions. Arthrography remains the reference diagnostic investigation with a good sensitivity and excellent spatial resolution. However, it is an invasive and operator-dependent technique. MRI of the knee, a non-invasive and independent method, allows the diagnosis of the majority of meniscal lesions. By using specific surface coils and appropriate sequences, MRI constitutes complete imaging technique allowing examination of all anatomical structures of the knee in all planes. Once MRI becomes more widely available, it should replace arthrography in the majority of clinical situations. The indications for arthrography will then be confined to contraindications of MRI.

Aging↗
PubMed2006

Regional differences of the prefrontal cortex in pediatric PTSD: an MRI study.

Previous studies have revealed altered structural development of the frontal lobes and prefrontal cortex (PFC) in children with symptoms of posttraumatic stress disorder (PTSD). This study is the first to provide a detailed structural analysis of the PFC in children with and without PTSD symptoms. We compared gray and white matter volume in four subregions of the PFC between said groups, then explored whether volume was associated with PTSD symptom severity and functional impairment. PFC measurements were extracted from magnetic resonance imaging (MRI) data from a sample of 23 children (ages 7-14) with a history of trauma and symptoms of PTSD, who had undergone assessment for PTSD symptoms and functional impairment using the Child and Adolescent version of the Clinician-Administered PTSD Scale (CAPS-CA). These measurements were compared to data from an age-equivalent control group of 24 healthy children. Children with PTSD symptoms showed a significantly larger volume of gray matter in the delineated middle-inferior and ventral regions of the PFC than did control children. Decreased volume of gray matter in the dorsal PFC correlated with increased functional impairment scores. Results indicate that increased volume of the middle-inferior and ventral PFC may be associated with trauma and PTSD symptoms in children. Furthermore, the neuroanatomy of the dorsal PFC may influence the degree of functional impairment experienced by children with PTSD symptoms.

Adolescent↗
PubMed1999

Herpes simplex virus encephalitis: chronic progressive cerebral MRI changes despite good clinical recovery and low viral load - an experimental mouse study.

Cranial magnetic resonance imaging (MRI) is a sensitive diagnostic tool for the in vivo detection of morphological abnormalities in herpes simplex virus encephalitis (HSVE). We performed a long-term MRI study in a mouse model of HSVE. Cranial MRI findings were compared with the viral load within brain tissue, the presence of HSV DNA in the cerebrospinal fluid (CSF), a daily clinical assessment and post-mortem neurohistopathological studies. A 1.5 T cranial MRI scanner with standard spin-echo sequences was used. Viral load within the brain and the presence of HSV DNA in cerebrospinal fluid were determined by a polymerase chain reaction assay. Clinically, animals were severely affected within the first 2 weeks and recovered thereafter. Focal histopathological and MRI abnormalities involved predominantly limbic structures, a pattern that mimics human disease. Severity and extent of abnormalities had increased at 6 months despite clinical improvement. HSV DNA was present in CSF during the acute disease only. Brain viral load peaked at day 10 and declined thereafter. MRI as an in vivo monitoring approach may reveal chronic progressive changes in HSVE, despite clinical recovery and low viral load in the brain. Secondary, not directly virus-mediated, mechanisms of tissue damage may contribute to tissue damage of HSVE.

Animals↗
PubMed2006

Novel image processing techniques to better understand white matter disruption in multiple sclerosis.

In Multiple Sclerosis (MS) patients, conventional magnetic resonance imaging (MRI) shows a pattern of white matter (WM) disruption but may also overlook some WM damage. Diffusion tensor MRI (DT-MRI) can provide important in-vivo information about fiber direction that is not provided by conventional MRI. The geometry of diffusion tensors can quantitatively characterize the local structure in tissues. The integration of both conventional MRI and DT-MRI measures together with connectivity-based regional assessment provide a better understanding of the nature and the location of WM abnormalities. Image processing and visualization techniques have been developed and applied to study conventional MRI and DT-MRI of MS patients. These include methods of: Image Segmentation for identifying the different areas of the brain as well as to discriminate normal from abnormal WM, Computerized Atlases, which include structural information obtained from a set of subjects, and Tractographies which can aid in the delineation of WM fiber tracts by tracking connected diffusion tensors. These new techniques hold out the promise of improving our understanding of WM architecture and its disruption in diseases such as MS. In the present study, we review the work that has been done in the development of these techniques and illustrate their applications.

Brain↗
PubMed1996

Localized right ventricular structural abnormalities in patients with idiopathic ventricular fibrillation: magnetic resonance imaging study.

Lethal arrhythmias, including ventricular tachycardia and ventricular fibrillation, may occur in the absence of apparent morphological abnormalities. However, a recent study using magnetic resonance imaging (MRI) has suggested that localized, minor structural abnormalities of the right ventricle are responsible for right ventricular outflow tract ventricular tachycardia in a number of patients. We demonstrated regional wall thinning and systolic dyskinesia of the right ventricle by MRI in two patients with idiopathic ventricular fibrillation in whom other cardiac imaging modalities failed to show abnormalities. This finding implies that minor structural abnormalities do exist in patients with so-called idiopathic ventricular fibrillation.

Adult↗
PubMed1991

Disc degeneration in magnetic resonance imaging. A comparative biochemical, histologic, and radiologic study in cadaver spines.

Magnetic resonance imaging (MRI) findings of 89 autopsied intervertebral discs from 22 cadaveric lumbar spines were correlated with biochemical composition, conventional radiography, and histologic structure to study the nature of disc intensity changes seen in MRI. Discs with a low signal intensity on T2-weighted MRI were characterized by shortening of relaxation times, dehydration, and decreases in total proteoglycan content and chondroitin-keratan sulfate ratios in the nucleus pulposus. This corresponded well with previously published studies. In histologic structure, no obvious differences between MRI findings were found. In conclusion, a low signal intensity in a lumbar disc on T2-weighted MRI probably reflects a true biochemical disc degeneration, but its relation to structural degenerative changes is uncertain. Therefore, MRI seems to be a sensitive and a specific imaging modality for detecting pathologic biochemical disc changes in the spine of a young adult.

Adult↗
PubMed1996

Significance of mesial temporal atrophy in relation to intracranial ictal and interictal stereo EEG abnormalities.

We studied 31 consecutive patients with temporal and extratemporal epilepsy who underwent presurgical evaluation with stereotaxic depth EEG (SEEG) to assess the relationships between amygdalo-hippocampal (AM-HF) atrophy and the location of SEEG seizure onset and SEEG interictal abnormalities. Scalp EEG recordings with sphenoidal electrodes had shown bitemporal ictal or interictal epileptic abnormalities in all. Patients underwent high quality MRI scans, including MRI volumetric measurements of mesial temporal structures. None had foreign tissue lesions. The final conclusions of the SEEG investigation coincided with the lateralization obtained by MRI volumetric measurements in the eight patients who had significant unilateral atrophy of the amygdala, hippocampus or both (> 2 SD below the mean of controls). In these patients with unilateral atrophy, all or > 75% of clinical seizures originated from the atrophic side. The seven patients with bilateral, but significantly asymmetrical, mesial atrophy had bilateral seizure onsets with > 70% originating from the more atrophic side in four, from the less atrophic side in two, and without predominance in one. The one patient with severe bilateral symmetrical atrophy had seizures originating equally from both sides. Five patients had no atrophy on MRI, but depth electrodes revealed predominant unilateral ictal temporal onsets in four of them. There was no significant correlation between the frequency of SEEG interictal spikes and the amount of AM-HF atrophy. However, we found a significant correlation between the severity of SEEG background disturbance in AM and HF and the degree of atrophy of these structures. Patients with unilateral atrophy were more frequently free of seizures after surgery than those with bilateral or no atrophy (P < 0.05). We conclude that unilateral mesial atrophy predicts ipsilateral mesial SEEG seizure onset despite bitemporal extracranial EEG foci. However, in patients with significant bilateral mesial atrophy, SEEG seizures may originate from either side, even in the presence of significant asymmetry. Finally, the identification of unilateral mesial atrophy has prognostic importance.

Adult↗
PubMed1996

Medial temporal lobe heterotopia as a cause of increased hippocampal and amygdaloid MRI volumes.

Magnetic resonance imaging (MRI)-based volumetric measurements of the hippocampus and amygdala are useful in detecting hippocampal and amygdaloid sclerosis in patients with temporal lobe epilepsy. In these pathological entities, volumetric MRI analysis shows the epileptogenic structures to be atrophic when compared to the normal, nonepileptogenic side. Described are 2 patients with increased hippocampal and amygdaloid volumes on the side of seizure onset due to medial temporal lobe heteroto pias. Care must be taken in the interpretation of volumetric MRI data to make certain that asymmetries in hippocampal and amygdaloid measurements are due to atrophy and sclerosis of the abnormal side and not to increased tissue such as heterotopic gray matter.

Adult↗
PubMed2000

Magnetic resonance imaging in primary bone tumors.

MRI plays a major role in the evaluation and treatment planning of bone tumors. It should be used following plain films and before biopsy. The MR appearance of most tumors is nonspecific; however, the entire extent of the tumor and its relationship to adjacent structures can be determined at MRI providing a road map for the surgeon. The role of dynamic enhancement is evolving and has not yet been determined.

Bone Neoplasms↗
PubMed1996

Skull base erosion in nasopharyngeal carcinoma: detection by CT and MRI.

It is generally accepted that computed tomography (CT) is superior to magnetic resonance imaging (MRI) in demonstrating bony erosion while MRI is better in delineating soft tissue abnormality. The ability to detect skull base erosion by CT and MRI was compared in a retrospective study of 114 patients with nasopharyngeal carcinoma (NPC). Involvement of the following structures was demonstrated on CT and MRI: pterygoid plates [CT--10 (9%) patients, MRI--8 (7%) patients]; pterygoid process [CT--22 (19%) patients, MRI--22 (19%) patients]; clivus [CT--17 (15%) patients, MRI--26 (23%) patients]; petrous apex [CT--20 (18%) patients, MRI--34 (30%) patients]; sphenoid body/sinus [CT--31 (27%) patients, MRI--32 (28%) patients]; sphenoid wing [CT--12 (11%) patients, MRI--16 (14%) patients]. Erosion of the foramen ovale could be seen on CT in 19 (17%) patients but tumour was noted in the foramen in 28 (25%) patients using MRI. Contrary to common belief, MRI appears to be more sensitive in detecting bony involvement in the petrous apex, the clivus and the sphenoid wing. MRI is, therefore, the preferred technique in demonstrating skull base involvement.

Cranial Fossa, Posterior↗
PubMed1995

Imaging of renal cell carcinoma with gadolinium-enhanced magnetic resonance: radiological and pathological study.

The use of gadolinium-DTPA enhanced MR imaging (Gd-MR) in detecting and staging of large and small renal neoplasm was investigated in 61 patients with 66 renal cell carcinoma confirmed at surgery. The purpose of the study was also to evaluate the signal intensity of the lesions and to correlate the contrast-enhanced pattern to the pathological components and architecture of the surgical specimens. Forty-four tumors were larger than 3 cm and 22 lesions were smaller than 3 cm. Unenhanced MRI detected all large lesions (44/44) and 63% (14/22) of small lesions, while Gd-MRI detected all large and small neoplasms (100%). The overall staging accuracy was 79 and 87% for plain MRI and Gd-MRI, respectively, but both modalities led to an overstaging of the disease. Enhanced MRI was an excellent staging modality for the evaluation of tumor vascular extension and tumor spread to adjacent structures. The most frequent Gd-MRI pattern of small RCC was hyperintensity, while large lesions were mostly hypointense. The presence of fibrohyaline components seemed responsible for the hyperintense pattern. No specific contrast-enhanced MRI pattern was observed according to the tumor architecture (alveolar, tubular or papillar) of noncystic lesions. On the contrary, cystic lesion appeared as an area of low signal intensity and the use of contrast media improved detection and characterization. The inhomogeneous signal intensity increased the detectability of the lesion.

Adult↗
PubMed1999

The role of MRI in dementia.

Neuroimaging techniques aimed at studying structural changes of the brain may provide useful information for the diagnosis and the clinical management of patients with dementia. Magnetic resonance imaging (MRI) may show abnormalities amenable to surgical treatment in a significant percentage of patients with cognitive impairment. MRI may also assist the differential diagnosis in dementia associated with metabolic or inflammatory diseases.MRI has the potential to detect focal signal abnormalities which may assist the clinical differentiation between Alzheimer's disease (AD) and vascular dementia (VaD). Severe temporal atrophy, hyperintensities involving the hippocampal or insular cortex, and gyral hypointense bands are more frequently noted in AD. Basal ganglionic/thalamic hyperintense foci, thromboembolic infarctions, confluent white matter and irregular periventricular hyperintensities are more common in VaD. The high sensitivity of MRI in detecting T2 hyperintense lesions and the low specificity off white matter lesions have resulted in a poor correlation between MRI findings and both neuropathological and clinical manifestations. In particular, MRI has disclosed a series of white matter focal changes in the elderly population, which are not necessarily associated with cognitive dysfunction. The recent advent of a new MRI method sensitive to the microstructural changes of white matter, the so-called diffusion tensor imaging, may be helpful in correlating clinical manifestations with white matter abnormalities.

Alzheimer Disease↗