PubMed Health⌕ Search

Biomedical subjects

S W Atlas

Publications and source records attributed to S W Atlas.

At least 19 recordsLinked to original sources
PubMed2001

Dorsal forebrain anomaly in Williams syndrome.

BACKGROUND: Williams syndrome (WMS) is a rare neurogenetic condition with a behavioral phenotype that suggests a dorsal and/or ventral developmental dissociation, with deficits in dorsal but not the ventral hemispheric visual stream. A shortened extent of the dorsal central sulcus has been observed in autopsy specimens. OBJECTIVE: To compare gross anatomical features between the dorsal and ventral portions of the cerebral hemispheres by examining the dorsal extent of the central sulcus in brain magnetic resonance images from a sample of subjects with WMS and age- and sex-matched control subjects. SUBJECTS: Twenty-one subjects having clinically and genetically diagnosed WMS (mean +/- SD age, 28.9 +/- 7.9 years) were compared with 21 age- and sex-matched typically developing controls (mean +/- SD age, 28.8 +/- 7.9 years). DESIGN: High-resolution structural magnetic resonance images were acquired. The extent of the central sulcus was qualitatively assessed via surface projections of the cerebral cortex. RESULTS: The dorsal central sulcus is less likely to reach the interhemispheric fissure in subjects with WMS than in controls for both left (P< .001, chi(2) = 15.79) and right (P< .001, chi(2) = 12.95) hemispheres. No differences between the groups were found in the ventral extent of the central sulcus. CONCLUSIONS: Anomalies in the dorsal region in patients with WMS are indicative of early neurodevelopmental problems affecting the development of the dorsal forebrain and are most likely related to the deficits in visuospatial ability and behavioral timing often observed in this condition.

Adult↗
PubMed2001

Single- versus multi-detector row CT of the brain: quality assessment.

PURPOSE: To assess the quality of brain computed tomographic (CT) studies obtained with a four-channel multi-detector row CT scanner compared with those obtained with a single-detector row CT scanner. MATERIALS AND METHODS: Forty-seven patients referred for brain CT were imaged with both single- and multi-detector row scanners. Single-detector row CT images were acquired by using a 5-mm-collimated beam in the transverse mode. Multi-detector row CT images were acquired in four simultaneous 2.5-mm-thick sections, which were combined in projection space to create two contiguous 5-mm-thick sections. Two neuroradiologists blinded to the acquisition technique independently evaluated the CT image pairs, which were presented in a stacked mode on two adjacent monitors. Each study was graded by using a five-point scale for posterior fossa artifact, overall image quality, and overall preference. RESULTS: Multi-detector row CT studies were acquired 1.8 times faster than single-detector row CT studies (0.92 vs 0.52 section per second). Multi-detector row CT posterior fossa artifact was less than single-detector row CT posterior fossa artifact in 87 (93%) of 94 studies. Overall preference was expressed for multi-detector row CT in 84 (89%) of 94 studies. The differences in mean posterior fossa artifact scores (P <.001) and mean overall image quality scores (P =.001) were significant. CONCLUSION: Brain CT images obtained with multi-detector row CT resulted in significantly less posterior fossa artifact and were preferred to single-detector row CT images.

Artifacts↗
PubMed2001

Regional and global changes in cerebral diffusion with normal aging.

BACKGROUND AND PURPOSE: We used quantitative diffusion MR imaging to investigate the microstructural changes that occur in white matter during normal aging in order to identify regional changes in anisotropy and to quantify global microstructural changes by use of whole-brain diffusion histograms. METHODS: Full diffusion tensor MR imaging was performed in 20 healthy volunteers, 20 to 91 years old. Thirteen subjects also underwent high-resolution T1-weighted imaging, so that diffusion images could be coregistered and standardized to normal coordinates for statistical probability mapping. Relative anisotropy (RA) was calculated, as was linear regression of RA with age for each pixel; pixels with a significant correlation coefficient were displayed. For histographic analysis, the average apparent diffusion coefficient (ADC) histograms were calculated on a pixel-by-pixel basis. Subjects were divided into two equal groups by the median age (55 years) of the population and plotted for statistical comparison. RESULTS: Regional analysis showed statistically significant decreases in RA with increasing age in the periventricular white matter, frontal white matter, and genu and splenium of the corpus callosum, despite the absence of signal abnormalities on visual inspection of conventional images. Significant increases in RA were found in the internal capsules bilaterally. ADC histograms showed higher mean ADC and reduced peak height and skew in the older age group on group comparisons. CONCLUSION: Quantitative diffusion histograms correlate with normal aging and may provide a global assessment of normal age-related changes and serve as a standard for comparison with neurodegenerative diseases.

Adult↗
PubMed2000

Whole-brain diffusion MR histograms differ between MS subtypes.

OBJECTIVE: To determine whether quantitative whole-brain MR diffusion histograms in patients with MS differ from those of normal control subjects. BACKGROUND: MRI detects macroscopic cerebral lesions in MS, but the white matter lesion burden on MRI correlates imperfectly to clinical disability. Previous reports have further suggested abnormalities in white matter of MS patients with no visible lesions on conventional MRI. METHODS: A total of 25 subjects (13 with MS [9 relapsing-remitting, 4 secondary progressive] and 12 healthy control subjects) underwent diffusion-weighted echoplanar MRI encompassing the entire brain. The average apparent diffusion coefficient (ADCave, or diffusion trace) was calculated on a pixel-by-pixel basis after segmentation of intracranial space from calvarium and extracranial soft tissues. Whole-brain ADCave histograms were calculated and plotted for statistical comparison. RESULTS: Mean whole-brain MR ADCave in MS patients was elevated and histograms were shifted to higher values compared with normal control subjects. Mean whole-brain ADCave of secondary progressive patients was shifted to higher values compared with relapsing-remitting patients. Whole-brain ADCave histograms of relapsing-remitting patients showed no significant difference from normal control subjects. CONCLUSION: Whole-brain MR diffusion histograms may quantitate overall cerebral lesion load in patients with MS and may be able to discern differences between clinical subgroups.

Adolescent↗
PubMed2000

Quantitative diffusion measurements in focal multiple sclerosis lesions: correlations with appearance on TI-weighted MR images.

OBJECTIVE: Relative hypointensity on T1-weighted MR imaging has been suggested as a putative disability marker. The purpose of our study was to determine if there are quantifiable diffusion differences among focal multiple sclerosis lesions that appear differently on conventional T1-weighted MR images. We hypothesized that markedly hypointense lesions on unenhanced T1-weighted images would have significantly increased diffusion compared with other lesions, and enhancing portions of lesions would have different diffusion compared with nonenhancing lesions. SUBJECTS AND METHODS: Average apparent diffusion coefficient (ADC) was calculated for 107 lesions identified on T2-weighted images in 16 patients with multiple sclerosis and was compared with the ADC of normal white matter in 16 age- and sex-matched control subjects. Seventy-five nonenhancing lesions (29 isointense, 46 hypointense) and 32 enhancing lesions (6 isointense, 26 hypointense) were categorized on the basis of unenhanced T1-weighted MR imaging. RESULTS: Hypointense and isointense nonenhancing lesions both showed significantly higher ADC than normal white matter (p < 0.0001). Hypointense nonenhancing lesions showed higher ADC values than isointense nonenhancing lesions (p < 0.0001). Diffusion in enhancing portions of enhancing lesions was decreased when compared with nonenhancing portions. CONCLUSION: Quantitative diffusion data from MR imaging differ among multiple sclerosis lesions that appear different from each other on T1-weighted images. These quantitative diffusion differences imply microstructural differences, which may prove useful in documenting irreversible disease.

Adolescent↗
PubMed2000

Diffusion measurements in intracranial hematomas: implications for MR imaging of acute stroke.

BACKGROUND AND PURPOSE: The purpose of our study was to analyze the diffusion properties of intracranial hematomas to understand the effects of hematomas on diffusion-weighted MR images of patients with acute stroke and to further our understanding of the evolution of signal intensities of hematomas on conventional MR images. We hypothesized that hematomas containing blood with intact RBC membranes (ie, early hematomas) have restricted diffusion compared with hematomas in which RBC membranes have lysed. METHODS: Seventeen proven intracranial hematomas were studied with conventional and diffusion MR imaging. Hematomas were characterized using conventional images to determine the stage of evolution and their putative biophysical composition, as described in the literature. Apparent diffusion coefficient (ADC) measurements for each putative hematoma constituent (intracellular oxyhemoglobin, intracellular deoxyhemoglobin, intracellular methemoglobin, and extracellular methemoglobin) were compared with each other and with normal white matter. RESULTS: Hematomas showing hemoglobin within intact RBCs by conventional MR criteria (n = 14) showed equivalent ADC values, which were reduced compared with hematomas containing lysed RBCs (P = .0029 to .024). Compared with white matter, hematomas containing lysed RBCs had higher ADC measurements (P = .003), whereas hematomas containing intact RBCs had reduced ADC measurements (P < .0001). CONCLUSION: Restricted diffusion is present in early intracranial hematomas in comparison with both late hematomas and normal white matter. Therefore, early hematomas would be displayed as identical to the signal intensity of acute infarction on ADC maps, despite obvious differences on conventional MR images. These data also are consistent with the biochemical composition that has been theorized in the stages of evolving intracranial hematomas and provide further evidence that paramagnetic effects, rather than restriction of water movement, are the dominant cause for their different intensity patterns on conventional MR images.

Acute Disease↗
PubMed1999

Pial involvement in Wegener's granulomatosis shown on MRI.

Involvement of the brain and meninges is rare in Wegener's granulomatosis (WG); it has been reported in 1.2-8 % of patients. Meningeal involvement in WG has been reported in imaging as being confined to the dura mater, and is thought to represent granulomatous infiltration. We present a case of WG with abnormal pial enhancement and involvement of the perivascular spaces on MRI, pathologically proven to represent granulomatous infiltration due to the primary disease rather than to infection.

Adult↗
PubMed1999

Diffusion-weighted MRI in acute lacunar syndromes. A clinical-radiological correlation study.

BACKGROUND AND PURPOSE: Clinical-radiological correlation studies in lacunar syndromes have been handicapped by the low sensitivity of CT and standard MRI for acute small-vessel infarction and their difficulty in differentiating between acute and chronic lesions. METHODS: We prospectively studied 43 patients presenting with a classic lacunar syndrome using diffusion-weighted MRI, a technique with a high sensitivity and specificity for acute small-vessel infarction. RESULTS: All patients were scanned within 6 days of stroke onset. An acute infarction was identified in all patients. Pure motor stroke was associated with lesions in the posterior limb of the internal capsule (PLIC), pons, corona radiata, and medial medulla; ataxic hemipareses with lesions in the PLIC, corona radiata, pons, and insular cortex; sensorimotor stroke with lesions in the PLIC and lateral medulla; dysarthria-clumsy hand syndrome with lesions in the PLIC and caudate nucleus; and pure sensory stroke with a lesion in the thalamus. Supratentorial lesions extended into neighboring anatomic structures in 48% of the patients. CONCLUSIONS: Lacunar syndromes can be caused by lesions in a variety of locations, and specific locations can cause a variety of lacunar syndromes. Extension of lesions into neighboring structures in patients with lacunar syndromes appears to be more frequent than previously described in studies using CT and standard MRI.

Acute Disease↗
PubMed1999

MR findings in AIDS-associated myelopathy.

BACKGROUND AND PURPOSE: The most common cause of spinal cord disease among patients with AIDS or those infected with HIV-1 is AIDS-associated myelopathy. The purpose of this study was to determine the MR characteristics of the spinal cord in this patient population and to correlate these findings with the clinical severity of myelopathy. METHODS: MR images of the spinal cord in 21 patients with documented HIV-1 infection or AIDS and a clinical diagnosis of AIDS-associated myelopathy were assessed retrospectively for atrophy, intrinsic signal abnormality, and abnormal enhancement. The clinical severity of myelopathy was graded by a neurologist on the basis of physical examination, and a qualitative correlation was made with the MR findings. RESULTS: MR findings were abnormal in 18 of the 21 patients. The most common feature was spinal cord atrophy (n = 15), typically involving the thoracic cord with or without cervical cord involvement, followed by intrinsic cord signal abnormality (n = 6), and normal-appearing cord (n = 3). Three patients had both cord atrophy and intrinsic cord signal abnormality. The cord signal abnormality was diffuse, without predilection for any specific distribution pattern. Enhancement was not seen in any of the 10 patients who received intravenous contrast material. Only one of 16 patients with moderate to severe myelopathy had normal MR findings, as compared with two of five patients with mild myelopathy. CONCLUSION: MR findings in the spinal cord are abnormal in the majority of patients with AIDS-associated myelopathy, typically showing spinal cord atrophy, with or without intrinsic cord signal abnormality. Patients with moderate to severe myelopathy have an increased frequency of spinal cord abnormalities, but a definite correlation between clinical severity of myelopathy and extent of MR abnormalities remains to be established.

Acquired Immunodeficiency Syndrome↗
PubMed1998

MRI white matter diffusion anisotropy and PET metabolic rate in schizophrenia.

A disturbance in the frontal-striatal-thalamic circuitry has been proposed for schizophrenia, but this concept has been based primarily on indirect evidence from psychopharmacology and analogies with animal research. Diffusion tensor imaging, a new MRI technique that permits direct assessment of the large axon masses stretching from the prefrontal cortex to the striatum, was used to study white matter axon bundles. Diffusion tensor images, high-resolution structural MRI and positron emission tomography scans with 18-fluorodexoyglucose were obtained on five patients with schizophrenia and six age- and sex-matched normal controls. Significantly lower diffusion anisotropy in the white matter of the prefrontal cortex in schizophrenic patients than in normal controls was observed in statistical probability maps. Co-registered PET scans revealed significantly lower correlation coefficients between metabolic rates in the prefrontal cortex and striatum in patients than in controls. These twin findings provide convergent evidence for diminished fronto-striatal connectivity in schizophrenia.

Adult↗
PubMed1998

Subarachnoid space disease: diagnosis with fluid-attenuated inversion-recovery MR imaging and comparison with gadolinium-enhanced spin-echo MR imaging--blinded reader study.

PURPOSE: To evaluate fluid-attenuated inversion-recovery (FLAIR) magnetic resonance (MR) imaging in a blinded reader study for the detection of proved subarachnoid space (SAS) disease. MATERIALS AND METHODS: FLAIR MR imaging was performed in 62 patients (21 with proved SAS or meningeal disease) and 41 control patients. A subset of 24 patients (eight patients with proved SAS disease and 16 control patients) also underwent gadolinium-enhanced T1-weighted MR imaging. FLAIR images were interpreted blindly and independently by two neuroradiologists. RESULTS: For SAS disease, the overall sensitivity, specificity, and accuracy of FLAIR for both readers were 85%, 93%, and 90%. In the 15 patients with inflammatory or neoplastic meningitis only (six patients with acute subarachnoid hemorrhage [SAH] excluded), the sensitivity, specificity, and accuracy of FLAIR for both readers were 82%, 93%, and 90%. All six acute SAH cases were interpreted as abnormal on FLAIR images by both readers. In the 24 patients who underwent both FLAIR and gadolinium-enhanced T1-weighted MR imaging, the sensitivity, specificity, and accuracy of FLAIR imaging were 86%, 91%, and 89%; the sensitivity, specificity, and accuracy of gadolinium-enhanced T1-weighted imaging were 43%, 88%, and 74%. CONCLUSION: FLAIR is highly sensitive and specific for the diagnosis of SAS disease. Unenhanced FLAIR is superior to gadolinium-enhanced T1-weighted MR imaging for the diagnosis of SAS disease. These data have important implications, because FLAIR is performed without the costs and inherent risks of intravenous contrast agents. FLAIR also appears to be highly sensitive but nonspecific for acute SAH.

Adolescent↗
PubMed1998

Diffusion-weighted MRI in acute subcortical infarction.

BACKGROUND AND PURPOSE: Conventional imaging lacks sensitivity and specificity for the detection of early subcortical cerebral infarction. The purposes of our study were (1) to determine the accuracy of diffusion-weighted (DW) MRI for early subcortical infarction and (2) to determine the efficacy of DW MRI for differentiating acute from nonacute subcortical infarctions when conventional MR demonstrates multiple infarctions. METHODS: Thirty-nine patients with clinically diagnosed acute subcortical infarction and 17 control subjects were imaged with both conventional and DW MRI from 7 hours to 4 days (mean, 2.0 days) after onset of symptoms. All images were read blinded to specific clinical findings. In all cases, the precise neuroanatomic locations of lesions were noted. These lesions were subsequently correlated by an experienced stroke neurologist to determine whether their locations correlated to the patients' symptoms. RESULTS: The accuracy of DW MRI for acute subcortical infarction was 94.6%. In 4 of 39 cases, the acute infarction was not detected on conventional MRI. In 24 of 39 cases, conventional MRI showed the acute lesion as well as multiple other subcortical lesions. In each of these 24 cases, the DW MRI showed a single lesion to be acute, and in all 24 cases, that lesion corresponded to the patients' acute symptoms. CONCLUSIONS: DW MRI has very high accuracy for acute subcortical infarction and can differentiate acute from nonacute lesions. These data have significant implications in guiding patient management and patient selection for clinical trials.

Acute Disease↗
PubMed1998

MR detection of hyperacute parenchymal hemorrhage of the brain.

BACKGROUND AND PURPOSE: The detection of hemorrhage in acutely ill patients is crucial to clinical management. The MR features that allow diagnosis of intracerebral hematomas of less than 24 hours' duration are described and the mechanistic basis of these features is investigated. METHODS: The clinical MR features of seven confirmed hyperacute intracerebral hematomas were compared with those of experimentally induced hematomas in a rat model in which detailed analyses of iron metabolism and morphometry were performed. RESULTS: In all patients and all animals, a hypointense rim on T2-weighted spin-echo images that was less marked on T1-weighted spin-echo images was seen surrounding a central isointense or heterogeneous region of hyperacute hematoma. Histologically, the clot showed interdigitation of intact erythrocytes and tissue at the hematoma-tissue interface without significant hemosiderin, ferritin, or phagocytic activity. Biochemically, the iron from the extravasated blood was present only as heme proteins within the first 24 hours. CONCLUSION: The hypointense rim on T2-weighted images, and to a lesser extent on T1-weighted images, is a distinctive feature of hyperacute hematoma. This pattern is consistent with magnetic susceptibility variations of paramagnetic deoxygenated hemoglobin within intact erythrocytes at a microscopically irregular tissue-clot interface. The detection of hemorrhage is important in the management of patients with acute stroke.

Acute Disease↗
PubMed1998

Diffusion-weighted MR of acute cerebral infarction: comparison of data processing methods.

BACKGROUND AND PURPOSE: Some investigators have proposed that either calculated diffusion trace images or apparent diffusion coefficient (ADC) maps, which require imaging with multiple diffusion sensitivities and/or postacquisition image processing, are essential for the accurate interpretation of diffusion-weighted images in acute stroke because of the possible pitfalls of regional diffusion anisotropy, magnetic susceptibility artifacts, and confounding T2 effects, all of which alter signal on diffusion-weighted MR images. The purpose of our study was to compare the sensitivity, specificity, and accuracy of simple, orthogonal-axis diffusion-weighted imaging for the diagnosis of early cerebral infarction with three other sets of postacquisition-processed images: isotropic diffusion-weighted, diffusion trace-weighted, and diffusion trace images. METHODS: Twenty-six consecutive adult patients with signs and symptoms consistent with a clinical diagnosis of early cortical and/or subcortical cerebral infarction and 17 control subjects were studied with multisection, single-shot, spin-echo echo-planar diffusion-weighted imaging at 1.5 T to generate a set of three orthogonal-axis diffusion-weighted images. Isotropic diffusion-weighted, diffusion trace-weighted, and diffusion trace (mean ADC) images were then generated off-line and all four sets of images were interpreted blindly by two neuroradiologists. RESULTS: The average sensitivity, specificity, and accuracy for the orthogonal-axis diffusion-weighted images were 98.1%, 97.1%, and 97.7%, respectively. The average sensitivity, specificity, and accuracy for isotropic diffusion-weighted images were 88.5%, 100%, and 93% respectively. The average sensitivity, specificity, and accuracy for diffusion trace-weighted images were 82.7%, 73.6%, and 79.1%, respectively. The average sensitivity, specificity, and accuracy for diffusion trace images were 50.0%, 85.3%, and 64.0%, respectively. CONCLUSION: Orthogonal-axis diffusion-weighted images have the highest sensitivity and accuracy and very high specificity for early cerebral infarction. Our data contradict the contention that quantitative diffusion maps, requiring imaging with multiple diffusion sensitivities and/or subsequent image processing, are necessary for clinical stroke imaging.

Acute Disease↗
PubMed1997

Intracranial aneurysms: detection and characterization with MR angiography with use of an advanced postprocessing technique in a blinded-reader study.

PURPOSE: To assess magnetic resonance (MR) angiography for the detection and characterization of angiographically proved intracranial aneurysms by using an advanced method of postprocessing, in a blinded-reader study. MATERIALS AND METHODS: One hundred fifty-eight vessels were examined with catheter angiography and three-dimensional time-of-flight MR angiography in 44 patients with 63 aneurysms and 15 patients with no aneurysm at catheter angiography. Postprocessing was performed off-line with an advanced multifeature-extraction, ray-tracing algorithm. MR angiograms were interpreted independently by three neuroradiologists blinded to the catheter angiographic results for presence, location, size, and morphology of the aneurysm. Proof of diagnosis was consensus reading of catheter angiograms. RESULTS: Mean sensitivity for detection of aneurysms was 75% (range, 70%-79%). As a screening tool (ie, detection of at least one aneurysm necessitating catheter angiography), mean sensitivity was 91% for all aneurysms and 95% for aneurysms larger than 3 mm. This method was not adequate for detection of lobulation or size of aneurysm. CONCLUSION: MR angiography with an advanced method of postprocessing can result in highly sensitive, specific studies for the diagnosis of intracranial aneurysms that are of sufficient size to be considered for surgical treatment, but it is inadequate for characterization of aneurysms.

Adult↗
PubMed1997

Magnetic resonance imaging of intracranial aneurysms.

Intracranial aneurysms are lesions with high morbidity and mortality, but in most cases represent treatable disease. Magnetic resonance (MR) imaging and in some cases MR angiography can make valuable contributions to their diagnosis and characterization. The ultimate tool for imaging these lesions, however, remains catheter angiography. This article focuses on saccular aneurysms, with a brief discussion on atherosclerotic fusiform aneurysms and mycotic aneurysms.

Aneurysm, Infected↗