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S W Atlas

Publications and source records attributed to S W Atlas.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1996

Functional activation during an auditory comprehension task in patients with temporal lobe lesions.

Functional magnetic resonance imaging (fMRI) was used to map regional brain activation during an auditory comprehension task in two normal controls and two patients with left temporal lobe lesions. Activity in the superior temporal and angular gyrus regions was detected in all normal subjects. In the patients, the spatial distribution of activation ipsilateral to the lesions differed from the pattern observed in contralateral cortex or in control subjects. These studies highlight the potential of fMRI for mapping abnormal functional anatomy in the human brain.

Adult↗
PubMed1996

Functional magnetic resonance imaging of regional brain activity in patients with intracerebral gliomas: findings and implications for clinical management.

Functional magnetic resonance imaging (fMRI) was performed in seven patients harboring intracerebral gliomas proven by histological analysis using a noninvasive blood oxygen level-dependent technique based on the documented discrepancy between regional increases in blood flow and oxygen use in response to regional brain activation. We combined fMRI with conventional magnetic resonance imaging (MRI) during motor or language task activation experiments to investigate the potential usefulness of mapping regional brain activity as part of treatment planning in patients with intracerebral gliomas, in whom preservation of areas of functioning brain tissue is critical. Statistical fMRI maps were generated and directly mapped onto conventional MRI scans obtained at the same session. Of the five patients cooperative enough to remain motionless for the study and perform the task, the location of activation in the primary sensorimotor cortex on the side of the tumor was clearly displaced compared with that in the normal contralateral hemisphere in four patients. Four of the five tumors in these patients showed fMRI activation within the periphery of (or immediately adjacent to) areas of presumed tumor based on spin-echo MRI. In some patients with neurological deficit, the extent of activation was reduced on the side of the tumor as compared with the normal hemisphere. The supplemental motor area and the ipsilateral primary motor cortex were also reproducibly activated during motor tasks. We conclude that blood oxygen level-dependent fMRI can localize areas of cortical function in patients undergoing treatment planning for gliomas so that therapy can be directed away from regions of residual function. Our preliminary data suggest that functioning cortex within or adjacent to tumor margins can be demonstrated, which may correspond to partial preservation of clinical function. Our preliminary data also suggest that there may be a quantifiable difference on fMRI between activation in tumor-bearing cortex and activation in corresponding normal cortex in the contralateral hemisphere. We postulate that the magnitude of this difference may relate to the severity of patient deficit.

Adolescent↗
PubMed1996

Neuroradiology.

Explore the source record for details and available documents.

Humans↗
PubMed1996

Functional magnetic resonance imaging of regional brain activity in patients with intracerebral arteriovenous malformations before surgical or endovascular therapy.

Functional magnetic resonance (MR) imaging was performed in six patients harboring proven intracerebral arteriovenous malformations (AVMs) using a noninvasive blood oxygen level-dependent technique based on the documented discrepancy between regional increases in blood flow and oxygen utilization in response to regional brain activation. Statistical functional MR maps were generated and overlaid directly onto conventional MR images obtained at the same session. In the six patients studied, a total of 23 separate functional MR imaging activation studies were performed. Of these, two runs were discarded because of motion artifacts. All of the remaining 21 studies demonstrated activation in or near expected regions for the paradigm employed. Qualitatively reproducible regional localizations of functional activity in unexpected sites were also seen. The authors' findings indicating aberrant mapping of cortical function may be explained on the basis of the plasticity of brain function, in that the developing brain can take over function that would normally have been performed by regions of brain encompassed by the lesion. Preliminary results in this study's small number of cases also indicate that activity demonstrated within the confines of the apparent AVM nidus may help predict the development of a posttherapy deficit. The authors demonstrate that functional MR imaging can be successfully and reproducibly performed in patients with intracerebral AVMs. Notwithstanding the paucity of normative data using functional MR imaging, the author' findings support cortical reorganization associated with these congenital lesions. Blood oxygen level-dependent MR imaging is a noninvasive method used to localize areas of eloquent cortex in patients harboring AVMs; it may prove to be of value in treatment planning.

Adolescent↗
PubMed1994

Neuroradiology.

Explore the source record for details and available documents.

Central Nervous System Diseases↗
PubMed1994

Intracranial aneurysms: depiction on MR angiograms with a multifeature-extraction, ray-tracing postprocessing algorithm.

PURPOSE: To compare a new method for postprocessing data, soft thresholding and depth cueing of unrestricted techniques (STANDOUT), with maximum intensity projection (MIP) for magnetic resonance (MR) angiograms of intracranial aneurysms. MATERIALS AND METHODS: Eighteen patients with 19 intracranial aneurysms were studied. Images generated with STANDOUT were compared with those of MIP for both three-dimensional (3D) time-of-flight (TOF) and 3D phase-contrast (PC) techniques. Images were assessed for detection of aneurysms, scored for delineation of aneurysmal features and overall MR angiographic characteristics, and compared with catheter angiograms. RESULTS: Both postprocessing techniques demonstrated aneurysms on most TOF and PC MR angiograms. Statistically significant improvement of aneurysmal features, aneurysmal neck definition, and delineation of adjacent arterial anatomy was seen on both TOF and PC MR angiograms with STANDOUT. Feature definition was most improved for smaller aneurysms. TOF and PC MR angiograms with STANDOUT showed improved elimination of artifactual intraluminal signal loss in normal large vessels, reduced artifactual narrowing of vessel caliber, and better small vessel delineation. CONCLUSION: STANDOUT has great benefits for postprocessing of intracranial MR angiograms, regardless of the technique of data acquisition.

Cerebral Arteries↗
PubMed1994

MR angiography in neurologic disease.

Magnetic resonance (MR) angiography has rapidly evolved over the past few years to become a technique that is commonly used in clinical practice as part of the diagnostic work-up of patients with suspected neurologic disease. In this review, the author provides a brief overview of the relevant biophysical principles and some fundamentals of flow imaging by using MR as a baseline for understanding and implementing MR angiography in these patients. A historical perspective is given as a way of emphasizing the need for a healthy degree of skepticism rather than enthusiasm alone when reading MR angiographic literature. The rationale and clinical needs for MR angiography are summarized. The available data from blinded reader studies are summarized for two major clinical entities in which MR angiography is often used in neurologic practice: atherosclerotic disease of the extracranial carotid bifurcation and intracranial aneurysms. Recent refinements and technical innovations are also noted.

Carotid Arteries↗
PubMed1994

Blinded-reader comparison of magnetic resonance angiography and duplex ultrasonography for carotid artery bifurcation stenosis.

BACKGROUND AND PURPOSE: We compared two-dimensional time-of-flight magnetic resonance angiography (MRA) and duplex ultrasonography with arteriography for the detection of 70% to 99% stenoses at the carotid artery bifurcation (ie, surgical disease according to findings of the North American Carotid Endarterectomy Trial). METHODS: Three blinded readers independently measured stenoses on MRA in 73 vessels from 38 patients. Duplex ultrasonography was available in 66 vessels from 35 of these patients, and blinded reading was performed by one reader. Comparison was made to arteriography. RESULTS: Magnetic resonance angiography demonstrated a sensitivity of 92.4%, specificity of 74.5%, and negative predictive value of 95.8% for 70% to 99% stenoses. Interobserver agreement was high (kappa = 0.91). Absence of signal at stenoses with evidence of distal flow usually, but not always, corresponded to surgical disease. Duplex ultrasonography demonstrated a sensitivity of 81.0%, specificity of 82.2%, and negative predictive value of 90.2% for surgical disease. There was no significant difference between MRA and duplex ultrasonography for the sensitivity or specificity in detecting 70% to 99% stenoses (P > .1, exact form of the McNemar test). MRA had no false positives or false negatives for complete occlusions of the carotid artery, whereas duplex ultrasonography missed one occlusion and falsely called two patent vessels occluded. In seven cases, both MRA and duplex ultrasonography overestimated stenoses to miscategorize them as surgical disease. CONCLUSIONS: Although the sensitivity and specificity of MRA and duplex ultrasonography are not significantly different for distinguishing surgical and nonsurgical degrees of stenosis at the carotid bifurcation, MRA has some advantages that may make it the screening test of choice. Concordant MRA and duplex ultrasonography for surgical disease does not necessarily obviate the need for catheter arteriography.

Aged↗
PubMed1994

Delineation of gliomas with various doses of MR contrast material.

PURPOSE: To examine the effects of different gadolinium doses on the delineation of gliomas, particularly the demonstration of abnormal enhancement on T1-weighted images extending beyond the zone of apparent signal abnormality on corresponding T2-weighted images. METHODS: During phase II clinical trials of gadoteridol, 23 patients with pathologically proved gliomas were studied by MR with various doses of gadoteridol, ranging from 0.05 to 0.3 mmol/kg. RESULTS: All of the gliomas were readily detected by T2-weighted images. Twelve of 23 patients demonstrated enhancement on T1-weighted images extending beyond the zone of apparent signal abnormality demonstrated on T2-weighted images. These findings were seen in none of the six patients (0%) studied at 0.05 mmol/kg, one of five patients (20%) studied at 0.1 mmol/kg, four of five patients (80%) studied at 0.2 mmol/kg, and seven of seven patients (100%) studied at 0.3 mmol/kg. CONCLUSIONS: The detection of symptomatic gliomas does not require a contrast agent because they are generally large and readily demonstrated on T2-weighted images. However, the area of postcontrast enhancement of gliomas seems to be greater with higher doses of contrast agent. The cause of the abnormal enhancement extending beyond the zone of apparent signal abnormality on T2-weighted images seen in this limited study is unknown and probably represents tumor infiltration. The frequency of detection of such findings appears to be proportional to the dose of contrast material used.

Brain↗
PubMed1994

Phase III multicenter trial of high-dose gadoteridol in MR evaluation of brain metastases.

PURPOSE: To assess the efficacy and safety profile of high-dose (0.3 mmol/kg cumulative dose) gadoteridol in patients with suspected central nervous system metastatic disease. METHODS: We studied 67 patients using an incremental-dose technique. Patient monitoring included a medical history, physical examination, vital signs, and extensive laboratory tests within 24 hours before and after the MR examination. Precontrast T1- and T2-weighted spin-echo studies were performed, followed by intravenous injection of 0.1 mmol/kg of gadoteridol. T1-weighted images were acquired immediately after and at 10 and 20 minutes after injection. At 30 minutes an additional 0.2 mmol/kg of gadoteridol was administered (0.3-mmol/kg cumulative dose), and T1-weighted images were acquired. Cases demonstrating abnormal MR findings were assessed for efficacy by unblinded and blinded reviewers and were analyzed quantitatively. RESULTS: Three adverse effects in two patients were considered to be related to gadoteridol administration. No adverse effects were serious; all self-resolved. Forty-nine cases showed abnormal MR findings and were included in the efficacy analysis. A significantly greater number of lesions was seen on the high-dose as opposed to the standard-dose images. Blinded and unblinded readers identified 5 and 8 patients, respectively, with solitary lesions on standard-dose examination and multiple lesions on high-dose examination. Two patients who had normal standard-dose findings had lesions identified on high-dose studies. Quantitative analysis of 133 lesions in 45 patients demonstrated significant increases in lesion signal intensity on high-dose studies when compared with standard-dose studies. CONCLUSION: Gadoteridol can be safely administered up to a cumulative dose of 0.3 mmol/kg. High-dose contrast studies provide improved lesion detectability and additional diagnostic information over studies performed in the same patients with a 0.1-mmol/kg dose and aid in patient diagnosis and treatment. High-dose gadoteridol study may facilitate the care of patients with suspected central nervous system metastasis.

Adolescent↗
PubMed1993

Delayed peripartum vasculopathy: cerebral eclampsia revisited.

Over a 2-year period, we treated 4 postpartum patients with acute neurologic problems appearing 4 to 9 days after delivery. Three patients either had no proteinuria or edema and therefore did not meet all accepted clinical criteria for the diagnosis of eclampsia. Magnetic resonance imaging (MRI) of the brain in all patients demonstrated high-signal foci most prominent in the parieto-occipital regions and the subcortical white matter. Cerebral angiogram in 2 patients revealed diffuse vasospasm. In 3 patients, MRI abnormalities resolved. MRI and angiographic abnormalities in our patients are identical to those of patients meeting accepted criteria for eclampsia. Our experience suggests that the current criteria for the diagnosis of eclampsia are too stringent, both in terms of clinical picture and days postpartum to cerebral manifestations.

Adult↗
PubMed1993

Rationale and clinical indications for contrast agents in MR imaging of the brain and spine.

This presentation explores clinical indications, limitations, and the scientific rationale for use of gadolinium contrast agents in MR imaging of the brain and spine. Enhancement of abnormal CNS tissues is related to structure and function of the blood-brain barrier under pathologic conditions, the prototype of which is tumor angiogenesis. Gadolinium administration can improve the diagnostic sensitivity of intracranial MR imaging, facilitating detection of leptomeningeal or ependymal disease spread and metastases. Moreover, use of contrast often provides greater diagnostic specificity by virtue of the presence and, in many cases, the absence of enhancement. This is particularly helpful in distinguishing metastases from other potential causes of high signal intensity on unenhanced spin-echo (SE) images. In addition to improving diagnosis of neoplasia, gadolinium use is often necessary to demonstrate most cranial neuropathies and to differentiate herniated disc from epidural fibrosis in the failed-back surgery syndrome. Advanced techniques that exploit gadolinium's properties (e.g., MR angiography, perfusion MR imaging) or increase its diagnostic effectiveness (e.g., fat suppression in the postoperative spine) are treated.

Brain↗
PubMed1993

Myelitis following chickenpox: a case report.

An 18-year-old woman presented with myelopathic symptoms and a T-8 sensory deficit during a primary varicella infection. There were significant MRI changes in both the cervical and thoracic regions. Following treatment with steroids and intravenous acyclovir, the patient improved clinically and the abnormalities on MRI improved.

Adolescent↗
PubMed1993

SPECT in patients with cortical visual loss.

Single-photon emission computed tomography (SPECT) with 99mTc-hexamethylpropyleneamine oxime (HMPAO) was used to investigate changes in cerebral blood flow in seven patients with cortical visual impairment. Traumatic brain injury (TBI) was the cause of cortical damage in two patients, cerebral ischemia in two patients and carbon monoxide (CO) poisoning, status epilepticus and Alzheimer's Disease (AD) each in three separate patients. The SPECT scans of the seven patients were compared to T2-weighted magnetic resonance image (MRI) scans of the brain to determine the correlation between functional and anatomical findings. In six of the seven patients, the qualitative interpretation of the SPECT studies supported the clinical findings (i.e., the visual field defect) by revealing altered regional cerebral blood flow (rCBF) in the appropriate regions of the visual pathway. MR scans in all of the patients, on the other hand, were either normal or disclosed smaller lesions than those detected by SPECT. We conclude that SPECT may reveal altered rCBF in patients with cortical visual impairment of various etiologies, even when MRI studies are normal or nondiagnostic.

Adult↗