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Biomedical subjects

R R Edelman

Publications and source records attributed to R R Edelman.

At least 109 records · Page 6Linked to original sources
PubMed1996

Noninvasive assessment of regional ventilation in the human lung using oxygen-enhanced magnetic resonance imaging.

The imaging of regional ventilation in the lungs is essential for the evaluation of a variety of pathological conditions, such as emphysema, pneumonia and pulmonary embolism. We propose a novel approach for ventilation scanning, using magnetic resonance imaging (MRI) and inhaled molecular oxygen as a contrast agent, that directly depicts transfer of oxygen across the alveolus into the pulmonary vasculature. Molecular oxygen is only weakly paramagnetic but produces substantial signal changes in the lungs because of their large surface area. Ventilation defects were shown in a patient with bullous emphysema, and ventilation-perfusion mismatches were shown in two patients with pulmonary embolism.

Humans↗
PubMed1996

[Magnetic resonance angiography of the carotid artery: effect of short and ultra-short echo times].

PURPOSE: To evaluate the influence of short and ultrashort echo times (TE) on the magnetic resonance (MR) signal in the carotid sinus and in carotid artery stenoses. MATERIAL AND METHODS: High resolution gradient-echo sequences without and with flow compensation using TE's ranging from 1.5 to 8.0 ms were compared on phantoms, eight healthy volunteers, and 10 patients with moderate and severe carotid artery stenoses. RESULTS: MR sequences with shortest TE's provided the best visualisation of stenotic regions in the carotid sinus and demonstrated a substantial reduction of signal loss due to spin dephasing in both phantom and patient studies. This was made possible using an improved gradient system with higher gradient strengths and shorter rise times with lower acquisition bandwidths and better signal-to-noise ratio. CONCLUSION: MR sequences with short and ultrashort TE's enable a better definition of the stenotic region and therefore guide adequate therapeutic decisions.

Adult↗
PubMed1996

Clinical outcome in ischemic stroke predicted by early diffusion-weighted and perfusion magnetic resonance imaging: a preliminary analysis.

Perfusion and diffusion-weighted magnetic resonance imaging (MRI) can demonstrate, respectively, cerebral ischemia and ischemic brain injury in the first several hours after onset of symptoms, when proton density and T2-weighted MRI may appear normal. It is hypothesized that these techniques could distinguish regions destined for infarction from those that will not progress to infarction. We provide preliminary evidence from an analysis of 19 patients with severely disabling clinical deficits attributable to ischemia in at least an entire division of the middle cerebral artery, that initial perfusion and diffusion MRI were more accurate than conventional MRI in predicting no, partial or complete improvement--17 of 19 cases (p < 0.0001) versus 10 of 19 cases, respectively. In the subset of patients studied within 6 h of onset, diffusion/perfusion MRI was an even better predictor than conventional MRI--11 of 12 versus four of 12, respectively. In this small sample of patients with severe clinical deficits, perfusion and diffusion MRI were highly accurate in distinguishing those who would improve from those who would not. These results need to be confirmed in a larger prospective study, which may support a future role in the initial screening, selection, and evaluation of patients with stroke for acute pharmacologic interventions.

Brain Ischemia↗
PubMed1996

Liver masses: replacement of conventional T2-weighted spin-echo MR imaging with breath-hold MR imaging.

PURPOSE: To evaluate breath-hold magnetic resonance (MR) imaging with single-shot and multishot T2-weighted fast spin-echo (SE) and inversion-recovery (IR) SE echo-planar (EP) SE (IR-SE-EP) sequences compared with conventional T2-weighted SE imaging for detection of liver masses. MATERIALS AND METHODS: Imaging with all sequences was performed in 32 patients on a 1.5-T whole-body system. Images were compared on the basis of lesion-to-liver contrast-to-noise ratio (C/N), lesion conspicuity, and image quality. Image analysis was performed by two experienced radiologists in consensus. RESULTS: Lesion-to-liver C/Ns were highest on fat-suppressed-half-Fourier-single-shot-fast-SE images. For solid lesions, the lesion-to-liver C/Ns were highest with IR-fast-SE, which was significantly better (P < .05) than IR-SE-EP and conventional SE techniques and also produced the best image quality. Sensitivity with IR-fast-SE was 96%; with fat-suppressed-half-Fourier-single-shot-fast-SE, 92%; with fat-suppressed-fast-SE, 89%; with IR-SE-EP, 83%; and with conventional SE, 78%. CONCLUSION: T2-weighted breath-hold imaging, particularly IR-fast-SE imaging, was more sensitive for hepatic masses than conventional SE imaging, with a substantial reduction in acquisition time. Half-Fourier-single-shot-fast-SE imaging was especially useful in patients who were unable to hold their breath.

Adult↗
PubMed1996

Detection of hyperacute primary intraparenchymal hemorrhage by magnetic resonance imaging.

BACKGROUND: MRI has become increasingly used in the acute setting to manage patients with stroke. There has been concern that MRI may not be sensitive in the detection of acute intracranial hemorrhage. We assessed whether strongly susceptibility-weighted MRI would be sensitive to intraparenchymal hemorrhage in the first few hours. CASE DESCRIPTIONS: In the course of our ongoing studies of MRI of acute ischemic stroke in more than 200 patients, 35 patients had MR studies within 6 hours. Six of these patients who presented with acute focal symptoms with definite time of clinical onset (2.5 to 5 hours) were found to have evidence of intraparenchymal hemorrhage. Standard T1- and T2-weighted MR scans were performed. In 5 of the patients, echo-planar imaging and gradient-echo sequences were performed to increase the sensitivity of magnetic susceptibility effects of the pulse sequences. Four of the cases were of putaminal hemorrhage and 2 were lobar hemorrhages. The hemorrhage was most evident as foci of T2* hypointensity (signal loss) and unambiguous on the more susceptibility-weighted sequences, particularly echo-planar gradient-echo images. CONCLUSIONS: MRI can detect hemorrhage within 2.5 to 5 hours of onset of clinical symptoms as regions of marked signal loss due to susceptibility effects, whereas conventional MR scans of ischemic stroke may appear normal. These results demonstrate that MR susceptibility sequences may be sensitive to hyperacute hemorrhage and suggest that MR may be an adequate screen for primary intraparenchymal hemorrhage.

Acute Disease↗
PubMed1996

EEG-triggered echo-planar functional MRI in epilepsy.

We investigated whether: (1) EEG recordings could be successfully performed in an MRI imager, (2) subclinical epileptic discharges could be used to trigger ultrafast functional MRI images, (3) artifact-free functional MRI images could be obtained while the patient was having the EEG monitored, and (4) the functional MRI images so obtained would show focal signal increases in relation to epileptic discharges. We report our results in two patients who showed focally higher signal intensity, reflective of increased local blood flow, in ultrafast functional MRI timed to epileptic discharges recorded while the patients were in the imager and compared with images not associated with discharges. One patient showed a focal increase despite a clinical and EEG history of generalized discharges. This approach may have the potential to identify brain regions activated during brief focal epileptic discharges.

Adult↗
PubMed1996

Noninvasive perfusion MRI in Alzheimer's disease: a preliminary report.

We performed functional MRI using the echo-planar imaging and signal targeting with alternating radio frequency (EPISTAR) technique in 11 patients with Alzheimer's disease (AD) and 8 age-matched control subjects. Seven of the AD patients had qualitatively apparent focal areas of hypoperfusion in the posterior temporoparietal-occipital regions. At the earliest inversion time producing cortical enhancement, the ratios of parieto-occipital and temporo-occipital to whole slice signal intensity were significantly lower in the AD patients than in the controls. Parieto-occipital hypoperfusion correlated with dementia severity as measured by the Blessed Dementia Scale. EPISTAR may prove to be a rapid, noninvasive alternative to other functional neuroimaging modalities in the evaluation of patients with dementia.

Aged↗
PubMed1996

Fetal anatomy revealed with fast MR sequences.

Although all the imaging studies in this pictorial essay were done for maternal rather than fetal indications, fetal anatomy was well visualized. However, when scans are undertaken for fetal indications, fetal motion in between scout views and imaging sequences may make specific image planes difficult to obtain. Of the different techniques described in this review, we preferred the HASTE technique and use it almost exclusively for scanning pregnant patients. The T2-weighting is ideal for delineating fetal organs. Also, the HASTE technique allows images to be obtained in 430 msec, limiting artifacts arising from maternal and fetal motion. MR imaging should play a more important role in evaluating equivocal sonographic cases as fast scanning techniques are more widely used. Obstetric MR imaging no longer will be limited by fetal motion artifacts. When complex anatomy requires definition in a complicated pregnant patient, MR imaging should be considered as a useful adjunct to sonography.

Female↗
PubMed1996

Magnetic resonance coronary angiography in heart transplant recipients.

BACKGROUND: Annual coronary angiography is routinely performed to evaluate cardiac allografts. Recently, magnetic resonance coronary angiography has been used to imagine native coronary arteries, but its use in transplant recipients, with rapid heart rates, metallic sternal sutures, and altered cardiac orientation, has not been described. Our goal was to describe the feasibility of noninvasive magnetic resonance coronary angiography in cardiac allograft recipients, detect flow-limiting focal stenoses, and quantify the altered coronary artery orientation. METHODS AND RESULTS: We performed magnetic resonance coronary angiography is 18 adult heart transplant recipients (15 men and 3 women) with use of a breath-hold ECG-gated segmented k-space technique. Multiple transverse and oblique images were obtained in each subject. A control population of 16 adult patients without transplant and without angiographic evidence of coronary disease provided a reference for the coronary artery length visualized by magnetic resonance coronary angiography. This technique identified the left main coronary artery in 15 of 15 transplant recipients with normal coronary anatomy. Magnetic resonance coronary angiography demonstrated a +25-degree anterior (clockwise) right coronary artery ostial rotation in transplant recipients (p = 0.0001 versus control group) with corresponding realignment of the left main ostium. By magnetic resonance coronary angiography, the mean contiguous length of coronary artery visualized in the transplant recipients was similar to that in the control subjects for all major vessels (p = not significant). Five transplant recipients had nine discrete stenoses (50% or greater luminal diameter) identified by contrast angiography, of which seven stenoses were identified as signal voids by magnetic resonance coronary angiography. coronary stenoses not seen by this technique were located in the distal one third of the artery. CONCLUSIONS: These data confirm and for the first time quantify the previously observed anterior rotation of the coronary ostia, which may be used to guide coronary engagement for subsequent interventions. In addition, these data demonstrate the potential of magnetic resonance coronary angiography to image noninvasively the coronary arteries and identify focal stenoses in cardiac allograft recipients.

Adolescent↗
PubMed1996

MR angiography of the head and neck.

A review of the basic physics and techniques for acquiring and evaluating magnetic resonance angiograms is provided, including time-of-flight and phase contrast techniques. Magnetic resonance (MR) angiography is becoming a routine method of evaluating carotid bifurcation atherosclerotic disease in both a screening and diagnostic capacity. The expanding clinical utility of MR angiography in the detection of intracranial aneurysms, characterization of arteriovenous malformations, and evaluation of intracranial atherosclerotic disease are also reviewed. Furthermore, MR angiography allows for the noninvasive diagnosis of arterial dissection. Magnetic resonance venography also allows the confirmation of the previously elusive and likely underdiagnosed entity of cerebral venous thrombosis.

Carotid Artery Diseases↗
PubMed1995

Identification of anomalous coronary arteries and their anatomic course by magnetic resonance coronary angiography.

BACKGROUND: Anomalous coronary arteries are a rare but recognized cause of myocardial ischemia and sudden death. Identification currently requires x-ray angiography, which may have difficulty defining the three-dimensional course of the anomalous vessel. Magnetic resonance coronary angiography (MRCA) has been shown to image coronary artery anatomy noninvasively. We hypothesize that MRCA may be useful in the identification of anomalous coronary arteries and their anatomic course. METHODS AND RESULTS: Sixteen patients (9 men, 7 women, age 44 to 81 years) with anomalous aortic origins of the coronary arteries by conventional x-ray angiography underwent MRCA. Multiple images of the major epicardial coronary arteries were obtained by use of a breathhold, fat-suppressed, segmented-k space, gradient-echo technique by investigators blinded to all patient data. Anomalous coronary artery pathology, by x-ray angiography, included right-sided left main coronary artery (n = 3), right-sided left circumflex artery (n = 6), separate left-sided left anterior descending and left circumflex arteries (n = 2), left-sided right coronary artery (n = 4), and an anteriorly displaced right coronary artery (n = 1). MRCA correctly identified the anomalous coronary vessel(s) in 14 of 15 patients. In 1 patient, the anomalous vessel was incorrectly identified, and in 2 patients the course of the anomalous vessel was not clearly seen; one of these was a nondominant, anomalous right coronary artery. CONCLUSIONS: MRCA is a useful technique for the noninvasive identification of anomalous coronary arteries and their anatomic course.

Adult↗
PubMed1995

Perioperative imaging strategies for carotid endarterectomy. An analysis of morbidity and cost-effectiveness in symptomatic patients.

OBJECTIVE: To assess the cost-effectiveness of four diagnostic strategies for the preoperative evaluation of symptomatic patients who are potential candidates for carotid endarterectomy (ie, 70% to 99% stenosis): (1) duplex sonography (DS), (2) magnetic resonance angiography (MRA), (3) contrast angiography (CA), and (4) the combination of DS and MRA supplemented by CA for disparate results. METHODS: Cost-effectiveness analysis based largely on published clinical trial data. Sensitivities and specificities of noninvasive tests were estimated from 81 patients undergoing prospective evaluation with DS, MRA, and CA. OUTCOME MEASURE: Incremental cost per quality-adjusted year of life gained. RESULTS: For a hypothetical cohort of symptomatic patients undergoing evaluation for carotid endarterectomy, the combination of tests resulted in the greatest quality-adjusted life expectancy of the four options considered. After incorporating the costs of testing, surgery, and stroke, we found that neither the MRA nor the CA strategy was cost-effective. The combination of tests was more effective but more costly than DS, resulting in an additional cost of $22,400 per quality-adjusted year of life gained. For centers that do not have adequate MRA, CA resulted in an additional cost of $99,200 per quality-adjusted year of life saved compared with DS. CONCLUSIONS: Our results suggest that for the preoperative detection of a 70% to 99% carotid stenosis, the combination of DS and MRA, supplemented by CA for disparate results, is associated with the lowest long-term morbidity and mortality and has a favorable cost-effectiveness ratio. The combination of tests, or DS alone when MRA is not available, could potentially replace the current practice of using CA alone in the preoperative evaluation of patients with symptomatic carotid stenosis.

Aged↗
PubMed1995

Shared neural substrates controlling hand movements in human motor cortex.

Voluntary hand movements in humans involve the primary motor cortex (M1). A functional magnetic resonance imaging method that measures relative cerebral blood flow was used to identify a distributed, overlapping pattern of hand movement representation within the posterior precentral gyrus, which contains M1. The observed pattern resembles those reported in nonhuman primates and differs from a somatotopically organized plan typically used to portray human motor cortex organization. Finger and wrist movements activated a wide expanse of the posterior precentral gyrus, and representations for different finger movements overlapped each other and the wrist representation. Multiple sites of activation occurred in the precentral gyrus for all movements. The overlapping representations may mediate motor and cognitive functions requiring coordinated neural processing for finger and wrist actions rather than discrete control implied by somatotopic maps.

Brain Mapping↗
PubMed1995

Acute human stroke studied by whole brain echo planar diffusion-weighted magnetic resonance imaging.

Our purpose was to use whole brain echo planar magnetic resonance imaging (MRI) to identify and characterize diffusion abnormalities in acute cerebral ischemia. We studied 40 patients as early as 3 hours after onset of signs and symptoms of cerebral ischemia. Diffusion-weighted imaging (DWI) of the entire brain could be completed in 3 seconds or, using seven different diffusion sensitivities (maximum b = 1,271 sec/mm2), in 48 seconds. Measurements and synthetic maps were made of apparent diffusion coefficients (ADC), a physiological parameter that characterizes the self-diffusion of water in tissue. Early ischemic lesions were identified with DWI as hyperintense regions of decreased ADC in all patients who subsequently developed infarction, before changes were evident on conventional MRI in cases studied earlier than 6 hours after onset of ischemic symptoms. Lesions as small as 4 mm in diameter were identified. The extent of lesions within white matter was best defined by controlling for the anisotropic effect of axonal orientation. The mean ADC (+/- SD) for control regions in the 36 patients was 9.15 (+/- 2.91) x 10(-4) mm2/sec. Mean ADC of ischemic regions was 56% of control values at 6 hours or less and stayed significantly reduced for 3 to 4 days after onset of ischemia. The relative ADC increased progressively over time to be pseudonormalized at 5 to 10 days and elevated in the chronic state, making the distinction of acute lesions adjacent to chronic infarcts readily apparent. DWI with echo planar imaging measures a unique physiological parameter that is sensitive to ischemic changes before conventional MRI. Its potential role in the quantitative study of human stroke pathophysiology and therapeutics is the subject of further investigation.

Adult↗