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Biomedical subjects

R R Edelman

Publications and source records attributed to R R Edelman.

At least 181 records · Page 10Linked to original sources
PubMed1992

Magnetic resonance angiography in the body.

Magnetic resonance angiography (MRA) is gaining wide acceptance as a clinical tool for evaluation of the carotid arteries and intracranial circulation. MR angiographic methods are far less widely employed in the body. However, several very powerful techniques have been developed which provide a wealth of clinical information and which may soon replace alternative imaging techniques for a variety of applications. As compared with MRA of the head and neck, these techniques require more interactive involvement by a physician and more familiarity with the imaging machine to derive their full benefit. Based on the experience of the authors and others working in the field, this article outlines strategies for MRA of the abdomen, pelvis and thorax, and reviews the clinical situations in which these techniques have proved useful.

Abdomen↗
PubMed1992

Image artifacts in fast magnetic resonance imaging.

Image artifacts are unwanted, spurious signal intensities that interfere with clinical diagnosis. This article gives an overview of image artifacts in magnetic resonance imaging. We discuss the causes of these artifacts, provide clinical examples, and offer solutions to avoid them.

Artifacts↗
PubMed1991

Stereoscopic display of MR angiograms.

Recent developments in magnetic resonance (MR) allow high resolution imaging of flowing blood. To overcome the tomographic nature of conventional MR acquisitions, projection angiograms can be produced. These angiograms are similar in their display of blood vessels to plain film or digital subtraction angiograms. However, the three-dimensional information inherent in them is partly lost when single projections are viewed. We describe a method of three-dimensional display consisting of stereo pairs of the MR angiograms. With these an examiner experienced in stereo viewing can recover depth perception.

Carotid Artery, Internal↗
PubMed1991

First-pass nuclear magnetic resonance imaging studies using gadolinium-DTPA in patients with coronary artery disease.

Nuclear magnetic resonance (NMR) imaging has been shown to accurately portray cardiac anatomy and function. To investigate the potential of NMR imaging for the assessment of coronary stenosis in patients with chest pain, ultrafast NMR imaging in conjunction with a T1 (longitudinal relaxation time) contrast agent was performed in 17 patients with chest pain who had undergone cardiac catheterization. These included 12 patients with significant coronary artery stenoses and 4 who underwent repeat NMR study after myocardial revascularization. Cardiac images at rest were obtained during rapid intravenous injection of gadolinium-DTPA (0.04 mM/kg). Electrocardiographic-gated images were acquired over 380 ms, with repetitive images obtained every 3 to 4 s. After contrast injection, there was pronounced signal enhancement in the right ventricular cavity, followed by enhancement in the left ventricular cavity and myocardium. Regional myocardium perfused by a diseased vessel demonstrated a lower peak signal intensity (p = 0.001) and lower rate of signal increase (p = 0.001) than did myocardium perfused by coronary arteries without stenosis. Repeat NMR study after revascularization showed an increase in peak signal intensity (p less than 0.002). These results demonstrate the clinical potential of dynamic gadolinium-DTPA-enhanced NMR imaging for the assessment of coronary artery disease in patients with chest pain. In combination with anatomic and functional NMR imaging, this technique has the potential to provide a comprehensive noninvasive cardiac evaluation of patients with suspected coronary artery disease.

Adult↗
PubMed1991

[MR angiography of the abdominal aorta: initial experience].

Flowing blood can be demonstrated as bright signal in MR-imaging resulting in MR-angiography (MRA). This study presents the results of MRA using the "time of flight"-effect in which projection angiograms along the longitudinal axis were established by a row of 2D-gradient echo (GE) images (FLASH) in breath-hold technique. The method was proven in 5 normal volunteers and evaluated against DSA in 21 patients with aortic diseases. The preliminary results demonstrate a satisfactory flow signal in the normally perfused aorta; thus occlusions, stenoses, and aneurysms could be defined clearly. In smaller vessels the signal was still insufficient. Diagnostic problems of vascular overlapping can be solved in most cases by rotating the angiograms, and by additional analysis of individual 2D-GE images. In the present form the quality of MRA is still inferior to that of DSA.

Angiography, Digital Subtraction↗
PubMed1991

Cineangiography of the heart in a single breath hold with a segmented turboFLASH sequence.

Six healthy volunteers and three patients with cardiac anomalies were studied in a comparison of segmented turboFLASH (fast low-angle shot) cine, a method of magnetic resonance imaging that permits an entire series of high-resolution cine images to be obtained in one breath hold, with standard cine. Segmented turboFLASH uses a gradient-echo sequence designed for short imaging times in combination with a segmented data acquisition method. Presaturation pulses were applied to eliminate the blood pool signal; the signal-to-noise ratio was assessed with a phantom. Standard hardware and image reconstruction methods were used. The breath-hold images consistently showed reduced ghosting and blurring from respiration. Because a very short echo time was used, segmented turboFLASH was relatively insensitive to dephasing caused by local field disturbances or flow. The authors conclude that, by reducing imaging times and eliminating respiratory artifact, segmented turboFLASH can be useful for performing cine studies of the heart and great vessels.

Cineangiography↗
PubMed1991

Cerebral venography with MR.

The authors describe a two-dimensional time-of-flight magnetic resonance (MR) angiography technique to create projection venograms of the head. The technique was applied to 27 healthy volunteers and 39 patients. The superior sagittal and straight sinuses, the internal cerebral veins, and the Galen vein were visualized in all the volunteers. Other veins were seen in a high percentage of subjects. Systematic comparison of digital subtraction angiography (DSA) after intraarterial contrast medium injection and MR venography in patients showed good correlation between the two techniques. MR venography proved helpful in identifying thrombosis or patency of cerebral veins and sinuses and showed collateral venous drainage and venous drainage from arteriovenous malformations. There was good correlation between conventional contrast angiography and MR venography. In conclusion, MR venography is considered reliable for showing the cerebral venous system and provides information additional to that of conventional spin-echo imaging.

Adolescent↗
PubMed1991

Liver transplantation: MR angiography with surgical validation.

Thirty patients (mean age, 45 years) were evaluated with magnetic resonance (MR) angiography before liver transplantation to assess the accuracy of MR angiography. A series of breath-hold, two-dimensional images were acquired and subsequently processed to form three-dimensional projection angiograms. Graphic information on blood flow in the portal vein was acquired by using presaturation bolus tracking. Correlative duplex ultrasound (US) was performed in 28 patients, and surgical or autopsy correlation was available in all cases. MR angiography demonstrated patency of the portal vein in 26 (96%) of 27 patients, made possible the diagnosis of portal venous occlusion in three of three patients, depicted reversed portal flow in one patient, and provided clear delineation of the extent of varices and specific portosystemic collateral vessels. When duplex US was successful, there was full agreement with MR angiographic results in assessing portal vein patency and flow direction. All of the MR findings were corroborated at surgical exploration or autopsy. The authors conclude that MR angiography is very accurate in the portal system and is valuable in preoperative assessment for liver transplantation.

Abdomen↗
PubMed1991

Fast time-of-flight MR angiography with improved background suppression.

A new technique for improving contrast in time-of-flight magnetic resonance (MR) angiography is described. A selective 180 degrees radio-frequency pulse was applied before data acquisition to suppress the signal intensity of stationary tissues. Vascular images were obtained in 1 second or less by using a single-shot, rapid gradient-echo sequence in conjunction with a very short echo time to minimize flow-related dephasing. Alternatively, the data acquisition could be divided into several segments that were combined to create an image. Because of the short imaging times, abdominal single-shot images were relatively insensitive to motion. The major drawback was decreased spatial resolution and limited signal-to-noise ratio. Spatial resolution of segmented flow images was comparable with that of standard gradient-echo images, but there was a marked reduction in the signal intensity of stationary tissues. For high-resolution MR angiography, the effective background suppression obtained by means of the segmented approach can improve the quality and reliability of images created by the maximum intensity projection algorithm.

Abdomen↗
PubMed1991

MR imaging of liver metastases at 1.5 T: similar contrast discrimination with T1- and T2-weighted pulse sequences.

The authors evaluated soft-tissue contrast on spin-echo (SE) proton density-weighted, SE T2-weighted, SE short-echo-time (TE) T1-weighted, and gradient-echo (GRE) images of 34 patients with known hepatic tumors who underwent high-field-strength (1.5-T) magnetic resonance imaging. For solid liver tumors, the difference in the mean lesion-liver contrast-to-noise ratios (C/Ns) with T1- (GRE and SE) and T2-weighted pulse sequences was not statistically significant (P greater than .05). For nonsolid liver tumors, the T2-weighted images provided significantly greater (P less than .05) mean lesion-liver C/N than T1-weighted GRE images. Mean liver signal-to-noise ratio was significantly greater on T1-weighted GRE (P less than .0001) and T1-weighted SE (P less than .05) images than on T2- and proton density-weighted images. Qualitative analysis of T1-weighted (SE and GRE) images and proton density- plus T2-weighted images showed that lesion conspicuity was similar in 25 of 32 patients (78%). The results suggest that liver tumor imaging at high field strength can be performed with short-TE T1-weighted (SE or GRE) or conventional T2-weighted pulse sequences.

Humans↗
PubMed1991

Middle cerebral artery: determination of flow velocities with MR angiography.

A magnetic resonance (MR) angiographic technique for noninvasive measurement of flow velocities in the intracranial cerebral arteries was studied. Velocity measurements were made in a phantom and in the middle cerebral artery of six volunteers. Velocities were assessed in the volunteers before, during, and after finger movement. Average values for mean maximal velocities determined with MR angiography were 69.8 cm/sec before, 77.2 cm/sec during, and 69.6 cm/sec after finger movement. Correlations between values obtained with MR angiography and transcranial Doppler (TCD) sonography were r = .86 and P = .0001 for values obtained at rest and r = .84 and P = .0001 for values obtained during finger movement. The velocity increase during finger movement compared with that at rest was 11% for MR angiography and 11.3% for TCD sonography. Values measured with TCD sonography, however, were less than those measured with MR angiography (P = .001). The results show the feasibility of measuring flow velocities in intracranial arteries with MR angiography.

Adult↗
PubMed1991

Coronary arteries: breath-hold MR angiography.

The authors describe a method for performance of ultrafast magnetic resonance (MR) angiography of coronary arteries with a standard clinical MR system and a body coil. Each image was obtained within a single breath hold by using an electrocardiography-gated, segmented, ultrafast, gradient-echo pulse sequence with an incremental excitation flip angle for the eight phase-encoding steps acquired per segment. By using overlapping 4-mm-thick sections, the coronary arteries were routinely depicted from the coronary ostia distally at MR in healthy subjects. Ultrafast MR angiography of the coronary arteries is feasible with use of a standard body coil. This technique offers considerable potential as an investigational tool and, with further development, may become a clinically useful imaging application.

Adult↗
PubMed1991

Fast selective black blood MR imaging.

To overcome the problems associated with gradient-echo (GRE) magnetic resonance (MR) angiography ("bright blood" imaging) and "black blood" imaging with presaturated spin-echo (SE) pulse sequences, the authors devised a new approach for black blood imaging. Their method, selective preinversion fast imaging with steady precession (turboFISP), uses a segmented GRE sequence for fast data acquisition. Nulling of vascular signal results, and stationary tissue appears bright. The method was compared with flow-compensated GRE imaging in a phantom and with GRE imaging and presaturated SE imaging in seven healthy volunteers and nine patients with various cardiac diseases. With phantoms, the selective preinversion turboFISP sequence produced better flow contrast than did GRE sequences. Selective preinversion turboFISP was often superior to SE imaging for depicting vessel lumina, particularly in patients with slowly flowing blood. Arteries appeared dark in selective black blood angiograms, but veins did not. Selective preinversion turboFISP can be used with bright blood GRE imaging to depict vessel lumina, and its capability for image acquisition within a breath hold and with cardiac gating minimizes artifacts from respiration and motion of the vessel wall.

Adult↗
PubMed1991

[Imaging of thoracic and abdominal aortic aneurysms using MR angiography].

Five patients with suspected dissecting aneurysm of the thoracic aorta and nine patients with fusiform aneurysm of the abdominal aorta underwent time-of-flight (TOF) MR angiography. MR angiography revealed dissecting aneurysms in four patients and a dilated ascending aorta without evidence of dissection in one patient. These findings correlated well with angiography, computed tomography and surgical findings. Proximal and distal extension as well as the relationship to vessels originating from the aortic arch was assessed correctly in all cases. There was a good correlation between MR angiography, CT, and angiography in the patients with abdominal aortic aneurysms. The status of the renal arteries was shown in all patients with MR angiography, but the inferior mesenteric artery was not regularly demonstrated. MR angiography is a promising method for non-invasive assessment of thoracic and abdominal aortic aneurysms.

Aortic Dissection↗
PubMed1991

Hepatic schistosomiasis: report of two cases and literature review.

Two Filipino patients were referred for evaluation of abnormal liver enzymes. Both patients were known to come from regions endemic for Schistosoma japonicum. The clinical laboratory and radiological features of these patients are presented. We highlight the findings of radiologic evaluation, including magnetic resonance imaging (MRI). The epidemiology, clinical manifestations, diagnostic strategies including a comparison of the utility of ultrasound, computed tomography, and MRI are reviewed. The pathophysiology responsible for hepatic manifestations of schistosomiasis is reviewed. An increased influx to the United States of persons from regions endemic for schistosomiasis, such as South America, Southeast Asia, and the Philippines, will result in an increase in the prevalence of the disease in this country. The diagnosis of hepatic schistosomiasis will need to be considered in populations at risk for contracting this common worldwide problem.

Adult↗
PubMed1991

Magnetic resonance imaging: a reliable test for the evaluation of proximal atherosclerotic renal arterial stenosis.

Symptomatic renal artery stenosis is a significant and treatable clinical problem. A reliable and accurate noninvasive method of screening for renal artery stenosis has not yet been found. We used magnetic resonance imaging to study 37 patients who had undergone recent renal angiography. Fourteen patients had normal renal arteries by angiography. In 23 patients either unilateral or bilateral stenosis or occlusion was present. The disease process in all patients appeared to be atherosclerosis. The average age of the 37 patients was 68 years. The magnetic resonance scans and angiograms were read independently by two different radiologists, each of whom was blinded to the clinical history and the results of the other study. Renal arterial stenoses found on angiogram and magnetic resonance scans were graded as absent (0% to 24%), mild (25% to 49%), moderate (50% to 74%), or severe (75% to 99%). The magnetic resonance imaging results concurred with the angiographic findings in 70 of 77 arteries (91%). Magnetic resonance imaging predicted the presence of a greater than 50% stenosis of the renal artery with a sensitivity of 100% and a specificity of 94%. Magnetic resonance imaging may prove to be the best noninvasive screening test for proximal atherosclerotic renal arterial stenosis.

Adult↗
PubMed1991

Evaluation of the extracranial carotid arteries: correlation of magnetic resonance angiography, duplex ultrasonography, and conventional angiography.

We compared duplex scanning, "bright blood" and "black blood" magnetic resonance angiography, and conventional angiography for evaluation of the extracranial carotid arteries. All three methods were applied to 39 vessels in 20 patients. Duplex scanning was inaccurate when compared to conventional angiography in six instances. In three instances the degree of stenosis was overgraded by the scanner, and in three cases the stenosis was undergraded. Magnetic resonance angiography was inaccurate when compared to conventional angiography in three instances. In all cases magnetic resonance angiography overgraded the degree of stenosis. By use of a greater than 70% stenosis as a positive study, the sensitivity of magnetic resonance angiography was 100% and the specificity 92%. With use of the same criteria, the sensitivity of duplex scanning was 86%, and specificity was 84%. In those evaluations where the results of the magnetic resonance angiography and duplex scanning were in agreement, the correlation with conventional angiography was 100%. We conclude that magnetic resonance angiography is an alternative means to duplex scanning for noninvasive carotid imaging. A combination of bright and black blood magnetic resonance angiography is precise in delineating lesions of the extracranial carotid artery and may ultimately eliminate the need for conventional angiography in the evaluation of carotid stenosis.

Angiography, Digital Subtraction↗