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Biomedical subjects

R R Edelman

Publications and source records attributed to R R Edelman.

At least 145 records · Page 8Linked to original sources
PubMed1994

Functional imaging of the kidney by means of measurement of the apparent diffusion coefficient.

PURPOSE: To determine the relationship between the apparent diffusion coefficient (ADC) and renal function. MATERIALS AND METHODS: Twenty-three volunteers and seven pigs underwent diffusion-sensitive magnetic resonance (MR) imaging of the kidneys with a stimulated-echo acquisition mode excitation and echo-planar imaging readout under various physiologic conditions. The effect of hydration and anisotropic diffusion was studied in human subjects, and the effect of renal artery stenosis, ureteral obstruction, and diuresis was studied in the animal model. RESULTS: The renal ADC values of dehydrated subjects were substantially increased with rehydration. Diffusion was highest in the medulla, with a pronounced radial component in the renal collecting system. In the pig model, induced renal artery stenosis resulted in immediate decrease in renal ADC; the degree of change was related to the flow deficit. The ADC also decreased with ureteral obstruction, but diuresis had no meaningful effect. CONCLUSION: In vivo measurement of ADC has the potential for use as a noninvasive means to explore the functional status of the kidney.

Adult↗
PubMed1994

Bronchopulmonary sequestration with MR angiographic evaluation. A case report.

Definitive diagnosis of pulmonary sequestration requires angiographic visualization of the anomalous feeding and draining vessels. The authors report a young woman who presented with persistent cough of two months' duration. Diagnosis of pulmonary sequestration was established with magnetic resonance (MR) angiography, which demonstrated abnormal feeding arteries to the sequestrum from the thoracic aorta with draining pulmonary veins.

Adult↗
PubMed1994

MR angiography of the carotid bifurcation: artifacts and limitations.

Although conventional angiography has traditionally been the preoperative study of choice before carotid endarterectomy, alternative noninvasive methods, particularly MR angiography, are being used increasingly for evaluation of the carotid bifurcation [1, 2]. In this essay, we illustrate the limitations of and artifacts associated with two-dimensional (2D) and three-dimensional (3D) time-of-flight (TOF) MR angiography vs conventional angiography when assessing disease of the carotid bifurcation.

Artifacts↗
PubMed1994

Hyperperfusion of ictal seizure focus demonstrated by MR perfusion imaging.

MR using a susceptibility-weighted sequence and dynamic contrast enhancement with gadolinium demonstrated relative hyperperfusion of the right temporoparietal cortex in a patient in focal status epilepticus. A single-photon emission CT (SPECT) scan also demonstrated hyperperfusion of the right temporoparietal cortex. Perfusion MR, SPECT, and electroencephalogram normalized when the seizures ended.

Adult↗
PubMed1994

Ultrafast magnetic resonance imaging. Segmented turboflash, echo-planar, and real-time nuclear magnetic resonance.

Ultrafast magnetic resonance imaging refers to a group of techniques developed with the sole purpose of acquiring images in a very rapid fashion. Ultrafast magnetic resonance imaging has other benefits besides capture of transient events. Not all patients have a stable heart rate, and many cannot tolerate remaining still and breathing quietly for long periods while lying inside of a scanner. Fast imaging reliably acquires data, even if the patient moves or is arrhythmic. This article describes strategies, applications, advantages, and limitations of ultrafast imaging.

Computer Systems↗
PubMed1993

A preliminary report comparing magnetic resonance coronary angiography with conventional angiography.

BACKGROUND: The ability to assess the patency of coronary arteries by noninvasive means would represent an important advance. We have developed a magnetic resonance imaging (MRI) coronary angiographic technique that permits the display of areas of abnormal coronary blood flow. We have compared this method with conventional contrast angiography for the identification of coronary-artery stenoses. METHODS: MRI coronary angiography was performed with an electrocardiographically gated sequence in 39 subjects, 33 to 84 years of age, who were scheduled for elective cardiac catheterization with coronary angiography. Sequential overlapping transverse and oblique sections were acquired during periods of breath-holding and were displayed as cine loops for analysis. MRI and conventional angiographic data were compared in a blinded manner. The four major epicardial coronary arteries were classified by MRI coronary angiography as being normal (or having only minimal irregularities) or as having disease that was moderately severe to severe. RESULTS: The sensitivity and specificity of MRI coronary angiography, as compared with conventional angiography, for correctly identifying individual vessels with > or = 50 percent angiographic stenoses were 90 percent and 92 percent, respectively. The corresponding positive and negative predictive values were 0.85 and 0.95, respectively. The sensitivity and specificity of the technique were 100 percent and 100 percent, respectively, for the left main coronary artery, 87 percent and 92 percent for the left anterior descending coronary artery, 71 percent and 90 percent for the left circumflex coronary artery, and 100 percent and 78 percent for the right coronary artery. CONCLUSIONS: MRI coronary angiography provides a new approach to evaluating the patency of coronary arteries. These preliminary data suggest that this technique may provide a noninvasive means of evaluating patients with known or suspected coronary artery disease. At its current stage of development, this procedure may be most helpful for excluding clinically important stenoses in patients referred for diagnostic contrast angiography.

Adult↗
PubMed1993

MRI evaluation of myocardial perfusion without a contrast agent using magnetization transfer.

We propose a new magnetic resonance imaging (MRI) technique that is sensitive to myocardial tissue perfusion that obviates the use of an extrinsic contrast agent. Significant advantages of such a technique are that it avoids accumulation of contrast agent when repeated studies are performed on the same subject and that it is completely noninvasive. The method makes use of a combination of magnetization transfer (MT) and T1sat (measured spin-lattice relaxation time in the presence of MT) weighting. In this Communication, we present observations from experiments with an isolated rat heart model that demonstrate increase of MT-weighted signal intensity and T1sat with flow. Also included are data showing that these effects can be made synergistic for enhancing the sensitivity to perfusion. We have observed about a 3% change in MT-weighted intensity and up to 10% change in MTT1sat-weighted intensity for a change of 1 ml/min in global flow rate.

Animals↗
PubMed1993

Monitoring the patient's EEG during echo planar MRI.

The recording of an EEG while the patient is undergoing magnetic resonance imaging (MRI) data acquisition, as far as we are aware, has not been previously accomplished. By careful selection and arrangement of analog multiplexed cable-telemetry equipment to eliminate both ferrous and RF sources, a stable, readable EEG can be obtained without interfering with the diagnostic quality of the MRI. This arrangement does not cause localized heating or burning at the electrode sites. This technical capability permits more accurate neurophysiological control during the acquisition of echo planar functional MRI studies as well as providing indications of anatomical localization of electrical sources.

Echo-Planar Imaging↗
PubMed1993

[Magnetic resonance tomographic identification and characterization of renal space-occupying lesions using GE-sequences with application of Gd-DTPA].

In modern magnetic resonance imaging (MRI) gradient echo (GE) sequences have been shown to be superior to conventional spin echo (SE) sequences in characterising renal masses and staging renal tumours. In this study MRI was carried out in patients with renal masses (n = 97, histologically proven n = 43) using a fast GE-sequence (multislice technique, TR/TE 80/5 ms) and an i.v. bolus application of gadolinium (Gd)-DTPA mostly in axial, in selected cases additionally in coronal slice orientation. MRI findings were compared with those of contrast-enhanced CT (n = 56). The results demonstrated that MRI under Gd-DTPA has a reliably good image quality and can characterise renal masses safely. Compared with CT in multislice MRI problems of partial volume effects can be reduced; complex renal cysts can be differentiated more safely from solid tumours with unclear CT findings due to a significantly higher contrast enhancement in MRI.

Adolescent↗
PubMed1993

Use of magnetic resonance angiography in the pretransplant evaluation of portal vein pathology.

The assessment of portal vein patency in patients selected as candidates for orthotopic liver transplantation should be accomplished noninvasively and with great accuracy. Magnetic resonance angiography (MRA) is a new technique that is completely noninvasive and is capable of graphically assessing portal vein anatomy and blood flow. In an attempt to establish the accuracy of portal venous MRA, 74 patients with established cirrhosis underwent abdominal MRA prior to liver transplantation. MRA findings were correlated with surgical findings at the time of transplantation in all patients, and were shown to be extremely accurate. The three-dimensional images generated by MRA and computer postprocessing allowed for correct identification of portal venous anatomy in all of the patients examined. We conclude that MRA is an extremely useful method of determining portal venous anatomy in potential liver transplant patients, and potentially offers greater definition and clarify compared with other non-invasive methods.

Humans↗
PubMed1993

Central venous occlusion: MR angiography.

The authors evaluated time-of-flight magnetic resonance (MR) angiography in 30 patients with suspected thoracic venous occlusion. The results of the MR studies were compared with results at contrast venography in 22 patients and at central venous cannulation in seven of the remaining eight patients. Twenty-eight patients had abnormalities on MR venograms; 21 of these abnormalities involved multiple veins. Eight patients had superior vena cava (SVC) occlusion with retrograde azygos blood flow, and two patients had nonocclusive SVC thrombus. Fifteen patients had thrombosis involving the brachiocephalic veins; 14, involving the subclavian veins; and eight, involving the internal jugular veins. Correlation was excellent between findings of venous obstruction and occlusion at contrast venography and MR angiography. MR imaging provided more comprehensive information than catheter venography on central venous anatomy and blood flow. For evaluation of central veins, MR angiography is an accurate and graphic technique that may succeed in cases in which other methods may give inadequate findings or may be impossible to perform.

Adult↗
PubMed1993

Human coronary arteries: projection angiograms reconstructed from breath-hold two-dimensional MR images.

The authors sought to render projection magnetic resonance (MR) angiograms depicting a substantial length of human coronary arteries from sequential breath-hold two-dimensional MR images. Tomographic images of the right and left anterior descending coronary arteries were collected with use of a segmented gradient-recalled sequence that incorporated fat suppression and prone positioning of the patient over a surface coil. After editing the images to eliminate overlapping chamber signals and after realigning the images, a maximum-intensity-projection algorithm was applied to create projection angiograms. For the 10 coronary arteries without severe narrowing, visualized length with projection MR angiography was 109 mm +/- 29 (mean +/- standard error of estimate) versus 121 mm +/- 29 with conventional coronary angiography (ranges, 62-147 mm and 70-180 mm, respectively). At conventional angiography linear regression indicated vessel length to be 1.03 times the length depicted at MR angiography with good correlation (r = .8). Results indicate good correlation between measurements of vessel length with both conventional and MR angiography.

Adult↗
PubMed1993

Fat-suppressed breath-hold magnetic resonance coronary angiography.

BACKGROUND: The ability to image the coronary arteries noninvasively would represent an advance in patient care. We have developed a magnetic resonance (MR) angiographic technique that allows the acquisition of complete images of coronary flow within a single breath-hold. By this method, the feasibility of noninvasive MR coronary angiography was evaluated in 25 subjects, including 19 healthy adult volunteers and six patients after diagnostic coronary angiography. METHODS AND RESULTS: Noninvasive MR coronary angiography was performed with a fat-suppressed ECG-gated gradient-echo sequence with k-space segmentation. Overlapping transverse sections were initially used to image coronary flow, with oblique images obtained after identification of proximal anatomy. The left main coronary artery was seen in 24 subjects (96%), with a mean diameter of 4.8 mm (range, 3.4-6.2 mm) and average length of 10 mm (range, 8-14 mm). The left anterior descending coronary artery was seen in 100% of subjects, with a mean proximal diameter of 3.6 mm (range, 2.6-4.3 mm) and for an average length of 44 mm (range, 28-93 mm). The left circumflex coronary artery was seen in 76% of subjects, with a mean proximal diameter of 3.5 mm (range, 2.6-4.3 mm) and for an average length of 25 mm (range, 9-42 mm). The right coronary artery was also identified in 100% of subjects, with a mean proximal diameter of 3.7 mm (range, 2.7-5.1 mm) and for an average length of 58 mm (range, 24-122 mm). Quantitative angiography of normal proximal segments demonstrated a good correlation with MR-determined lumen diameters (r = 0.86, p < 0.002). Occluded vessels in patients with coronary artery disease displayed an absence of flow signal distal to the occlusion, whereas vessels with significant angiographic stenoses demonstrated signal loss corresponding to the area of the stenosis, with visualization of the more distal vessel. CONCLUSIONS: Breath-hold MR coronary angiography provides visualization of the major epicardial vessels. In the future, MR coronary angiography may provide a noninvasive means for the evaluation of patients with known or suspected coronary artery disease.

Adult↗
PubMed1993

MR angiography: present and future.

MR angiography is a rapidly evolving technique for noninvasive vascular imaging. Since 1985, when it was first shown to be clinically feasibls, the imaging techniques and hardware used for MR angiography have greatly improved. No longer is MR angiography a mere academic curiosity; it is already widely used to diagnose stenoses of carotid bifurcations and intracranial aneurysms. MR angiography supplements, and in some cases supplants, duplex sonography and CT for the study of suspected venous thrombosis in the chest, abdomen, and pelvis. With continuing technical developments, MR angiography most likely will replace conventional X-ray angiography in the presurgical workup of patients who are candidates for carotid endarterectomy or liver transplantation. Even MR angiography of the coronary arteries, considered implausible just a few years ago, has become feasible with the implementation of fast imaging techniques that suppress artifacts from respiratory and cardiac motion. Nonetheless, substantial problems remain that must be overcome before the full clinical potential of MR angiography can be realized. Despite the superficial similarities between MR angiograms and conventional angiograms, fundamentally different features of blood vessels are depicted. MR angiography is susceptible to a variety of artifacts that can exaggerate or simulate pathologic changes. The patient's cooperation is essential. The spatial resolution of MR angiography is inferior to its conventional counterpart, although the gap is being narrowed. This article reviews the basic principles of MR angiography and flow artifacts and surveys existing and future clinical applications.

Artifacts↗
PubMed1993

Imaging of the portal venous system in patients with cirrhosis: MR angiography vs duplex Doppler sonography.

OBJECTIVE: To determine the relative performances of MR angiography and duplex Doppler sonography in the evaluation of the portal venous system in patients with portal hypertension, we compared two-dimensional time-of-flight MR angiography and duplex Doppler sonography in 60 sequential patients with cirrhosis. All 60 subsequently underwent liver transplantation. SUBJECTS AND METHODS: MR imaging and duplex Doppler sonography were performed on the same day, and in all patients the imaging findings were validated at surgical exploration. Five transplantation candidates had surgical portosystemic shunts in situ at the time of imaging. MR images were acquired during breath-holding, and flow in the portal vein was evaluated with presaturation bolus-tracking MR imaging. Sonography included color Doppler and pulsed gated Doppler images of the portal vein. MR angiograms and sonograms were analyzed independently and prospectively for patency of the portal vein, patency of surgical shunts, and grade and distribution of portosystemic collateral vessels. Scores on both imaging techniques were compared by using regression analysis. RESULTS: MR angiograms showed all five cases of portal vein occlusion and all 55 cases of patent portal veins. Sonograms showed three of five cases of portal vein occlusion and 52 of 55 cases of patent portal veins. The techniques concurred in assessing flow direction in 54 (90%) of 60 patients, and both procedures enabled detection of occlusive portal vein thrombus in one patient. We found a significant correlation (p < .001) between the grades of gastric varices detected with MR angiography and surgery but no significant correlation between the grades seen on sonography and found at surgery. Shunt patency in four of five patients and shunt occlusion in one were correctly assessed on MR angiograms, whereas three of these shunts were not visible on sonograms. CONCLUSION: Our results show that MR angiography is more reliable than duplex Doppler sonography for evaluating the portal venous system in patients with portal hypertension caused by cirrhosis.

Esophageal and Gastric Varices↗