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Biomedical subjects

R R Edelman

Publications and source records attributed to R R Edelman.

At least 127 records · Page 7Linked to original sources
PubMed1995

Dynamic contrast-enhanced subtraction MR angiography of the lower extremities: initial evaluation with a multisection two-dimensional time-of-flight sequence.

PURPOSE: To determine the clinical feasibility of a contrast material--enhanced two-dimensional (2D) magnetic resonance (MR) angiographic sequence in lower extremity arteries. MATERIALS AND METHODS: Four healthy volunteers and 12 patients underwent dynamic contrast-enhanced MR angiography; all patients also underwent conventional angiography. A 2D multisection gradient-echo sequence with image subtraction was used for all MR imaging examinations. RESULTS: Oblique-coronal contrast-enhanced MR angiography was completed in less than 4 minutes, with a 256 x 512 matrix. The arterial contrast enhancement ratio was 2.0 +/- 0.8 (standard deviation), and the pre- and post-contrast contrast-to-noise ratios were 2.1 +/- 13.8 and 46.2 +/- 18.7, respectively. The sensitivity for MR angiography was 100% and specificity was 69% for distinction of vessels with greater than 50% stenoses from normal or mildly stenotic vessels. CONCLUSION: Dynamic contrast-enhanced 2D MR angiography is capable of increasing intraarterial signal intensity and depicting small vessel anatomy of the lower extremities over a large field of view in a short imaging time.

Adult↗
PubMed1995

Brain lesions in patients with multiple sclerosis: detection with echo-planar imaging.

PURPOSE: To evaluate the detection of brain lesions with echo-planar imaging relative to conventional spin-echo (SE) imaging. MATERIALS AND METHODS: In 17 patients (three men, 14 women; mean age, 31 years) with multiple sclerosis, the following were compared: single-shot proton-density- and T2-weighted and thin-section T2-weighted echo-planar, proton-density- and T2-weighted multishot echo-planar, and conventional SE sequences. Quantitative and qualitative criteria as well as lesion detectability were evaluated. The proton-density-weighted SE sequence was used as the standard of reference. RESULTS: Multishot sequences were superior to single-shot sequences in image quality and lesion detectability. With the multishot proton-density-weighted sequence, 53 of 54 large lesions and 23 of 30 small lesions were detected; with the single-shot proton-density-weighted sequence, 38 of 54 large lesions and five of 30 small lesions were detected. CONCLUSION: With multishot echo-planar sequences, detectability of large lesions is similar to that with conventional SE imaging. Susceptibility artifact is diminished in comparison to single-shot echo-planar sequences.

Adult↗
PubMed1995

Renal vasculature in potential renal transplant donors: comparison of MR imaging and digital subtraction angiography.

PURPOSE: To compare magnetic resonance (MR) angiography with a selective inversion-recovery sequence and digital subtraction angiography (DSA) in renal transplant donors. MATERIALS AND METHODS: Thirteen potential donors underwent MR imaging at 1.5 T and conventional angiography. Blinded evaluation of imaging findings was performed. A selective inversion-recovery sequence was used to obtain MR arteriograms. RESULTS: Eight accessory vessels were present; MR angiography showed 100% sensitivity in accessory vessel detection. Both studies depicted early arterial branching in two vessels, mild fibromuscular dysplasia in one patient, normal renal size in all patients, and prominent fetal lobulation in two kidneys. A small cyst was detected with MR imaging only. Minor venous anomalies were noted in three patients, though these were not surgically confirmed owing to contralateral surgery. CONCLUSION: Despite the small study population, MR angiography with this sequence appears to have potential value in pretransplantation evaluation of the kidney. Advantages include short examination time, noninvasiveness, avoidance of iodinated contrast media, no radiation, and lower cost than DSA.

Adult↗
PubMed1995

Preoperative assessment of the carotid bifurcation. Can magnetic resonance angiography and duplex ultrasonography replace contrast arteriography?

BACKGROUND AND PURPOSE: Noninvasive studies are used with increasing frequency to assess the carotid bifurcation before endarterectomy. Therefore, assessment of their diagnostic accuracies is essential for appropriate patient management. We prospectively evaluate two noninvasive tests, magnetic resonance angiography (MRA) and duplex ultrasonography (DU), as potential replacements for contrast arteriography (CA). METHODS: A blinded comparison of three-dimensional time-of-flight (TOF) MRA, two-dimensional TOF MRA, and DU in 176 arteries was performed. CA was used as the standard of comparison. RESULTS: Three-dimensional TOF MRA had a sensitivity of 94%, a specificity of 85%, and an accuracy of 88% for the identification of 70% to 99% stenosis; two-dimensional TOF MRA had a sensitivity and specificity that were approximately 10% lower than those of three-dimensional TOF MRA. DU resulted in a sensitivity of 94%, a specificity of 83%, and an accuracy of 86%. Combining data from three-dimensional TOF MRA and DU, allowing for CA only for disparate results, yielded a sensitivity of 100%, a specificity of 91%, and an accuracy of 94% among concordant noninvasive tests, with CA required in 16% of arteries. MRA accurately differentiated 17 carotid occlusions from 16 high-grade (90% to 99%) stenoses, whereas with DU two patent arteries were identified as occluded and one occluded artery was identified as patent. CONCLUSIONS: Three-dimensional TOF MRA is the most accurate noninvasive test. Combined use of MRA and DU results in a marked increase in accuracy to a level that obviates the need for CA in a majority of patients.

Aged↗
PubMed1995

Blood-pool MR contrast material for detection and characterization of focal hepatic lesions: initial clinical experience with ultrasmall superparamagnetic iron oxide (AMI-227).

OBJECTIVE: AMI-227 is an ultrasmall superparamagnetic iron oxide colloid known to enhance tissue T1 and T2 relaxation rates. Animal studies show that AMI-227 has an estimated blood half-life of more than 200 min. In this study, we evaluated the clinical utility of AMI-227 as an MR contrast agent for detection and characterization of focal hepatic lesions, with MR imaging done while the contrast agent is in the intravascular space (blood-pool phase). SUBJECTS AND METHODS: Twenty-two patients with known or suspected focal hepatic masses underwent T1- and T2-weighted MR imaging of the liver at 1.5 T before and immediately after drip infusion of AMI-227 at doses of 0.8, 1.1, or 1.7 mg Fe/kg. Unenhanced and contrast-enhanced images were analyzed qualitatively (lesion detection and tissue characterization) and quantitatively (lesion-liver contrast-to-noise ratio). RESULTS: AMI-227 enhanced signal in normal liver and blood vessels on T1-weighted images and decreased signal in these tissues on T2-weighted images. Qualitatively and quantitatively, lesion-liver contrast was increased for solid tumors (non-cyst and nonhemangioma) at all three doses (p < .02) on both T1- and T2-weighted images. Differentiation between blood vessels and small lesions was easier on contrast-enhanced images, which allowed increased confidence in excluding lesions. Unique enhancement patterns were noted for hemangiomas, solid tumors, and cysts. CONCLUSION: Initial clinical experience suggests that AMI-227 is a useful contrast agent for detection and characterization of focal hepatic lesions.

Adult↗
PubMed1995

Diffusion and perfusion imaging techniques.

Diffusion imaging techniques including the Stejskal-Tanner and the stimulated emission of amplitude echoes (STEAM) pulse sequences are discussed. The calculation of apparent diffusion coefficient (ADC) maps is reviewed. The perfusion imaging techniques of blood oxygen level dependent (BOLD) and first pass bolus perfusion techniques as well as the newer technique of echo-planar imaging with signal targeting and altering radiofrequency (EPISTAR) are also discussed. Finally, the theory of intravoxel incoherent motion (IVIM) and its relationship to both diffusion and perfusion phenomena is examined.

Brain Diseases↗
PubMed1995

Magnetic resonance angiography of the abdomen.

The applications of abdominal MR angiography have been slow as compared with its applications in the head and neck mainly because of greater technical difficulties in dealing with respiratory motion and the use of the body coil, which has a poorer signal-to-noise ratio than head or surface coils. Further work is needed to reduce motion sensitivity and improve spatial resolution. Flow contrast and depiction of slowly flowing blood could be improved with the use of intravascular contrast agents. 52MR angiography is the imaging method of choice in the evaluation of the portal venous system, systemic veins, and aortic disease. With further technical improvements, it seems likely that applications of MR angiography will also be extended to smaller vessels.

Abdomen↗
PubMed1995

Echo planar imaging of the abdomen.

Echo planar imaging (EPI) is an ultrafast magnetic resonance (MR) imaging method first proposed more than 15 years ago. With EPI, all the information necessary to create an image is obtained very rapidly (typically on the order of 50-150 ms). Special hardware modifications are needed, particularly in the magnetic field gradients and data acquisition systems, to permit such high-speed imaging. In the abdomen, EPI images are insensitive to degradation from breathing or peristaltic motion. The essentially infinite repetition time and lack of motion-induced blurring can improve lesion characterization compared with standard imaging methods. Segmented EPI permits high-resolution T2-weighted images to be acquired within a single breath-hold. Diffusion imaging, which was previously restricted to the brain, can now be done in the abdomen because of the relative insensitivity of EPI images to bulk motion. Diffusion imaging of the kidney has been found to correlate with its functional status. By using EPI readouts, MR angiography can be done more quickly. Further work is needed to improve the spatial resolution and overcome magnetic susceptibility artifacts, particularly with single-shot EPI. Nonetheless, EPI offers considerable potential for improved anatomical and functional imaging of the abdomen.

Abdomen↗
PubMed1994

Signal targeting with alternating radiofrequency (STAR) sequences: application to MR angiography.

We describe a time of flight subtraction method for cine MR angiography that provides nearly perfect suppression of background signal intensity with excellent flow contrast. The method consists of a preparation phase, during which the longitudinal magnetization of the target tissue is inverted on alternate acquisitions and the background tissue is presaturated, followed by a readout phase using a cine segmented turboFLASH sequence with a shared echo modification to improve temporal resolution. With appropriate alternation of the phases of the radiofrequency excitation pulses, there is cancellation of the background signal intensity but flow signal is optimized. By using a thick section (up to 25 mm), substantial portions of the vascular territory are encompassed in a single plane. This permits rapid, dynamic assessment of flow patterns in areas such as the circle of Willis, carotid bifurcation, or renal arteries. Applications of the method for bright and dark blood cine MR angiography are demonstrated.

Aorta, Abdominal↗
PubMed1994

In vivo measurement of water diffusion in the human heart.

Existing magnetic resonance methods for diffusion imaging, including echo planar, are ineffective in the beating heart due to motion-induced signal attenuation. To overcome this problem, we used a diffusion-weighted stimulated echo-echo planar magnetic resonance imaging sequence. The two lobes of the diffusion-sensitizing gradient were synchronized to the same point in successive cardiac cycles in order to fix the cardiac position and avoid bulk motion effects. The apparent diffusion coefficients (ADCs) of the interventricular septum in 12 healthy subjects for diffusion gradients along the x-, y-, and z-directions were 1.40 +/- 0.27, 1.48 +/- 0.35, and 1.78 +/- 0.27 x 10(-3) mm2/s. The ADCs of the interventricular septum in a second group of 15 healthy subjects for diffusion gradients along the short axis, horizontal and vertical long axes were 0.92 +/- 0.15, 1.50 +/- 0.15, and 1.10 +/- 0.24 x 10(-3) mm2/s. Because the ADCs were less than the measured values for skeletal muscle and their standard deviations were low, it seems unlikely that bulk motion effects made the dominant contribution to the measured myocardial ADC for the interventricular septum, although motion and/or susceptibility artifacts frequently degraded measurements in the free wall of the left ventricle. Additional evidence that ADC was not predominantly determined by wall motion was obtained in a third group of patients with various cardiac abnormalities, in whom there was only a weak correlation between ADC and ejection fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[The role of magnetic resonance angiography prior to the transjugular placement of a portosystemic stent shunt (TIPS)].

The authors employed magnetic resonance angiography (MRA) to guide catheter placement for transjugular intrahepatic portosystemic stent shunt (TIPS) procedures in 14 of 24 patients, and compared the results to the 10 patients who did not have prior planning based on MRA. Two-dimensional time-of-flight venography was performed during breath holding, and projection venograms were formatted in sagittal, coronal and axial planes. MRA defined venous anatomy sufficiently well to shorten the procedure and helped to minimize invasiveness. With MRA guidance, intrahepatic needle punctures were significantly fewer (without MRA guidance: mean 12.1; with MRA guidance: mean 3.5, p < 0.001) and associated complications were absent (without MRA guidance: failed placement, N = 1; bleeding requiring blood transfusions, N = 2; death complicating intraperitoneal haemorrhage with haemobilia, N = 1, and hepatic capsular perforation, N = 1). The average time for the procedure was 2.8 hours without MRA guidance and 1.8 hours with MRA guidance (p < 0.0005). The authors conclude that MR angiography is a useful technique to define portal and hepatic venous anatomy prior to TIPS, and planning based on MRA may decrease the difficulty and length of the procedure.

Adult↗
PubMed1994

[The in-vivo diffusion measurements of the liver, kidneys, spleen and m. erector with an echo-planar imaging system in normal subjects].

A diffusion sensitive pulse sequence using a stimulated echo (STEAM) type excitation and echo-planar (EPI) readout was developed on a 1.5 T echo-planar MR imaging system. Using this sequence the authors measured the apparent diffusion coefficients (ADC) of water in normal human liver, spleen, muscle and kidney in 12 volunteers. ADCs measured in normal volunteers were: liver, 1.39 +/- 0.16 x 10(-3) mm2/s, spleen, 0.95 +/- 0.15 x 10(-3) mm2/s, muscle, 1.99 +/- 0.16 x 10(-3) mm2/s, kidney, 3.54 +/- 0.47 x 10(-3) mm2/s. A large scatter of the ADCs in the kidneys was found in the different degrees of hydration status among the volunteers and also due to inter-subject variability. With further clinical experience, in vivo diffusion measurements of the abdominal organs may prove helpful in the identification and classification of abdominal disease by MRI.

Adult↗
PubMed1994

Intracranial vertebrobasilar system: MR angiography.

PURPOSE: To determine the reliability of magnetic resonance (MR) angiography in depicting normal vascular anatomy and its usefulness in detecting vascular disease compared with those of digital subtraction angiography (DSA). MATERIALS AND METHODS: Sixty patients with symptoms referable to disease of the vertebrobasilar system were examined with MR angiography and DSA. RESULTS: In patients with normal DSA results, all vertebral arteries (VAs) and basilar arteries (BAs) were also visualized with MR angiography. MR angiography demonstrated 117 of 120 superior cerebellar arteries and 80 of 90 posterior inferior cerebellar arteries but only 30 of 58 anterior inferior cerebellar arteries. MR angiography demonstrated disease of the VAs and BAs with 100% sensitivity. Stenoses were differentiated from occlusions in all cases. However, the degree of stenosis was overestimated in 63% of patients. In six patients with occlusive disease, collateral flow was correctly analyzed with selective saturation. CONCLUSION: Despite its limitations, MR angiography is a clinically important noninvasive technique for screening patients for macroangiopathy of the posterior arterial supply to the brain.

Adolescent↗
PubMed1994

Abdominal diffusion mapping with use of a whole-body echo-planar system.

PURPOSE: To measure apparent diffusion coefficients (ADCs) of water in liver, spleen, kidney, and muscle. MATERIALS AND METHODS: Ten volunteers (seven women and three men, aged 19-31 years [mean, 24 years]) and nine patients (five women and four men, aged 49-70 years [mean, 62 years]) (liver cyst, n = 3; liver hemangioma, n = 3; liver cirrhosis, n = 2; hepatocellular carcinoma, n = 1; and liver metastasis, n = 1) underwent magnetic resonance (MR) imaging. A stimulated-echo acquisition mode (STEAM)-type excitation and echo-planar imaging (EPI) readout was used in a 1.5-T echo-planar MR imaging system. RESULTS: ADCs measured in volunteers were liver, 1.39 x 10(-3) mm2/sec +/- 0.16; spleen, 0.95 x 10(-3) mm2/sec +/- 0.15; muscle, 1.99 x 10(-3) mm2/sec +/- 0.16; and kidney, 3.54 x 10(-3) mm2/sec +/- 0.47 (mean +/- standard deviation). Distinctive ADC values were found in organs with abnormalities. ADCs in patients with hepatic disease included liver cysts, 3.9-5.3; liver hemangiomas, 2.0-2.8; liver metastases from an islet cell tumor, 1.2; hepatocellular carcinoma, 1.7; and liver cirrhosis, 0.9-1.2 x 10(-3) mm2/sec. CONCLUSION: In vivo diffusion measurements of abdominal organs obtained with MR imaging may prove helpful in the identification and classification of abdominal disease.

Abdomen↗
PubMed1994

Contrast-enhanced echo-planar MR imaging of myocardial perfusion: preliminary study in humans.

PURPOSE: To evaluate the usefulness of T1- and T2*-weighted echo-planar magnetic resonance (MR) imaging in the assessment of cardiac perfusion. MATERIALS AND METHODS: Sixteen subjects underwent MR imaging. Fifteen subjects were healthy volunteers and one had coronary artery disease. T2*-weighted echo-planar imaging with free induction decay was performed in 11 subjects and T1-weighted inversion-recovery spin-echo echo-planar imaging was performed in five. Images were obtained before and after administration of gadopentetate dimeglumine. RESULTS: The contrast-to-noise ratio for pre- and postcontrast T2*-weighted images obtained with an echo time of 16 msec (n = 8) was -9.9 +/- 3.4, and the contrast enhancement ratio was -0.37 +/- 0.07. The values for T2*-weighted images obtained with an echo time of 30 msec (n = 3) were -9.5 +/- 6.8 and 0.44 +/- 0.02, respectively. For T1-weighted echo-planar imaging, the values were 26.7 +/- 8.0 and 4.6 +/- 2.8, respectively. CONCLUSION: Inversion-recovery spin-echo echo-planar imaging provides excellent temporal resolution, myocardial detail, and myocardium-blood pool contrast, with minimal artifact. It is presently the technique of choice for the MR imaging evaluation of myocardial perfusion.

Adult↗
PubMed1994

Hepatic hemangiomas: a multi-institutional study of appearance on T2-weighted and serial gadolinium-enhanced gradient-echo MR images.

PURPOSE: To define the appearance of hepatic hemangiomas on T2-weighted and serial gadolinium-enhanced gradient-echo magnetic resonance (MR) images. MATERIALS AND METHODS: In four university hospitals, with 1.0- or 1.5-T MR imaging, T2-weighted and T1-weighted gradient-echo images were obtained in 66 adult patients before and at 1, 45, and 90 seconds and 10 minutes after injection of a gadolinium chelate. Hemangiomas were categorized as small (< 1.5-cm-diameter), medium (1.5-5.0-cm), and large (> 5.0-cm) tumors. RESULTS: In all, 154 hemangiomas were depicted (81 small, 56 medium, and 17 large tumors). All 154 lesions were hyperintense on T2-weighted images. Three patterns of contrast enhancement were observed: (a) uniform enhancement at 1 second (35 of 81 small lesions and no medium or large lesions), (b) peripheral nodular enhancement progressing centripetally to uniform enhancement (75 of all 154 lesions), and (c) peripheral nodular enhancement with persistent hypointensity centrally (44 of all 154 lesions, including 16 of 17 large lesions). CONCLUSION: Three patterns of enhancement of hemangiomas were observed. High signal intensity on T2-weighted images provided complementary information.

Adult↗
PubMed1994

Qualitative mapping of cerebral blood flow and functional localization with echo-planar MR imaging and signal targeting with alternating radio frequency.

PURPOSE: To create qualitative maps of cerebral blood flow (CBF) with the EPISTAR (echo-planar imaging and signal targeting with alternating radio frequency) technique. MATERIALS AND METHODS: The EPISTAR technique was performed in a pig model of hypercapnia and then tested in 26 volunteers by using various paradigms for cortical activation. Echo-planar images were acquired with and without use of a radio-frequency inversion pulse applied to inflowing arterial spins. A qualitative map of CBF was then created by subtracting the image obtained without the radio-frequency pulse from that obtained with the radio-frequency pulse. RESULTS: Progressively more distal portions of the tagged vessels were seen as the inflow time was lengthened until cortical enhancement was seen for inflow times of approximately 1 second or longer. Signal intensity increases from rest to sensorimotor activation ranged from 13% to 193%. CBF changes in the motor strip, primary visual cortex, and the motor area for eye movements were well localized to the cortical gray matter ribbon. CONCLUSION: The EPISTAR technique is a rapid, noninvasive means for creating qualitative maps of CBF.

Animals↗