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Biomedical subjects

R R Edelman

Publications and source records attributed to R R Edelman.

At least 217 records · Page 12Linked to original sources
PubMed1988

FRODO pulse sequences: a new means of eliminating motion, flow, and wraparound artifacts.

Magnetic resonance images of the spine, chest, abdomen, and pelvis are commonly degraded by ghost artifacts. The authors have developed a new technique named FRODO (Flow and Respiratory artifact Obliteration with Directed Orthogonal pulses) to suppress these artifacts. Signal from tissues responsible for the artifacts is eliminated by use of radio frequency pulses specifically optimized for high selectivity to saturate proton magnetization over one or more independently defined slabs (large rectangular volumes) of tissue. Ghost artifacts from pulsatile flow in the heart and blood vessels, as well as from respiratory motion and swallowing, are suppressed. Additional applications of this technique include elimination of intraluminal signal in blood vessels and suppression of wraparound artifact along the phase-encoding axis. Preliminary clinical experience suggests that the FRODO technique, in conjunction with other flow compensation methods, may provide a definitive solution to the problem of motion in spine imaging. FRODO pulse sequences may also prove useful for imaging of blood vessels, heart, abdomen, and other areas where motion, flow, or wraparound artifacts limit image quality.

Abdomen↗
PubMed1988

Rapid MR imaging.

During the past few years major improvements have been made in MR systems resulting in increased S/N, which is now being traded for more rapid imaging times. As discussed, there are three general strategies to decrease acquisition time and more will likely surface. Gradient-echo imaging, which has provided the most clinical experience to date, can be used for rapid imaging, functional studies and unique contrast mechanisms such as susceptibility imaging. While the contrast mechanisms and ultimate clinical utility require further study, it seems likely that gradient-echo imaging will become a routine part of clinical MR imaging.

Humans↗
PubMed1987

Cardiac function: evaluation with fast-echo MR imaging.

Magnetic resonance (MR) imaging of the heart has, to date, been limited in its ability to evaluate cardiac function. The authors have implemented a technique for functional assessment of the heart using shorter echo times than those generally used for conventional spin-echo imaging. With these short echo times, multiple images can be obtained in a multisection mode approximately within the isovolumetric phases of the cardiac cycle. This permits a pair of image stacks to be obtained, one in end systole and the other in end diastole. With the use of a modified Simpson rule, left ventricular volume and ejection fraction were calculated and compared with results obtained from contrast material-enhanced ventriculography. Preliminary results indicate that this method has promise for the evaluation of a variety of functional parameters in the heart. The short acquisition times for this functional study permit it to be combined with a tissue characterization study within the time constraints of a clinical MR imaging session.

Heart Function Tests↗
PubMed1987

Magnetite albumin microspheres: a new MR contrast material.

A superparamagnetic MR contrast agent was synthesized by incorporating 150-250-A particles of magnetite (Fe3O4, Fe2O3) in 1-5 microns human serum albumin microspheres. Magnetite albumin microspheres (MAM) target almost exclusively to the reticuloendothelial system after IV administration, are stable in vitro and in vivo, and possess a long shelf life. The agent has a large magnetic susceptibility effect that selectively reduces T2 with little effect on T1. Biodistribution studies that use a dose of 20 mg MAM/kg show prompt clearance from the blood pool with marked decrease in T2 for rat liver (40%) and spleen (45%) with a small decrease in liver (5%) and spleen (10%) T1 values. Pulmonary T1 and T2 decrease transiently over the first 24 hr, while no significant changes were observed in other tissues. Imaging of a rabbit VX2 tumor model resulted in a 200% increase in the contrast ratio of VX2 tumor to normal liver on T2-weighted and mixed T1-/T2-weighted pulse sequences after administration of contrast agent. The extreme potency, excellent targeting, and apparent lack of toxicity of this agent suggest that MAM probably will have a clinical application in detecting focal hepatic and splenic lesions.

Animals↗
PubMed1987

Magnetite albumin suspension: a superparamagnetic oral MR contrast agent.

Suspensions of magnetite albumin microspheres (MAM), a new biodegradable particulate iron superparamagnetic MR contrast material, were evaluated in vitro and in vivo as an oral contrast agent. MAM is stable over a broad range of pH and tolerates proteolytic enzyme exposure over 24 hr in vitro. MAM possesses a much larger magnetic moment than do paramagnetic contrast agents. The transverse relaxation rate (R2) of MAM can be as much as 40 times the longitudinal relaxation rate (R1). In vitro spectroscopy studies confirm the potency of MAM in promoting T2 relaxation at concentrations of 10-1000 mg/l. Preliminary studies in rabbits and dogs show that in contrast to oral gadolinium-DTPA, which causes increased signal in bowel, MAM causes marked signal loss in the stomach and small bowel on both T1- and T2-weighted pulse sequences. Radionuclide labeling studies of MAM suspension with 99mTc show no evidence of absorption of MAM suspension from the gastrointestinal tract in small animals. Superparamagnetic suspensions such as MAM that reduce bowel signal on T1- and T2-weighted pulse sequences offer the unique benefit of reducing motion artifacts throughout the gastrointestinal tract, which should allow for improved evaluation of intra- and retroperitoneal diseases, particularly with high-field strength and gradient-echo "fast-scan techniques." Unlike paramagnetic material, MAM appears effective as a small-bowel contrast material.

Administration, Oral↗
PubMed1986

Magnetic resonance imaging of the kidney.

After a few years of the use of clinically oriented imaging, magnetic resonance (MR) can now be measured against the other cross-sectional radiologic imaging techniques. Its superior sensitivity in demonstrating diseases of the central nervous system and heart has yet to be matched by similar success in the detection of abdominal disease. However, MR is evolving further and improvements in hardware, software, and pulse sequence selection are expected to continue. We present here the experience accumulated to date in the MR evaluation of the kidney in its normal and diseased states.

Adult↗
PubMed1986

Detection of hepatic metastases: analysis of pulse sequence performance in MR imaging.

Forty-three patients with liver metastases were imaged using 14 different pulse sequences (average, 7.5 sequences per patient) to allow direct comparison of their performance. "T2-weighted" spin-echo (SE) images, "T1-weighted" inversion recovery (IR) images, and "T1-weighted" SE images were obtained using a wide range of timing parameters. Pulse sequence performance was quantitated by measuring liver signal-to-noise (S/N) ratios and cancer-liver signal difference-to-noise (SD/N) ratios. Data were standardized to reflect a constant imaging time of 9 minutes for all pulse sequences. The SE 2,000/120 (TR [repetition time]/TE [echo time]) sequence resulted in the greatest SD/N ratio of the T2-weighted SE sequences but also yielded the low S/N ratios, poor anatomic resolution, and motion artifacts common to all T2-weighted SE images. IR sequence images were also sensitive to motion artifacts because of the use of a long TR (1,500 msec). Short TR/TE T1-weighted SE sequences (SE 260/18) had the greatest SD/N ratio (P less than .05), S/N ratio, and anatomic resolution. Furthermore, extensive signal averaging appears to be a powerful solution to all types of motion artifacts in the abdomen.

Adenocarcinoma↗
PubMed1986

MR gated subtraction angiography: evaluation of lower extremities.

We report the first clinical experience with a new method for projective imaging of blood vessels (angiography) using magnetic resonance. Vascular contrast is produced noninvasively by the phase response of moving protons. Diastolic and systolic gated images produce, respectively, flow signal and flow void; the difference image is a map of the pulsatile flow: an arteriogram. Preliminary studies are presented of the lower extremities of one healthy volunteer and four patients (one each with occlusive disease, soft-tissue tumor, arteriovenous malformation, and venous femoral-popliteal graft). Patient data are compared with accompanying conventional arteriograms, and the new method is discussed.

Adult↗
PubMed1986

Oblique planes of section in MR imaging.

Magnetic resonance (MR) imaging allows freedom in choosing oblique planes of section and rotation of the image plane with respect to the frequency-encoded (F) and phase-encoded (P) dimensions. A general method is described for understanding geometric relationships between the fixed magnetic coordinate system, patient positioning, and the flexible observer's coordinate system. Oblique planes of section are clinically useful in studying organs with an axis of symmetry that is oblique to the magnet coordinate system, such as the heart. Rotation of the image plane can be used to move motion artifacts away from anatomic regions of interest, such as the liver and spine. Appropriate use of oblique section selection and image rotation can improve MR image quality and diagnostic value of the patient study.

Humans↗
PubMed1986

Rapid MR imaging with suspended respiration: clinical application in the liver.

The authors demonstrate that it is possible to obtain highly T1-weighted images of the abdomen using a suspended respiration partial saturation (SRPS) method in a breath-holding interval. T2*-weighted images, which reflect tissue T2 as well as variations in the static magnetic field, can also be rapidly obtained. The authors studied five healthy subjects and 19 patients with a variety of liver abnormalities, including benign and malignant hepatic neoplasms, fatty liver infiltration, ascites, and hematoma. On T1-weighted multisection acquisitions, the entire liver can be screened for mass lesions in a single 20-second breath-holding interval. Phase-contrast SRPS images are sensitive to fatty infiltration of the liver. SRPS images are more sensitive to variations in magnetic susceptibility than spin-echo images are, which has been proved to be of value in the detection of hemorrhage. With continued pulse sequence development and clinical study, this method has the potential to become the method of choice for evaluation of the upper abdomen.

Adult↗
PubMed1986

Intravascular signal in MR imaging: use of phase display for differentiation of blood-flow signal from intraluminal disease.

Intravascular signal from flowing blood is frequently observed on magnetic resonance (MR) images and may be indistinguishable from partial or complete vascular occlusion caused by thrombus or tumor. With a phase-display reconstruction method, qualitative assessment of large-vessel patency within the abdomen was undertaken in 15 healthy subjects and 12 patients with angiographically or surgically documented intravascular thrombus or tumor. Computed tomographic (CT) scans were available in all patients for correlation. MR studies were performed with a multisection spin-echo pulse sequence and two-dimensional Fourier transform spatial encoding. Data acquired from a single sequence was reconstituted in two ways to provide both routine anatomic images and a pictorial representation of large-vessel flow on a phase-sensitive image. With this method, reliable and easy differentiation of intraluminal thrombus and tumor from blood flow signal within large vessels was achieved. Information from these phase-display images compared favorably with findings from angiography and contrast-enhanced CT in the determination of luminal patency and obstruction.

Blood Circulation↗
PubMed1986

MR-guided aspiration biopsy: needle design and clinical trials.

Nonferrous needles of pure brass, titanium, or copper, and ferrous needles of different alloys of stainless steel were analyzed for the size, area, and distribution of the image artifact created when the needles were placed in a 0.6-T magnet. Results demonstrated that a stainless steel prototype needle (type 316) would be visible on magnetic resonance images and would provide an artifact similar to that seen in computed tomographic-guided biopsies. Further testing of this prototype included assessment of the effect on the artifact when changes were made in annealing properties, gauge, length, needle-tip geometry, pulse sequence, and orientation relative to the magnetic field. To date, three human liver biopsies have been successfully and safely performed using a stainless steel type 316 needle.

Aged↗
PubMed1986

Multiphasic MR imaging: a new method for direct imaging of pulsatile CSF flow.

A new technique is described that allows for the creation of pure pulsatile flow magnetic resonance (MR) images in a single acquisition. Five to 16 electrocardiographically gated images spanning the entire cardiac cycle are obtained with use of a gradient-echo pulse sequence. The section can be varied from 4 mm thick to full thickness projection. Taken singly, each image provides direct assessment of flow direction and velocity. Subtraction of image pairs eliminates signal detected from stationary protons, producing images of pulsatile flow. In this study the technique was used to image the flow of cerebrospinal fluid (CSF) in healthy subjects and in one patient with syringohydromyelia. The data suggest that multiphasic MR imaging provides a powerful means for the noninvasive assessment of CSF pulsatile flow dynamics and may have potential clinical application for the investigation of a variety of abnormalities such as normal pressure hydrocephalus, syrinx, and spinal block.

Cerebrospinal Fluid↗
PubMed1986

Magnetic resonance imaging of the thoracical spinal cord and spine with surface coils.

We report the results obtained at 0.6 T with the use of surface coils in 77 patients who presented with obvious or suspected thoracic myelopathy. There were 16 patients with primary tumors diagnosed for the first time, 9 patients with residual tumors, 17 with metastatic neoplasms, 13 with hydrosyringomyelia, 5 with vertebral fracture and secondary pathology involving the cord, 5 with thoracic disc protrusions, 2 with multiple sclerosis, 2 with arteriovenous malformations, 2 with cystic arachnoiditis, and 6 with a variety of congenital abnormalities (low tethered cord, intradural lipoma, lipomyelomeningocele). The significantly improved signal to noise ratios provided by surface coils allow high quality thin section imagning which, combined with the high tissue contrast resolution obtainable with suitable pulse sequences, makes MR the preferred initial imaging technique over myelography and CT myelography. In an interesting spectrum of lesions, MR can obviate the need for traditional invasive procedures.

Adolescent↗
PubMed1985

Projective imaging of pulsatile flow with magnetic resonance.

Noninvasive angiography with magnetic resonance is demonstrated. Signal arising in all structures except vessels that carry pulsatile flow is eliminated by means of velocity-dependent phase contrast, electrocardiographic gating, and image subtraction. Background structures become in effect transparent, enabling the three-dimensional vascular tree to be imaged by projection to a two-dimensional image plane. Image acquisition and processing are accomplished with entirely conventional two-dimensional Fourier transform magnetic resonance imaging techniques. When imaged at 0.6 tesla, vessels 1 to 2 millimeters in diameter are routinely detected in a 50-centimeter field of view with data acquisition times less than 15 minutes. Studies of normal and pathologic anatomy are illustrated in human subjects.

Angiography↗