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A D Elster

Publications and source records attributed to A D Elster.

At least 37 records · Page 2Linked to original sources
PubMed1996

Changing of the guard at the American Journal of Roentgenology: the Robert Berk era revisited.

As determined by the Executive council of the American Roentgen Ray Society, the editorship of the American Journal of Roentgenology (AJR) is a time-limited position. This policy allows for the perpetual influx of new ideas and ensures continued dynamism in the leadership of the Journal. The AJR now has a new editor in chief, Lee F. Rogers, M.D., as well as a new office staff and a new home for the editorial office, Winston-Salem, NC. As we look with anticipation to the future of the Journal under the guidance of Lee Rogers, the time is appropriate to reflect on the legacy of journalistic excellence and innovation that Robert N. Berk has left us.

History, 20th Century↗
PubMed1996

Contrast-enhanced magnetization transfer saturation imaging improves MR detection of herpes simplex encephalitis.

Cranial MR imaging was performed in three patients in whom herpes simplex encephalitis was subsequently proved. In all cases, the postcontrast T1 weighted MR images obtained with magnetization transfer saturation showed greater central nervous system involvement than was apparent on the conventional MR images. Specifically, the postcontrast magnetization transfer images were superior at delineating generalized meningeal enhancement as well as focal areas of brain involvement not seen on noncontrast T2-weighted images orconventionalpostcontrast T1-weightedimages.

Brain↗
PubMed1996

Magnetization transfer or spin-lock? An investigation of off-resonance saturation pulse imaging with varying frequency offsets.

PURPOSE: To characterize near-resonance saturation pulse MR imaging on a 1.5-T scanner in order to gain insight into underlying mechanisms that alter tissue contrast and to optimize the technique for neuroimaging. METHODS: Off-resonance saturation pulses were applied to T1-weighted, spin-density-weighted, and T2-weighted sequences at frequency offsets ranging from 50 Hz to 20,000 Hz down field from water resonance. Suppression ratios were determined at each offset for phantom materials (MnCl2 solution, gadopentetate dimeglumine, corn oil, water, and agar), normal brain structures, and a variety of brain lesions. RESULTS: Signal suppression of MnCl2 on T1-weighted images occurred at offsets of less than 2000 Hz even though no macromolecules were present in the solution. Only those phantom materials and tissues with short or intermediate T1 relaxation times and relatively large T1/T2 ratios were sensitive to changing frequency offsets. Suppression of brain increased from approximately 20% at 2000 Hz offset to approximately 45% when the offset was reduced to 300 Hz. In human subjects, the net effect of reducing the frequency offset was to increase T2 contrast on T1-weighted, spin-density-weighted, and T2-weighted images. Distilled water and contrast material did not suppress except at very low offsets ( < 300 Hz). A frequency offset of 300 Hz was optimal for maximizing conspicuity between most contrast-enhancing lesions and adjacent brain while preserving anatomic detail. CONCLUSION: Suppression of MnCl2 indicates that magnetization transfer is not the sole mechanism of contrast in near-resonance saturation MR imaging. Spin-lock excitation can reasonably explain the behavior of the phantom solutions and the increase in T2 contrast of tissues achieved as the frequency offset is decreased from 2000 Hz to 300 Hz. Below 300 Hz, saturation is presumably caused by spin-tip effects. With our pulse design, an offset of 300 Hz is optimal for many routine clinical imaging examinations.

Adult↗
PubMed1995

Suture closure in the human chondrocranium: CT assessment.

PURPOSE: To chronicle the development of ossification centers, sutures, and synchondroses in the chondrocranium throughout childhood by using computed tomography (CT). MATERIALS AND METHODS: One hundred eighty-nine children (age range, newborn to 18 years; median age, 4.0 years) without skull base deformity were referred for cranial CT. The closure of 18 sutures and synchondroses was graded. RESULTS: In the occipital bone at birth, six components were identified. The Kerckring ossicle rapidly fused to the supraoccipital bone within the 1st month. At age 1-3 years, the posterior and anterior intraoccipital synchondroses began to fuse. The occipitomastoidal, petro-occipital, and spheno-occipital synchondroses remained partially open into the teenage years. In the sphenoid bone at birth, 13 ossification centers were identified; most assimilated into the sphenoidal body during the first 2 years. Pneumatization of the sphenoid sinus appeared at age 1-2 years and advanced posteriorly over the next 3-5 years. CONCLUSION: The complex process of skull base development is chronicled, which provides CT standards for judgment of the patterns and timing of sutural or synchondrosal closure.

Adolescent↗
PubMed1995

Postnatal development of the central skull base: normal variants.

PURPOSE: To illustrate the normal variants and developmental anomalies of the skull base on computed tomographic (CT) scans. MATERIALS AND METHODS: One hundred eighty-nine children (age range, newborn to 18 years; median age, 4.0 years) without skull base deformity were referred for cranial CT. Normal developmental variants in the sphenoid and occipital bones were characterized. RESULTS: Sixteen normal variants of central skull base development were identified including anterior foramen in the presphenoid, remnant of the craniopharyngeal canal in the anterior portion of the postsphenoid, rounded defects in the central sphenoid, clefts and fissures along the basiocciput and basisphenoid, basioticum variants, notochordal remnant in the midline of the basiocciput, and fusion variants of the Kerckring ossicle with the supraoccipital portion of the occipital bone. CONCLUSION: The location and CT appearance of the 16 variants and anomalies are related to the known embryologic origin of this region. Recognition of such variants may prove necessary in evaluation of patients with skeletal dysplasias and disorders of skull base development.

Adolescent↗
PubMed1995

Combined effects of magnetization transfer and gadolinium in cranial MR imaging and MR angiography.

Magnetization transfer (MT) imaging is an MR technique in which image contrast is altered by applying RF pulses that saturate a restricted pool of hydrogen protons associated with cell membranes, proteins, and other macromolecules. Protons in this restricted pool, unlike those in tissue-free water, are not visible on MR due to their short T2 relaxation times. However, these restricted protons modulate the observed signal from free water by dipolar and chemical exchange interactions. In MT imaging, specifically tailored RF pulses are applied to saturate selectively the restricted macromolecular pool. This saturation is "transferred" to the free protons, causing their signal amplitude to decrease [1]. Increased signal intensity due to T1 shortening caused by gadolinium administration does not depend upon macromolecular interactions and is not appreciably suppressed by MT pulses (Fig. 1). Consequently, MT pulses act synergistically with gadolinium to increase the visibility of enhancing lesions by preferentially suppressing nonenhancing background tissue [2]. The purpose of this paper is to demonstrate the principles underlying the synergistic effects of MT saturation and paramagnetic contrast agents and to illustrate these effects in clinical MR imaging and MR angiography.

Brain↗
PubMed1995

Lumbar spondylolysis: reactive marrow changes seen in adjacent pedicles on MR images.

OBJECTIVE: In a search for ancillary MR findings for the diagnosis of spondylolysis, we performed a retrospective study to characterize changes in MR signal intensity of marrow within lumbar pedicles at the level of a spondylolytic defect. These reactive marrow changes were classified according to the anatomic-pathologic scheme developed for degenerative disk disease by Modic et al. MATERIALS AND METHODS: Two neuroradiologists retrospectively reviewed MR images of 60 patients with lumbar spondylolysis confirmed by conventional radiography or CT. The MR signal of each pedicle at the level of a pars defect was compared on T1- and T2-weighted sagittal images to that at the next higher level. When both observers concurred that the signal of the involved pedicle differed significantly from that of its neighbor, this signal change was classified into one of three types (type I: hypointense on T1-weighted images, hyperintense on T2-weighted images; type II: hyperintense on T1-weighted images, isointense or hyperintense on T2-weighted images; type III: hypointense on both T1- and T2-weighted images). RESULTS: Changes in MR signal intensity of pedicles adjacent to spondylolytic defects were observed in 24 (40%) of the 60 patients. Type I changes were seen in three patients, all less than 24 years old. Type II changes were seen in 17 patients with a median age of 35 years. Type III changes were seen in four patients with a median age of 51 years. The distribution of changes in signal intensity in the pedicle as a function of age was significant (p = .001). CONCLUSION: Categories of changes in MR signal intensity, similar to those described adjacent to degenerating disks, can be seen in lumbar pedicles adjacent to a spondylolytic defect of the pars interarticularis and are distributed as a function of age. Awareness of this finding may aid in establishing the correct diagnosis of spondylolysis on MR imaging and prevent erroneous interpretation of abnormal signal intensity in the pedicles in these patients.

Adult↗
PubMed1995

Lumbar spondylolysis without spondylolisthesis: recognition of isolated posterior element subluxation on sagittal MR.

PURPOSE: To document the occurrence of isolated dorsal subluxation of posterior elements in cases of lumbar spondylolysis without spondylolisthesis both quantitatively (using spinal canal measurements) and qualitatively (by visual inspection) on sagittal MR images. METHODS: Retrospective analysis identified 63 patients with lumbar spondylolysis (confirmed by CT or conventional radiography) who had undergone MR imaging. From these we identified 12 patients with pars interarticularis defects but no evidence of spondylolisthesis. Measurements of anteroposterior spinal canal diameters were performed in these 12 patients to ascertain whether the sagittal canal diameter at the level of the spondylolysis exceeded the normal range as determined from 100 control subjects. RESULTS: In 9 of 12 patients the spinal canal was abnormally widened at the level of the spondylolysis because of dorsal subluxation of posterior elements. In 5 of these patients, the subluxation was readily visible on midline sagittal MR images. In 4 patients, spinal canal measurements were necessary to document this phenomenon. CONCLUSION: In the majority of patients with spondylolysis but without spondylolisthesis, sagittal MR images can show isolated dorsal subluxation of posterior spinal elements.

Adolescent↗
PubMed1995

Seizure-induced transient hippocampal abnormalities on MR: correlation with positron emission tomography and electroencephalography.

We report transient focal abnormalities on MR in a patient having frequent electrographic seizures that were not obvious clinically. Marked mass effect (confirmed with volumetric studies) and abnormal T2 signal intensity in the right hippocampal region correlated with electroencephalographic ictal activity and with increased positron-emitting radiotracer uptake in the medial temporal lobe. The follow-up MR 2 months later, after electroencephalography findings normalized, revealed no hippocampal abnormalities.

Aged↗