Biomedical subjects
A D Elster
Publications and source records attributed to A D Elster.
What are the relative accuracies of sonography and MR angiography?
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Cranial tissues: appearance at gadolinium-enhanced and nonenhanced MR imaging with magnetization transfer contrast.
PURPOSE: To determine the relative contrast of normal cranial tissues at magnetization transfer (MT) spin-echo magnetic resonance (MR) imaging. MATERIALS AND METHODS: MR imaging at 1.5 T was performed with conventional spin-echo techniques without and with off-resonance MT saturation pulses. The signal intensities of normal cranial tissues were measured in 10 healthy volunteers on spin-density- and T2-weighted images and in 10 patients on T1- weighted images obtained before and after administration of gadopentetate dimeglumine. RESULTS: MT saturation produced a significant (P < .01) reduction in signal from all tissues except cerebrospinal fluid and fat. Several gray matter structures had higher signal intensity than white matter on T1-weighted MT images. After administration of gadopentetate dimeglumine, imaging with the MT sequence increased visualization of normally enhancing structures. CONCLUSION: MT saturation pulses produce new patterns of tissue contrast that differ substantially from those seen on conventional spin-echo images.
Cerebral infarction: effects of dose and magnetization transfer saturation at gadolinium-enhanced MR imaging.
PURPOSE: To determine contrast enhancement after cerebral infarction at T1-weighted magnetic resonance (MR) imaging with delayed, gadolinium-enhanced, and magnetization transfer (MT) techniques. MATERIALS AND METHODS: Ten patients aged 40-81 years with recent infarctions (< 7 days) were prospectively studied at MR imaging. Gadoteridol (0.1 mmol/kg [standard dose] and an additional 0.2 mmol/kg [high dose]) was administered before imaging with and without MT saturation and after a 15-minute delay. Two neuroradiologists ranked enhancement conspicuity. RESULTS: interobserver concordance was excellent (kappa = .86). Pairwise comparisons revealed high-dose MT images were ranked highest, followed by high-dose delayed non-MT images (P < .01). Standard-dose MT images and initial high-dose non-MT images were ranked intermediately but were not distinguishable from each other (P > .05). Initial and delayed standard-dose MT images were ranked lowest (P < .01) and were not distinguishable from each other. CONCLUSION: MT saturation and high-dose gadoteridol individually and synergistically improve the depiction of contrast enhancement.
Neuroradiology.
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"Crisscross" MR imaging: improved resolution by averaging signals with swapped phase-encoding axes.
At conventional magnetic resonance imaging, the number of phase-encoding steps is often chosen to be less than the number of readout samples, resulting in reduced spatial resolution in the phase-encoding direction. Signal averaging improves the signal-to-noise ratio of the image but does not affect this asymmetry in resolution. By swapping the phase- and frequency-encoding directions between excitations and averaging the resultant data sets ("crisscross" imaging), equal spatial resolution can be obtained in both principal directions. Increased spatial resolution can be obtained with this method with no increase in imaging time, and the method can potentially be applied in echo-planar and three-dimensional Fourier transform imaging.
Patient screening prior to MR imaging: a practical approach synthesized from protocols at 15 U. S. medical centers.
The article by Boutin et al. [1] in this issue of the AJR documents a surprinsingly great variation in the MR screening procedures used at different academic centers throughout the United States. Although considerable literature now exists concerning the MR imaging of patients with ferromagnetic implants, devices, and foreign bodies [2-4], no uniform screening protocol to identify such patients has yet been adopted. The Safety Committee of the Society for Magnetic Resonance Imaging (SMRI) has recommended that "each imaging site should develop a standardized policy for screening patients with suspected metallic foreign bodies" [5]. To date, however, the SMRI has neither proposed nor endorsed a specific screening protocol for general use.
The internationalization of the American Journal of Roentgenology: 1980-1992.
OBJECTIVE: The purpose of this study was to determine whether significant changes have occurred in the number of foreign articles published in the American Journal of Roentgenology since 1980. MATERIALS AND METHODS: A total of 3398 articles published in AJR during two 3-year periods (1980-1982 and 1990-1992) were classified by type, subject, radiologic technique, organ system, and national origin. Additionally, 2865 manuscripts submitted to AJR from 1990 to 1992 were analyzed to determine the probability of manuscript acceptance based on country of origin. RESULTS: From 1980 to 1992, 158 (10%) of 1610 articles published in AJR originated from institutions outside the United States. By 1990-1992, international articles accounted for 441 (25%) of 1788 published papers (p < .00001). Although the total number of published articles from most nations increased during the decade, Korea, Japan, and Germany made the largest advances. International contributions in the 1990s were most numerous in the following areas: adult radiology, abdominal/gastrointestinal imaging, pulmonary/thoracic imaging, sonography, and interventional radiology. Notwithstanding these trends, manuscripts submitted from international sources are somewhat less likely to be accepted for publication than those originating from the United States (acceptance rate for major papers 27% vs 33%, p = .01). CONCLUSION: The American Journal of Roentgenology is becoming increasingly internationalized, with Korea, Japan, and Germany making particularly striking advances in the past decade.
Does MR imaging have any known effects on the developing fetus?
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Distinction between degenerative and isthmic spondylolisthesis on sagittal MR images: importance of increased anteroposterior diameter of the spinal canal ("wide canal sign").
OBJECTIVE: The purpose of this study was to determine whether a visually apparent increase in the anteroposterior diameter of the spinal canal ("wide canal sign") can be used reliably to differentiate degenerative from isthmic spondylolisthesis on midline sagittal MR images. We hypothesized that the wide canal sign would be present only in isthmic spondylolisthesis, where the vertebral ring is disrupted by defects in the pars interarticularis. MATERIALS AND METHODS: The midline sagittal MR images of 100 control subjects without spondylolysis or spondylolisthesis were analyzed to establish the normal range of sagittal canal diameters at the various lumbar levels. Midline sagittal MR images of the lumbar spine were reviewed in 53 patients in whom either isthmic (n = 35) or degenerative (n = 18) spondylolisthesis was confirmed with conventional radiography and/or CT. For each spinal level, the sagittal canal ratio, defined as the maximum anteroposterior diameter of the canal at that level divided by the diameter of the canal at L1, was calculated. From our analysis of the control subjects, a normal sagittal canal ratio was determined to be less than 1.25. A sagittal canal ratio of 1.25 or greater at the level of a spondylolisthesis was considered to represent an abnormally increased sagittal canal diameter (wide canal sign), indicating the presence of bilateral pars interarticularis defects. Using this sign alone, two neuroradiologists who had no knowledge of the true diagnosis classified the type of spondylolisthesis in a randomized subgroup of 34 age-matched adults (all more than 40 years old and with grade I isthmic or degenerative spondylolisthesis). RESULTS: In the 100 subjects without spondylolisthesis and in the 18 patients with degenerative spondylolisthesis, the sagittal canal ratio did not exceed 1.25 (mean values, 0.93-0.99) at any level of the lumbar spine. Conversely, the sagittal canal ratio at the level of isthmic spondylolisthesis exceeded 1.25 (mean value, 1.56) in 34 of 35 patients. In patients more than 40 years old, in whom degenerative spondylolisthesis is prevalent and misdiagnosis of isthmic spondylolisthesis is potentially more likely, both neuroradiologists were 100% accurate in correctly assigning the type of spondylolisthesis when using the wide canal sign alone. CONCLUSION: The wide canal sign on midline sagittal MR images (corresponding to an sagittal canal ratio > or = 1.25) is a reliable predictor of the presence of defects of the pars interarticularis at the level of a spondylolisthesis. This sign could be useful for distinguishing degenerative from isthmic spondylolisthesis when degenerative sclerosis in the pars interarticularis mimics spondylolysis, when direct axial imaging of the pars interarticularis has not been done, or when imaging is technically inadequate.
High-resolution, dynamic pituitary MR imaging: standard of care or academic pastime?
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Use of statistical analysis in the AJR and Radiology: frequency, methods, and subspecialty differences.
OBJECTIVE: The statistical procedures appearing in Radiology and the AJR were analyzed to determine the types of statistical tests used in major articles, their relative frequencies, and whether these methods differed according to radiologic subspecialty. MATERIALS AND METHODS: Six hundred sixty-nine major articles published in Radiology or the AJR during 1993 were reviewed for statistical content. These articles were first classified by radiologic subspecialty or principal focus according to the named journal section where each appeared (e.g., breast imaging, musculoskeletal radiology, neuroradiology). The statistical methods used in each article were then assigned to one of 18 categories (e.g., descriptive, basic t- and z-tests, correlation/regression techniques, and nonparametric statistics). RESULTS: Of the 669 major articles analyzed, 294 (44%) used no statistical methods or descriptive statistics only, 179 (27%) used only one type of statistical method, 102 (15%) used two methods, and 94 (14%) used three or more methods. Statistical techniques were most likely to be used in articles classified as cardiac (85% used statistical analysis) or contrast agents (79%), but least likely to be used in gastrointestinal/abdominal imaging (45%), radiotherapy (44%), or miscellaneous topics (29%). Five basic categories of statistical methods--basic z- and t-tests, basic decision statistics (sensitivity, specificity), basic contingency table analysis (chi 2, McNemar), correlation/regression techniques (linear regression, Pearson coefficients), and basic nonparametric tests (Wilcoxon, Mann-Whitney U)--account for the complete statistical analysis appearing in approximately 80% of the major articles. CONCLUSION: Approximately half the major articles appearing in Radiology or AJR used no statistics, descriptive analysis only, or a simple inferential test employing t-tests or confidence intervals; advanced statistical techniques were found in only 20% of articles. Statistical analysis was most likely to be used in articles dealing with cardiac radiology or contrast agents and least likely to be used in articles on abdominal/gastrointestinal radiology, radiotherapy, and miscellaneous radiologic topics.
A method for using MR to evaluate the effects of cardiovascular disease on the brain: the cardiovascular health study.
PURPOSE: To do a pilot study for the Cardiovascular Health Study (a population-based, longitudinal study of coronary heart disease and stroke in adults 65 years of age and older designed to identify risk factors related to cerebrovascular disease, particularly stroke): (a) to determine the feasibility of adding brain MR to the full-scale study; (b) to evaluate the reliability of standardized MR image interpretation in a multicenter study; and (c) to compare the prevalence of stroke determined by MR with that by clinical history. METHODS: Protocol-defined MR studies were performed in 100 subjects with clinical histories of stroke and 203 subjects without reported histories of stroke. MR scans were independently evaluated by two trained neuroradiologists for the presence of small (< or = 3 mm) and large (> 3 mm) "infarctlike" lesions. The sizes of the cerebral sulci and lateral ventricles and the extent of white matter disease were graded on a scale of 0 to 9. RESULTS: Eighty percent of the Cardiovascular Health Study participants who were invited to undergo MR studies agreed to do so; 95% of those agreeing to the procedure successfully completed the exams. Intrareader and interreader reliability of infarctlike lesion identification was high for large lesions (kappa, 0.71 and 0.78, respectively) but not for small lesions (kappa, 0.71 and 0.32, respectively). Relaxed intrareader and interreader kappa scores for sulcal and ventricular sizes and extent of white matter disease were greater than 0.8 MR evidence of infarctlike lesions was present in 77% of the participants with histories of stroke but was also present in 23% of the participants without clinical histories of stroke. Seventy-nine percent of the infarctlike lesions were larger than 3 mm. CONCLUSIONS: This preliminary study indicates that a large, prospective, epidemiologic study of elderly subjects using MR scans of the brain for identification of cerebrovascular disease is feasible and that the interpretative results are reproducible, and suggests that MR evidence of stroke is more prevalent than reported clinical history of stroke.