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J C Ehrhardt

Publications and source records attributed to J C Ehrhardt.

At least 19 recordsLinked to original sources
PubMed1992

Subcortical and temporal structures in affective disorder and schizophrenia: a magnetic resonance imaging study.

Volumetric measurements of subcortical and temporal structures were done on a sample of 54 schizophrenic patients, who were compared with 48 bipolar patients and 47 normal controls. We observed the male schizophrenic patients to have significant enlargement in the putamen and lesser enlargement in the caudate. We found the right temporal lobe to be larger than the left across all diagnostic groups, although bipolar females failed to have this asymmetry. We did not replicate the finding of decreased hippocampal, amygdala, or temporal lobe volume in our schizophrenic patients. Nor did we find significant differences between our bipolar patients and controls in the structures measured, with the exception of the right hippocampus. Our findings are consistent with a developmental defect in pruning of subcortical brain regions or with a compensatory synaptic increase secondary to decreased input from other brain regions such as the prefrontal cortex or anterior temporal lobe structures. Coupled with the lack of temporal lobe asymmetry in bipolar females, these findings suggest that different types of gender-specific neurodevelopmental abnormalities may occur in affective versus schizophrenic psychosis, which may reflect the effects of hormonal influences on brain development in predisposed individuals.

Adult↗
PubMed1991

T1 and T2 relaxation times in schizophrenia as measured with magnetic resonance imaging.

T1 and T2 relaxation times were measured in ten brain regions on the right and left side in a sample of 27 schizophrenic patients and 37 normal controls. The schizophrenic patients showed a prolongation of T2 relaxation time, and to a lesser extent of T1 relaxation time, which was more predominantly localized in the right hemisphere and in gray matter structures. These results may indicate that metabolic, physiological, or neurochemical brain function in schizophrenia is related in some way to a change in tissue fluid in neuronal cell bodies or interstitial gray matter.

Adult↗
PubMed1991

Automated identification of left ventricular borders from spin-echo magnetic resonance images. Experimental and clinical feasibility studies.

Gated cardiac magnetic resonance imaging (MRI) permits detailed evaluation of cardiac anatomy, including the calculation of left ventricular volume and mass. Current methods of deriving this information, however, require manual tracing of boundaries in several images; such manual methods are tedious, time consuming, and subjective. The purpose of this study is to apply a new computerized method to automatically identify endocardial and epicardial borders in MRIs. The authors obtained serial, short-axis, spin-echo MRIs of 13 excised animal hearts. Also obtained were selected short-axis, spin-echo ventricular images of 11 normal human volunteers. A method of automated edge detection based on graph-searching principles was applied to the ex vivo and in vivo images. Endocardial and epicardial areas were used to compute left ventricular mass and were compared with the anatomic left ventricular mass for the images of excised hearts. The endocardial and epicardial areas calculated from computer-derived borders were compared with areas from observer tracing. There was very close correspondence between computer-derived and observer tracings for excised hearts (r = 0.97 for endocardium, r = 0.99 for epicardium) and in vivo scans (r = 0.92 for endocardium, r = 0.90 for epicardium). There also was a close correspondence between computer-generated and actual left ventricular mass in the excised hearts (r = 0.99). These data suggest the feasibility of automated edge detection in MRIs. Although further validation is needed, this method may prove useful in clinical MRI.

Animals↗
PubMed1991

MR evaluation of CNS tumors: dose comparison study with gadopentetate dimeglumine and gadoteridol.

In phase II and III trials of gadoteridol (Gd-HP-D03A), a new nonionic, low-osmolar contrast agent, 40 patients with intracranial neoplasms underwent magnetic resonance (MR) imaging with experimental doses of 0.05-0.3 mmol/kg. Fifteen patients also underwent contrast studies with the standard dose (0.1 mmol/kg) of gadopentetate dimeglumine. Both gadopentetate dimeglumine and gadoteridol appear to have a similar effect when given in equal doses (0.1 mmol/kg, n = 5). Lesion enhancement and delineation were better at higher experimental doses (0.2 or 0.3 mmol/kg, n = 7) and worse at a lower experimental dose (0.05 mmol/kg, n = 3). Quantitative analysis of 10 lesions examined with identical imaging protocols revealed a directly proportional relationship (r = .975) between lesion contrast ratio and dose over a range of 0.05-0.3 mmol/kg. Phantom experiments support the clinical results. Improved enhancement, detection, and delineation of central nervous system (CNS) neoplasms resulting from increased injected doses of gadoteridol have the potential to be clinically significant and may justify the possibly higher cost of increased contrast material dosage. Lower doses may not be adequate for the evaluation of most CNS tumors.

Adult↗
PubMed1990

Developmental abnormalities of the corpus callosum in schizophrenia.

Magnetic resonance imaging was used to evaluate neuroanatomical and neuropathologic abnormalities in a consecutive series of 140 patients with schizophrenia for comparison with normal controls. Partial agenesis of the corpus callosum, a rare neurodevelopmental abnormality, was found in two patients, one of whom also had a callosal lipoma. Evidence is presented suggesting that this finding represents an increased prevalence of partial agenesis in schizophrenia. The corpus callosum develops embryologically in intimate relationship to the hippocampal formation, fornix, septum pellucidum, and cingulate gyrus. In individuals with callosal agenesis, abnormalities also occur in the development of these limbic structures. Recent neuropathologic studies have suggested the occurrence of abnormal neurogenesis in the hippocampal formation and in the cingulate gyrus in schizophrenic patients. An increased prevalence of callosal agenesis and its related limbic abnormalities would further support investigation into neurodevelopmental abnormalities of these anatomical regions in schizophrenia.

Adult↗
PubMed1990

Magnetic resonance imaging of the brain in schizophrenia. The pathophysiologic significance of structural abnormalities.

In a second large series of schizophrenic patients studied with magnetic resonance imaging at the University of Iowa, Iowa City, earlier findings of decreased frontal, cerebral, and cranial size were not replicated. In this second series, control subjects were selected to be educationally equivalent to the schizophrenic patients, a modification in design that may partially account for the failure to replicate. By means of coronal images, ventricular volume was compared in patients and controls and found to differ to a highly significant degree, with the frontal horns being possibly slightly more enlarged than the rest of the ventricular system. A prominent sex effect was also observed, with most of the increased ventricular size occurring in the male patients. Within the male patients, the thalamus was also observed to be significantly smaller, a finding that could be consistent with periventricular injury. Patients with prominent negative symptoms had significantly larger ventricular size than did those with the mixed or positive subtypes. Because of its superior resolution, magnetic resonance imaging appears to offer a more sensitive index of ventricular enlargement than that provided by computed tomography.

Adult↗
PubMed1990

Structural brain abnormalities in bipolar affective disorder. Ventricular enlargement and focal signal hyperintensities.

Structural brain abnormalities were examined in a sample of 48 patients with bipolar affective disorder who were compared with 54 schizophrenic patients and 47 normal controls. As in our previous work using computed tomographic scanning, lateral ventricular enlargement was due to a diagnostic effect. In this study, the effect was more prominent in the schizophrenic men, while a trend was seen in the bipolar men. Women in both groups did not differ significantly from normal subjects. This finding is possibly consistent with the fact that men have a higher frequency of birth anomalies such as hydrocephalus. Since one cause of such birth anomalies might be periventricular hemorrhage or infarction, we also evaluated all scans for the presence of small focal regions of signal hyperintensity. A significant increase in the number of focal signal hyperintensities was noted in the bipolar patients, in comparison with normal subjects, but not in the schizophrenics. The bipolar patients with focal signal hyperintensities had a trend toward larger ventricular size than those without. The pathophysiological significance of these findings is unclear.

Adult↗
PubMed1990

Quantification of antibiotic drug potency by a two-compartment radioassay of bacterial growth.

The two-compartment radioassay for microbial kinetics based on continuous measurement of the 14CO2 released by bacterial metabolism of 14C-labeled substrate offers a valuable approach to testing the potency of antimicrobial drugs. By using a previously validated radioassay with gram-positive and gram-negative bacteria, a group of protein synthesis inhibitors was evaluated for their effect on microbial growth kinetics. All tested drugs induced changes in both the slopes and intercepts of the growth curves. An exponential growth model was applied to quantify the drug effect on the processes of bacterial 14CO2 liberation and cell generation. The response was measured in terms of a generation rate constant. A linear dependence of the generation rate constant on the dose of spectinomycin was observed with Escherichia coli. Sigmoidal-shaped curves were found in the assays of chloramphenicol and tetracycline. The implications of dose-response curves are discussed on the basis of the receptor site concept for drug action. The assay sensitivities for chloramphenicol and tetracycline were similar to those obtained by the cell counting method, but the sensitivity of the radioassay was at least 10 times greater for spectinomycin.

Anti-Bacterial Agents↗
PubMed1989

Bacterial growth kinetics: modelling and evaluation of two-compartment radioassay.

Quantitative measurements of bacterial growth may be made using a radioassay technique. This method measures, by scintillation counting, the 14CO2 derived from the bacterial metabolism of a 14C-labeled substrate. Mathematical growth models may serve as reliable tools for estimation of the generation rate constant (or slope of the growth curve) and provide a basis for evaluating assay performance. Two models, i.e., exponential and logistic, are proposed. Both models yielded an accurate fit to the data from radioactive measurement of bacterial growth. The exponential model yielded high precision values of the generation rate constant, with an average relative standard deviation of 1.2%. Under most conditions the assay demonstrated no changes in the slopes of growth curves when the number of bacteria per inoculation was changed. However, the radiometric assay by scintillation method had a growth-inhibiting effect on a few strains of bacteria. The source of this problem was thought to be hypersensitivity to trace amounts of toluene remaining on the detector.

Bacteria↗
PubMed1988

Validation studies for brain blood flow assessment by radioxenon tomography.

A tomographic technique has been used recently for cerebral blood flow measurements with inhaled radioxenon. Based on experiments in a specially developed dynamic phantom and on studies in primates in vivo, we have analyzed the validity of this method for measurements of both regional and total blood flow in the brain. We have also examined the errors introduced into flow computations as a function of changes in such parameters as: rate of xenon input, size of region of interest, magnitude of regional flow rates, and inter-regional flow differences. Our findings indicate a reasonable degree of accuracy for flow measurements in gray matter regions that are 3 cm in diameter or larger, while white matter blood flow is generally overestimated. The accuracy for regional flow assessments degrades as a function of: diminishing region size, increasing inter-regional flow differences, and flow rates in excess of 100 ml/100 g/min. Measurements for brain regions 2 cm or smaller in diameter can be in error by 25-50% as a result of partial volume averaging. Although the technique is not ideal for accurate flow measurements in small regions of the brain, it nevertheless provides a convenient means of assessing perfusion in major vascular territories of the brain in routine clinical applications.

Animals↗
PubMed1988

New methods of examining gamma camera collimators.

New methods are proposed and described to examine the quality of gamma camera collimators in two special performance categories, namely, uniformity in regional efficiency and regional variations in channel tilt. These two performances are critical areas for SPECT imaging. Results obtained from experimental and commercial collimators illustrate the variability seen for these performance characteristics in currently available collimators.

Quality Control↗
PubMed1987

Radiometric assay of bacterial growth: analysis of factors determining system performance and optimization of assay technique.

A quantitative technique for the measurement of 14CO2 released from a bacterial culture was evaluated. The technique uses liquid scintillation counting to record 14CO2 accumulation on a fluor-impregnated filter paper within a double-chambered scintillation vial that also houses the bacterial growth medium. We have successfully identified and corrected the major causes for a variably low detection efficiency, and also established the optimum mixture of reagents for the detection system. Incorporation of Triton X-100 into the scintillation fluid used for the detector reduced the variability between identical assays in a single batch from 50% to 5%, and, in conjunction with an increase in the scintillator concentration, raised the counting efficiency from 30% to 70-88%. The response of the improved detector is linear over a wide range of count-rates. Another significant modification was the interchange of growth and detector chambers. Overall, a 40-fold increase in count-rate during the exponential phase of bacterial growth was obtained by improving 14CO2 detection efficiency, increasing the rate of 14CO2 transfer from liquid to gas phases and enlarging the growth supporting capacity of the detector system. The minimum detection time for bacterial growth was shortened and the exponential phase of bacterial proliferation was lengthened by at least 2 hr. High counting efficiency, precision, and linearity make the improved detector a sensitive and reliable tool for radiometry of bacterial growth and metabolism.

Bacteria↗
PubMed1986

Structural abnormalities in the frontal system in schizophrenia. A magnetic resonance imaging study.

Thirty-eight schizophrenics and 49 normal controls underwent magnetic resonance imaging. Midline sagittal cuts indicated that the schizophrenics had significantly smaller frontal lobes, as well as smaller cerebrums and craniums. The findings are consistent with some type of early developmental abnormality that might retard brain growth and therefore skull growth. These findings are confirmed on a smaller sample of patients on whom we have coronal cuts. Decreased cerebral and cranial size are associated with prominent negative symptoms, although decreased frontal size is not. Decreased cranial and cerebral size was also associated with impairment on some cognitive tests. These findings are consistent with the hypothesis that some schizophrenics may have a type of early developmental abnormality associated with prominent negative symptoms and cognitive impairment. Further, the results suggest that schizophrenics may have a type of structural frontal system impairment. Thus, they provide anatomic evidence for the "hypofrontality hypothesis."

Adult↗
PubMed1986

A controlled magnetic resonance imaging study of corpus callosum thickness in schizophrenia.

Two previous postmortem studies reported an increased thickness of the corpus callosum in schizophrenic patients compared to psychiatric controls. We report an in vivo study of the corpus callosum in schizophrenic patients (n = 38) and healthy controls (n = 41) using magnetic resonance (MR) brain imaging. A significant increase in mean callosal thickness was found in the middle and anterior, but not the posterior, parts of the callosal body. However, when the patients and controls were compared by gender and handedness, schizophrenic men were found not to differ from control men in callosal thickness, regardless of handedness, whereas schizophrenic women were found to have a highly significant increase in callosal middle and anterior thickness compared to control women. The data suggest that increased callosal thickness in schizophrenia is gender related, a factor that is not considered by postmortem studies. The implications of increased callosal dimensions in female schizophrenics are discussed.

Adult↗
PubMed1986

Measurement of left ventricular mass in vivo using gated nuclear magnetic resonance imaging.

Alterations of left ventricular mass occur in a variety of congenital and acquired heart diseases. In vivo determination of left ventricular mass, using several different techniques, has been previously reported. Problems inherent in some previous methods include the use of ionizing radiation, complicated geometric assumptions and invasive techniques. We tested the ability of gated nuclear magnetic resonance imaging to determine in vivo left ventricular mass in animals. By studying both dogs (n = 9) and cats (n = 2) of various sizes, a broad range of left ventricular mass (7 to 133 g) was examined. With a 0.5 tesla superconducting nuclear magnetic resonance imaging system the left ventricle was imaged in the transaxial plane and multiple adjacent 10 mm thick slices were obtained. Endocardial and epicardial edges were manually traced in each computer-displayed image. The wall area of each image was determined by computer and the areas were summed and multiplied by the slice thickness and the specific gravity of muscle, providing calculated left ventricular mass. Calculated left ventricular mass was compared with actual postmortem left ventricular mass using linear regression analysis. An excellent relation between calculated and actual mass was found (r = 0.95; SEE = 13.1 g; regression equation: magnetic resonance mass = 0.95 X actual mass + 14.8 g). Intraobserver and interobserver reproducibility were also excellent (r = 0.99). Thus, gated nuclear magnetic resonance imaging can accurately determine in vivo left ventricular mass in anesthetized animals.

Animals↗
PubMed1986

Impact of MR imaging on clinical diagnosis and management: a prospective study.

The clinical value of magnetic resonance (MR) imaging was prospectively evaluated in 189 patients referred for examination of the brain or spine. Comparison of the attending physician's diagnosis, proposed treatment, and estimated prognosis before and after MR imaging indicated a substantial effect of the additional information provided by this study. A suspected diagnosis was refined or changed in 16% of all patients, and the physician's level of confidence in the diagnosis changed in over half of the cases in which the diagnosis was unchanged. In two-thirds of all cases the physician indicated that the treatment or estimated prognosis was altered.

Brain Diseases↗