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Biomedical subjects

M Stubgaard

Publications and source records attributed to M Stubgaard.

28 records · Page 2Linked to original sources
PubMed1986

Changes in eye position during growth and adult life as based on exophthalmometry, interpupillary distance, and orbital distance measurements.

The association between eye position and age is analysed in a material comprising 267 subjects aged 5-20 years and 187 aged 21-80. The study was prompted by a previous longitudinal finding of a 3 mm increase in exophthalmometry value from age of 10 to 18 years, and by a literature almost devoid of similar investigations in young age groups. The increase in Hertel value during growth could be confirmed. An adult mean value of 16.0 mm in females and 16.6 mm in males was achieved in late teen-age years, the level being stable after that. The adult range was 11-23 mm. After a similar marked increase in the young, interpupillary distance and orbital width also showed some slight trends in adults. A suggested decrease in orbital width towards old age was consistent with a secular trend, while a concomitant increase in interpupillary distance was unexpected, the combined result being a more divergent (relative) eye position with age (P less than 0.01). There was no significant correlation between exophthalmometry and refractive value. Fixed upper Hertel value limits of normal are hard to give; clinically it is the changes that matter. Modelling of facial bony structures and soft tissue contours is discussed.

Adolescent↗
PubMed1986

Changes in refraction and corneal curvature during growth and adult life. A cross-sectional study.

A cross-sectional analysis was performed regarding refractive value (spherical equivalent) and keratometry in a sample comprising 454 subjects aged 5-80 years. The refractive range was + 5.5 to -6.75D. According to the requirements of a parallel study of eye position and age, eyes with excessive ametropia had been excluded, but otherwise the sample was considered refractively unselected. Concerning refractive distribution, the present data supplement previous investigations of adults by the first author. Myopia increased from 6% in the age group 5-10 years to a peak level about 35% in adults aged 20-40, with a subsequent decrease towards old age, where hypermetropia showed a significantly increasing share. Concerning corneal curvature radius, male and female mean values (7.93 and 7.75 mm) showed no variation through the age span under study, however with a tendency of decreasing at old age (significantly in males only). The possible association with refractive change by age is discussed. Corneal astigmatism showed the established shift from predominantly with-rule in the very young to more against-rule and oblique astigmatism cases in older subjects.

Adolescent↗
PubMed1985

A new H+ suppressor: RP 40 749 versus placebo and cimetidine. Ambulatory 48-hour intragastric pH monitoring in normal men.

Six normal male test persons had nasogastric glass electrodes placed in the antrum for four periods of 48 h each, separated by wash-out periods of 9 days. The electrodes were connected to a portable pH-monitoring system enabling continuous pH recording and storing during and after four different drug or placebo treatments arranged in a double-blind, cross-over experimental design. Data were read out and stored in a computer for later analysis. RP 40 749, a new gastric acid secretion inhibitor acting within the parital cell, raised the median 24-h intragastric pH significantly not only during medication but also during the day after its discontinuation. It also proved to be a significantly more potent H+ suppressor than cimetidine. The same was true for inhibition of nocturnal intragastric acidity, for which cimetidine seemed comparably ineffective. The efficacy of RP 40 749 is comparable to that of omeprazole.

Adult↗
PubMed1985

Effect of sucralfate on gastroesophageal reflux in esophagitis.

Gastroesophageal reflux was assessed in 18 patients with endoscopically and histologically verified esophagitis, and 15 asymptomatic normal subjects, by a portable receiving system. The qualitative evaluation of the frequency of reflux episodes, normalized mean pH, normalized mean [H+] and the acid clearance rate is found to be indicative of gastroesophageal reflux. Twelve weeks of treatment with sucralfate in an open clinical trial resulted in a significant reduction of gastroesophageal reflux and the elimination of esophageal mucosal damage. Barrett++'s epithelium was found in a rather high proportion and proved to be resistant to treatment. It is suggested that the observed improvement is due to the barrier protecting properties of sucralfate restoring the motor function of the distal esophagus.

Adult↗
PubMedDate not supplied

In vivo quantification of the unidirectional influx constant for Gd-DTPA diffusion across the myocardial capillaries with MR imaging.

The authors present an in vivo method for measuring the unidirectional influx constant (Ki) for gadolinium diethylenetriaminepentaacetic acid (DTPA) diffusion across the capillary membrane in the human myocardium with magnetic resonance imaging. Ki is related to the extraction fraction (E) and the perfusion (F) by the equation Ki = E.F.Ki was obtained by using the longitudinal relaxation rate (R1) as a measure of the myocardial concentration of Gd-DTPA in the mathematical model for transcapillary transport across capillary membranes. Myocardial enhancement after Gd-DTPA injection was followed by using inversion-recovery Turbo-FLASH (fast low-angle shot) images obtained in real time. The results were comparable to those obtained from studies with positron emission tomography in humans and invasive studies in animals. A method for obtaining the input function noninvasively is also presented. Comparison with direct arterial blood sampling showed that the noninvasive input function may be even more accurate with regard to timing and curve shape than the invasive input function. The procedure may therefore prove useful in clinical studies.

Adult↗
PubMedDate not supplied

A method for MR quantification of flow velocities in blood and CSF using interleaved gradient-echo pulse sequences.

The aim of this study was to establish a rapid method for in vivo quantification of a large range of flow velocities using phase information. A basic gradient-echo sequence was constructed, in which flow was encoded along the slice selection direction by variation of the amplitude of a bipolar gradient without changes in sequence timings. The influence of field inhomogeneities and eddy currents was studied in a 1.5 T interleaved sequences for calibration and in vivo flow determination were constructed, and flow information was obtained by pairwise subtraction of velocity-encoded from velocity non-encoded phase images. Calibration was performed in a nongated mode using flow phantoms, and the results were compared with theoretically calculated encoding efficiencies. In vivo flow was studied in healthy volunteers in three different areas using cardiac gating; central blood flow in the great thoracic vessels, peripheral blood flow in the popliteal vessels, and flow of cerebrospinal fluid (CSF) in the cerebral aqueduct. The results show good agreement with results obtained with other techniques. The proposed method for flow determination was shown to be rapid and flexible, and we thus conclude that it seems well suited for routine clinical MR examinations.

Aorta↗
PubMedDate not supplied

Evaluation of relaxation time measurements by magnetic resonance imaging. A phantom study.

Several circumstances may explain the great variation in reported proton T1 and T2 relaxation times usually seen. This study was designed to evaluate the accuracy of relaxation time measurements by magnetic resonance imaging (MRI) operating at 1.5 tesla. Using a phantom of nine boxes with different concentrations of CuSO4 and correlating the calculated T1 and T2 values with reference values obtained by two spectrometers (corrected to MRI-proton frequency = 64 MHz) we found a maximum deviation of about 10 per cent. Measurements performed on a large water phantom in order to evaluate the homogeneity in the imaging plane showed a variation of less than 10 per cent within 10 cm from the centre of the magnet in all three imaging planes. Changing the gradient field strength apparently had no influence on the T2 values recorded. Consequently diffusion processes seem without significance. It is concluded that proton T1 and T2 relaxation times covering the majority of the biologic range can be measured by MRI with an overall accuracy of 5 to 10 per cent. Quality control studies along the lines indicated in this study are recommended.

Magnetic Resonance Spectroscopy↗
PubMedDate not supplied

Determination of flow velocities from magnetic resonance multiple spin-echo images. A phantom study.

The purpose of this study was to evaluate a method for the quantification of through-plane flow velocities by magnetic resonance imaging (MRI) from the flow characteristics of conventional multiple spin-echo (MSE) signals. Simulated inflow-outflow-dependent signals, as well as images of a flow phantom were generated and the logarithm of the flow-dependent signal value was plotted against echo time. The normalized slope of the resulting curve was calculated using a least-square fit to simulated and experimental data and was corrected for T2 relaxation effects by subtraction of a slope obtained at zero flow. After this correction, and with certain restrictions regarding the flow velocity (v), maximum number of echoes in the slope calculation and slice thickness (L), the normalized slope of the MSE signal becomes equal to the quotient v/L, and from this relation the flow velocity can be determined. The validity of the proposed method was examined for different flow velocities and for two opposite flow directions. The influence of the size of the region of interest and the number of spin echoes used in the calculation of the slope on the accuracy of the velocity determination was also studied. The sensitivity of the method to flow-induced phase changes was examined in the phantom by comparing the results obtained with different strengths of the slice-selective gradient as well as by comparing results from even-echo data with those from odd-echo data.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗