Biomedical subjects

H Eggers

Publications and source records attributed to H Eggers.

At least 19 recordsLinked to original sources

PubMed2005

Free-breathing whole-heart coronary MRA with 3D radial SSFP and self-navigated image reconstruction.

Respiratory motion is a major source of artifacts in cardiac magnetic resonance imaging (MRI). Free-breathing techniques with pencil-beam navigators efficiently suppress respiratory motion and minimize the need for patient cooperation. However, the correlation between the measured navigator position and the actual position of the heart may be adversely affected by hysteretic effects, navigator position, and temporal delays between the navigators and the image acquisition. In addition, irregular breathing patterns during navigator-gated scanning may result in low scan efficiency and prolonged scan time. The purpose of this study was to develop and implement a self-navigated, free-breathing, whole-heart 3D coronary MRI technique that would overcome these shortcomings and improve the ease-of-use of coronary MRI. A signal synchronous with respiration was extracted directly from the echoes acquired for imaging, and the motion information was used for retrospective, rigid-body, through-plane motion correction. The images obtained from the self-navigated reconstruction were compared with the results from conventional, prospective, pencil-beam navigator tracking. Image quality was improved in phantom studies using self-navigation, while equivalent results were obtained with both techniques in preliminary in vivo studies.

Adult↗

PubMed2004

Fast isotropic volumetric coronary MR angiography using free-breathing 3D radial balanced FFE acquisition.

A shortcoming of current coronary MRA methods with thin-slab 3D acquisitions is the time-consuming examination necessitated by extensive scout scanning and precise slice planning. To improve ease of use and cover larger parts of the anatomy, it appears desirable to image the entire heart with high spatial resolution instead. For this purpose, an isotropic 3D-radial acquisition was employed in this study. This method allows undersampling of k-space in all three spatial dimensions, and its insensitivity to motion enables extended acquisitions per cardiac cycle. We present initial phantom and in vivo results obtained in volunteers that demonstrate large volume coverage with high isotropic spatial resolution. We were able to visualize all major parts of the coronary arteries retrospectively from the volume data set without compromising the image quality. The scan time ranged from 10 to 14 min during free breathing at a heart rate of 60 bpm, which is comparable to that of a thin-slab protocol comprising multiple scans for each coronary artery.

Artifacts↗

PubMed2001

Projection reconstruction balanced fast field echo for interactive real-time cardiac imaging.

A balanced fast field echo (FFE) sequence (also referred to as true fast imaging with steady precession (true FISP)), based on projection reconstruction (PR) is evaluated in combination with real-time reconstruction and interactive scanning capabilities for cardiac function studies. Cardiac image sequences obtained with the balanced PR-FFE method are compared with images obtained with a spin-warp (2D Fourier transform (2DFT)) technique. In particular, the representation of motion artifacts in both techniques is investigated. Balanced PR-FFE provides a similar contrast to spin-warp-related techniques, but is less sensitive to motion artifacts. The use of angular undersampling within balanced PR-FFE is examined as a means to increase temporal resolution while causing only minor artifacts. Furthermore, a modification of the profile order allows the reconstruction of PR images at different spatial and temporal resolution levels from the same data. This study shows that balanced PR-FFE is a robust tool for cardiac function studies.

Artifacts↗

PubMed2001

[Control of low Legionella concentrations in pool water].

The Legionella proof is necessary in pool water according to DIN 19 643 in case of possible aerosol formation. In lab tests it was proven that the direct spatulation of 1 ml water offers high-grade proof with high correlation of the determined concentration to the actual germ content. With very small germ concentrations, however, preceding filtration of larger sample volumes is necessary. During the investigation of routine samples a Legionella proof was possible thereby in individual cases, whereas direct spatulation remained negative.

Bacteriological Techniques↗

PubMed2000

Reversed spiral MR imaging.

Reversed spiral imaging is discussed as an approach that provides strong intrinsic T *(2) contrast without the need for long repetition times. In comparison to the conventional forward spiral method, the T *(2) contrast achieved by reversing the spiral k-space trajectory is similar and differs only for very fast relaxing species. The flow and motion sensitivity of the reversed approach is the same if flow compensation is applied, except for a flow-dependent voxel shift and the sign of the artifact pattern. By simulations as well as phantom and in vivo experiments, it is shown that the image quality in reversed spiral imaging is comparable to that obtained with the forward spiral method.

Blood Flow Velocity↗

PubMed1999

Real-time interactive magnetic resonance imaging with multiple coils for the assessment of left ventricular function.

Interactive real-time examination of left ventricular function in healthy volunteers both under rest and stress conditions has been performed. For this purpose, a system combining an interactive user interface, an ultrafast segmented echo-planar imaging sequence, and real-time reconstruction and display of the acquired images was designed. Magnetic resonance images were acquired at rates of up to 20 images per second with multiple receiver coils. By using a sliding window reconstruction technique, reconstruction rates of up to 60 images per second were achieved with a latency of < 100 msec. The quality of the real-time images was evaluated both qualitatively and quantitatively and was found to be appropriate for the determination of left ventricular function. It is concluded that the combination of dedicated components provides a convenient modality for the high-quality visualization of left ventricular function under rest and stress conditions at video frame rates with magnetic resonance imaging. J. Magn. Reson. Imaging 1999;10:826-832.

Echo-Planar Imaging↗

PubMed1999

Resampling of data between arbitrary grids using convolution interpolation.

For certain medical applications resampling of data is required. In magnetic resonance tomography (MRT) or computer tomography (CT), e.g., data may be sampled on nonrectilinear grids in the Fourier domain. For the image reconstruction a convolution-interpolation algorithm, often called gridding, can be applied for resampling of the data onto a rectilinear grid. Resampling of data from a rectilinear onto a nonrectilinear grid are needed, e.g., if projections of a given rectilinear data set are to be obtained. In this paper we introduce the application of the convolution interpolation for resampling of data from one arbitrary grid onto another. The basic algorithm can be split into two steps. First, the data are resampled from the arbitrary input grid onto a rectilinear grid and second, the rectilinear data is resampled onto the arbitrary output grid. Furthermore, we like to introduce a new technique to derive the sampling density function needed for the first step of our algorithm. For fast, sampling-pattern-independent determination of the sampling density function the Voronoi diagram of the sample distribution is calculated. The volume of the Voronoi cell around each sample is used as a measure for the sampling density. It is shown that the introduced resampling technique allows fast resampling of data between arbitrary grids. Furthermore, it is shown that the suggested approach to derive the sampling density function is suitable even for arbitrary sampling patterns. Examples are given in which the proposed technique has been applied for the reconstruction of data acquired along spiral, radial, and arbitrary trajectories and for the fast calculation of projections of a given rectilinearly sampled image.

Algorithms↗

PubMed1999

Multiple-dose pharmacokinetics, safety, and tolerability of bosentan, an endothelin receptor antagonist, in healthy male volunteers.

The multiple-dose pharmacokinetics, safety, and tolerability of oral bosentan, a selective endothelin receptor antagonist, were investigated in healthy male volunteers. In study A, an ascending-dose, double-blind, placebo-controlled trial, doses of 100, 200, 500, and 1000 mg bosentan or placebo were given once daily for 8 days as tablets (100 and 500 mg dose strength). In study B, a double-blind, placebo-controlled trial, 500 mg tablets of bosentan or placebo tablets were given once daily for 8 days with two additional single intravenous dose administrations of 250 mg bosentan 48 hours before the first and 24 hours after the last oral dose. The drug was very well tolerated. No effects on pulse rate, ECGs, or clinical laboratory tests were observed. Marginal effects on blood pressure were seen in subjects only when standing. The oral bioavailability of bosentan was 43% to 48%, with a small interindividual variability of 20%. Doses above 500 mg did not lead to significant further increases in plasma levels of bosentan. From the first to the last day of the oral treatment phase, plasma concentrations of bosentan decreased by 30% to 40% due to a 2-fold increase in plasma clearance. Absorption and plasma protein binding did not change. The 24-hour urinary excretion of 6 beta-hydroxycortisol was increased in parallel by approximately 1.7-fold, indicating induction of cytochrome P450 3A isozymes. The two metabolites of bosentan reached plasma concentrations well below those of bosentan and will most likely not contribute to the pharmacological activity.

Administration, Oral↗

PubMed1997

Absorption of tretinoin in rats and rabbits following oral and dermal application.

To assess the teratogenic potential of Airol cream (0.05% tretinoin, CAS 302-79-4), plasma concentrations were compared after repeated dermal applications of the maximum dose which could be applied reliably and after oral administration of the highest non-teratogenic dose. The test preparation was applied dermally in two equal portions to rats and rabbits at 2 g/animal/d (equivalent to a tretinoin dose of 3.7 mg/kg/d) and at 6 g/kg/d (equivalent to 3 mg tretinoin/kg/d), respectively. After a single oral administration of 2 mg/kg, Cmax and AUC for tretinoin in rat plasma were 285 +/- 14.6 ng/ml and 595 +/- 123 ng h/ml, respectively. Corresponding values for the rabbit were 78.4 +/- 16.9 ng/ml and 126 +/- 25.4 ng h/ml. In both species, plasma concentrations of tretinoin after dermal application were consistently below the assay quantification limit (< 5 ng/ml and < 2 ng/ml for rat and rabbit, respectively), despite marked irritation of the skin. Thus repeated topical application of the test preparation produced plasma concentration of tretinoin which were well below the plasma concentrations produced by a non-teratogenic oral dose of 2 mg/kg in the rat and rabbit.

Administration, Oral↗

PubMed1995

Review of limited systemic absorption of orlistat, a lipase inhibitor, in healthy human volunteers.

Orlistat, a lipase inhibitor, acts locally in the gastrointestinal tract. Systemic absorption is not required for its efficacy, but knowledge of the extent of its systemic absorption is important for its safe use in obese patients, the intended target population. Pharmacokinetic screening was carried out by monitoring plasma concentrations of unchanged orlistat in 25 phase 1 studies (including two mass balance studies) in normal and obese healthy volunteers. The results of these studies indicate an extremely low degree of systemic absorption for orlistat when administered with a hypocaloric, well-balanced diet with 20% to 30% of calories derived from fat (50-80 gm). To further characterize the pharmacokinetics and excretion pathways of orlistat, two mass balance studies using 14C-labeled orlistat were conducted. After oral dosing of radiolabeled orlistat with a fatty meal (28-30 gm fat), almost the entire dose was recovered from fecal samples; little was found in plasma and urine. It is concluded that systemic absorption of orlistat is negligible; at a clinically efficacious dose level, orlistat is unlikely to produce systemic lipase inhibition.

Clinical Trials, Phase I as Topic↗

PubMed1995

Chemical stability, biological activity and cellular uptake of a cisplatin analogue having a 1,2-diarylethyleneamine ligand in cultures of human breast cancer cells.

The platinum(II) complex PtCl2(meso-6), which has the estrogenic ligand meso-1,2-bis(2,6-dichloro-4- hydroxyphenyl)ethylenediamine (meso-6), has been reported to be an effective antitumor drug for estrogen-receptor(ER)-positive tumors in animal experiments. The goal of this study was to investigate whether the observed biological effects could be ascribed to the intact PtCl2(meso-6). Cultures of the ER-positive human breast cancer cell line MCF-7 were used as the in vitro test system. In culture medium containing 10% fetal calf serum, PtCl2(meso-6) had a half-life of about 2 h, as determined by HPLC analysis, and no PtCl2(meso-6) was detectable after 10 h. The Pt complex bound irreversibly to serum protein. After 30 min, the diamine ligand was found released, with a maximum conversion of about 35% at 24 h. At this time the culture medium still had estrogenic activity, i.e. it induced ER processing in the MCF-7 cells. This indicates that the estrogenic effect was elicited by the released diamine ligand. In contrast, the growth-inhibitory activity of the medium preincubated with PtCl2(meso-6) was lost at a rate similar to the rate of loss of PtCl2(meso-6) from the medium. This accords with the platinum complex being the main cytotoxic entity. When MCF-7 cells were incubated with PtCl2([3H]meso-6), no free Pt complex could be identified in cellular extracts, and most of the cell-associated radioactivity coeluted with meso-6 in HPLC analysis. After 12 h, only 1.4% of the total cellular platinum was bound to DNA, but no tritium label could be detected. In conclusion, diamine ligand is released from the Pt(II) complex and can account for the estrogenic effects so far ascribed to PtCl2(meso-6).

Antineoplastic Agents↗

PubMed1995

Neonatal lensectomy and intraocular lens implantation: effects in rhesus monkeys.

PURPOSE: To compare the effects of a lensectomy with and without intraocular lens (IOL) implantation on a neonatal rhesus monkey eye. METHODS: A lensectomy and anterior vitrectomy was performed on 75 monkeys during the first 16 days of life; 21 of these monkeys also had an IOL implanted into the posterior chamber. The eyes were examined at regular intervals using biomicroscopy, applanation tonometry, and ophthalmoscopy. RESULTS: The pseudophakic monkeys were studied until they were 92.5 +/- 5.8 weeks of age and the aphakic monkeys until they were 80.4 +/- 5.7 weeks of age. Pupillary membranes (100% versus 55.5%; P < 0.01) and lens regeneration into the pupillary aperture (28.6% versus 5.6%; P = 0.02) occurred more often in the pseudophakic than the aphakic eyes. As a result, the pseudophakic eyes required more reoperations than the aphakic eyes to keep the visual axis clear (P < 0.01). There was not a significant difference in the incidence of ocular hypertension between the pseudophakic and aphakic eyes (9.5% versus 12.7%; P = 0.34). Pupillary capture of the IOL optic occurred in 52% and haptic breakage in 33% of the pseudophakic eyes. All of the eyes with broken haptics had a prominent Soemmerring's ring varying in maximum thickness from 0.6 to 2 mm. Nine of the haptics from the seven eyes with broken IOLs had eroded into the iris, two into the ciliary body, and one into the anterior chamber. CONCLUSIONS: Implanting an IOL into a neonatal monkey eye after a lensectomy and anterior vitrectomy increases the likelihood of a reoperation being necessary. Haptics frequently erode into the iris and ciliary body and may break because of stress placed on the optic-haptic junction by forward movement of the IOL.

Animals↗

PubMed1991

Cimetidine alters the disposition kinetics of the monoamine oxidase-A inhibitor moclobemide.

The influence of cimetidine on the absorption and disposition of moclobemide was examined in eight healthy male subjects. A single 100 mg intravenous and 100 mg oral dose of moclobemide was administered before and after 2 weeks of cimetidine administration (200 mg five times a day). The data on intravenous administration indicated that cimetidine produced a statistically significant alteration in the following disposition parameters (mean values for control versus cimetidine): systemic clearance, 46.6 versus 28.3 L/hr; mean residence time, 2.1 versus 3.2 hours; elimination half-life, 1.6 versus 2.3 hours. There was no significant difference in the steady-state volume of distribution. The absolute oral bioavailability of moclobemide increased significantly after cimetidine administration (54% versus 68%), as did the maximum plasma concentration after a single oral dose (575 versus 787 ng/ml). There were no differences in the mean absorption time or time to achieve maximum concentration. The values of systemic and apparent oral clearances of moclobemide after cimetidine administration were directly related to the corresponding control values before cimetidine. In contrast, the percentage change in clearance was essentially independent of the corresponding initial control clearance value.

Adult↗

PubMed1990

Determination of the new fluoroquinolone fleroxacin and its N-demethyl and N-oxide metabolites in plasma and urine by high-performance liquid chromatography with fluorescence detection.

A high-performance liquid chromatographic method is described for the determination of the new fluoroquinolone fleroxacin and its metabolites in plasma and urine. Plasma samples are deproteinized with acetonitrile, and, after evaporation and reconstitution of the supernatant, samples are analysed on a reversed-phase column. The limit of quantification is 10-20 ng/ml for the parent drug and 10 ng/ml for the metabolites, using a 0.2-ml sample. Urine samples are diluted with the mobile phase. An aliquot is then injected directly onto the column. The limits of quantification are 1 micrograms/ml for the parent drug and 0.5 micrograms/ml for the metabolites, using a 0.1-ml sample. The method has been successfully applied to pharmacokinetic studies of human volunteers and patients.

Anti-Infective Agents↗

PubMed1990

[Birth weight of newborn infants in relation to body height and body weight of parents with special reference to duration of pregnancy].

Using the data of the 1985 GDR somatogram standards (birthweight percentiles calculated from 51,570 liveborn singletons) the impact of parental weight and length on the birthweight were calculated. Peristatic factors in combination with the genetic 'anlage' act first of all via maternal weight. Body height and/or length of mother and father are more representative for the genetic constitution. Their impact on neonatal weight seems to be less significant, however statistically calculable. The paternal 'anlage' is relatively modified by the intrauterine environment (maternal constitution).

Birth Weight↗

PubMed1990

[Neonatal percentile values for the GDR--1985. Correlation of body weight and length in newborn infants (calculation of birth weight/body length in cm. with reference to gestational age)].

Taking account of the gestational age (28th to 42nd completed week of pregnancy) the sex-related ratio of birth weight to length (g/cm) for newborn infants is reported. This shows that observation of the correlation between birth weight and length with reference to gestational age makes a more accurate classification of newborn infants possible, rather than using a two dimensional classification (birth weight week of gestation).

Birth Weight↗

PubMed1989

[Immunosuppressive and cytostatic effectiveness of the poplar mushroom Tricholoma populinum LANGE].

Dry powders or extracts of the fruit bodies of Tricholoma populinum given per as or injected intraperitoneally respectively caused a suppression of the number of plaque forming cells of mice as shown by the hemolysis-plaque-assay. Extracts of the fungi inhibited above that the incorporation of 3H-thymidine into mitogen-stimulated human lymphocytes as observed in the lymphocyte transformation test and retarded the proliferation of cultivated bovine aortic endothelial cells.

Animals↗

PubMed1989

[Pregnancy in adolescence--psychosocial development of young mothers and their children].

Hitherto existing concepts on circumstances favouring pregnancies in adolescents have mainly focussed attention on physically precocious maturity, on social risks and on the type of personality of the pregnant adolescents. Based on our material this opinion seems to be in need of correction. Changing of the validity of these factors may be suggested due to psychosocial conditions in connection with both the acceleration of maturity and a new estimation of sexuality including heterosexual development at earlier stages of life. Children from 100 juvenile mothers were clinically and psychologically investigated at the age of 7 years. Neither serious social problems in the children nor considerable deviations of mean average of the physical, mental or social age specific standards could be observed.

Adolescent↗