PubMed Health⌕ Search

Biomedical subjects

G Hagemann

Publications and source records attributed to G Hagemann.

At least 19 recordsLinked to original sources
PubMed1992

[Dose requirements for projection techniques in x-ray diagnosis].

The dose required in x-ray diagnosis depends upon the demands made on a diagnostically optimal x-ray film or in fluoroscopy, and upon the technical quality of the equipment. The actual dose requirement, derived from field studies, is juxtaposed on the basis of representative examples with the maximum permissible dose requirement in accordance with the prescribed minimum sensitivity values of the x-ray film. The ideal dose requirement has been stated by Cohen et al. (1981) by a formula basing on parallel beam, maximum quantum yield and Bucky grid effect depending on the signal to noise ratio and object contrast. This was checked by means of contrast detail diagrams measured at the hole phantom, and was additionally compared with measurement results obtained by Wust et al. (1989) with acrylic glass phantoms. The optimal dose requirement is obtained by the maximum technically possible approach to the ideal requirement level. Examples are given, besides for x-ray equipment with Gd2 O2 S screen film systems for grid screen mammography, and new thoracic examination systems for mass screenings. Finally, a few values concerning the dose requirement or the analogous time required for fluorescent screening in angiography and interventional radiology, are stated, as well as for dentistry and paediatric x-ray diagnostics.

Angiography↗
PubMed1991

[Digital radiography: optimization of chest radiographs using a modified exposure control].

Phototiming over the lung fields frequently compromises the signal-to-noise ratio available in the mediastinal and diaphragmatic regions of the chest. A moderate dose increase would be justified if a significant improvement in diagnostic performance could be achieved. We compared the impact of mediastinal phototiming (150 kVp, 150 cm FFD, 1.0 mm focus, 12:1 grid [higher kVp chosen to minimize dose increase]) to standard lungfield phototiming (125 kVp, 150 cm FFD, 1.0 mm focus, 12:1 grid) on the detectability of simulated pulmonary nodules (wax, 0.5-2.5 cm in diameter) superimposed on human volunteers in storage phosphor radiographs (1744 x 2144 pixels, 10 bit). ROC analysis of 1920 observations by 8 readers showed a significantly higher (p less than 0.03) detectability of simulated pulmonary nodules with mediastinal phototiming (ROC area = 0.89) than standard lungfield phototiming (ROC area = 0.84).

Humans↗
PubMed1991

[Comparative studies of the standardization of erysipeloid immune sera "Dessau" from swine using the mouse-protection test and ELISA].

Different serological methods were used in determining the valence of red murrain immune sera. By using a grow test it is possible to accomplish an immunological differentiation of the immune sera. The used ELISA was tested in comparison to the conventional mouse protective test (PRIGGE, 1950) with regard to its valuation of immune sera. Both procedures have been tested on a possible correlation. In almost all cases a correlation between high titres in ELISA and a mouse protective value over 100 I.E. could be proven. The statistical processing of the test results proved an assumed correlation of both procedures. But it is necessary to carry out further research in order to be able to recommend this procedure as an alternative for the mouse protection test.

Animals↗
PubMed1990

[Minimum resolution at a given dose for quality assurance of x-ray pictures].

The Federal German Board of Physicians ("Bundesärztekammer") has recently issued guide principles for quality assurance in x-ray diagnosis. These include the basic measurements defining important image details, sensitivity of screen-film combinations and exposure times. The conditions required for meeting the guide principles were tested, using low contrast grids for simulating tissues. Practical consequences from these measurements for radiographic techniques and for the use of test grids in quality assurance are detailed.

Germany, West↗
PubMed1990

Time courses of lidocaine effects on sodium membrane currents in small and large neurons.

Time courses of effects of lidocaine on sodium currents and sodium dependent action potentials were studied in somata of small and large neurons. Cultured rat sensory spinal ganglion cells (diameter: 30 microns) and neurons of the buccal ganglion of Helix pomatia (diameter: 150 microns) served as the test cells. The latency of the suppressive action of lidocaine was the longer the larger the of the cells was. Maximal blocking effects occurred within 10 min in sensory spinal ganglion cells and within 40 min in snail neurons. Model calculations based on the assumptions (i) that lidocaine is distributed in the extra- and intracellular space by simple diffusion and (ii) that the drug concentration at the outer surface of the cells is elevated stepwisely, revealed a strong dependency of intracellular concentration changes on the size of the cells. From these findings it is concluded that lidocaine blocks sodium channels primarily from the intracellular side.

Action Potentials↗
PubMed1989

[Detection of Erysipelothrix rhusiopathiae specific antibodies in the serum of experimentally-infected swine by ELISA and immunoblotting].

In an attempt to characterize the immuno response of the animal organism to experimental infection, ELISA and immunoblotting were used to test the antibody levels of erysipelas hyperimmune sera (HIS) which had been induced by Erysipelothrix rhusiopathiae. Also, 5 pigs were accidentally chosen to check on individual curves of antibody formation, following periodical inoculation up to HIS collection. All HIS verified and confirmed by the mouse protective test responded by high titres. Yet, the results so far obtained from HIS titration have failed to be conclusive as to valency. The animals selected for these experiments exhibited differentiated antibody levels during the phase of immunisation, although they were at one and the same level, when measured by the final titre, following last boostering. The desired rise in antibody levels was achieved only by the 4th to 9th boostering in almost all cases. Extinction values determined by ELISA were confirmed or supplemented by the results obtained from immunoblotting.

Animals↗
PubMed1985

[Image quality assurance in x-ray diagnostic units. Information on DIN 6868 standard series].

The Working Group for Standardisation justifies and comments on the establishment of a standard series for image quality assurance in X-ray diagnostic services (DIN 6868). In order to promote compliance with these standards, the users are given some background information on the structure of the standard series and on the recommended procedures to be followed. The definitions for the various hierarchically arranged tests, such as constancy test, status test, acceptance test as well as a definition for the term "base-line image quality" are explained.

Germany, West↗
PubMed1978

[New intensifying screens in clinical radiology III: Screen-film combinations in mammography (author's transl)].

An industrial film was compared with four commercially available screen-film combinations with respect to dose, definition and signal to noise ratio. The demanded minimum resolving power requires definition of an object of 100 micrometer size. However, the defined minimum object sizes are approx. 180 micrometer with close-distance projection and approx. 240 micrometer with greater distance. In this study, therefore, the signal to noise ratios were measured at defined object sizes of 5 lp/mm and 2 lp/mm. The screen-film combinations have approximately the same values as the industrial film for a size of 250 micrometer (2 lp/mm) or are definitely higher. The signal to noise ratio of the Alpha M combination is superior by 50%, although the sensitivity of the combination is 4 to 6 times greater. The signal to noise ratio of the MinR system in 25% higher than that of the industrial film, the required dose being lower by a factor of 8. This results in skin doses of 0.7 rads instead of 6 rads with tissue layers of 4.8 cm thickness.

Female↗
PubMed1977

[The effect of bleomycin, ICRF 159 and of simultaneous X-ray application on CHO-fibroblasts].

The cell damage of the cytostatics Bleomycin and ICRF 159 were studied experimentally by the use of the following parameters: colony survival, colony-size-spectrometry and multiplicity of CHO-Fibroblasts. Series of increasing drug concentrations and simultaneous irradiation with 200 rds were measured. In the above mentioned tests an additive and no potentiating effect of damage by the cytostatics in combination with irradiation of 200 rds was found. Compared with Bleomycin, ICRF 159 showed a higher degree of damage to CHO-Fibroblasts.

Animals↗
PubMed1976

[Clinical and hemodynamic aspects of myocardial diseases (author's transl)].

Definition, arrangement into primary and secondary forms and classification of myocardial diseases are used irregularly in the literature. The great variety of clinical and hemodynamic parameters are shown with reference to our own patients and an attempt is made to arrange them in individual types. Followup examinations show that signs of congestive failure, heart size and other clinical and hemodynamic parameters may be considerably altered. For this reason it is proposed to describe myocardial diseases accoridng to clinical and hemodynamic parameters in order to obtain a closer insight into the pathomechanism of these diseases.

Cardiomegaly↗