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Biomedical subjects

W W Seelentag

Publications and source records attributed to W W Seelentag.

12 recordsLinked to original sources
PubMed1985

131-Iodine capsules in thyroid therapy: an individually controlled study of their uptake kinetics as compared to liquid 131-iodine.

We investigated the uptake of therapeutic doses of 131-Iodine in capsular form which were given to 16 patients with benign thyroid disease, and compared it to the uptake of a diagnostic dose of liquid 131-Iodine given to the same patients. The aim of this study was to determine the additional radiation dose sustained by the gastric mucosa, and thus, to establish the safety of this galenic form of 131I. It was found that the average capsule-dissolution time was about 12 min, with a large standard deviation of about 7 min. Using these data and a theoretical radiation-dose calculation, we estimated that the maximum dose to the gastric mucosa was approximately 250 rad (250 cGy) for a therapeutic activity of 5 mCi (185 MBq), which is the maximum dose which may be given as single application to out-patients in Switzerland. Thus, 131I administered in capsular form is a safe galenic form for therapeutic use in patients with thyroid disease.

Adenoma↗
PubMed1979

Stripping of X-ray bremsstrahlung spectra up to 300 kVp on a desk type computer.

The direct result of a spectrometric measurement is a pulse height distribution. In the energy region up to 300 keV three corrections in particular need to be applied to get the photon spectrum: corrections for K-escape, Compton scattering and inefficient photon absorption. A simple 'stripping' procedure is described which may be implemented on a desk type computer. All data necessary are either available in the literature or may be derived from the measurement of very heavily filtered X-ray spectra. The accuracy of the procedure is better than +/- 5% of the peak value. Results are compared with a more detailed stripping procedure, based on Monte Carlo calculated data.

Computers↗
PubMed1978

[Developments in ionography (author's transl)].

Common aspects and differences of xeroradiography and ionography are reviewed briefly. Tendencies connected with latent image formation in ionography, and the development of electrostatic latent images are set out. Apart from gaseous absorbers, liquid or solid absorbers may be employed for latent image formation. A sensitivity increase in gaseous inography may be achieved by charge amplification, although with reduced resolution. As an alternative to aerosol and liquid development methods based on the distortion of deformable layers are described. A procedure yielding multiple copies with different image characteristics (edge contrast) via copies of the latent image is outlined. Finally possible closed ionography systems are mentioned which are necessary for real time imaging.

Humans↗
PubMedDate not supplied

Saturation curve in gases of high atomic number at pressures up to 8 atm. I. Krypton and xenon.

The saturation curve has been studied in xenon and in krypton up to a pressure of 8 atm. An empirical formula has been found that describes the fraction of current collected over a wide range of voltages, pressures, ionization intensities, and electrode spacings. This is of practical value in the design of ionography chambers. For krypton the collection fraction fKr = (1 + 0.25eta-1.74)-1, and for xenon fXe = (1 + 0.16eta-1.88)-1, where eta = Fp-0.7Vd-2q-1/2 with F = 3.61 X 10(-7) and 2.50 X 10(-7) for krypton and xenon, respectively. The ranges of the variables covered in the experiments were p = 1-8 atm, V = 5-25000 V, d = 0.3-1.3 cm, and q = 4 X 10(-9)-6 X 10(-8) A/cm3.

Atmospheric Pressure↗
PubMedDate not supplied

Saturation curve in gases of high atomic number at pressures up to 8 atm. Part II: Freon 13-B1, and mixtures of Freon with xenon and krypton.

The saturation curve has been studied in Freon 13-B1 (CF3Br) and in mixtures of Freon with xenon and krypton up to a pressure of 8 atm. The enhanced initial recombination due to the electron affinity of Freon has been evaluated and an empirical formula constructed that describes the fraction of current which escapes initial recombination over a wide range of voltages, pressures, and electrode spacings. After correction for this initial recombination, the general saturation curve for Freon and for mixtures of this gas with krypton and xenon has been derived and, again, convenient empirical formulae established which allow the current collection efficiency to be calculated for any given parameters within the range investigated. These formulae are of practical value in the design of image-forming ionization chambers.

Chlorofluorocarbons, Methane↗