[en] Short communication

[en] A fit programme tested in the practice of reactor dynamics, how-ever applicable in general, is described. The parametrization is performed for either damped or undamped sinusoidal oscillations, which are present as a data table in form of distinct data. There-by it concerns, e.g. time-dependent state variables of reactor physics like neutron flux, power density, or xenon concentration in the reactor core. The parameters F₀, b, T, t₀, and anti F of the function F(t) = F₀ x exp ((b(t-t₀)) x sin ((t-t₀) x 2π/T) + anti F are computed iteratively of the data given distinctly by application of the method of the minimum least squares. An analogous algorithm and a subroutine written in PL/1 are introduced. The following properties of the programme are particularly useful for application: 1) The time-range for parametrization of a curve table is at all selectable. 2) The programme permeates an independent calculation of the starting data for the iteration. 3) An error analysis is performed after the successfully ended iteration. (orig.)

No abstract available

[en] Short communication

No abstract available

[en] Some methods for three-dimensional optimization in intracavitary radiation treatment are described. Radiobiological and clinical experience demonstrates the necessity of optimization in the clinical use of sealed radioactive sources

No abstract available

[en] According to preliminary experiences and the literature presently available, the intracavitary short-term treatment with high dose performances of gynaecologic tumours might be of the same value as long-term treatment with radium and low dose performances as far as healing success is concerned. The problems of a comparative investigation are referred to. The disadvantage of the short-term treatment might be the narrow margin of the dosage which necessitates a much exacter dosing of the application. The latter can be achieved very rationally by using modern optimization techniques. The long-term therapy can be improved by applying artificial radionuclides by afterloading technique (already realised) and by optimization. (orig.)

[en] With HDR (high dose rate) afterloading treatment, a very critical dependence of normal tissue reaction (rate of side effects of organs at risk) on dosage was demonstrated compared with the effect of low dose rate application. Furthermore, a stronger dependence of normal tissue reaction (steeper curves) on application of a single HDR afterloading fraction compared with that on total dose application over several weeks was observed. All these observations require exact dosage of HDR afterloading application to all points of organs at risk concerned in order to compensate the radiobiologically critical dosage of HDR. On the other hand, a threshold of 7 to 7.5 Gy per single fraction at organs at risk should not be exceeded. Therefore, HDR afterloading treatment requires optimization of source arrangement or source movement in order to receive good results. Since 1976, computer optimization of the movement of a highly active Ir-192 source is used, since 1987, an IBM PC AT is used for this calculation. The computer optimization programme, its data output and isodose calculation parts, is briefly discussed. 3 refs.; 5 figs

[en] In this study a system of dose measurement and dosage in the interstitial therapy is proposed. The radioactivity needed for the individual patient can be calculated by means of a simple formula. The author discusses rules for the distribution of the sources, clinical priciples and the possibility of a combination with the external deep therapy. (orig)