[Radiation therapy in two cats with pituitary tumors]. / Strahlentherapie bei zwei Katzen mit Hypophysentumoren.

Two cats with large pituitary neoplasms (adenoma and adenocarcinoma) were treated with fractionated radiation therapy. Total doses of 40 Gy, respectively 36 Gy, were applied in 10 fractions of 4 Gy, and 3.6 Gy respectively. Side effects were minimal and transient. Anesthesia was well tolerated. Improvement of clinical signs could be observed during radiation therapy in both cats. One cat had a complete, the other a partial tumor response. One cat (suspicion of adenoma) was euthanized 1 3/4 years after therapy due to unrelated disease. No tumor was found on histopathology, however a small focal necrosis of brain tissue in the irradiated field was observed. The second animal with a pituitary adenocarcinoma was euthanized because of tumor recurrence 1 1/2 years after therapy. Radiation therapy was effective, despite the low total doses of radiation applied.

Some notions and units in radioepidemiology and radiation protection. A structured list for the epidemiologist.

An annotated list of some notions and units used in radioepidemiology is presented, with special emphasis on differentiating between the realms of radiation physics, radiation biology, radioepidemiology and radiation protection.

[Are additional filters made of niobium superior to the copper filter in dental radiology?]. / Sind Zusatzfilter aus Niobium in der zahnärztlichen Radiologie dem Kupferfilter uberlegen?

At a dental X-ray unit the effect of an additional filter made of niobium has been tested in the molar region of the mandible with respect to dose reduction. It has been compared against the effect of an additional filter made of copper. With regard to the same dose at the film, radiation dose at the surface of the patient proved to be slightly more reduced after application of the copper filter than after application of the niobium filter. Radiographs have been made by exposure of intraoral dental films (Kodak film Ultra Speed D) together with a hydroxyapatite step-wedge. Measurements of optical density resulted in the same values after application of the copper filter and the niobium filter, respectively. Reduced image contrast due to application of one of these additional filters proved to be helpful. In short, an additional copper filter placed in the X-ray beam shows identical or better results when compared against an additional filter made of niobium.

Effect of negative pions, relative to 140 kV -- 29 MeV photons and 20 MeV electrons, on proliferation of Ehrlich ascites carcinoma cells.

The effect of negative pions (peak and plateau), photons (140 kV and 29 MeV), and 20 MeV electrons on the proliferative capacity of Ehrlich ascites carcinoma cells was investigated. Proliferative survival curves plotted for the modalities employed are presented. Under the experimental conditions used, the peak pions were more effective than plateau pions by a factor of about 1.4. For 50% survival, 140 kV X-rays had the same effect as peak pions but the latter was more effective (factor 1.2) at 10% survival level. When 140 kV X-rays were taken as the standard, following are the RBE values calculated as 50% survival level: plateau pions --0.73; peak pions --about 1.0; 29 MeV photons --0.73 and 20 MeV electrons --0.6. The results obtained are compared with those reported on other tumor systems and biological test objects.

Chromatid breaks induced in Chinese hamster cells by low doses (12--100 rad) of pi--mesons.

Monolayer cultures of the fibroblast-like Chinese hamster cell-line 19/1 were irradiated in the G2-phase of the cell cycle by pi--mesons (6 rad/min peak-pion dose rate). Frequencies of induced single- and isochromatid breaks, acentric fragments and interchanges were compared with data obtained from 140 kV X-rays. The RBE-values were for the pion dose peak between 0.8--1.2 and for the pion dose plateau 0.5--0.9. Whereas for single chromatid breaks there was no significant difference between X-rays and peak pions for identical physical doses, the isochromatid breaks alone showed a significantly higher frequency for 100 rad peak pions.

Preclinical radiobiology with pions: RBE--values for mouse skin damage as a function of single doses of pions.

The macroscopic reaction of the mouse skin was used to derive RBE values for negative pi-Mesons. Hind limbs of mice were irradiated with pions or X-rays. The pions were produced by the 590 MeV accelerator of the Schweizerisches Institut für Nuklearforschung (SIN). Early reaction was assessed over a period of 6--30 days after irradiation with single doses (20--45 Gy). The radiation damage was scored using an arbitrary scale of effect. The time pattern of development of the skin reaction and the subsequent healing after exposure both to pions and X-rays were similar, indicating that depletion and repopulation of the basal cells of the skin were comparable, both after pions and X-rays. RBE values as a function of pion doses at the peak (dose maximum), plateau and at the postpeak (12 mm downstream of the dose maximum) were computed with nonparametric statistical methods. The RBE at the peak and at the plateau relative to X-rays of the same dose rate was 1.15--1.25 and 0.85, respectively. The RBE of peak pions manifested a marked dependence on dose, when plateau pions were chosen as reference radiation. In this experiment there was no significant difference in RBE between peak and postpeak. The importance of some experimental condition (dose rate, irradiation volume) is discussed.

Effect of negative pi mesons on vascular permeability of brain in neonatal rats.

Neonatal rats and their radiation-induced cerebral petechial hemorrhages were used as an experimental system for evaluating the effects of negative pions on healthy tissue and especially on the microvasculature. Dose response curves for peak and plateau pions (dose range 150--250 rad and 100--400 rad, respectively) were obtained and compared with those of 200 kV X-rays of corresponding dose rates. The RBE of the peak pions was 1.1, that of the plateau pions 0.6 resulting in a peak/plateau ratio of 1.8. Implications were made as to the importance of this favorable peak/plateau relationship since the response of the capillary endothelium to pion-irradiation might be one of the limiting factors in radiotherapy.