Radiobiologia, radiotherapia最新文献

The effect of irradiation, metronidazole and iso-metronidazole on survival and number of tumor cells was analysed in vitro in mice that were inoculated with La-hemocytoblastosis--or Ehrlich-ascites-tumor cells after processing. It was shown that metronidazole and iso-metronidazole nearly have the same radiosensitizing activity on these conditions. The effect was dependent on concentration of compounds and cell type. With intraperitoneal application the iso-metronidazole was eliminated from Lewis-lung-carcinoma more slowly than from blood.

In a review of literature the presented studies on radiogenic liver injuries are summarized. Whereas in the past the liver tissue was supposed to be radioresistant nearly completely, to newer knowledge this organ has to be classed with most radiosensitive tissues at all. The early picture of a liver injury in man is characterized by the veno-occlusive syndrome. Like in Budd-Chiari-Syndrome a congestion begins in the central veins and the centrolobular sinusoids, that has severest threatening consequences for the patients with extensive liver irradiation. The clinic picture is demonstrated. At present no suitable animal model exists for this disease yet. The presented pathological and electron microscopical findings do not allow any final estimation of the pathogenesis in this disease. The radiogenic late-effects are manifested in the liver in a centrolobular fibrosis, also starting from the Glisson's triangles, with cirrhotic reconstruction of liver architecture. The great compensatory power of the organ does not cause clinical pictures to be effected in radiotherapeutic practice with only partial liver irradiation in most cases. The dose-time-relation of the radiogenic hepatitis shows a very little alpha-/beta-value. With this the liver renders as typical late-effect tissue and should be spared effectively by choice of small single doses.

In this paper some radioanalytical methods will be described for assessing the contents of various elements in the human body. In vivo methods are necessary for this problem. Protein content can be estimated by means of in vivo measurements of nitrogen, bone minerals by means of the total body content of calcium. Fat contains a high concentration of carbon. Carbon in fat can be estimated and from this the total body fat can be calculated. Toxic elements such as lead, cadmium and mercury are assessed by in vivo measurements, both related to occupationally exposed workers and to members of the public.

Six week old male Swiss albino mice taken from an inbred colony were irradiated with 0.6 and 1.2 Gy of low 60Co gamma rays in the presence (Experimental) and absence (Control) of MPG. Results indicated the infliction of radiation insult and subsequent repair in the testes to be dose dependent, that is higher the dose greater the damage and sluggish the reparative activity. A greater number of surviving germ cells in the experimental tests with fewer dead cells reflected the protective efficiency of the drug against radiation damage to the cell population. Thus MPG not only protects against radiation induced cell death and depletion but also changes the mitotic rate of the stem cells by which an accelerated recovery was brought about.

Adult healthy specimens of Channa punctatus (fish) were exposed to three doses (i.e. 2.25, 4.50 and 9.00 Gy) of gamma radiations from a 60Cobalt source. Five animals were autopsied at each post-irradiation intervals of 1, 2, 3, 7 and 14 days. The liver was fixed in Bouin's fluid and after processing in a routine way, it was examined histologically and compared with control group. The radio lesions appeared on day 2 in 2.25 Gy dose group and on day 1 in 4.50 and 9.00 Gy dose groups. Signs of recovery was seen on day 7 in 2.25 Gy dose group. Liver exhibited normal picture on day 14 in 2.25 and 4.50 dose group but in 9.00 dose group the lesions persisted. The radiation effects were found dose dependent.

Radiation induced changes in the crypts of jejunum were studied in adult Swiss albino mice exposed to 4.5 Gy, 9.0 Gy and 12.0 Gy of 60Co gamma rays. Two parameters--mitotic figures and pyknotic nuclei and necrotic cells were studied quantitatively to assess the radiation damage and subsequent recovery. Their number in the crypt section was counted at 6 hours, 1, 2, 4, 6, 8 and 14 days after irradiation. In all the three exposure groups the minimum value for mitotic figures was obtained on day 1 when the pyknotic nuclei and necrotic cells were highest. On day 2 partial recovery was seen in both the parameters studied and by day 8 in mice exposed to 4.5 Gy and by day 14 in mice exposed to 9.0 Gy and recovery was complete. However, in mice exposed to 12.0 Gy no mice survived till the last autopsy interval and the normal values were never attained.

Starting point for automatic adaptation of a dose distribution is a starting variant which parameters values are fixed as a matter of experience. On base of this starting variant a limited number of variants is produced and the "quality" of the attained dose distribution in each case is expressed by an added measure function value. A gradual improvement of adaptation of dose distribution to individual geometry of patients is done by pointed search of new parameter values for field breadths, field beginning points, field weights, and field insolation directions.

By means of computed tomography three dimensional compensators can be calculated as dose compensatory bodies for irradiation fields in radiotherapy. This is important especially for shell-type field irradiation and for bilateral total body irradiation. The dose homogeneity, attainable by compensators, is measured at a plexiglas phantom and represented and the use of compensators is described in practice.

In the present information results of clinical studies are represented to show the effectiveness of therapy with 6.3 MeV fast neutrons in 45 patients with superficial tumors in head and neck area. The reaction of tumor and of normal tissue was studied in dependence on different physical and biological factors. Two variants of neutron therapy planning were estimated by means of mathematical models of a factor of time-dose-fractionation for neutron (TDFN) from clinical point of view. Results of changes in oxygen-tension within the tumor are represented in 20 patients with metastases in cervical lymph-nodes during neutron therapy. The obtained data show a correlation of regression and reoxygenation rate of the tumor to its initial volume. The reaction of the tumor in therapy with fast neutrons was studied in dependence on its morphological structure. Complete regression of epidermoid and nonepidermoid cancer types was seen in 42 or 89% of the cases. With corrections for adipose tissue and the extent of dose fraction of fast neutrons the clinical test of the mathematical model of TDFN-factor made discernible that the reaction of normal tissue can be prognosticated quite exactly by means of this model in neutron therapy.