[Dosis-performace-effects on the pluripotent hematopoietic stem cell. Results of partial body irradiation using 8MeV-x rays].

It was the aim of this study of document the influence of various dose rates on the CFU'S compartment. The information obtained should serve as a guideline to the design of radiotherapeutic programs with less hemopoietic toxicity in clinical radiation therapy. CBA mice were subjected to partial body X-ray irradiation from a linear accelerator (8MeV). The effect of dose rates of 6,70, 520 and 2800 R/min on CFU'S were studied in the irradiated and shielded marrow immediately after irradiation and 5,24 resp. 48 hours, 1 week and 3 weeks later. The following conclusions can be made: The reduction of CFU'S is significantly greater for low dose rates. After a dose of 150 R CFU'S reach normal values at 2 weeks, after 300 R at 3 weeks. With 450 R they are still subnormal at 3 weeks. A rebound phenomenon with increased CFU'S is seen at 3 weeks with 150 R and 300 R. An increase of CFU'S in shielded marrow is seen immediately after irradation. This increase is not dependent on the dose rate. The clinical implications of these findings are discussed.