RBE of 10 kV X rays determined for the human mammary epithelial cell line MCF-12A.
The dependence of relative biological effectiveness (RBE) on photon energy is a topic of extensive discussions. The increasing amount of in vitro data in the low-energy region indicates this to be a complex dependence that is influenced by the end point and cell line studied. In the present investigation, the RBE of 10 kV X rays (W anode) was determined relative to 200 kV X rays (W anode, 0.5 mm copper filter) for cell survival in the dose range 1-10 Gy and for induction of micronuclei in the range 0.5-3.6 Gy for MCF-12A human mammary epithelial cells. The RBE for cell survival was found to increase with decreasing dose, being 1.21+/-0.03 at 10% survival. Considerably higher values were obtained for micronucleus induction, where the RBE(M) obtained from the ratio of the linear coefficients of the dose-effect curves was 2.6+/-0.4 for the fraction of binucleated cells with micronuclei and 4.1+/-1.0 for the number of micronuclei per binucleated cell. These values, together with our previous data, support a monotonic increase in RBE with decreasing photon energy down to the mean energy of 7.3 keV used in the present study.
Lehnert
Anna
A
Institute of Radiation Physics, Forschungszentrum Dresden-Rossendorf, Dresden, Germany. A.Lehnert@fz-rossendorf.de
Dörr
Wolfgang
W
Lessmann
Elisabeth
E
Pawelke
Jörg
J
D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D042361:Mammary Glands, Human / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects*; D048629:Micronuclei, Chromosome-Defective / Q000528:radiation effects*; D017785:Photons; D011829:Radiation Dosage; D012062:Relative Biological Effectiveness; D014965:X-Rays