THE F-VALUE CANNOT BE RULED OUT AS A CHROMOSOMAL FINGERPRINT OF RADIATION QUALITY

The F value, the ratio of inter- to intrachromosomal interchanges, as a biomarker for densely ionizing radiation which was proposed by Brenn er and Sachs (Radiat. Res. 140, 134-142, 1994) has been a matter of re peated discussion. We examined our experimental data on radiation-indu ced chromosome aberrations in human peripheral blood lymphocytes for t he F value as measured by the ratio of dicentrics to centric rings. Be cause of the rarity of aberrations, the F value showed a considerable variability, with a large error range particularly in the low-dose ran ge of low-LET radiation. However, the data showed a general trend that the F value tended to be lower for high-LET than low-LET radiations. The differential F value was more pronounced at low doses and diminish ed with increasing dose; the F values of all radiations tended to conv erge toward a similar value at high doses. The limiting F value at the lowest doses, or the F, value, was dependent on LET for high-energy r adiations that can produce an array of DNA double-strand breaks along the track of the charged particle. However, LET and dose dependence we re not seen for the low-energy photons, where spatially uncorrelated r andom breaks were produced by independent photoabsorption events. (C) 1998 by Radiation Research Society.