Does the limiting F value at very low doses depend systematically on linear energy transfer?

Schmid, E,, Braselmann, H, and Bauchinger, M, Does the Limiting F Value at Very Low Doses Depend Systematically on Linear Energy Transfer? Radiat. Res . 152, 563-566 (1999), The debate on the validity of the ratios of radiation-induced yields of chr omosome aberrations, in particular the F value (dicentrics/ring chromosomes ), as a chromosomal fingerprint of radiation quality is still in progress, From a recent analysis of their experimental data, Sasaki et al. (Radiat, R es. 150, 253-258, 1998) noted that despite a considerable variability in th e data, the limiting F value at the lowest doses, or the F-0 value, obvious ly decreased with increasing LET, indicating that the LET could be a factor that determines the F value. We have reassessed here our own 13 cytogeneti c data sets that cover a range of dose-averaged LET of 0.5 to 150 keV/mu m in terms of this F-0-value approach, but we could not confirm such a depend ence on LET at very low doses. The validity of the F value as a biomarker t herefore remains questionable. For a final evaluation, scoring of a far gre ater number of cells at low doses would be necessary to reduce the large er ror ranges of F values, (C) 1999 by Radiation Research Society.