LET dependence of yield ratios of radiation-induced intra- and interchromosomal aberrations in human lymphocytes.

PURPOSE: To investigate the LET dependence of various yield ratios of intra- and interchromosomal aberrations in order to quantify proximity effects for illegitimate rejoining of chromosome breaks.

MATERIALS AND

METHODS

Calculations are based on 13 human lymphocyte data sets obtained from in vitro irradiation experiments with various radiation qualities covering an LET range of 0.5 to 150keV/microm. A total of 93000 first-division metaphases was analysed for all categories of chromosome-type aberrations.

RESULTS

No dose dependence was found for the various yield ratios of chromosomal aberrations. No LET dependence became apparent for the yield ratio of inter- to intrachromosomal exchange-type aberrations (dicentrics/centric rings = F value). However, a clear LET dependence was found for the yield ratio of intra-arm intrachanges to inter-arm intrachanges (interstitial deletions/centric rings = G ratio) and for the yield ratio of intra-arm intrachanges to interchromosomal exchanges (interstitial deletions/dicentrics = H ratio).

CONCLUSION

Measurements of intrachanges are informative for interpretation and quantification of proximity effects in the formation of radiation-induced chromosome aberrations. In particular, yield ratios for intra-arm intrachanges are likely to have a high potential as an indicator of high-LET radiations.