DNA content proportionality and persistence of radiation-induced chromosomal aberrations studied by FISH

Chromosome aberrations induced by radiation have been used for the purpose of dosimetry for a long time. Translocations are especially useful for retrospective dosimetry, since they are assumed to be stable. The method of chromosome painting (FISH) has facilitated objective scoring of aberrations considerably. Translocation frequencies, obtained by FISH, for retrospective dosimetry rely on the main assumptions of neutral selection value and that the distribution of aberrations over the chromosomes is a known function of the DNA content of the chromosomes. Data scrutinising the two above-mentioned assumptions indicate deviations from both. Other factors potentially causing problems for retrospective dosimetry, such as inter-individual variations in background and induction patterns, are discussed. Finally, a brief analysis of the statistical power of dosimetry studies shows that establishing low doses (approximately 0.25 Gy) with good precision requires a great effort, which is probably unrealistic for individual dose estimates in epidemiological studies.