Rise and fall of biological dosimetry in ionizing radiation effects

Philippe Voisin, Patrick Gourmelon Internat.Conf. "Diagnosis and treatment of radiation injury", Rotterdam, 30 august-3 september 1998

Radiation induced changes in some biological parameters can be directly measured on the irradiated organism. They are a useful complement of the sometimes non-existent clinical symptomatology and of an often incomplete physical reconstruction. An estimation of the exposure level can then be obtained by comparison to a so-called dose-effect calibration curve. Nevertheless, this concept of biological dosimetry has two major drawbacks. For many years, the scoring of unstable chromosome aberrations in peripheral blood lymphocytes stated an accurate reference in case of acute, whole-body and homogeneous irradiation. However, most of radiation overexposure can be heterogeneous, fractionated or delayed. New methods must be added to the conventional cytogenetics in order to set up a multiparametric panel. They have been searched for in all the quantitative biology areas: cytogenetics (translocations, micronuclei, prematurely condensed chromosomes) but also cytology (apoptosis), biophysics or biochemistry fields (membrane alterations, enzymatic factors). Some of these parameters looked promising. The assessment of radiation alterations through these biological parameters often proved valid at the molecular and cellular levels. They cannot be easily extrapolated to the larger scale systems, organs and whole-body, except in some well defined conditions. Consequently the related aspect of dose assessment might be reappraised and the terms of molecular or cellular bioindicators could be more appropriate than biological dosimeter. At the organ and the organism level, the biological dosimetry definition should be replaced by the concepts of bioindicators of prognosis and bioindicators of diagnosis. We feel the challenge for the future may be the exploration of such new concepts.