Radiation dose–response curves: cell repair mechanisms vs. ion track overlapping

Abstract

Abstract. Chromosome aberrations in human lymphocytes exposed to different doses of particle radiation: 150 MeV and spread out Bragg peak proton beams, 22 MeV/u boron beam and 199 V/u carbon beam were studied. For comparison, an experiment with 60 Co γ-rays was also performed. We investigated distributions of aberration frequency and the shape of dose-response curves for the total aberration yield as well as for exchange and non-exchange aberrations, separately. Applying the linear-quadratic model, we could derive a relation between the fitted parameters and the ion track radius which could explain experimentally observed curvature of the dose-response curves. The results compared with physical expectations clearly show that the biological effects of cell repair are much more important than the ion track overlapping.

Initial radiation DNA damage observed in prematurely condensed chromosomes of G2-phase human lymphocytes and analytical model of ion tracks

“…Protons were delivered by Phasotron; 60 Co γray irradiation was done on the remote radiation therapy unit ROKUS M. Monoenergetic 22.1 MeV/u 11 B beam was delivered by the U 400M cyclotron of the Flerov Laboratory of Nuclear Reactions, JINR (Dubna, Russia). Details of the irradiation procedure and beam characteristics are given elsewhere [14,20,21].…”

“…As discussed in our previous paper [14] devoted to the chromosome aberrations of the human lymphocytes, the quadratic term can represent contributions resulting both from the physical effect of the overlapping ion tracks and from the biological repair mechanisms which effectiveness is not known exactly. Thus, we have proposed to determine the curvature ratio β/α theoretically, assuming only that the ion tracks of an effective interaction radius R eff can overlap and produce locally in this overlapping region a double dose.…”

“…Recently, we have proposed a simple analytical model describing the observed linear-quadratic dependence of the chromosome aberration yield on the radiation dose induced by heavy charged particles [14]. The method is based on the assumption that the non-linear term of linear-quadratic response function arises solely by the ion track overlapping effect.…”

Dynamics of systems on the nanoscale

“…Papers [14][15][16][17] are devoted to the analysis of the structural changes and damage of biological objects exposed to ionizing radiation.…”

“…Experimental data accompanied by quantitative analysis of chromosome aberrations in human lymphocytes exposed to different doses of particle radiation are presented in reference [16]. Distributions of aberration frequency and the shape of dose-response curves for the total aberration yield as well as for exchange and nonexchange aberrations were investigated.…”