Analysis of chromosome aberrations in human peripheral lymphocytes induced by 5.4 keV x-rays

Abstract

Irradiation of human lymphocytes by x-rays has been seen, in past studies, to produce increasing frequencies of chromosome aberrations at lower x-ray energies. However, in one earlier irradiation experiment with chromium x-rays, the relative biological effectiveness (RBE) did not appear to be larger than that of hard x-rays, especially at higher doses. A possible reason for this unexpected result may have been the irradiation and culture conditions. We have, therefore, in the present study used a technique that has been developed in our laboratory to ensure uniformity of irradiation within lymphocytes and to avoid artefacts due to the cell cycle kinetics. Monolayers of 3-h-stimulated lymphocytes were exposed to 5.4 keV x-rays. A linear-quadratic dose-response was found for dicentrics. The comparison to an earlier finding with 220 kV x-rays shows the expected result of the RBE of the 5.4 keV x-rays to be above that of 220 kV x-rays. The intercellular distribution of dicentrics did not differ significantly from a Poisson distribution.

FISH-based analysis of 10- and 25-kV soft X-ray–induced DNA damage in 184A1 human mammary epithelial cells

“…Moreover, the investigation of unstable excess fragments and dicentrics in cell line 184A1 (Beyreuther et al 2009) resulted in similar RBE values of 1.17 ± 0.12 and 1.31 ± 0.21 for cell irradiation with 25-kV X-rays and of 1.92 ± 0.26 and 1.72 ± 0.29 for those with 10-kV X-rays, respectively, both in comparison with 200-kV X-rays. These results are in good accordance with chromosomal aberration studies on human lymphocytes, which revealed RBE values in the range from 1.4 to 1.9 for mammographic X-rays (Schmid et al 2002;Mestres et al 2008) and 10-kV X-rays (Roos and Schmid 1998), respectively. By contrast, the investigation of the micronuclei per binucleated cell in a different human mammary epithelial cell line, namely MCF-12A, resulted in a slightly higher RBE M of 1.44 ± 0.17 for 25-kV X-rays (Lehnert Table 3 Regression coefficients, the derived dose-response ratios (DRR) and their standard errors (SE) obtained for the quadratic dose-effect relationships of the total translocations and the minimum number of breaks The resulting DRR (±SE) were calculated as square root of the ratio of the b-coefficients a The a-coefficient was not significantly different from zero (p B 0.05) .…”

“…Roos and Schmid 1998;IAEA 2001;Schmid et al 2002;Mestres et al 2008). The major source for the dissenting dose responses obtained in the present work was the very low number of chromosomal aberrations in the low-dose region, which precluded the determination of significant a-coefficients by the fit procedure.…”

RBE of low energy electrons and photons

“…A review of RBE values for chromosome aberration data for x-rays and gamma rays was published by Hill (2004). In this review we report on RBE values for chromosome aberrations obtained from recent and earlier publications including Beyreuther et al (2009), George et al (2009), Mestres et al (2008), Nasonova et al (2006), Büermann et al (2005), Krumrey et al (2004), Schmid et al (2002 and Roos and Schmid (1998). For completeness, we also include data by Sasaki et al (1989), Lloyd et al (1975Lloyd et al ( , 1986, Bauchinger et al (1983), Prosser et al (1983), Alpen et al (1993) and the classic work by Virsik et al (1977).…”

A Comparison of Cs-137 γ Rays and 320-kV X-Rays in a Mouse Bone Marrow Transplantation Model

“…The RBE estimate is based on data from several studies for different end points using different energy photons. [17][18][19][20][21] Thus, a target X-ray dose of 4.62 Gy (intended rather than measured dose) was chosen to compare to the highest target dose of g rays (6.0 Gy g rays; 6.0/1.3 ¼ 4.62 Gy Xrays). Measured radiation doses obtained using TLDs are expected to be proportional to the average absorbed radiation dose to bone marrow.…”