AFRRI's Gamma-Ray, X-Ray, and Fission-Neutron Calibration Curves for the Lymphocyte Dicentric Assay: Application of a Metaphase Finder System

摘要

Facilities are established at the Armed Forces Radiobiology Research Institute (AFRRI) to perform radiation-induced chromosome aberration analysis for biological dosimetry. Whole blood from healthy human volunteers was used after obtaining informed consent. Peripheral blood lymphocytes were exposed in vitro to different types of radiation; sup 60 Co gamma rays (E(gamma) = 1.25 MeV, mean of the absorbed dose distribution of the lineal energy, y(sub D) = 1.9 keV/micrometers, 1 Gy/min); x rays (250 kV(sub p), E = 83 keV, y(sub D) = 4 keV/ micrometers, 1 Gy/min); or a fission-spectrum neutron source (E = 0.71 MeV, y(sub D) = 65 keV/micrometers, 0.25 Gy/min). Distribution of radiation-induced dicentrics among cells exhibited Poisson statistics as characterized by the Papworth method (Papworth 1970). Dose-response relationships for the yield of dicentrics for photon sources were fitted with a linear-quadratic model using the maximum-likelihood method and for the neutron source by a weighted linear regression method. Comparison of the data with other published studies is presented. The dose-response relationships for dicentric induction by low-and high-linear energy transfer (LET) radiation are consistent with the single- and two-track model of aberration formation, Y = alpha D + beta D(sup 2). An increase in y(sub D) resulted in an increase in dicentric yield. As expected, fission neutrons induced a significantly higher yield of dicentrics than that caused by low-LET sources. The linear component of the model, corresponding to damage caused by single-tracks, is predominant with fission neutrons so that the dose-effect relationship is essentially linear. An automated metaphase finder system with a satellite scoring utility was used to improve data collection.