The Use of the Dicentric Assay for Biological Dosimetry for Radiation Accidents in Bulgaria

Abstract

This paper details the construction of a 137Cs gamma calibration curve that has been established for dicentric assay and the testing and validation of the curve through biological dosimetry in three situations of suspected workplace overexposure that arose accidentally or through negligence or lack of appropriate safety measures. The three situations were: (1) suspected 137Cs contamination in a factory air supply; (2) suspected exposure to an industrial 192Ir source; and (3) accidental exposure of construction workers to radiation from a 60Co radiotherapy source in a hospital medical physics department. From a total of 24 potentially-exposed subjects, only one worker was found to have a statistically significant dose (0.16 Gy, 95% confidence intervals 0.02-0.43 Gy). In all other cases, the main function of the biological dosimetry was to reassure the subjects that any dose received was low.

Implementation of a dose–response curve for γ-radiation in the Portuguese population by use of the chromosomal aberration assay

“…Applied to radiation protection, biological dosimetry is an important and independent method that complements physical dosimetry, as well as a vital factor for diagnosis and for assessment of the prognosis of subjects who have been irradiated [1,2]. In the first few weeks following an accidental overexposure, the estimation of dose is usually done by means of a combination of physical reconstruction of exposure scenarios and biological dosimetry [3].…”

“…The biologically estimated dose is obtained by comparing the observed yield of unstable chromosomal aberrations (dicentrics and centric rings) in peripheral blood lymphocytes of the studied subjects, with a standard dose-response curve obtained after in vitro irradiation [2,[8][9][10]. According to the IAEA [11], each laboratory must have its own dose-response curve, since several factors can influence the dose-effect relationships such as culture conditions or dicentric scoring efficiency [2,3,[12][13][14][15][16]. The main advantages of scoring dicentrics is its high specificity for ionizing radiation, low background in non-exposed populations (about 1 dicentric per 1000 cells) and a low detection limit, about 0.1 Gy for low-LET radiation if 500-1000 metaphases are scored [6,11,17,18].…”

“…The dicentric assay is the "gold standard" for dose assessment and is mandatory in cases of unanticipated exposures [7]. The biologically estimated dose is obtained by comparing the observed yield of unstable chromosomal aberrations (dicentrics and centric rings) in peripheral blood lymphocytes of the studied subjects, with a standard dose-response curve obtained after in vitro irradiation [2,[8][9][10]. According to the IAEA [11], each laboratory must have its own dose-response curve, since several factors can influence the dose-effect relationships such as culture conditions or dicentric scoring efficiency [2,3,[12][13][14][15][16].…”

Dose-Response Curve of Chromosome Aberrations in Human Lymphocytes Induced by Gamma-Rays

“…In radiation protection, biodosimetry is an important and independent method that complements physical dosimetry, as well as a vital factor for diagnosis and  Corresponding author. E-mail address: k_lusiyanti@batan.go.id for assessment of the prognosis of subjects who have been irradiated [1,2].…”

“…For low-LET radiation (e.g. γ rays and X-rays), the dose-response curve for dicentrics fits better to a linear-quadratic model (LQ) Y = a + ˛αD + ˇβD 2 , where Y is the yield of dicentrics, a is the background frequency of dicentrics and α and β are the linear and dose squared coefficient [7][8][9].…”