Purpose: Inhomogeneous exposures to ionizing radiation can be detected and quantified with the dicentric chromosome assay (DCA) of metaphase cells. Complete automation of interpretation of the DCA for whole-body irradiation has significantly improved throughput without compromising accuracy, however, low levels of residual false positive dicentric chromosomes (DCs) have confounded its application for partial-body exposure determination. Materials and methods: We describe a method of estimating and correcting for false positive DCs in digitally processed images of metaphase cells. Nearly all DCs detected in unirradiated calibration samples are introduced by digital image processing. DC frequencies of irradiated calibration samples and those exposed to unknown radiation levels are corrected subtracting this false positive fraction from each. In partial-body exposures, the fraction of cells exposed, and radiation dose can be quantified after applying this modification of the contaminated Poisson method. Results: Dose estimates of three partially irradiated samples diverged 0.2–2.5 Gy from physical doses and irradiated cell fractions deviated by 2.3%–15.8% from the known levels. Synthetic partial-body samples comprised of unirradiated and 3 Gy samples from 4 laboratories were correctly discriminated as inhomogeneous by multiple criteria. Root mean squared errors of these dose estimates ranged from 0.52 to 1.14 Gy2 and from 8.1 to 33.3%2 for the fraction of cells irradiated. Conclusions: Automated DCA can differentiate whole- from partial-body radiation exposures and provides timely quantification of estimated whole-body equivalent dose.
Bibliographical noteFunding Information:
CytoGnomix, PHE, and DNRI acknowledge sponsorship by the International Atomic Energy Agency under Coordinated Research Project ‘E35010’, entitled ‘Applications of Biological Dosimetry Methods in Radiation Oncology, Nuclear Medicine, and Diagnostic and Interventional Radiology (MEDBIODOSE)’. PHE is grateful to H. Thierens, A. Vraal, and V. Vanderickel for irradiating blood samples and MULTIBIODOSE (EU FP7/2007–2013, agreement No. 241536) for support.
© Copyright © 2020 Taylor & Francis Group LLC.
- Ionizing radiation
- chromosomal aberrations
- inhomogeneous exposure
- software automation