Biological dosimetry after exposure to neutrons: International comparison exercise of blood irradiations carried out at PTB and Columbia University as part of the BALANCE Project

The aim of the BALANCE project is to use biological dosimetry to perform an individual dose estimation for a large number of persons in the event of radiation exposure involving neutrons. Originally, it was assumed that such hazards would emanate from terrorist attacks with a so‑called “improvised nuclear device” (IND) or from accidents in nuclear power plants; however, the concern currently also extends to the use of tactical nuclear weapons.

Biological dosimetry is based on dose‑response curves generated in vitro, which have to be established beforehand in the laboratories involved in the analysis. The best choice is presently the counting of dicentric chromosomes (Figure 1) in lymphocytes in human peripheral blood samples. The partners in the network of approved laboratories (RENEB, the European network for biological and retrospective physical dosimetry) are preparing for such radiological events and require the dose‑response curves for the relevant neutron energy spectra. Funding from the U.S. National Institutes of Health (NIH) has provided the opportunity to establish these curves within the scope of an international comparison with the partner from the Columbia IND Neutron Facility (CINF) at Columbia University and to conduct subsequent interlaboratory comparisons for validation. In addition, it was possible to compare the manual evaluation to the faster automatic evaluation of dicentric chromosomes.

Figure 1: Typical image of a metaphase showing damaged blood cells after irradiation. The dicentric (dic) and one acentric (ace) chromosomal aberrations are marked.

For the blood irradiations performed at PTB (Figure 2), a deuterium beam with an energy of 3.4 MeV and an ion current of 50 µA was generated using PTB’s tandem accelerator and directed onto a beryllium disk. The nuclear reaction ⁹Be(d,n) generates an intense neutron field of broad energy distribution, which is similar to the spectrum from the Hiroshima nuclear explosion.

Figure 2: Blood samples in PTB’s intense neutron field.

The project manager distributed the irradiated samples to the RENEB network partners for evaluation. The results for dicentric chromosomal aberrations (Figure 1) from eight laboratories were subsequently analyzed by a biostatistician and recently published.

PTB’s unique range of different neutron energies and intensities has already been used for several national and European projects and represents an important resource for biological dosimetry and the study of biological radiation effects.

References

[1] International comparison exercise for biological dosimetry after exposures with neutrons performed at two irradiation facilities as part of the BALANCE project, Endesfelder D, Kulka U, Bucher M, Giesen U, Garty G, Beinke C, Port M, Gruel G, Gregoire E, Terzoudi G, Ainsbury E, Moquet J, Prieto MJ, Domene MM, Barquinero JF, Pujol-Canadell M, Vral A, Baeyens A, Wojcik A, Oestreicher U; Cytogenetic and Genome Research, https://doi.org/10.1159/000530728

[2] Förderung durch: Grant number U19-AI067773 to the Center for High‑Throughput Minimally Invasive Radiation Biodosimetry, from the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH). CINF: Columbia IND Neutron Facility, Columbia University, Irvington, New York, USA

Contacts

U. Giesen, Department 6.4, Working Group 6.45

U. Oestreicher, BfS, Oberschleißheim