The origin of neutron biological effectiveness as a function of energy

Abstract

The understanding of the impact of radiation quality in early and late responses of biological targets to ionizing radiation exposure necessarily grounds on the results of mechanistic studies starting from physical interactions. This is particularly true when, already at the physical stage, the radiation field is mixed, as it is the case for neutron exposure. Neutron Relative Biological Effectiveness (RBE) is energy dependent, maximal for energies ~1 MeV, varying significantly among different experiments. The aim of this work is to shed light on neutron biological effectiveness as a function of field characteristics, with a comprehensive modeling approach: this brings together transport calculations of neutrons through matter (with the code PHITS) and the predictive power of the biophysical track structure code PARTRAC in terms of DNA damage evaluation. Two different energy dependent neutron RBE models are proposed: the first is phenomenological and based only on the characterization of linear energy transfer on a microscopic scale; the second is purely ab-initio and based on the induction of complex DNA damage. Results for the two models are compared and found in good qualitative agreement with current standards for radiation protection factors, which are agreed upon on the basis of RBE data.

Comprehensive track-structure based evaluation of DNA damage by light ions from radiotherapy-relevant energies down to stopping

“…In particular, it has been quantified how the complexity of DNA damage on the nanometre scale and its clustering on the micrometre scale vary with increasing LET, and indications have been obtained that both scales might be related to the induction of biological effects such as chromosome aberrations or cell killing. Results analogous to those presented here have also been recently employed to demonstrate the origin of the energy dependence of neutron RBE2930. The comprehensive PARTRAC predictions of DNA damage as a function of charged particle LET in the cell nucleus constitute a rich database, which can be queried for different applications.…”

“…essentially down to its full stopping. Recently, this achievement has been utilized to investigate the energy-dependent RBE of neutrons2930.…”

A novel vertebrate system for the examination and direct comparison of the relative biological effectiveness for different radiation qualities and sources

“…Thus, it is of great importance and relevance to define the RBE, the ratio between the reference photon and the experimental beam doses resulting in a biological isoeffect,one of the traditionally defined parameter of a new radiation quality. Paramount experiments have been conducted in order to measure the RBE at different high LET sources at particle accelerator facilities worldwide using in vitro cell cultures, the gold standard of radiobiology (Kuhne et al 2009;Beyreuther et al 2009;Jones et al 2011;Seth et al 2014;Baiocco et al 2016;Jones 2016). The RBE is known to be variable and influenced by different factors such as tissue type, biological endpoint, treatment regimen, ion type (L€ uhr et al 2017).…”

Development of zebrafish embryo model, an alternative in vivo vertebrate system for radiation biology research

“…The RBE is known to be variable and influenced by different factors such as tissue type, biological endpoint, treatment regimen, ion type (Lühr et al, 2017). There has been a considerable amount of research performed in order to measure the RBE at different high LET sources at particle accelerator facilities worldwide using in vitro cell cultures, the gold standard of radiobiology (Kuhne et al, 2009, Jones et al, 2011, Seth et al, 2014, Baiocco et al, 2016, Jones, 2016. This energy dependence of biological effect of neutron beams is far well known (Baiocco et al, 2016, Bateman et al, 1961, Hall et al, 1975, Field, 1976.…”

“…There has been a considerable amount of research performed in order to measure the RBE at different high LET sources at particle accelerator facilities worldwide using in vitro cell cultures, the gold standard of radiobiology (Kuhne et al, 2009, Jones et al, 2011, Seth et al, 2014, Baiocco et al, 2016, Jones, 2016. This energy dependence of biological effect of neutron beams is far well known (Baiocco et al, 2016, Bateman et al, 1961, Hall et al, 1975, Field, 1976. We have observed that the 1 MeV mean energy mixed neutron-photon beam proved to be 4 times more effective biologically than the 18 MeV mean energy mixed neutron-photon radiation.…”