Effect of a static magnetic field on nanodosimetric quantities in a DNA volume

Abstract

Short title: Effect of a magnetic field on track structure Index Terms: Radiotherapy, nanodosimetry, magnetic field, secondary electrons, Geant4, Monte Carlo, cluster size Abstract Purpose: With the advent of MRI (magnetic resonance imaging) guided radiation therapy it is becoming increasingly important to consider the potential influence of a magnetic field on ionising radiation. This paper aims to study the effect of a magnetic field on the track structure of radiation to determine if the biological effectiveness may be altered.Methods: Using the Geant4-DNA (GEometry ANd Tracking 4) Monte Carlo simulation toolkit, nanodosimetric track structure parameters were calculated for electrons, protons and alpha particles moving in transverse magnetic fields up to 10 Tesla. Applying the model proposed by Garty et al. the track structure parameters were used to derive the probability of producing a double strand break (DSB).Results: For simulated primary particles of electrons (200 eV -10 keV), protons (300 keV -30 MeV) and alpha particles (1 MeV -9 MeV) the application of a magnetic field was shown to have no significant effect (within statistical uncertainty limits) on the parameters characterising radiation track structure or the probability of producing a DSB.Conclusions: The null result found here implies that if the presence of a magnetic field were to induce a change in the biological effectiveness of radiation, the effect would likely not be due to a change in the track structure of the radiation.

Investigation of track structure and condensed history physics models for applications in radiation dosimetry on a micro and nano scale in Geant4

“…(Huang et al 2012)), the study of the effect of radiation in cellular targets other than the nucleus (e.g. (Byrne et al 2013, Byrne et al 2016) or in the presence of a magnetic field (Bug et al 2010, Lazarakis et al 2012b. This work has also impact in microdosimetry which is a powerful approach in radiation protection in nuclear labs, aviation and space missions (e.g.…”

Biological effects of static magnetic field exposure in the context of MR-guided radiotherapy

“…The classical paradigm of radiation-induced biological damage posits DNA as the primary site of interaction. MC track structure studies have shown that MRI strength SMF has negligible impact on radiobiologically important micro- 42 and nanodosimetric 43,44 quantities. Yet, approximately half of the papers comprising the scientific literature reported statistically significant difference in the biological end point measured when SMF was combined with ionising radiation relative to ionising radiation exposure alone.…”

“…The absence of SMF-induced changes to the yield and complexity of direct DNA damage produced by ionising radiation [42][43][44] at field strengths in the range utilised in relevant biological studies in the literature (Table 1) suggests that an alternative mechanism is responsible for the SMF-related modification to radiobiological injury. This is supported by studies in which the application of SMF before or after irradiation produced a significant effect vs no SMF, thus removing possible changes to the macroscopic dose distribution as a potential variable.…”

“…43 A follow-up study found that SMF (up to 10 T) had no significant influence on double strand formation probability for Geant4-DNA simulated electron ( 200 eV-10 keV), proton ( 300 keV-30 MeV) and α particle (1 MeV-9 MeV) track structures. 44 Only direct damage to DNA was considered in these works; further simulation incorporating radiochemical transport, including the effect of magnetic fields on such processes is necessary. 43 Moreover, there is limited evidence to support the general assumption in MC studies that SMF does not alter interaction cross-sections, only particle transport.…”

Double-strand breaks in lymphocyte DNA of humans exposed to [18F]fluorodeoxyglucose and the static magnetic field in PET/MRI

“…Moreover, various cell and animal studies found that SMF in combination with ionising radiation produces a significantly different outcome compared with ionising radiation alone [13]. Since synergisms were observed even when the SMF was applied before or after irradiation, changes of the dose distribution by SMFs can likely be excluded as a relevant interaction mechanism [13], as supported by Monte Carlo simulations [14,15]. A recent review on combined effects of the two agents [13] concluded that the current evidence is insufficient to identify the underlying mechanism(s) of the observed synergisms.…”