A calibration method for realistic neutron dosimetry in radiobiological experiments assisted by MCNP simulation

Abstract

Many studies on biological effects of neutrons involve dose responses of neutrons, which rely on accurately determined absorbed doses in the irradiated cells or living organisms. Absorbed doses are difficult to measure, and are commonly surrogated with doses measured using separate detectors. The present work describes the determination of doses absorbed in the cell layer underneath a medium column (DA) and the doses absorbed in an ionization chamber (DE) from neutrons through computer simulations using the MCNP-5 code, and the subsequent determination of the conversion coefficients R (= DA/DE). It was found that R in general decreased with increase in the medium thickness, which was due to elastic and inelastic scattering. For 2-MeV neutrons, conspicuous bulges in R values were observed at medium thicknesses of about 500, 1500, 2500 and 4000 μm, and these were attributed to carbon, oxygen and nitrogen nuclei, and were reflections of spikes in neutron interaction cross sections with these nuclei. For 0.1-MeV neutrons, no conspicuous bulges in R were observed (except one at ~2000 μm that was due to photon interactions), which was explained by the absence of prominent spikes in the interaction cross-sections with these nuclei for neutron energies <0.1 MeV. The ratio R could be increased by ~50% for small medium thickness if the incident neutron energy was reduced from 2 MeV to 0.1 MeV. As such, the absorbed doses in cells (DA) would vary with the incident neutron energies, even when the absorbed doses shown on the detector were the same.

Realistic dosimetry for studies on biological responses to X-rays and γ-rays

“…Ref. [ 9 ]). The cells were assumed to be at 100% confluence, and the atomic composition of cells was taken to be the same as a tissue-equivalent plastic (TEP) (density = 1.127 g/cm 3 ; mass composition: 76.2% oxygen, 11.1% carbon, 10.1% hydrogen and 2.6% nitrogen).…”

“…In view of these potential ambiguities, it is relevant to study in more detail the realistic photon dosimetry in radiobiological experiments. The task is in fact related to the concept behind a recent study on the calibration coefficients for realistic neutron dosimetry in radiobiological experiments [ 9 ]. Based on a similar concept, the present task was to enable quantification of the absorbed dose ( D A ) in exposed cells or living organisms due to photons through the dose ( D E ) recorded by a detector located external to the targeted cells or living organisms.…”

Conversion coefficients for determination of dispersed photon dose during radiotherapy: NRUrad input code for MCNP

“…The concept stemmed from our previous work on the determination of the conversion coefficient between the dose absorbed in an irradiated cell layer and the dose recorded by an external dosimeter [13]. For illustration purposes, five targeted tissues, namely, testes, colon, liver, left lung and brain, were studied.…”

Modeling kV X-ray-Induced Coloration in Radiochromic Films

“…The realistic amount of energy transferred to the EBT3 film active layer was obtained through Monte Carlo simulation and determination of the calibration coefficient R (=DA/DE) [6,7], where DA was the actual dose delivered to the EBT3 film active layer and DE was the dose recorded by an external ionization chamber.…”

“…In our Monte Carlo model, the interaction and the transport of the generated secondary electrons were implemented, and dose dispersion [5] in the film active layer was also considered. The realistic amount of energy transferred to the EBT3 film active layer was obtained through Monte Carlo simulation and determination of the calibration coefficient R (=D A /D E ) [6,7], where D A was the actual dose delivered to the EBT3 film active layer and D E was the dose recorded by an external ionization chamber. Atomic scale and macroscopic scale models were employed to model the coloration of EBT3 films, as in the previous model [3].…”