scholarly journals High-Accuracy Relative Biological Effectiveness Values Following Low-Dose Thermal Neutron Exposures Support Bimodal Quality Factor Response with Neutron Energy

2022 ◽  
Vol 23 (2) ◽  
pp. 878
Laura C. Paterson ◽  
Amy Festarini ◽  
Marilyne Stuart ◽  
Fawaz Ali ◽  
Christie Costello ◽  

Theoretical evaluations indicate the radiation weighting factor for thermal neutrons differs from the current International Commission on Radiological Protection (ICRP) recommended value of 2.5, which has radiation protection implications for high-energy radiotherapy, inside spacecraft, on the lunar or Martian surface, and in nuclear reactor workplaces. We examined the relative biological effectiveness (RBE) of DNA damage generated by thermal neutrons compared to gamma radiation. Whole blood was irradiated by 64 meV thermal neutrons from the National Research Universal reactor. DNA damage and erroneous DNA double-strand break repair was evaluated by dicentric chromosome assay (DCA) and cytokinesis-block micronucleus (CBMN) assay with low doses ranging 6–85 mGy. Linear dose responses were observed. Significant DNA aberration clustering was found indicative of high ionizing density radiation. When the dose contribution of both the 14N(n,p)14C and 1H(n,γ)2H capture reactions were considered, the DCA and the CBMN assays generated similar maximum RBE values of 11.3 ± 1.6 and 9.0 ± 1.1, respectively. Consequently, thermal neutron RBE is approximately four times higher than the current ICRP radiation weighting factor value of 2.5. This lends support to bimodal peaks in the quality factor for RBE neutron energy response, underlining the importance of radiological protection against thermal neutron exposures.

María Pedrosa-Rivera ◽  
Javier Praena ◽  
Ignacio Porras ◽  
Manuel Pedro Sabariego ◽  
Ulli Köster ◽  

The experimental determination of the relative biological effectiveness of thermal neutron factors is fundamental in Boron Neutron Capture Therapy. Present values have been obtained using mixed beams consisting of both neutrons and photons of various energies. A common weighting factor has been used for both thermal and fast neutron doses, although such an approach has been questioned. At the nuclear reactor of the Institut Laue-Langevin a pure low-energy neutron beam has been used to determine thermal neutron relative biological effectiveness factors. Different tumor cell lines, corresponding to glioblastoma, melanoma, and head and neck squamous cell carcinoma, and non-tumor cell lines (lung fibroblast and embryonic kidney) have been irradiated using an experimental arrangement designed to minimise neutron-induced secondary gamma radiation. Additionally, the cells were irradiated with photons at a medical linear accelerator, providing reference data for comparison with that from neutron irradiation. Survival and proliferation were studied after irradiation, yielding the Relative Biological Effectiveness corresponding to the damage of thermal neutrons for the different tissue types.

2019 ◽  
Vol 18 ◽  
pp. 153303381987130
Francois Chevalier ◽  
Dounia Houria Hamdi ◽  
Charlotte Lepleux ◽  
Mihaela Temelie ◽  
Anaïs Nicol ◽  

Chondrosarcomas are malignant tumors of the cartilage that are chemoresistant and radioresistant to X-rays. This restricts the treatment options essential to surgery. In this study, we investigated the sensitivity of chondrosarcoma to X-rays and C-ions in vitro. The sensitivity of 4 chondrosarcoma cell lines (SW1353, CH2879, OUMS27, and L835) was determined by clonogenic survival assays and cell cycle progression. In addition, biomarkers of DNA damage responses were analyzed in the SW1353 cell line. Chondrosarcoma cells showed a heterogeneous sensitivity toward irradiation. Chondrosarcoma cell lines were more sensitive to C-ions exposure compared to X-rays. Using D10 values, the relative biological effectiveness of C-ions was higher (relative biological effectiveness = 5.5) with cells resistant to X-rays (CH2879) and lower (relative biological effectiveness = 3.7) with sensitive cells (L835). C-ions induced more G2 phase blockage and micronuclei in SW1353 cells as compared to X-rays with the same doses. Persistent unrepaired DNA damage was also higher following C-ions irradiation. These results indicate that chondrosarcoma cell lines displayed a heterogeneous response to conventional radiation treatment; however, treatment with C-ions irradiation was more efficient in killing chondrosarcoma cells, compared to X-rays.

RSC Advances ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 6845-6858 ◽  
N. T. Henthorn ◽  
J. W. Warmenhoven ◽  
M. Sotiropoulos ◽  
A. H. Aitkenhead ◽  
E. A. K. Smith ◽  

Relative Biological Effectiveness (RBE) is a controversial and important topic in proton therapy. This work uses Monte Carlo simulations of DNA damage for protons and photons to probe this phenomenon, providing a plausible mechanistic understanding.

2019 ◽  
Vol 186 (2-3) ◽  
pp. 172-175 ◽  
Werner Friedland ◽  
Pavel Kundrát ◽  
Janine Becker ◽  
Markus Eidemüller

ABSTRACT The biophysical simulation tool PARTRAC has been primarily developed to model radiation physics, chemistry and biology on nanometre to micrometre scales. However, the tool can be applied in simulating radiation effects in an event-by-event manner over macroscopic volumes as well. Benchmark simulations are reported showing that PARTRAC does reproduce the macroscopic Bragg peaks of proton beams, although the penetration depths are underestimated by a few per cent for high-energy beams. PARTRAC also quantifies the increase in DNA damage and its complexity along the beam penetration depth. Enhanced biological effectiveness is predicted in particular within distal Bragg peak parts of therapeutic proton beams.

1970 ◽  
Vol 10 (04) ◽  
pp. 365-379 ◽  
J.S. Wahl ◽  
W.B. Nelligan ◽  
A.H. Frentrop ◽  
C.W. Johnstone ◽  
R.J. Schwartz

Abstract Thermal Neutron Decay Time (TDT) logging tools in 3-3/8 and 1-11/16-in. diameters have been developed for detection and evaluation of water saturation in cased holes. These tools utilize a system of movable and expandable detection time-gates which are automatically adjusted as the log is being run. The two principal detection gates are positioned in time after the neutron burst according to an optimization criterion. An additional gate, delayed until most of the decay has taken place, permits correction for background. This place, permits correction for background. This Scale Factor gating method provides, in each bed, a thermal-decay-time measurement of maximum statistical precision consistent with removal of borehole effects present in the early part of the decay period Increased reliability is afforded by use of digital techniques. Thermal neutron decay time tools employ capture-gamma-ray detection. This choice was based on an extensive series of experiments made to compare gamma-ray detection and direct detection of thermal neutrons. Measurements of thermal neutron decay time constant are affected by local changes in neutron density in the vicinity of the sonde, caused by flow of neutrons by diffusion from one medium to another. The measured decay time constant (T meas) of neutron density at any point may differ, therefore, from the intrinsic decay time constant (T int) produced by absorption alone. The basic physics of neutron diffusion and absorption is reviewed. When the borehole and the formation have different decay time constants and diffusion coefficients, diffusion couples the two regions. Consideration of such effects sheds light on the conditions required for reduction of borehole effects on measured values of the decay time constant. The choice of source-detector spacing is affected. and, for accurate quantitative interpretation, departure curves are required. Departure curves are presented showing the effects of varying cement thickness, casing diameter. and casing fluids Illustrative log examples are shown. Introduction The Thermal Neutron Decay Time (TDT) log provides a determination of the time constant for provides a determination of the time constant for the decay of thermal neutrons in the formation. Hence, it reflects primarily the neutron absorptive properties of the formation. These properties are properties of the formation. These properties are useful in formation evaluation. The most important area of application is in logging cased hole. Because chlorine is by far the strongest thermal neutron absorber of the common earth elements, the TDT log responds largely to the amount of NaCl present in the formation water. As a result, this present in the formation water. As a result, this log resembles the usual open-hole resistivity logs and is easily correlatable with them. When information on lithology and porosity is known or is provided by open-hole logs, a log of neutron provided by open-hole logs, a log of neutron absorption properties permits the solution of a wide variety of problems: saturation determination, oil-water contact location, detection of gas behind casing, etc. Measurements of the thermal neutron decay time constant are made by first irradiating the formation with a pulse of high-energy neutrons from a neutron generator in the sonde, and then, a short time after the neutron source is turned off, determining the rate at which the thermal neutron population decreases. After each neutron burst, the high-energy neutrons are quickly slowed down to thermal velocities by successive collisions with the nuclei of elements in the formation and borehole. The relative number of thermal neutrons remaining in the formation is measured during detection intervals which follow each burst. Between each burst and the beginning of the first detection interval is a delay time which permits the originally fast neutrons to reach thermal permits the originally fast neutrons to reach thermal energy and allows "early" borehole effects to subside. SPEJ p. 365

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