Room: Exhibit Hall
Purpose: Published data indicates that neutrons are more efficient at damaging DNA than photons at the same absorbed dose. Conventional detectors cannot directly measure the enhanced biological damage. The goal is to evaluate the ability of a dosimeter, whose mechanism for dose detection is DNA double-strand breaks (DSB), to measure this.
Methods: To compare damage between neutrons and photons, DNA dosimeters (4097 base pair double-stranded DNA) were irradiated using three conditions. The first was irradiation with a mixed beam (neutron 741 mSv/hr; Î³ 18.05 mSv/hr) from a Mark II TRIGA reactor for 13.5 hours over three days to reach 10 Sv neutron dose. The second was irradiation with 6 MV photons (Varian 600 C/D) to doses ranging from 4 to 23 Gy inside a water tank. The last was irradiation using an IrÂ¹â?¹Â² source to doses ranging from 4 to 20 Gy in air. For all sets, the storage conditions were the same, and delivery time (average dose rate) was fixed to eliminate effects of dose rate on response. The probability of DSB (PDSB) was calculated for all samples and graphed versus dose. Linear fits were applied to the 6 MV and IrÂ¹â?¹Â² PDSB vs. dose plots. These were used to find the dose with the equivalent damage for 10 Sv of neutrons (PDSB = 0.063Â±0.003).
Results: The 6 MV linac predicted a corresponding dose of 2.7Â±1.24 Gy, while the IrÂ¹â?¹Â² predicted a corresponding dose of 0.0027Â±1.31 Gy.
Conclusion: Since 10 Sv neutron damage does not correspond to 10 Gy of photon damage, these results suggest that the DNA dosimeter is not effectively accounting for the complexity of damage induced by neutrons. Further study and analysis of the dosimeter will be conducted.
Funding Support, Disclosures, and Conflict of Interest: Research funded in part by Cancer Prevention and Research Institute of Texas RP170345 & RP140105.
Not Applicable / None Entered.