Comparison of various dose quantities in tissue and tissue substitutes at neutron energies between 20 MeV and 100 MeV
Using kerma factor data for H, C, N, and O in the neutron energy range from 20 MeV to 100 MeV provided by recent calculations and evaluations, the absorbed dose conversion factor α(t,p) from A-150 tissue substitute plastic (p) to ICRU standard tissue (t) was calculated. The results show a constant value of α(t,p) = 0.92 with uncertainties of about 5% from 20 MeV to 50 MeV and of 7% above 50 MeV. Dose distributions from measurements with low pressure proportional counters are used to determine the mean quality factors in C and O. The dose distributions and the quality factors exhibit strong similarities for C and O. Combined with mean quality factors of A-150 plastic and with evaluated kerma factors, the ratio β(t,p) of dose equivalent in ICRU tissue to that in A-150 plastic was calculated. The result indicates that, due to the excess of C in A-150 plastic, the TEPC may overestimate the ambient dose equivalent by about 15% for neutron energies above 20 MeV. These findings confirm the suitability of the TEPC as dose equivalent meter for radiation protection and also suggest that for neutron therapy dosimetry the excess of C in A-150 plastic should be taken into account by using α(t,p) = 0.92 at neutron energies above 20 MeV.
Publication Source (Journal or Book title)
Radiation Protection Dosimetry
Schrewe, U., Alberts, W., Newhauser, W., Brede, H., & DeLuca, P. (1997). Comparison of various dose quantities in tissue and tissue substitutes at neutron energies between 20 MeV and 100 MeV. Radiation Protection Dosimetry, 70 (1-4), 17-20. https://doi.org/10.1093/oxfordjournals.rpd.a031937