Investigating the TEPC radiation quality factor response for low energy accelerator based clinical applications

The use of a tissue equivalent proportional counter (TEPC) filled with propane based tissue equivalent gas simulating a 2 microm diameter tissue sphere has been investigated to estimate the radiation quality factor of the neutron fields used in in vivo neutron activation measurements at the McMaster University 3 MV Van de Graaff accelerator. The counter response to estimate the effective quality factor based on the definitions of Q(L) provided in ICRP 26 and 60 as a function of neutron energy has been examined experimentally using monoenergetic and continuous neutron spectra in the energy range of 35 to 600 keV. In agreement with other studies, the counter failed to provide a flat R(Q) response and showed a sharp drop below 200 keV neutron energy. Development of an algorithm to evaluate the quality factors using measured dose-mean lineal energy, yD, and comparison of the algorithm with other reported algorithms and analytical methods developed for the improvement in TEPC dose equivalent response has been reported.