Microdosimetry on a Mini-Reactor UTR-KINKI for Educational Uses and Biological Researches

Abstract

Microdosimetry study has been carried out at the education and research mini-reactor of Kinki University (UTR-KINKI) using a tissue equivalent gas proportional counter (TEPC). The microdosimetric single event spectra for 0.5, 1, 2, 3 and 5 microm site sizes were obtained in the lineal energy range from 1 to 1000 keV/microm. Neutron and gamma-ray fractional doses were estimated from the single event spectra. The neutron dose fraction was varied from 35 to 55% for 0.5 to 5 microm site size. The averaged lineal energy, y(D), for each site size was likewise estimated and found to be dependent on the site size. The averaged lineal energy for neutron was slightly larger than that of the fission neutrons from (252)Cf, and the averaged lineal energy for gamma-ray had similar site-size-dependence of 25 keV gamma-rays and 250 kV X-rays. Relative biological effectiveness was found to be 4.1 +/- 0.13 for UTR-KINKI using Tilikidis's 2 Gy-response function. The estimated RBE for UTR-KINKI neutrons is quite close to the previous biological experimental value of 4.3 +/- 0.6 for micronucleated cells in gill cell of Medaka and 4.6 +/- 0.5 for induction of lymphocyte apoptosis in the thymus of ICR mice.

Boron Neutron Capture Therapy: Microdosimetry at Different Boron Concentrations

“…The Tilikidis weighting function at 2 Gy has been previously employed in microdosimetry of neutron fields for BNCT [17,26,27]. Estimating RBE through a single-response function offers a physics-based approach and facilitates intercomparisons between different BNCT facilities [28,29].…”

Application of Tissue Equivalent Proportional Counter (TEPC) in Intercalibration with NaI (Tl) Spectrometer

“…The fall at about 8.55 𝑘𝑒𝑉/𝜇𝑚 is the electron edge and, 4. the fall at around 176.25 𝑘𝑒𝑉/𝜇𝑚 is the proton edge. A proton-edge and electron-edge structures are produced when deposited energy reaches its corresponding maximum values for electrons and protons respectively (Endo, 2009). The proton-and electron-edges are useful in the lineal energy calibration, which will be discussed later in section 3.1.…”

“…By using the lineal energy corresponding to the position in the event-size spectrum, a calibration factor can be calculated for the spectrum to convert all the "position" (i.e., channel number) to lineal energy. The proton-edge (p-edge) is usually denoted around 140 𝑘𝑒𝑉/𝜇𝑚 for propane TE gas in a 2 µm simulated site sized TEPC (Endo, 2009).…”

“…Electrons will also create an "edge" in the event-size spectrum. The electron-edge (e-edge) is usually observed around 10 𝑘𝑒𝑉/𝜇𝑚 for propane TE gas in a 2 µm simulated site sized TEPC (Endo, 2009).…”