title: Determinations of Ngas and Prepl factors from commercially available parallel-plate chambers: AAPM Task Group 21 protocol.
abstract: Using a Farmer chamber as a reference dosimeter, we have measured the Ngas (cavity-gas calibration factor) and Prepl (replacement correction factor) values for four parallel-plate chambers: a Holt chamber, a Capintec chamber, a Markus chamber, and an SHM chamber. Ngas determinations were done primarily using 60Co photons and nominal 18-MeV electrons for Ngas determinations. For Prepl determinations, we used nominal 18-, 15-, 12-, 9-, 6-, and 4-MeV electrons.
mesh_terms: D002138:Calibration; D003037:Cobalt Radioisotopes; D004583:Electrons; D011827:Radiation; D011874:Radiometry / Q000295:instrumentation*; D011882:Radiotherapy, High-Energy
chemical_list: D003037:Cobalt Radioisotopes