Absorbed dose comparison among commercial ionization chambers in polystyrene and acrylic phantoms

Using the AAPM Task Group 21 protocol, photon and electron doses were compared in polystyrene and acrylic phantoms. The ionization chambers used were a Farmer graphite chamber, a PTW acrylic chamber, a homemade polystyrene chamber, and an Exradin air-equivalent chamber, all being of cylindrical type. A Memorial parallel-plate polystyrene chamber was also included. 60Co, 4-, 6-, and 18-MV x rays as well as 9- and 20-MeV electron beams were investigated.