[Clinical calibration dosimetry in JSMP-01: measurements using Farmer-type cylindrical ion chambers.]

The Japan Society of Medical Physics (JSMP) Task Group published Standard dosimetry of absorbed dose in external beam radiotherapy (Standard dosimetry 01) as a new high-energy photon and electron dosimetry protocol in 2002. In this study, we present Standard dosimetry 01 as the JSMP-01 protocol for the convenience of users. This protocol is based on using an ion chamber having a (60)Co absorbed dose to water calibration coefficient, N(D,w), which is calculated from a (60)Co exposure calibration coefficient, N(c). We present dose comparisons between a reference chamber and various Farmer-type cylindrical chambers with different wall materials. The absorbed dose to water was compared at the calibration depths of 5 cm for a (60)Co beam, 10 cm for photons, and d(c) = 0.6 R(50) - 0.1 (cm) for electrons according to JSMP-01. The JARP chamber in the Kyushu Regional Center which meets third-order standards in Japan was used as the reference chamber. The absorbed dose to water for the Farmer-type chambers determined according to JSMP-01 agreed with that for the JARP chamber within 1% for photon and electron beams. The doses obtained by JSMP-01 and the Japan Association of Radiological Physics protocol (JARP-86) were also compared for photon and electron beams. For the Farmer-type chambers with photon beams, JSMP-01 results were up to 1.5% higher than JARP-86 results. For electron beams JSMP-01 results were higher than JARP-86 results by 1.3-2.8%.