RESUMO
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%.
Assuntos
Fazendeiros , Radiometria , Calibragem , Elétrons , Humanos , Fótons , Radioterapia de Alta Energia , ÁguaRESUMO
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 plane-parallel chambers. The absorbed dose to water was compared at the calibration depth of 5 cm for a (60)Co beam and d(c) = 0.6R(50) - 0.1 (cm) for electron beams according to JSMP-01. The absorbed dose to water calibration coefficients, [N(D,w)](Co) and [N(D,w)](18E), for the plane-parallel chambers were also determined by (60)Co and electron beam cross-calibrations using a reference chamber. The dose for the plane-parallel chambers derived from [N(D,w)](Co) and [N(D,w)](18E) was compared to that for the reference chamber using electron beams. The JARP chamber in the Kyushu Regional Center which meets third-order standards in Japan was used as the reference chamber. The doses for the plane-parallel chambers determined according to JSMP-01 agreed with that for the JARP chamber within 1% and 2% for (60)Co and electron beams, respectively. For electron beams, the doses for the plane-parallel chambers calculated from [N(D,w)](Co) and [N(D,w)](18E) were within 1.5% and 1.0% compared to those for the JARP chamber, respectively, except for the Exradin A10 chamber.
