Experimental determination of pCo perturbation factors for plane-parallel chambers.
Phys Med Biol
; 52(23): 7167-81, 2007 Dec 07.
Article
en En
| MEDLINE
| ID: mdl-18030000
For plane-parallel chambers used in electron dosimetry, modern dosimetry protocols recommend a cross-calibration against a calibrated cylindrical chamber. The rationale for this is the unacceptably large (up to 3-4%) chamber-to-chamber variations of the perturbation factors (pwall)Co, which have been reported for plane-parallel chambers of a given type. In some recent publications, it was shown that this is no longer the case for modern plane-parallel chambers. The aims of the present study are to obtain reliable information about the variation of the perturbation factors for modern types of plane-parallel chambers, and-if this variation is found to be acceptably small-to determine type-specific mean values for these perturbation factors which can be used for absorbed dose measurements in electron beams using plane-parallel chambers. In an extensive multi-center study, the individual perturbation factors pCo (which are usually assumed to be equal to (pwall)Co) for a total of 35 plane-parallel chambers of the Roos type, 15 chambers of the Markus type and 12 chambers of the Advanced Markus type were determined. From a total of 188 cross-calibration measurements, variations of the pCo values for different chambers of the same type of at most 1.0%, 0.9% and 0.6% were found for the chambers of the Roos, Markus and Advanced Markus types, respectively. The mean pCo values obtained from all measurements are [Formula: see text] and [Formula: see text]; the relative experimental standard deviation of the individual pCo values is less than 0.24% for all chamber types; the relative standard uncertainty of the mean pCo values is 1.1%.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Radiometría
/
Radioisótopos de Cobalto
Tipo de estudio:
Clinical_trials
/
Diagnostic_studies
País/Región como asunto:
Europa
Idioma:
En
Revista:
Phys Med Biol
Año:
2007
Tipo del documento:
Article
País de afiliación:
Alemania
Pais de publicación:
Reino Unido