Results supporting calculated wall correction factors for cavity chambers

Thick walled cavity ionization chambers are used by primary standard laboratories as primary air kerma standards in 137Cs and 60Co gamma-rays. Application of the cavity theory requires correction for the effects of photon attenuation and scattering in the chamber walls. For more than a decade there...

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Bibliographic Details
Published in:Physics in medicine & biology 2003-11, Vol.48 (21), p.3581-3594, Article 3581
Main Authors: Büermann, L, Kramer, H-M, Csete, I
Format: Article
Language:English
Subjects:
Algorithms
Biological and medical sciences
Calibration - standards
Computer Simulation
Equipment Failure Analysis - methods
Equipment Failure Analysis - standards
Linear Models
Medical sciences
Models, Statistical
Quality Assurance, Health Care - methods
Quality Assurance, Health Care - standards
Radiometry - instrumentation
Radiometry - methods
Radiometry - standards
Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects)
Reproducibility of Results
Scattering, Radiation
Sensitivity and Specificity
Technology. Biomaterials. Equipments. Material. Instrumentation
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Summary:Thick walled cavity ionization chambers are used by primary standard laboratories as primary air kerma standards in 137Cs and 60Co gamma-rays. Application of the cavity theory requires correction for the effects of photon attenuation and scattering in the chamber walls. For more than a decade there have been intensive discussions about the validity of wall correction factors determined by more traditional extrapolation methods versus those calculated by Monte Carlo methods. For existing primary standards the alternative methods lead to results that differ by up to 50% of the correction itself. This report presents both experimental and theoretical results which strongly support the validity of calculated wall correction factors. Moreover, it is demonstrated that, in selected cases, the application of a linear extrapolation method leads to errors in the determination of the air kerma reaching up to 13%.
ISSN:0031-9155
1361-6560
DOI:10.1088/0031-9155/48/21/009