Activity determination of 192Ir solid sources by ionization chamber measurements using calculated corrections for self-absorption

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Abstract

A re-entrant-well ionization chamber calibrated in terms of activity for standard solution sources and a spherical ionization chamber calibrated in terms of air kerma rate were used to determine independently the activity of a typical 192Ir brachytherapy source. Corrections for absorption and attenuation of photons inside the source and the capsule were calculated with Monte Carlo methods. The results of both methods agree within 1%. It is concluded that the specification of brachytherapy sources in terms of activity and reference air kerma rate yield consistent results if the real geometry and composition of the source are taken into account.

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