Constancy checks of HDR well-type ionization chambers in the linac era: Potential use of a 90Sr source

Abstract

A methodology using a90Sr source, originally designed for constancy checks of parallel-plate ionization chambers, was proposed for constancy checks of HDR brachytherapy well-type ionization chamber (WTIC). The 90Sr source was positioned on the top of the WTIC, a reference reading value was established, and the constancy variation was calculated by the difference between each subsequent measurement and the reference value. This methodology was validated by calibrated 192Ir sources measurements and an acceptable tolerance limit for constancy variation of 1.5% was suggested.