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

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.

Calibration of the 90Sr+90Y ophthalmic and dermatological applicators with an extrapolation ionization minichamber.

(90)Sr+(90)Y clinical applicators are used for brachytherapy in Brazilian clinics even though they are not manufactured anymore. Such sources must be calibrated periodically, and one of the calibration methods in use is ionometry with extrapolation ionization chambers. (90)Sr+(90)Y clinical applicators were calibrated using an extrapolation minichamber developed at the Calibration Laboratory at IPEN. The obtained results agree satisfactorily with the data provided in calibration certificates of the sources.