Validity of the interval method for the determination of the anisotropy factor of high dose rate 192Ir sources.

Purpose: This study investigates the validity of the interval method to determine the anisotropy factors of high dose rate (HDR) 192Ir sources.

Methods And Materials: A calculation method, which is one of the various numerical implementations of the Sievert integral and known as the interval method, is applied to determine the anisotropy factors of a HDR 192Ir source. Calculated results from r = 1 cm to 10 cm are compared to published data.

Results: The comparison shows that the error resulting from the interval method increases from 1.3 to 28.1% as the radial distance increases from r = 1 cm to 10 cm and is significantly smaller than that previously reported.

Conclusions: The interval method might be considered as a method that provides a very rough estimate of the anisotropy of HDR 192Ir sources whenever no conclusive anisotropy data is available.