Calibration Methods for 192Ir High Dose Rate Brachytherapy Sources
Abstract
The calibration of 192Ir high dose rate source is needed to verify the value certified by the manufacturer before clinical use. Three calibration techniques, in air, in cylindrical phantom and well type chamber were performed to calibrate twelve sources of the 192Ir during March 1999 to August 2003. It was found that almost kerma rates obtained from all calibration systems were less than the manufacturer's by a maximum of 2:35 % except only one measured by in cylindrical phantom method for source number 10 which was 0.38% more. The mean discrepancies were -1.43% ± 0.63 in the range of -0.46% to -2.35% for in air, -0.84 % ± 0.67 in the range of 0.38% to - 2.19% for in phantom, and -1.26% ± 0.42 in the range of -0.73% to -2.07% for well type chamber. The results of all calibration systems agreed within 1.46%. It is not only more reproducibility and simpler set up, but also less time-consuming to use well type chamber for source calibration comparing with the other two techniques. For the institute where only the Farmer chamber is available, the measurements in phantom are easier and quicker to set up than using in air measurement technique.
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