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High dose rate intracavitary brachytherapy machine (RALSTRON-20 B) provides us a high efficient method of treatment as well as high safety in radiation protection for staff. It is now worldwidely used in many hospitals. Srinagarind Hospital is one of those which uses this kind of machine. Because of its high dose rate if the treatment times and source positions were small magnitude error, it could lead to tremendous false given doses. Following this problem, patient may receive Suboptimal doses, that leads to failure of treatment, or over doses that leads to serious complications. To get good performance and high accuracy of treatment, this machine has to be tested regularly before used in patients. Perspex pelvic phantom had been used together with the Farmer Dosimeter which had been calibrated from the Secondary Standard Dosimetry Laboratory (SSDL). The phantom and the Farmer Dosimeter were set in the same way as in the treatment of patients. Thirty values of the doses at the reference point A were measured in phantom for a certain peroid of time and then compared to the dose at the same point by DOSEPAC-100 program. Moreover, 30 values of bladder and rectal doses were also measured in the patients during treatment by OPD-5 smiconductor detectors. The doses from the measurement and the doses from computation were then compared.
From the comparison values of both methods, it was finally found that they were not more than 3% different (the differences not more than 5% can be generally accepted) by paired t-test data analysis. So far, RALSTRON-20 B and DOSEPAC-100 can be used credibly with high accuracy.