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Dose rate definition with microSelectron-HDR and Selectron-MDR in brachytherapy for carcinoma of the cervix
M M el-Baradie1, N Fournier-Bidoz, T Inoue
1Department of Radiation Oncology, Osaka University Medical School, Suita, Japan.
Background:
Reproducibility of dose rate at point A is the main characteristic of Manchester system for dose prescription for cancer cervix brachytherapy. Here, we investigated dose rate variations at point A in the application of Selectron-MDR and microSelectron-HDR.
Materials And Methods:
All applications were compared for their physical aspects (loading and geometry). Two points A(rev) and A(or) (revised and original definitions) were checked for dose rate variations. Here we proposed a tool "dose rate radium equivalent" (Ra-eq.DR) to cancel the effect of source decay on the variation of dose rate values.
Results:
Both techniques showed very similar geometry, tandem-ovoid loading ratio, and Ra-eq.DR at A(rev) and A(or). However, the best reproducibility of dose rate was achieved with A(or). Also, time variable-dose rate definition affected the difference between the 2 treatments modalities.
Conclusions:
Clear definition of both the point of dose prescription and the time variable used for dose rate calculation are important for brachytherapy for cancer of the cervix.