A linear source table to determine the treatment times for cylindrical applicators used in high-dose rate brachytherapy

Purpose: It is a good practice for quality assurance purposes to check the high-dose rate brachytherapy source dwell times obtained from any computerized treatment planning system (TPS) by independent hand calculations. The aim of this work was to prepare a table that would help to calculate the total dwell times for cylindrical applicators used for high-dose rate brachytherapy. Methods and Materials: The results of an earlier investigation of dose rate per unit source strength at different distances from the microSelectron-high-dose rate ¹⁹²Ir source and the relative weights for dwell times obtained from optimized plans were used to prepare a linear source table. Results: This table gives the product of source strength and total dwell times to deliver 1000. cGy at various distances for active lengths ranging from 1 to 8. cm and for treatment distances of 1 to 2.25. cm. One can use this table to determine the total dwell time necessary to deliver the prescribed dose at a specific distance for the source strength at the time of treatment. This can be compared with the total dwell time calculated by the computerized TPS. Conclusion: The linear source table makes the determination of total dwell time very easy and would help the clinical physicist to check the accuracy of results of the TPS quickly.