Impacts of applicators on 192Ir brachytherapy dosimetry

Abstract

Objective To study the impacts of different applicators on dose distribution in 192Ir brachytherapy. Methods The inner tubes of two cylinder applicators from Nucletron, #101.001 and#084.350, were made of plastic and stainless steel, respectively. The cylinder parts of them were made of plastic, and had four different radiuses: 1.00 cm, 1.25 cm, 1.50 cm, and 1.75 cm. EGSnrc program was used to simulate dose distribution when applicators were present in a phantom, and the results calculated by the treatment planning system were compared with the results of EGSnrc. The impacts of applicators on dose distribution were analyzed with different materials, thickness, and numbers of resident source. Results There was no significant relationship between dose deviation and the radius for the two applicators. When an applicator was present, the actual dose delivered to a patient was smaller than the planned dose. The dose deviation of the applicator#101.001 was no more than 1%, while the dose deviation of the applicator#084.350 was close to 3%. The dose deviation remained the same when the number of resident source changed. Conclusions The plastic applicator, if possible, is the best choice for brachytherapy right now. In a long term, in order to promote the accuracy of brachytherapy, current dosimetry algorithm should be improved, and the impacts of the applicator made of metal, such as stainless steel, on dose distribution should be taken into account. Key words: Applicator; Brachytherapy; Dosimetry