The Effect of Positional Movement of a Semiflexible Applicator on Dose Distrubutions in Low Dose Rate Brachytherapy for Cervical Carcinoma

Objective: Current study aims to detect the movements of a semiflexible applicator (TORE's applicator) in the first 24 hours and to analyze its effect on the calculated point A, bladder and rectum doses in low dose rate brachytherapy (LDR-BT) applications. Material and Methods: Eighty films were evaluated on 18 cervical carcinoma patients (20 applications) who were treated with curative radiotherapy. The comparison of the reference points and doses at critical organs were performed by using a reference axis which was fixed to bony landmarks in the pelvis. To evaluate the movement of the applicator, distance of the upper point and lower point of the tandem to the reference axis were measured. Additionally, the angular deviation of the applicator was tested. Results: The movements of the upper point and lower point of the tandem in x, y, z axes were 5.30 +/- 6.33 mm, 2.80 +/- 2.24 mm, 6.65 +/- 8.33 mm and 3.45 +/- 4.32 mm, 3.75 +/- 3.59 mm, 3.05 +/- 3.08 mm, respectively. The mean differences were 3.30 +/- 2.99 degrees in alpha-angle and 5.65 +/- 4.76 degrees in beta-angle. The mean percent dose changes in point A, bladder and rectum were 1.5 +/- 1.2%, 3.7 +/- 3.1%, 4.4 +/- 4.0%, respectively. Conclusion: Our study demonstrates that there are some movements of the applicator during LDR-BT, however these movements do not result in significant dose changes in target volumes and critical organs. Therefore, positional correction is not required. In conclusion, CT-compatible TORE's applicator that allows an advantage for CT-based 3D planning is useful and safe for brachytherapy.