[Effect of Brachytherapy Source Dwell Position on Dose Distribution in Cervical Cancer Therapy].

Purpose: To investigate the effect of different source dwell positions on dose distribution in the treatment of cervical cancer with brachytherapy.

Methods: Treatment planning data for cervical cancer patients were used. Treatment plans were created at 1 mm intervals, varying up to 5 mm. For intracavitary brachytherapy and intracavitary and interstitial brachytherapy, the following dose parameters were evaluated: 90% high-risk clinical target volume (HR-CTV D_90%), rectum 2 cm³ dose (Rectum D_{2 cc}), small intestine 2 cm³ dose (Small D_{2 cc}), sigmoid colon 2 cm³ dose (Sigmoid D_{2 cc}), bladder 2 cm³ dose (Bladder D_{2 cc}), point A dose.

Results: In intracavitary brachytherapy, the HR-CTV D_90%, Rectum D_{2 cc}, Small D_{2 cc}, and Sigmoid D_{2 cc} doses increased as the source dwell position changed in the direction. On the other hand, the dose of Bladder D_{2 cc} increased when the source position changed in the outward direction. The same trend was observed in the case of intracavitary and interstitial brachytherapy.

Conclusion: It was shown that a 1 mm change in the source dwell position can affect the dose by up to 2% or more. The accuracy of the source dwell position is very important and should be checked before using the device.