A simple technique to minimize needle displacement in gynecologic interstitial brachytherapy: Use of fully stretched elastic tapes

Abstract Purpose Previous studies on reproducibility in gynecologic high-dose-rate interstitial brachytherapy (HDRIB) have reported caudal needle displacements as high as 14–27.9 mm. The needle-template units in these studies were, however, sutured to the perineum, which gradually moved away from the target due to edema. To overcome the caudal force from the edema, we have been using fully stretched elastic tapes that exert cranial force on the template. To evaluate the effectiveness of our technique, caudal needle displacements relative to the target were investigated using CT coordinates. Methods and Materials Twenty-nine gynecologic cancer patients were treated using HDRIB. The template was pressed into the perineum using two elastic tapes. All patients underwent pretreatment and posttreatment CTs to obtain craniocaudal coordinates for the needles and the clinical target volume. Results The median displacements for the 533 needles relative to the clinical target volume were −0.8 mm (range, −5.7 to +4.7 mm). Absolute craniocaudal displacement >3 mm was observed in only 14.4% of the needles, with a maximum displacement of only 5.7 mm. Conclusions The use of elastic tapes achieved smaller displacements compared to those in previous reports. This was a simple but effective technique to minimize needle displacement for gynecologic HDRIB.