ESTRO 2025 - Abstract Book

S256

Brachytherapy - Gynaecology

ESTRO 2025

before being deployed in multiple interstitial and combined intracavitary/interstitial implants (fig 2).

Initial registration between the live US image and the MR is accomplished by placing the freehand transrectal US probe within the patient in a known location, such as the top of the vaginal canal/cervix area. The corresponding MR/US fusion is then locked within the electromagnetic field, any movement of the freehand probe will update both the US and MR images correspondingly. Needles can easily be identified with an overlay on the live US when a stylet equipped with a miniature EM tracker is inserted. In case of multiple needles, the trajectory of each needle can be digitally saved within the EM frame of reference. HR-CTV contours can be overlaid on the live US to help highlight the area of interest. Conclusion: A novel system has been developed and clinically tested to enhance the capabilities of US imaging for gyn brachytherapy procedures by incorporating clarifying MR information and easy needle recognition. These features can help guide the practitioner during the procedure to a geometrically more robust implant with actionable feedback.

Keywords: Ultrasound, electromagnetic guidance

3160

Mini-Oral Application of Polyethylene Glycol Hydrogel in Concurrent Chemoradiotherapy for Cervical Cancer to Prevent Radiation-induced Rectal Injury Junfang Yan, Yuxuan Wang, Fuquan Zhang Department of Radiation Oncology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China Purpose/Objective: The purpose of this study was to evaluate the safety and efficacy of polyethylene glycol (PEG) hydrogel in reducing rectal radiation dose and radiation-induced rectal injury during cervical cancer brachytherapy.