ESTRO 2025 - Abstract Book

S202

Brachytherapy - General

ESTRO 2025

2872

Digital Poster A novel dedicated mobile system for image-guided adaptive gynecological brachytherapy planning: a single centre experience Francesca Buonanno 1 , Valentina d'Alesio 1 , Federica Gherardi 1 , Eva Iannacone 1 , Gianluca Ametrano 1 , Marcello Serra 1 , Cecilia Arrichiello 1 , Mario Petrazzuoli 2 , Marco Gagliardi 1 , Mariateresa Coppola 1 , Simone Pezzella 1 , Paolo Muto 1 1 Department of Radiation Oncology, Istituto Nazionale Tumori—IRCCS—Fondazione G. Pascale, Napoli, Italy. 2 Department of Radiotherapy, AOU Federico II, Napoli, Italy Purpose/Objective: The standard gynecological BT planning procedure includes the simulation CT to perform the contouring and calculate dose distributions. Performing 3D-adaptive treatment planning and dosimetry for each BT fraction is critical for enhancing the accuracy and safety of high radiation dose delivery to the tumor target. For this purpose, a dedicated mobile CBCT has been installed in our hospital. Here we present a primary evaluation of the imaging performance and protocols for image-guided gynecological BT planning. Material/Methods: The scanner has a 121 cm diameter ring gantry with an X-ray source (60–120 kV) and a flat panel detector (43.2 × 43.2 cm 2 ) rotating independently. The system features non-isocentric imaging, dynamic collimation, legs with motorized wheels, battery-powered mobility and wireless remote control via tablet-PC. As an initial stage, a phantom study was conducted to evaluate 3D imaging performance with a focus on pelvis protocols. For the 3D imaging quality test, the Catphan 600 was used. Images were acquired by using three pre-loaded protocols. No manual adjustments have been made to scan settings (kV, prefiltering, mAs, field of view). Image quality metrics were evaluated. CT number accuracy and linearity, image uniformity, noise, spatial resolution, and low contrast detectability were all assessed in order to compare the scan protocols.

Results: Concerning the CT number linearity of eight inserts, no significant differences were observed between the protocols. The image uniformity values were found to be within ±4 Hounsfield units (HU), with a range of 9.1–12.3 HU for standard deviations. The resolution level was 21 line-pairs-per-centimeter (lp/cm) on average. For image low-contrast detectability, the minimum diameter of distinguishable contrast holes reached 1 mm at a 0.5% resolution.