ESTRO 2025 - Abstract Book

S4338

RTT - Treatment planning, OAR and target definitions

ESTRO 2025

sets replicating standard workflows. Spinal cord delineation on MRL images, replicating an online SC ’cord of the day’, were also contoured. Contours were compared to simultaneous truth and performance level estimation (STAPLE) [4] contours using overlap metrics. Radiotherapy plans were optimised using standard workflow SC contours. SC doses were compared to the true position of the SC, the online MRL ‘cord of the day’ doses. Results: Radiotherapy plans using standard non-adaptive workflow delineated SC for optimisation resulted in the true MRL SC ‘cord of the day’ position receiving up to 27% excess dose (table 1 & 2).

No difference was seen in contour delineation between standard CT/MR and MRL imaging. SC contours had high levels of clinician consensus with low inter-observer variability across imaging modalities (dice similarity coefficient 0.92-0.94, Friedmann test P value 0.15).