ESTRO 2025 - Abstract Book

S4080

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2025

1975

Digital Poster Implementation of surface-guided radiotherapy for motion management of end-expiration breath-hold liver stereotactic body radiotherapy patients Orla McKivitt 1 , Michael Roche 1 , Kate Lawless 1 , Paul Collins 1 , Triona O' Donovan 1 , Aoife O' Connell 1 , Eoin McGrath 1 , Sean M O'Cathail 1 , Aisling Barry 1,2 1 Department of Radiation Oncology, Cork University Hospital, Cork, Ireland. 2 Cancer Research@UCC, University College Cork, Cork, Ireland Purpose/Objective: Stereotactic ablative body radiotherapy (SABR) to the liver requires accurate management of respiratory motion (1). Treatment of patients in end-expiration breath-hold (EEBH) has been shown as a reproducible method of minimising liver motion (2). Surface guided radiotherapy (SGRT) in this setting is under-reported. The aim of this study is to demonstrate how our department implemented liver SABR using SGRT alone as a motion management solution when treating patients in EEBH. Material/Methods: Current departmental protocols were adapted and new processes developed to achieve an EEBH liver SABR pathway using SGRT. This included the development of; motion assessment procedures using a 2D kV cine protocol, CT simulation procedures, EEBH workflows within SGRT, machine and plan QA procedures and staff training packages. Results: See fig 1. for developed patient pathway. In our experience, consistency of EEBH coaching is key to patient compliance. Specific in-house training for radiation therapists (RTs) was developed. A motion assessment procedure was created to quantify intra-fractional motion of the liver during EEBH, using SGRT, prior to CT-simulation. SGRT surfaces are captured in free-breathing (FB) and EEBH to track patient motion. Five kV cine images are acquired for a duration of 15 seconds while the patient is in EEBH. SGRT is used to ensure EEBH is achieved to the same depth and maintained during each image. Treatment margins can be adjusted if residual motion of the liver is detected during motion assessment. Multiphase IV contrast CT-simulation in EEBH is performed, using SGRT for monitoring. Arterial and venous phase IV contrast scan protocols were developed for optimum enhancement of the lesion. SGRT protocols were created with tolerances of 1mm and 1 degree in each direction and beam hold trigger after 1 second of misalignment. Regions of interest (ROI) were defined and tested for camera block during gantry rotation and imaging. Five liver SABR patients have been successfully treated in EEBH using SGRT at our centre.