ESTRO 2025 - Abstract Book

S4037

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

ESTRO 2025

135

Digital Poster Implementation of a multi-phase intravenous contrast CT-simulation protocol for liver stereotactic ablative radiotherapy in end-expiration breath hold

Orla McKivitt, Marguerite Hussey, Denise O' Riordan, Vivien Keathing Department of Radiation Oncology, Cork University Hospital, Cork, Ireland

Purpose/Objective: CT-simulation of stereotactic ablative radiotherapy (SABR) liver patients can be challenging. Visualisation of the tumour can be difficult due to the similar attenuation factor of the tumour versus the normal liver tissue. Imaging with intravenous contrast (IVC) during different vascular phases can help improve accurate target delineation 1 . In this centre, multi-phase IVC CT-simulation scans are performed in free-breathing (FB) and end-expiration breath hold (EEBH). The aim of this study is to demonstrate the workflow adopted by this centre to introduce EEBH multi phase IVC for liver SABR patients. Material/Methods: Patients are scanned in the head-first supine position, arms above head with a VacBag. Surface-guided radiotherapy (SGRT) is used for monitoring of FB and EEBH compliance during CT acquisition. 85ml of IVC (Omnipaque 350, GE healthcare) is injected at a flow rate of 3ml/sec. The late arterial phase CT is performed 35 seconds post contrast injection while the patient is in FB. The second CT is performed a minimum of 60 seconds post contrast injection for the portal venous phase while the patient is in EEBH 2 . See fig.1 for workflow.