ESTRO 2024 - Abstract Book

S3455

Physics - Dose calculation algorithms

ESTRO 2024

Marie Murphy, Erica Bennett, Laura Barry, Dr. Paul Kelly

Bon Secours Radiotherapy, in partnership with UPMC Hillman Cancer Centre, Cork, Ireland

Purpose/Objective:

Background

Liver Stereotactic Ablative Radiotherapy (SABR) requires appropriate respiratory motion management. Additionally, inter and intrafraction organ at risk motion is frequently encountered. Other patient-specific factors can also influence the accuracy and reproducibility of treatment. A scenario-adapted algorithm may be optimal for delivering linear accelerator-based SABR with the goal of minimising Planning Target Volume.

Aims/objectives

To develop a practical algorithm that will permit all patients to be optimally treated using motion management and IGRT strategies based on patient and tumour-specific factors. The algorithm utilises modern linear accelerator capabilities for accurate treatment delivery.

Material/Methods:

Prior to treatment planning, patients have three Gold AnchorTM fiducial markers placed in close proximity to the tumour as an outpatient under ultrasound guidance. One week later patients undergo pre CT assessment where the Radiation Therapist assesses the patient for factors that can influence optimal scan acquisition and appropriate motion-management strategy, including:

• Co-morbidities eg shoulder arthritis

• Ability to lie flat

• Patient comfort: is analgesia or oxygen required?

• Patient comprehension

• Patient breath-hold capabilities

• Other factors, e.g. anxiety, claustrophobia

If the patient is able to successfully achieve breath-hold, this technique is preferred. Otherwise a 4DCT-simulation scan is acquired. In all cases CT is followed by a contrast-enhanced planning MRI and motion assessment in the case of 4DCT. Institutional policy dictates that should GTV motion exceed 5mm in any phase a gated-strategy is adopted.

Results: