ESTRO 2024 - Abstract Book

S4126

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2024

3199

Digital Poster

Improving precision & evaluating open fixation mask in Whole-Brain RT: Optical Surface Guidance

Arpit Saini, Eva Samsøe

Zealand University Hospital, Department of Clinical Oncology, Radiotherapy, Naestved, Denmark

Purpose/Objective:

This study investigates the integration of surface-guided radiotherapy (SGRT) to facilitate the clinical application of a partially open mask for whole-brain radiation therapy (WBRT). The primary objective is to enhance patient comfort without compromising treatment quality. Additionally, we assess the impact of optical surface guidance on the positional accuracy of the optical surface monitoring system (OSMS) setup in comparison to the traditional laser setup. We calculate uncertainty errors for both methods to establish institution-specific margins.

Material/Methods:

Sixteen patients underwent WBRT with a palliative fractionation regimen of 3 Gy x 10. Patients were divided into retrospective (n=12) and prospective (n=4) groups. Retrospective patients were positioned using room lasers, while prospective patients were aligned using OSMS. A pair of orthogonal kV images were acquired to correct translational and rotational deviations through standard matching procedures. Continuous MV images were obtained to monitor intra-fraction deviations. Post-treatment kV images were captured to quantify the correlation of intra-fraction setup/motion errors between real-time deltas (RTDs) from OSMS and pre/post-treatment kV images.

Results:

In the laser setup, the systematic and random components of the absolute inter-fraction setup error, derived from onboard imaging (OBI), averaged 0.14 cm, 0.11 cm, 0.12 cm, and 0.12 cm, 0.16 cm, 0.14 cm in the vertical, longitudinal, and lateral directions, respectively. For the OSMS setup, the systematic and random components of the absolute inter- and intra-fraction setup error were 0.10 cm, 0.18 cm, 0.08 cm, and 0.04 cm, 0.08 cm, 0.07 cm in the vertical, longitudinal, and lateral directions, respectively. The OSMS setup demonstrated a significant reduction in systematic and random errors in the vertical and lateral directions compared to the laser setup. Moreover, PTV margins were reduced to 0.31 cm and 0.27 cm in the vertical and lateral directions for the OSMS setup, from 0.47 cm and 0.44 cm for the laser setup. The longitudinal margin increased to 0.56 cm for the OSMS compared to 0.42 cm for the laser setup. The OSMS setup exhibited reduced mean and standard deviations of absolute inter-fraction setup deviations in translational and rotational directions.

Conclusion:

Optical Surface Monitoring System (OSMS) proves to be a promising alternative to the conventional laser setup for precise patient positioning and WBRT monitoring. OSMS allows for a significant reduction in treatment margins, which