S2755
RTT - Patient preparation, immobilisation, and verification protocols
ESTRO 2026
1 Oxford, GenesisCare, Oxford, United Kingdom. 2 OUH, NHS, Oxford, United Kingdom
Purpose/Objective: Radiotherapy to the stellate ganglia represents a novel, non-invasive approach to modulating sympathetic activity in patients with refractory ventricular arrhythmias. Within the ongoing MR- guided ventricular arrhythmia trial, GenesisCare implemented this treatment for the first time on the MRIdian MR-Linac. As the MRIdian system had not previously been used for head-and-neck regions at Oxford, a radiographer-led project was undertaken to design and evaluate the effectiveness of a modified H&N immobilisation system in ensuring reproducible, safe delivery of radiotherapy to the stellate ganglia. Material/Methods: For treatment, patients would need MR simulation on the MRIdian (pilot, TRUFI, and tracking sequences) followed by contrast-enhanced CT, both in their treatment mask. An MR-safe Orfit head-and-neck board with five-point mask and optional custom Accuform headrest was employed alongside a foam mattress, with knee and foot supports for comfort.Initial attempts to integrate the H&N bottom coil inside of the mask compromised mask effectiveness and reproducibility, rendering it unfit for use. The solution was to position the H&N board on top of the torso bottom coil, meaning a conventional radiotherapy treatment mask could be made [1]. Unfortunately, the H&N board sitting on the bottom coil meant the board could not be indexed. Radiographers designed an in-house wooden adaptor bridging the coil-board gap to resolve the issue (Figure 1), enabling the final immobilisation solution (Figure 2).Simulation trials on volunteers found that image quality was suitable with this setup, whilst confirming reproducibility and immobilisation effectiveness. These trials also highlighted the need for robust hearing protection, properly fitted earplugs were found to be suitable. Collaboration with physicists and oncologists supported equipment fabrication, validation, and workflow approval.
Figure 2 Results:
Five patients have been successfully treated to date (target = 13). Immobilisation reproducibility was high, with all daily bony matches within the 2mm tolerance specified in protocol and negligible intrafraction motion observed on continuous imaging. Mean treatment duration was approximately 40 minutes. Minor immobilisation challenges included patients’ ability to lay flat, resolved with the use of custom headrests when required. Conclusion: Head-and-neck immobilisation stellate ganglia radiotherapy is achievable on the MRIdian MR-Linac. The radiographer-led design and validation of a reproducible immobilisation and imaging workflow enabled safe implementation of MR-guided stellate ganglion radiotherapy. This work highlights the capacity of radiographers to lead technical innovation in MR-guided workflows and paves the way for future MR-Linac applications in complex head-and-neck and functional radiotherapy indications. References: 1. Cuccia F, Alongi F, Belka C, Boldrini L, Hörner-Rieber J, McNair H, Rigo M, Schoenmakers M, Niyazi M, Slagter J, Votta C, Corradini S. Patient positioning and immobilization procedures for hybrid MR-Linac systems. Radiation Oncology. 2021;16:183.Figure 1: Custom radiographer-designed adaptor bridging the 3.5cm coil-to-board gap.The adaptor restored full indexing capability and ensured secure, reproducible immobilisation while maintaining MR compatibility.Figure 2: Final immobilisation configuration for MR-guided stellate ganglion radiotherapy.The final setup integrated the indexed H&N board, five-point mask, and custom headrest. Keywords: MR-Linac, Immobilisation, Stellate Ganglion
Digital Poster 5019
Figure 1
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