ESTRO 2024 - Abstract Book

S4155

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2024

[1] Fast, Martin, et al. "Tumor trailing for liver SBRT on the MR-Linac." International Journal of Radiation Oncology* Biology* Physics 103.2 (2019): 468-478.

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Digital Poster

Real Time Motion Tracking for MR-guided Spine SBRT (Pilot Study)

Yao Ding 1 , Martin C Tom 2 , Debra N Yeboa 2 , Gizem Cifter 1 , Tina M Briere 1 , Eun Young Han 1

1 UT MD Anderson Cancer Center, Radiation Physics, Houston, USA. 2 UT MD Anderson Cancer Center, Radiation Oncology, Houston, USA

Purpose/Objective:

Spine SBRT delivers high dose of radiation with utmost precision to targets near the spinal cord and is an established treatment option for patients with spinal metastases. However, during traditional Linac based treatment with CBCT image guidance, the spinal canal is often used for treatment alignment and as a surrogate structure for cord dose tolerance. MR-guided spine SBRT enables clear visualization and real-time monitoring of the true spinal cord during treatment. This may allow for dose-escalation and/or increased cord dose constraints, thus improving treatment for patients with epidural disease who otherwise may not be ideal candidates for spine SBRT. The aim of this study was to assess the feasibility of real-time motion tracking of the spinal cord and patient motion quantitively using 2D-cine MRI on the MR-Linac system. Four patients and two healthy volunteers were recruited on IRB-approved protocols. Each person had 2 MR simulations – one shortly after simulation (MR-sim-1) for spine treatment and the other shortly after spine treatment (MR-sim-2), which usually occurs one or two weeks after simulation. Each MR linac scan consists of a pre T2 3D MRI scan, cine MRI in sagittal and coronal planes for 25 min, and post T2 3D MRI scan. The difference between pre- and post-3D MRIs demonstrated the intrafractional motion assessed in RayStation, and the cine MRI provided real-time patient motion data analysed by Motion Monitoring Research Package (v4.0). The difference of two pre 3D MRIs between MR-sim-1 and MR-sim-2 represented interfractional patient setup changes. In this analysis, the range (Max-Min) of motion was obtained from 4 patients (PT 1-4) and 2 healthy volunteers (V1 and V2) immobilized with the Klarity SBRT system during MRI scans of their cervical (C), thoracic (T), and/or lumbar spines (L). Material/Methods:

Results: