JRSBRT 10.1-2, p. 75-84 (PDF)

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Magnetic resonance-guided Linac for stereotactic body radiotherapy of spinal metastases
Yutaka Natsuaki and Benjamin P. Ziemer

Spinal metastases are a common and challenging complication in oncology, often leading to significant morbidity. Advances in surgery and radiotherapy for primary cancers have markedly improved overall patient survival leading to increased chances of metastatic disease spread, and thus increasing the need for less invasive, personalized treatment strategies if this arises. Stereotactic body radiotherapy (SBRT) has emerged as a standard-of-care modality, providing durable local control; however, the proximity of tumors to spinal cord and other critical neural structures necessitates exceptional precision in targeting and dose delivery. Linear accelerators guided by magnetic resonance (MR) represent a major technological advancement by combining high-resolution soft tissue imaging with real-time adaptive radiotherapy. These systems enable superior visualization compared to computed tomography scans normally used in radiotherapy, daily plan adaptation, and intra-fraction motion management beyond the capabilities of conventional image guidance. This review explains the clinical rationale for MR-guided SBRT in spinal metastases, the technological foundations of MR-Linac systems, clinical workflows, and early outcome data using this technology. Special attention is given to challenges specific to spinal applications, such as MR imaging artifacts caused by spinal instrumentation. Established MR metal artifact reduction techniques and emerging artifact reduction methods based on artificial intelligence are discussed as potential solutions to improve image quality. While early results are promising, further development is needed in integrating advanced imaging modality technologies, beam delivery, workflow optimization, and clinical validation. MR-Linac SBRT offers a transformative approach to personalized, high-precision radiotherapy and has the potential to refine the standard of care for spinal metastases.

Keywords: MR-Linac, spinal metastases, adaptive radiotherapy, stereotactic radiosurgery, real-time imaging