Proton beam therapy: neuroradiology considerations and challenges

Proton beam therapy (PBT) is increasingly used in paediatric neuro-oncology due to its favourable dose distribution and potential to reduce treatment toxicity. As its clinical use expands, neuroradiologists play a central role in recognising therapy-related changes and supporting long-term surveillance. This review outlines key neuroradiological considerations across the PBT pathway. MRI is fundamental to planning, but its integration requires modified workflows, specialised immobilisation equipment, and tailored sequence design to balance geometric accuracy, signal-to-noise constraints, and patient tolerability. Ongoing sequence optimisation-including the use of high-resolution isotropic volumes and advanced reconstructions-aims to improve delineation of target structures and organs at risk. During treatment, anatomical changes such as tumour or cyst evolution may alter proton range, necessitating interval imaging and, in selected cases, adaptive replanning. Post-treatment assessment presents further challenges, as PBT may produce distinct radiological appearances compared with photon therapy. These include patterns of pseudoprogression, variations in white matter and microvascular injury, and a spectrum of vascular complications. Accurate interpretation is essential to distinguish treatment effects from recurrence and to guide further management. Advances in MRI-only workflow development, synthetic CT generation, ultra-high-field imaging, and computational modelling offer opportunities to further improve treatment precision and refine the characterisation of post-treatment effects. As PBT becomes more widely delivered, this review will aid neuroradiologists at referring centres who will increasingly encounter its distinct post-treatment appearances, highlighting the importance of familiarity with these patterns in routine practice and aiding standardisation of post-treatment imaging protocols.