Radiotherapy remains one of the essential treatment modalities for brain gliomas, brain metastases, pediatric neuroblastomas, and primary central nervous system lymphomas. With continuous advancements in modern radiotherapy techniques, patients have achieved significantly improved local control rates and prolonged survival. However, the long-term complications associated with radiotherapy have become increasingly evident. Radiation-induced brain injury (RIBI) is a clinical syndrome characterized primarily by neurological dysfunction following focal or whole-brain radiotherapy. It negatively impacts patients’ quality of life and imposes a considerable burden on families and society. With the rapid development of medical imaging and artificial intelligence technologies, multimodal imaging techniques, including structural magnetic resonance imaging, diffusion-weighted imaging, functional magnetic resonance imaging, perfusion imaging, positron emission tomography-computed tomography metabolic imaging, and radiomics, have demonstrated significant potential for early detection, dynamic monitoring, and quantitative evaluation of RIBI. Meanwhile, treatment strategies for RIBI are shifting from traditional symptomatic and supportive care toward multidimensional interventions aimed at protecting the blood-brain barrier, modulating neuroinflammation, and implementing precise targeted therapies. Additionally, emerging studies have explored neuromodulation techniques and gut-brain axis regulation, offering new directions for the prevention and treatment of RIBI. Although conventional imaging methods remain valuable for diagnosing RIBI, they exhibit notable limitations in the early stages of the disease and in differentiating RIBI from tumor recurrence. This review focuses on the current state of technological development, key findings, and existing limitations, with the aim of providing a theoretical foundation and technical support for the early identification and precise intervention of RIBI.