irradiation
noun [ U ] medical specialized uk/iˌreɪ.diˈeɪ.ʃən/ us/iˌreɪ.diˈeɪ.ʃən/
（用来治疗或诊断用的）光（或其他辐射）
light or other types of radiation used in order to treat or diagnose a medical condition
X-rays are a form of irradiation. X光是一种辐射。