Role of Fluorodeoxyglucose PET/Computed Tomography in Post-radiation Treatment Inflammatory Changes

Radiation therapy induces inflammatory changes in normal tissues that can persist for months and confound fluorodeoxyglucose positron emission tomography/computed tomography interpretation, particularly when assessing for tumor recurrence. This review examines the pathophysiology, time course, and imaging characteristics of post-radiation inflammatory changes across major organ systems including pulmonary, head and neck, gastrointestinal, genitourinary, musculoskeletal, and cardiovascular sites. Key topics include the conformational pattern of inflammatory uptake matching the radiation field, limitations of standardized uptake value-based quantitative criteria, optimal timing considerations, common pitfalls in interpretation, and emerging strategies, including novel radiotracers and multimodality imaging for differentiating post-treatment inflammation from residual or recurrent malignancy.