Project Abstract Overview: This project aims to develop a reliable 18F-fluorodeoxyglucose (18F-FDG) PET/MRI method with novel metal artifact correction techniques to provide early identification of prosthetic complications causing persistent postsurgical pain (PPSP) following total hip arthroplasty (THA). Relevance: THA is one of the most rapidly growing procedures to treat the end-stage hip joint pain and dysfunction, and its annual cases are estimated to reach 572,000 by 2030. Unfortunately, a substantial number of patients experience PPSP after the procedure, which, without proper treatment, can significantly impair the quality of life. However, the early identification of pain generators for these patients is very difficult because the current diagnostic methods including X-ray, CT, and MRI, have limited sensitivity to pain and suffer from severe artifacts induced by metal in prostheses. Therefore, there is a pressing need for a novel diagnostic approach to accurately identify the abnormal inflammatory changes causing persistent pain to guide the appropriate treatment matched to the exact sources of pain. Approach: We propose the use of 18F-FDG PET/MRI for early identification of sources of PPSP following THA. Our previous 18F-FDG PET/MRI study of chronic pain syndromes demonstrated promising improvements in detecting sites of painful inflammation. However, the severe metal artifacts near metallic prostheses limit the application of 18F-FDG PET/MRI to THA patients. Therefore, our first aim in this project is the development of metal-aware attenuation correction for PET to enable reliable 18F-FDG PET near the metallic prosthesis. Our second aim is the development of high-resolution hip MRI at 3T with metal artifact correction to improve our ability for identifying structural causes of PPSP symptoms. Our third aim is to validate the improvements by 18F- FDG PET/MRI in detection of the pain generators compared to PET/CT and conventional MRI. This will be accomplish