Fig. 4

Patient (case # 3) with a history of knee prosthesis implantation performed 12 months before imaging. The results of ¹⁸F-FDG PET/CT (upper row) and ⁶⁸Ga-citrate PET/CT (lower row) are presented. a–d The green arrows indicate an increased ¹⁸F-FDG uptake at both the bone prosthesis interface and the knee synovium. e–h A similar pattern of ⁶⁸Ga-citrate uptake was evident. The imaging results were considered positive, and the case was subsequently confirmed as true positive. d, h In contrast to the femoral portion, there was no increased radiotracer uptake along the bone prosthesis interface of the elongated tibial stem component (indicating no loosening or infection of a specific prosthesis segment, blue arrows)