Clinical evaluation of dynamic [18F]FDG PET imaging to distinguish infection from inflammation in fracture-related infections.

BACKGROUND Standard [18F]FDG PET/CT is widely used to detect infections, but is limited in differentiating bacterial infection from inflammation due to overlapping uptake patterns. This distinction is particularly challenging in fracture-related infection (FRI), due to multiple factors, including recent surgery, soft tissue injury, fracture healing, and surgical implants. Dynamic [18F]FDG imaging over time may overcome this limitation by capturing a rapid, sustained uptake seen in infections, driven by ongoing immune and microbial activity, as opposed to the potentially slower uptake in inflammation. This study investigates the potential of dynamic [18F]FDG PET/CT using time-activity curves (TACs) to distinguish infection from inflammation in patients with suspected FRI. METHODS A prospective study was performed in patients referred for [18F]FDG PET/CT examination to detect (the extent of) FRI from December 2021 until November 2024. Final clinical diagnosis of FRI was established according to the criteria defined by the FRI consensus group and used as a reference standard. Dynamic PET imaging was performed using a long axial field-of-view PET/CT system over a 65-minute period after [18F]FDG injection. TACs were analyzed to compare uptake patterns between confirmed infections and inflammation, and diagnostic accuracy was calculated and compared to conventional standard imaging. RESULTS Thirty-one patients with 33 fractures suspected of infection were included. Infection was clinically confirmed in 14 fractures (42%). Diagnosis of FRI based on dynamic imaging using TACs resulted in a high sensitivity of 86%, specificity of 100%, PPV of 100% and NPV of 90%, resulting in a diagnostic accuracy of 94%. In the infection group, Fracture SUVpeak increased progressively over time, while in the inflammation group, uptake appeared to reach a plateau (p < 0.001). Visual interpretation of the dynamic imaging yielded a diagnostic accuracy of 82%. For standard imaging, quantitative and visual assessments showed diagnostic accuracies of 91% and 88%, respectively. CONCLUSION This proof-of-concept study demonstrates that dynamic [18F]FDG PET/CT using TACs can distinguish infection from inflammation in patients with suspected FRI, with high diagnostic accuracy observed, and suggesting a potential advantage over standard imaging. Larger-scale studies are needed to validate these results and explore the full clinical potential of dynamic imaging in infection management.