Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Interpretation Criteria for Assessment of Antibiotic Treatment Response in Pyogenic Spine Infection

Abstract Purpose The objective of the study was to determine if fluorodeoxyglucose positron emission tomography/computed tomography ( 18 F-FDG PET/CT) can assess the response of patients with pyogenic spine infection to antibiotic treatment in a clinically useful time frame. Methods Twenty-eight patients with suspected pyogenic spine infection had baseline 18 F-FDG PET/CT. Patients with proven or probable infection were divided into good and poor responders to antibiotic therapy based on clinical criteria. These patients had a follow-up 18 F-FDG PET/CT 6-8 weeks later. Results Six of 28 patients were deemed negative for infection based on 18 F-FDG PET/CT. Two patients were excluded because of discrepancies in interpretation. Of the 20 patients deemed positive for infection, 13 had a pathogen isolated and all showed 18 F-FDG uptake in bone and/or soft tissue at baseline. Patients with a poor clinical response to treatment had persistent 18 F-FDG uptake in bone and/or soft tissue on follow-up. Patients with good clinical response had uptake confined to the margins of the destroyed disc. None of these patients had recurrent infection, even if antibiotics had already been discontinued at the time of the follow-up scan. Conclusions 18 F-FDG uptake confined to the margins of a destroyed disc after antibiotic therapy of pyogenic spine infection must not be considered indicative of persistent infection and likely represents mechanically induced inflammation. 18 F-FDG uptake in bone or soft tissue does indicate active infection. Quantification of activity could not reliably differentiate patients with active infection from those without active infection and those who had had a successful response to therapy. The pattern of activity is critical to accurate interpretation.