Aim: The role of 18F-fluorodeoxyglucose-positron-emission tomography (FDG-PET) in the clinical management of patients with inflammatory diseases (e.g., chronic inflammatory diseases, fever of unknown origin, ostemyelitis, prosthesis infections) is still under investigation. The aim of the present study was to evaluate the usefulness of PET in the diagnostic work-up of patients with spondylodiscitis and to compare it with magnetic resonance imaging (MRI).
Methods: This retrospective study included 33 patients with suspected/confirmed spondylodiscitis. Two groups were created: 1) disease definition (n=24); and 2) treatment assessment (N.=16, 21 exams). Disease status was defined on the basis of data collected for symptoms, hematological parameters, imaging studies and histological findings, when available. Qualitative and semiquantitative analysis of the PET images was performed. The minimum duration of follow-up was 6 months.
Results: For the Disease Definition group, FDG-PET showed a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 92.9%, 50%, 72.2%, 83.3%, and 75%, respectively, and MRI showed a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 100%, 50%, 76.9%, 100%, and 81.3%, respectively. For the Treatment Assessment group, FDG-PET showed a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 90%, 81.8%, 81.8%, 90%, and 85.7%, respectively, and MRI showed a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 100%, 16.7%, 58.3%, 100% and 61.5%, respectively. No significant differences were observed between qualitative and semiquantitative evaluation of PET scans.
Conclusion: PET and MRI showed similar accuracy in the diagnosis of spondylodiscitis, indicating that PET can be used when MRI is doubtful or unavailable. PET was more accurate and more specific than MRI in treatment assessment, suggesting that PET should be preferred over MRI for determining when treatment can be safely discontinued.