Role of regional 18F FDG PET/CT in clinically suspected osteomyelitis and prosthesis infection equivocal on triple phase 99m-Tc methylene diphosphonate (MDP) bone scintigraphy with SPECT/CT

1386 Objectives: Triple phase bone scintigraphy is a useful investigation to assess infections of the bone. However, in patients with implants/prosthesis, the interpretation is complicated by presence of reactive and reparative osteoblastic activity which can lead to increased tracer uptake lasting for a variable period of time. 18F-FDG PET/CT may help improve diagnostic confidence in such cases. Our aim is to assess the role of 18F-FDG PET/CT in cases of suspected osteomyelitis and prosthesis infection which are equivocal on 99m-Tc MDP bone scintigraphy. MATERIALS AND METHODS: Patients with clinically suspected osteomyelitis and prosthesis infection were initially assessed by triple phase 99m-Tc MDP bone scintigraphy with regional SPECT/CT. Patients with negative or unequivocally positive triple phase bone scan were excluded. Equivocal cases included patients with minimal or mild radiotracer activity in the affected region in flow and pool images with increased uptake in delayed phase and with CT findings suspicious for osteomyelitis. Patients with equivocal findings underwent regional 18F- FDG PET/CT. 99m Tc-MDP bone scintigraphy and FDG PET/CT results were correlated with final diagnosis confirmed by follow up, biochemical, culture and sensitivity and biopsy Results: Results: Twenty-four patients (10 female and 14 male) underwent both the scans with a median age of 38 (range 10-77).Fourteen patients had implants in situ. FDG PET/CT was positive in 13 (54%) and was negative in 11 patients. The pattern and the degree of FDG uptake were taken into consideration. All the FDG PET/CT positive patients were finally confirmed to have infection. Among the 11 patients with negative PET/CT scans for bone infection 4 patients had synovitis and one patient was diagnosed to have fibrous dysplasia, remaining 6 PET/CT negative patients no other definite diagnosis. CONCLUSION: Regional 18F-FDG PET/CT can be a useful modality to improve diagnostic certainty in patients with clinically suspected osteomyelitis and bone prosthesis related infections but equivocal findings on triple phase 99m-Tc MDP bone scintigraphy.