Background: The occurrence of osteomyelitis in diabetic foot often dictates different treatment approach. The diagnosis of osteomyelitis, though, is sometimes difficult. When X rays are not diagnostic or equivocal, a nuclear medicine studies are often performed. In common practice bone scan with Tc99m-MDP combined with In111 labeled leucocytes scintigraphy are used. Although highly sensitive, these procedures may be hampered by coexisting pathological processes such as neuroarthropathy, trauma, or cellulites. In addition, poor resolution of the In111 images, complicates the interpretation weather the observed uptake (e.g. infection) is in the soft tissue or within the bone. Positron emission tomography (PET) using 2-Deoxy-2-[18F]-Fluoro-D-Glucose (FDG) is a useful clinical tool for the assessment of malignancies. FDG, a nonspecific tracer of increased intracellular glucose metabolism, accumulates in sites of infection and inflammation as well. PET is highly sensitive but may lack the ability to define the anatomic location of a focus of increased FDG accumulation. The hybrid PET/CT technology, providing precise registration of metabolic and structural imaging data, obtained in one session on a single device, may improve diagnosis and localization of infection.
Goals: The present study assesses the role of PET/CT imaging using FDG for the diagnosis of diabetic foot osteomyelitis.
Methods: Fourteen diabetic patients (M=10, F=4; age range 29–70 years) with 18 clinically suspected sites of infection underwent PET/CT following the injection of 185–370 MBq FDG for suspected osteomyelitis complicating diabetic foot. PET, CT and hybrid images were independently evaluated for the diagnosis and localization of an infectious process. Additional data provided by PET/CT for localization of infection in the bone or soft tissues was recorded. The final diagnosis was based on histopathological findings and bacteriological assays obtained at surgery or clinical and imaging follow up.
Results: PET detected 14 foci of increased FDG uptake suspected as infection in 10 patients. PET/CT correctly localized 8 foci in 4 patients to bone, indicating osteomyelitis. PET/CT correctly excluded osteomyelitis in 5 foci in 5 patients, with the abnormal FDG uptake limited to infected soft tissues only. One site of mildly increased focal FDG uptake was localized by PET/CT to diabetic osteoarthropathy changes demonstrated on CT. Four patients showed no abnormal increased FDG uptake, and no further evidence for an infectious process in the foot on clinical and imaging follow up.
Conclusion: FDG-PET can be used for diagnosis of diabetes-related infection. The precise anatomic localization of increased FDG uptake provided by PET/CT enables accurate differentiation between osteomyelitis and soft tissue infection.
