(18)F-FDG PET and PET/CT for the diagnosis of diabetic foot osteomyelitis.

Diabetic foot infection is a heavily dreaded complication of diabetes, frequently leading to prolonged hospi-talisation, disability and amputation 1-3. It usually occurs in, mostly long-standing, foot ulcers and is difficult to diagnose and notoriously demanding to treat 1-5. Diagnosis rests on meticulous clinical examination to identify local and/or systemic symptoms of inflammation 1,6,7. However, local signs of inflammation are not entirely reliable, because their development may be prevented by both peripheral arterial disease and diabetic polyneuropathy 3,4,6,8. If infection spreads to the bone, osteomyelitis ensues 1,9. The latter also poses extreme difficulties for diagnosis 9 : its likelihood is particularly high in the event of exposed bone, but the accuracy of this clinical sign is far from ideal 9-12. Finally, foot problems may occasionally present in diabetic children and adolescents: they are mostly skin and nail disorders, minor infections and neuropathic osteoarthropathy 8,13. Such cases call for particularly meticulous monitoring and early diagnosis to avoid the development of more severe foot pathology in adulthood 8,13. Imaging studies are of paramount importance for the timely diagnosis of diabetic foot infections, especially osteomyelitis 12,14-17. Plain X-rays are inexpensive and readily available, but their sensitivity for osteomyelitis is rather low and they may yield false negative results in the early stages 9,16. Technetium methyl-diphosphonate (99m Tc-MDP) bone scan and radiolabelled leukocyte scans are widely used to diagnose osteomyelitis, but their precision in the anatomical localisation of bone infection is not ideal 14-16. Conversely, Magnetic Resonance imaging (MRI) can provide more accurate information in terms of anatomical localisation (including the metaphysis), and it offers the additional advantage that it may be used for patient follow-up and treatment monitoring 16-18. Using the aforementioned modalities, diagnosis of osteomyeli-tis is no longer difficult in the foot clinic. Of these, MRI, 99m Tc-MDP bone scan and radiolabelled leukocyte scans are positive early enough to enable diagnosis, whereas plain radiographs may be negative in early, minor bone infection and only enable detection of severe osteomyeli-tis with periosteal reaction, cortical disruption, sequestra (i.e. fragments of necrotic bone) and/or abscesses 14-17. In a comparative analysis, plain radiographs have exhibited 69% sensitivity and 80% specificity, while the corresponding values for bone scintigraphy were 83% and 75%, and for MRI 100% and 75% 19. Fluorine-18-flurodeoxyglucose positron emission tomography (18 F-FDG-PET) and hybrid technique with computed tomography (PET/CT) have now emerged as alternative imaging modalities for the diagnosis of osteomy-elitis in the diabetic foot …