Asad Nawaz

Diagnostic Performance of FDG-PET, MRI, and Plain Film Radiography (PFR) for the Diagnosis of Osteomyelitis in the Diabetic Foot

BackgroundThe early and accurate diagnosis of osteomyelitis in the diabetic foot is essential to provide appropriate treatment and obviate long-term complications of the disease. The currently employed non-invasive imaging modalities such as plain film radiography (PFR) lack the sensitivity to accurately exclude osteomyelitis, while magnetic resonance imaging (MRI) is limited by its low specificity and contraindications in certain patients. Therefore, accurate non-invasive detection of osteomyelitis in the diabetic foot remains a challenge. [18F]-2-fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) has been proven useful in other settings to detect infection. In this ongoing prospective study, we assessed the diagnostic performance of FDG-PET to diagnose osteomyelitis in the diabetic foot and compared it with that of MRI and PFR.MethodsPatients who met the prespecified criteria for complicated diabetic foot underwent FDG-PET, MRI, and PFR of the feet. Each imaging study was then interpreted in a blinded fashion for presence of osteomyelitis or other abnormalities. The gold standard for diagnosis in each patient was based on surgical, microbiological, and clinical follow-up results.ResultsOne hundred ten consecutive patients have been enrolled to date into this prospective project. FDG-PET correctly diagnosed osteomyelitis in 21 of 26 patients and correctly excluded it in 74 of 80, with sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of 81%, 93%, 78%, 94%, and 90%, respectively. MRI correctly diagnosed osteomyelitis in 20 of 22 and correctly excluded it in 56 of 72, with sensitivity, specificity, PPV, NPV, and accuracy of 91%, 78%, 56%, 97%, and 81%, respectively. PFR correctly diagnosed osteomyelitis in 15 of 24 and correctly excluded it in 65 of 75, with sensitivity, specificity, PPV, NPV, and accuracy of 63%, 87%, 60%, 88%, and 81%, respectively.ConclusionFDG-PET is a highly specific imaging modality for the diagnosis of osteomyelitis in diabetic foot and, therefore, should be considered to be a useful complimentary imaging modality with MRI. In the setting where MRI is contraindicated, the high sensitivity and specificity of FDG-PET justifies its use after a negative or inconclusive PFR to aid an accurate diagnosis.

Relation between popliteal-tibial artery atherosclerosis and global glycolytic metabolism in the affected diabetic foot: a pilot study using quantitative FDG-PET.

BACKGROUND We evaluated the extent and the degree of active atherosclerosis in the popliteal-tibial arteries by quantitative techniques using [(18)F]-2-fluoro-2-deoxy-d-glucose-positron emission tomography (FDG-PET). An effort was made to determine whether there was a positive correlation between the level of ongoing atherosclerosis and subsequent chronic ischemia in the diabetic foot. METHODS A total of 115 diabetic patients were enrolled in this prospective research study and underwent lower-extremity FDG-PET and magnetic resonance imaging. We selected 36 diabetic patients with complicated diabetic foot for this analysis (11 men, 25 women; mean age, 59.5 years; age range, 36-85 years). Ten nondiabetic control participants (6 men, 4 women; mean age, 59.7 years; age range, 27-88 years) were also included for comparison. Only patients with blood glucose levels less than 200 mg/100 mL were enrolled in this study. The metabolic volumetric product (MVP), for each patient was calculated multiplying foot average maximum standard uptake value (SUV(max)) by foot volume. Pearson correlation analysis between foot mean SUV(max) alone and the degree of atherosclerosis and between the foot MVP and the degree of atherosclerosis was performed as measured by FDG-PET. A t test was used to assess for significant differences in foot SUV(max) and foot MVP among varying degrees of atherosclerosis, using P < .05 as the criterion for statistical significance. RESULTS Foot SUV(max) significantly correlated (P < .05) with the ratio of popliteal-tibial artery SUV(max) to background SUV (Pearson correlation coefficient = 0.49). Foot MVP was also significantly correlated (P < .05) with the ratio of popliteal-tibial artery SUV(max) to background SUV (Pearson correlation coefficient = 0.69). CONCLUSIONS Using FDG-PET, one may be able to detect and quantify the degree of increased metabolic activity of early active atherosclerosis and the associated chronic tissue ischemic effects at the regional level and globally throughout the whole body during the asymptomatic phase of disease.