SLR - November 2021 - Stephanie K. Ragan

Comparison of the Diagnostic Accuracy of Diffusion-Weighted and Dynamic Contrast-Enhanced MRI with 18f-Fdg Pet/Ct to Differentiate Osteomyelitis from Charcot Neuro-Osteoarthropathy in Diabetic Foot

Reference: Ana I Garcia Diez et al. Comparison of the Diagnostic Accuracy of Diffusion-Weighted and Dynamic Contrast-Enhanced MRI with 18f-Fdg Pet/Ct to Differentiate Osteomyelitis from Charcot Neuro-Osteoarthropathy in Diabetic Foot . European Journal of Radiology. 2020. 132

Level of Evidence: II

Scientific Literature Review

Reviewed By: Stephanie K. Ragan, DPM
Residency Program: Hennepin Healthcare – Minneapolis, MN

Podiatric Relevance: Early differentiation and treatment of diabetic foot osteomyelitis (DFO) from Charcot Neuro-osteoarthropathy (CN) is imperative to prevent deformity, resultant morbidity and decrease risk of amputation. The gold standard for diagnosis of osteomyelitis is bone biopsy which is not without risks. Radiographs are not sensitive and require weeks to detect changes. Three-phase bone scans are sensitive but not specific for DFO. MRI is able to differentiate osteomyelitis and osteoarthopathy, although it is challenging. This study aimed to compare the diagnostic accuracy of diffusion-weighted imaging (DWI) and dynamic contrast-enhanced-magnetic resonance imaging (DCE-MRI) involving two regions of interest (ROI) sizes with 18 fluorodeoxyglucose positron emission tomography/computed tomography ((18F-FDG PET/CT) to differentiate DFO from CN.

Methods: Thirty-one patients with DFO or CN were examined and underwent MRI, DWI, DCE-MRI and PET/CT. Two evaluators then independently evaluated the DWI, and DCE-MRI parameters including Ktrans, Kep, Ve, internal area under the gadolinium curve at 60s [iAUC60] and time intensity curve [TIC] using two different ROI sizes and 18F-FDG PET/CT parameters including visual assessment, SUVmax, delayed SUVmax and percentage changes between SUVmax and delayed SUVmax.

Results: Higher values in DWIr, Ktrans, iAUC60 for all ROI sizes were found in the DFO group compared to the CN group. TIC shape analysis revealed that partterns I and II indicated CN and patterns III and V indicated DFO, with low sensitivity but high specificity. Better reliability and diagnostic accuracy between diabetic foot osteomyelitis and Charcot neuro-osteoarthropathy was found using DWIr, Ktrans and iAUC60 for large ROIs. Significantly higher accuracy was found with visual assessment of 18F-FDG PET/CT than MRI parameters even in patients receiving antibiotic treatment or statins.   

Conclusions: This study indicates that providers may utilize 18F-FDG PET/CT to differentiate DFO from CN when MRI is not available or is inconclusive.  It also indicates that some parameters of the DCE-MRI such as DWIr, Ktrans and iAUC60 are superior to differentiate DFO from CN. Although this study indicates that this methodology can assist physicians in differentiating DFO from CN, it also requires the physician to understand and accurately apply these principles or have a radiologist on staff that has the ability and time to run these parameters. Likely there would be a large learning curve for the modern podiatrist.

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