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

Purpose: To compare the diagnostic accuracy of diffusion-weighted imaging (DWI) and dynamic contrast-enhanced-magnetic resonance imaging (DCE-MRI) involving two region of interest (ROI) sizes with 18-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) to differentiate diabetic foot osteomyelitis (DFO) from Charcot neuro-osteoarthropathy (CN).

Method: Thirty-one diabetic patients were included in this prospective study. Two readers independently evaluated DWI (apparent diffusion coefficient [ADC] and high-b-value signal pathological-to-normal bone ratio [DWIr]) and DCE-MRI parameters (K^trans, K_ep, V_e, internal area under the gadolinium curve at 60 s [iAUC₆₀] and time intensity curve [TIC]) using two different ROI sizes, and ¹⁸F-FDG PET/CT parameters (visual assessment, SUV_max, delayed SUV_max, and percentage changes between SUV_max and delayed SUV_max). Techniques were compared by univariate analysis using the area under the receiver operating characteristic curve [AUC]. Reliability was analyzed with Kappa and Intraclass correlation [ICC].

Results: DWIr, K^trans and iAUC₆₀ showed better diagnostic accuracy (AUC = 0.814-0.830) and reliability (ICC > 0.9) for large than for small ROIs (AUC = 0.736-0.750; ICC = 0.6 in K^trans, 0.8 in DWIr and iAUC₆₀). TIC showed moderate diagnostic performance (AUC = 0.739-0.761) and reliability (κ 0.7). Visual assessment of ¹⁸F-FDG PET/CT demonstrated a significantly higher accuracy (AUC = 0.924) than MRI parameters. Semi-quantitative ¹⁸F-FDG PET/CT parameters did not provide significant improvement over visual analysis (AUC = 0.848-0.903).

Conclusion: DWIr, K^trans and iAUC₆₀ allowed reliable differentiation of DFO and CN, particularly for large ROIs. Visual assessment of ¹⁸F-FDG PET/CT was the most accurate technique for differentiation.