Objective: To compare apparent diffusion coefficient [ADC] values between infectious spondylodiscitis and spinal malignant tumors. In addition, to determine sensitivity, specificity, accuracy, positive predictive value [PPV], and negative predictive value [NPV] using ADC value cutoff point for diagnosis of infectious spondylodiscitis.

Materials and Methods: Eighteen patients with 53 vertebral marrow lesions of suspected infectious spondylodiscitis or spinal malignant tumors acquired between March 2015 and March 2016 were prospectively performed diffusion-weighted MR imaging with ADC mapping. The authors measured the minimal ADC values [min ADC], mean ADC values [mean ADC] and maximal ADC values [max ADC] of the enhancing lesions or hyperintense T2 marrow lesions. These parameters were compared between infectious spondylodiscitis and spinal malignant tumors to find the ADC value cutoff point for diagnosis of infectious spondylodiscitis.

Results: The mean ADC values of the infectious spondylodiscitis were found to be significantly higher than those of the spinal malignant tumors, 1.30±0.28 x10^-3 mm²/second and 1.10±0.20 x10^-3 mm²/second, respectively. Sensitivity, specificity, accuracy, PPV, and NPV of the diagnosis of infectious spondylodiscitis using mean ADC value cutoff points of 1.116x10^-3 mm²/second were 75%, 68%, 71.7%, 72.4%, and 70.8%, respectively.

Conclusion: Diffusion-weighted MR imaging has a role in differentiating between infectious spondylodiscitis and spinal malignant tumors, especially when imaging findings on conventional images are inconclusive.

Keywords: MRI, DWI, ADC value, Infectious spondylodiscitis, Spinal malignant tumors