Spondylodiscitis of the thoraco-lumbar spine: diagnostic performance of dual-energy CT vs MRI

Objective: Dual-energy computed tomography (DECT) could combine the high-resolution bone window images made available by multi-detector CT technology with its capability to identify bone marrow edema (BME) in the spine, for diagnosing spondylodiscitis. Our objective was to compare the diagnostic performance of contrast-enhanced MRI and non-contrast DECT to identify spondylodiscitis of the thoraco-lumbar spine. Materials and methods: This prospective study included 77 consecutive participants (39 males; mean age of 61) who underwent DECT and MRI (within 7 days) between January 2020 and October 2023. DECT data were post-processed on a dedicated offline workstation (SyngoVia® VB20) by using a three-material decomposition algorithm. Four radiologists, blinded to clinical data, evaluated non-contrast DECT and contrast-enhanced MRI images. The diagnosis of spondylodiscitis was based on vertebral edema, disc edema, endplate erosions, and paraspinal involvement. Diagnostic accuracy values were calculated by using biopsy as a standard of reference. A multi-reader multi-case analysis was performed. Results: Biopsy revealed a diagnosis of spondylodiscitis in 46 patients (60%). Thoracic and lumbar spondylodiscitis were diagnosed in 37/46 (80%) and 9/46 (20%) patients, respectively. DECT and MRI overall sensitivity, specificity, and AUC were 0.91, 0.89, and 0.90, and 0.94, 0.93, and 0.93, respectively. At lumbar and thoracic levels, the difference between AUC values between DECT and MRI was not significant (p = 0.15). For DECT and MRI, a very good inter-reader agreement was achieved (k = 0.90 and k = 0.97, respectively). Conclusions: Contrast-enhanced MRI represents the most accurate imaging tool for the diagnosis of spondylodiscitis. However, only a non-significant drop in diagnostic performance was achieved by evaluating non-contrast DECT images. Key points: Question To compare the diagnostic performance of contrast-enhanced MRI and non-contrast DECT for identifying spondylodiscitis of the thoraco-lumbar spine. Findings MRI was not significantly superior compared to DECT in diagnosing spondylodiscitis, whereas the inter-reader agreement was near perfect for both MRI and DECT. Clinical relevance DECT represents a fast and accurate imaging tool for the demonstration of BME, erosions, and peri-vertebral inflammation in thoraco-lumbar spondylodiscitis.