Incremental value of diffusion weighted imaging over conventional MRI for the diagnosis of osteomyelitis of extremities

Objective To determine the incremental value of diffusion weighted imaging (DWI) over conventional MR imaging in diagnosing extremity osteomyelitis (OM). Materials and methods In this cross-sectional study, three experienced musculoskeletal radiologists evaluated clinically suspected cases of extremity OM in two rounds—first on conventional MR imaging, and then conventional MR imaging combined with DWI 4–6 weeks later. The readers recorded a result of the presence or absence of OM and their diagnostic confidence on a 1–5 scale. Mean and minimum apparent diffusion coefficient (ADC) were measured. Pathology diagnosis served as the reference standard. Statistical analysis utilized intraclass correlation (ICC) and Conger’s kappa. Results A total of 213 scans of suspected OM were reviewed by three musculoskeletal radiologists with no significant changes in sensitivity (0.97, 0.97), specificity (0.97, 0.94), positive predictive value (0.91, 0.87), or negative predictive value (0.98, 0.98) between conventional MR imaging and MR imaging combined with DWI, respectively. Reader confidence did not significantly change with the addition of DWI (4.55 and 4.70, respectively). A high inter-reader agreement was observed for the diagnosis of OM, soft tissue abscess, and intraosseous abscess in both rounds. A higher mean (1.46+/−0.43 × 10 −3 mm 2 /s > 0.64+/−0.47 × 10 −3 mm 2 /s) and minimum (1.18+/−0.45 × 10 −3 mm 2 /s > 0.37+/−0.44 × 10 −3 mm 2 /s) ADC value was associated with OM ( p -value < 0.0001) with odds ratios of 1.34 and 1.31, respectively, for mean and minimum ADC of the involved bone. Conclusion DWI-derived ADC increase is associated with OM. The use of DWI slightly increases reader confidence in the diagnosis of OM; however, no significant incremental value over conventional MR imaging is seen for the final diagnosis of OM.