Cellular magnetic resonance imaging for the differentiation of infectious and degenerative vertebral disorders: Preliminary results

Abstract

Purpose: To evaluate macrophage imaging using the ability of superparamagnetic iron oxide (SPIO) magnetic resonance imaging (MRI) to differentiate infectious vertebral osteomyelitis and degenerative disk-related inflammatory endplates. The in vivo demonstration of the different distribution of macrophages in those two disorders may allow a more accurate characterization of vertebral endplate abnormalities than classical extracellular MR changes. Materials and Methods: In 12 patients with endplate abnormalities (six cases of bacteriologically proven spondylodiscitis, six cases of disk degeneration-related endplate changes), two MRI sessions were realized: before and 24 hours after injection of SPIO. The signal-to-noise ratio (SNR) of endplates were qualitatively and quantitatively compared on pre- and post-SPIO injection T1 and T2-weighted (T2w) MR images (Wilcoxon signed rank test). Results: In the infection group, the SNR of abnormal end-plates showed a significant signal loss on T2w MR images (P = 0.03) but not on T1w images (P = 0.46). In the degenerative spine group, no significant signal loss was observed on T1 (P = 0.6) nor on T2w MR images (P = 0.6). Signal loss was only visually observable in abnormal endplate in one patient of the spondylodiscitis group on T2w MR images. Conclusion: MRI of the spine with iron oxide injection differentiates infection from aseptic inflammation on quantitative analysis, but the use of SPIO makes direct visual evaluation less satisfactory. © 2009 Wiley-Liss, Inc.