Can USPIO-enhanced spinal MR imaging help distinguish acute infectious osteomyelitis from chronic infectious and inflammatory processes?

By using a rabbit model of vertebral osteomyelitis, Bierry et al (1) utilized ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles to depict phagocytic macrophages that accumulated at sites of infection. The authors have taken advantage of a paradoxical dose-dependent T1-weighted signal intensity phenomenon that occurs when areas of high (adjacent normal spinal marrow) and lower (macrophages recruited into spinal abscess) iron accumulation demonstrate low and higher signal intensity, respectively. Although further studies are still needed to characterize the time course of changes during establishment of infection, this study provides proof of the principle that nanoparticles may permit magnetic resonance (MR) imaging to help identify and characterize areas of infection in the spine. What remains to be determined is whether this approach can be used to distinguish osteomyelitis from inflammation, degenerative change, and postoperative change.