Erratum: Combined off-resonance imaging and T2 relaxation in the rotating frame for positive contrast MR imaging of infection in a murine burn model (Journal of Magnetic Resonance Imaging (2010) 32 (1172-1183))

Purpose: To develop novel magnetic resonance (MR) imaging methods to monitor accumulation of macrophages in inflammation and infection. Positive-contrast MR imaging provides an alternative to negative-contrast MRI, exploiting the chemical shift induced by ultra-small superparamagnetic iron-oxide (USPIO) nanoparticles to nearby water molecules. We introduce a novel combination of off-resonance (ORI) positive-contrast MRI and T2r relaxation in the rotating frame (ORI-T2r) for positive-contrast MR imaging of USPIO. Materials and Methods: We tested ORI-T2r in phantoms and imaged in vivo the accumulation of USPIO-labeled macrophages at the infection site in a mouse model of burn trauma and infection with Pseudomonas aeruginosa (PA). PA infection is clinically important. The USPIO nanoparticles were injected directly in the animals in solution, and macrophage labeling occurred in vivo in the animal model. Results: We observed a significant difference between ORI-T2r and ORI, which leads us to suggest that ORI-T2r is more sensitive in detecting USPIO signal. To this end, the ORI-T2r positive contrast method may prove to be of higher utility in future research. Conclusion: Our results may have direct implications in the longitudinal monitoring of infection, and open perspectives for testing novel anti-infective compounds.