Combined off-resonance imaging and relaxation in the rotating frame for positive contrast imaging of infection in a murine burn model testing a novel anti-infective compound.

We developed a novel molecular magnetic resonance (MR) imaging method to monitor accumulation of macrophages at the infection site infection. Positive-contrast molecular MR imaging provides an alternative to negative-contrast molecular MRI imaging, exploiting the chemical shift induced by ultra-small superparamagnetic iron-oxide (USPIO) nanoparticles to nearby water molecules. We introduced a novel combination of off-resonance (ORI) positive-contrast MRI and T2p relaxation in the rotating frame (ORI-T2()) for positive-contrast MR imaging of USPIO. We used this new method for testing a new anti-infective compound M50 following Pseudomonas aeruginosa infection.