Off-resonance saturation MRI of superparamagnetic nanoprobes: Theoretical models and experimental validations

► Theoretical model for ORS MR imaging and quantification of SPPM is described. ► ORS contrast of SPPM is highly affected by its concentration and relaxation times. ► SPPM with short PEG corona have higher r2 rate and larger ORS contrast enhancement. ► ORS theory allows for quantification of ORS contrast of SPPM with known T1 and T2.