Common contrast enhanced MRI study relies on low retention and inert contrast. With the emerging trend of using paramagnetic metal for theragnostic study, few nanoparticles have been reported to have T1 enhancement property. In this research, we try to model the kinetics of such nanoparticles in mouse with A549 tumor. A novel three compartment model were introduced to explain the behavior of Mn-BRNP nanoparticles within mouse blood circulation system. This is the first study to explore reactive contrast agent with high retention, and successfully derived kinetic parameters that characterize the drug uptake behavior.