Understanding immune cell behaviour is important for evaluating therapeutic response in pre-clinical models. We monitor cell migration in a mouse model of cervical cancer by labeling cells with superparamagnetic iron oxide (SPIO). Simultaneous pre-clinical PET/MRI confirmed that the balanced steady-state free precession (bSSFP) sequence lacks specificity to SPIO-labeled cells within the tumor. We tested TurboSPI, a multi-echo single point imaging technique with compressed sensing that provides high temporal resolution 3D R2* mapping in under 45 minutes. These maps exhibit superior SPIO specificity compared to bSSFP images and enabled us to do both qualitative and quantitative cell tracking.