Visualization of irradiated liver parenchyma may assist safety margin assessment in radiotherapy. We demonstrate that an MR imaging technique has the ability to visualize irradiated liver parenchyma after 30-Gy irradiation in a tumor-bearing rat model. In this technique, superparamagnetic iron oxide (SPIO) is administered to label Kupffer cells (KCs) before, rather than after irradiation. A dose of 30-Gy is a lower, more clinically relevant dose than that used in the previous studies. Our results suggest that 30-Gy irradiation delays the recovery of hepatic T2*-weighted signal after SPIO administration. Presumably, irradiation delays degradation process of SPIO in the KCs.