Some of the gadolinium based contrast agents are shown to produce enhancements on T1-weighted images long after their administration in certain brain structures in humans, raising questions about the safety of these agents. The enhancement is thought to be due to dechelation of the contrast agents. Understanding the pathophysiological effects requires systematic pre-clinical studies. As a first step towards this goal we conducted longitudinal in vivo studies in rodents administered Magnevist and Omniscan for ten days to quantify the temporal profile of enhancement using relaxometry and investigate if this enhancement has an effect on the tissue microstructure. Our results show that Ominiscan lowers both T1 and T2 starting from week 2 post contrast administration. However, such changes were not observed in Magnevist and saline treated animals. The contrast agents do not appear to have significant effect on any of the DTI measures.