Ultrasmall iron oxide particle contrast agent and MRI can be used to monitor the effect of anti-rejection treatment

Background. The purpose of the study was to investigate the feasibility of monitoring anti-rejection treatment using a blood pool contrast agent and magnetic resonance (MR) imaging. Methods. Allogeneic heterotopic heart transplantations in rats were performed. in one group (treated group), a mild acute rejection was developed and subsequently treated and MR imaging was performed before and after anti-rejection treatment. In the other group (nontreated group), a mild acute rejection was developed and allowed to progress without treatment and MR examinations were performed before and after the advance of the acute rejection. After injecting ultrasmall superpararriagnetic contrast agent, the relative change of signal intensity (SI) over time was measured. The SI difference between both radiological investigations for every animal was calculated; hence, every animal served as its own control. Results. In both treated and nontreated groups, a significant difference over time was found between the two MR examinations seen as a decrease in the treated group and an increase in the nontreatment group. Conclusion. It is concluded that the effect of anti-rejection treatment can be detected using a blood pool agent and MR imaging, as a change in SI corresponding to changes in the vascular permeability.