MRI investigations of graft rejection following organ transplantation using rodent models.

This chapter examines the magnetic resonance imaging (MRI) investigations of graft rejection following organ transplantation using rodent models. The emerging noninvasive MRI methodologies for evaluating acute allograft rejection as potential alternatives for surveillance biopsy are described. In the renal transplantation model, most of the allogeneic kidney grafts show mild acute rejection on postoperative day (POD) 3, with light interstitial edema and some foci of lymphoplasmacytic infiltration in the perivascular space and in the surrounding interstitium, but the glomeruli are within the normal range. On POD 4, the allografts undergo moderate acute rejection with lymphoplasmacytic in filtration found over the entire interstitium. On POD 5, extensive interstitial lymphoplasmacytic in filtration is found with hemorrhage. The combined information criterion is used to select the order of the autoregression (AR) model, and the AR coefficients are estimated by Burg's method, which is based on the minimization of the sum of the forward and backward squared prediction errors. The results shows that the two-pronged approach to detect the initiation of graft rejection and to monitor the function of a transplanted organ during various stages of the graft rejection process using the noninvasive MRI methodology is very attractive and merits further development.