Hemodynamic effect of iodinated high-viscosity contrast medium in the rat kidney - A diffusion-weighted MRI feasibility study

RATIONALE AND OBJECTIVES. TO assess the abilities of dynamic diffusion-weighted MRI to demonstrate the effects in vivo of a high-viscosity iodinated contrast agent on medullary and cortical blood flow in the rat kidney, METHODS. Dynamic diffusion-weighted, echoplanar MR images obtained from five b-value single-shot acquisitions and their isotropic apparent diffusion coefficient maps were obtained from nine rats anesthetized by pentobarbital sedation, before and after intravenous injection of a high-viscosity, dimeric iso-osmolar iodinated contrast medium (iodixanol), and compared with those obtained from four control rats that received saline. RESULTS. The mean baseline apparent diffusion coefficient values were 1.64 +/- 0.05 x 10(-3) mm(2)/s for the cortex and 1.75 +/- 0.06 x 10(-3) mm(2)/s for the medulla, In the iodixanol group, a significant decrease in renal diffusion was observed at 12 minutes and lasted at least until 24 minutes. The decrease in diffusion occurred earlier for the cortex and lasted less than for the medulla, There was no significant modification in diffusion over time in the control group. CONCLUSIONS. This preliminary experience in rats shows that dynamic diffusion-weighted MRI can be used to study noninvasively the in vivo renal hemodynamic response after injection of iodinated contrast.