Four-dimensional MRI of renal function in the developing mouse.

The major roles of filtration, metabolism and high blood flow make the kidney highly vulnerable to drug-induced toxicity and other renal injuries. A method to follow kidney function is essential for the early screening of toxicity and malformations. In this study, we acquired high spatiotemporal resolution (four dimensional) datasets of normal mice to follow changes in kidney structure and function during development. The data were acquired with dynamic contrast-enhanced MRI (via keyhole imaging) and a cryogenic surface coil, allowing us to obtain a full three-dimensional image (isotropic resolution, 125 microns) every 7.7 s over a 50-min scan. This time course permitted the demonstration of both contrast enhancement and clearance. Functional changes were measured over a 17-week course (at 3, 5, 7, 9, 13 and 17 weeks). The time dimension of the MRI dataset was processed to produce unique image contrasts to segment the four regions of the kidney: cortex (CO), outer stripe (OS) of the outer medulla (OM), inner stripe (IS) of the OM and inner medulla (IM). Local volumes, time-to-peak (TTP) values and decay constants (DC) were measured in each renal region. These metrics increased significantly with age, with the exception of DC values in the IS and OS. These data will serve as a foundation for studies of normal renal physiology and future studies of renal diseases that require early detection and intervention.