MRI ANATOMY OF THE RAT-KIDNEY AT 1.5 T IN DIFFERENT STATES OF HYDRATION

The objective of this study was to determine correlation between struc tural anatomy and surface coil spin-echo MR imaging of the rat kidney and the effect of hydration state on MR signal intensities of the cort ex and medulla, Twelve rats were studied in a pilot study with a 3-inc h surface coil in a 1.5 T magnet under five different states of hydrat ion, Serum and urine osmolality measurements were obtained immediately prior to each scan, Signal intensity measurements were made from both T-1- and T-2-weighted images of the cortex and medulla of both kidney s in each state of hydration, Gross and histological anatomy of the ra t kidneys was correlated with the MR images. Four distinct layers were detected in vivo on MRI images of the rat kidney; these correlated wi th the histological layers. T-1-weighted cortico-medullary differentia tion was most pronounced at 48 h dehydration; T-2 corticomedullary dif ferentiation was greatest at 72 h of dehydration. We concluded that di fferent parts of the mammalian nephron can be identified by MR imaging and that cortico-medullary differentiation is affected by the hydrati on state of the animal.