Different strategies for MRI measurements of renal cortical volume

First, to measure renal cortical volume (Vc) using different MRI methods combined with a semiautomatic segmentation method. Second, to compare MRI measurements of Vc using the semiautomatic segmentation method with a manual segmentation method. Third, to evaluate the reproducibility of Vc measurements.

A total of 22 pigs, 13 with healthy kidneys and nine with diseased kidneys, underwent MRI with two non-contrast-agent methods (MRI 100 x 900 and MRI 300 x 1100) and one contrast-agent method (MRI Gd). For each of these methods, Vc was estimated using semiautomatic (Vc(100 x 900), Vc(300 x 1100), and Vc(Gd)), as well as manual (Vc MANUAL) segmentation. Reference volumes were estimated by stereological means (Vc STEREOLOGY). MRI-derived volumes were compared with reference volumes using a two-tailed paired t-test, and variances between methods were visualized with Bland Altman plots. Reproducibilities were analyzed using covariance analysis.

Neither measurements of Vc 100 x 900, Vc 300 x 1100, nor Vc Gd differed markedly from Vc STEREOLOGY using semiautomatic segmentation. Vc was comparable when semiautomatic and manual segmentations were performed at the same scan. Reproducibility of MRI estimated Vc values offered intra- and interindividual differences <5%.

Vc can in both healthy and diseased kidneys be measured accurately with MRI using both semiautomatic and manual segmentation, and measurements can be obtained with a high reproducibility. Measurements of Vc 100 x 900 may in the future become suitable in patients with chronic renal failure.