Figure 4

Semi-automatic and quantitative analysis of anatomical structures in the healthy kidney. Left panel: Representative radio-opacity histograms of the entire kidney of a four months old male mouse, after 13 days of PTA staining are shown and allow the volumetry of the renal pelvis, medulla and cortex due to the uptake of PTA according to tissue opacity. The different classes of grey values are represented as partially overlain Gaussian distributions. The depiction of inflection points allows the segmentation of the curve into different portions, reflecting pelvis and associated tissue (A) Medulla (B) and pelvis, which can be quantified absolutely (frames) or relatively as the percentage of the whole kidney volume. The distribution of the specific grey value portion is illustrated by 2D CT images of frontal sections of the corresponding kidney (right panel). (A) Left panel: 15.57%, which equates to 32.5 mm³ (red frame) of the whole kidney volume is represented by the left grey value portion to the first inflection point. Right panel: This portion of low radio-opacity belongs to parts of the nearly unstained renal pelvis (rp) and the lumen of renal vessels (rv), depicted in green within the 2D frontal section of the kidney. B, Left panel: A middle class of grey values of 13.5%, which equates to 28.2 mm³ (red frame), defined by two inflection points of the surrounding envelopes, correlates to the medulla (m) and to blood vessel walls within the cortex (c) as shown in the right panel, according to the distribution of the green color. (C) Left panel: The major volume portion (70.93%), which equates to 148 mm³ (red frame) of the kidney is represented by a Gaussian curve in the range of the highest radio-opacity. Right panel: This distribution correlates with the most compact structure within the kidney – the cortex (c), depicted in green. The cortex thickness (cth) is defined as distance from renal capsule to the border of the medulla (red line).