Figure 1.
Exemplary illustration of perfusion MRI.
Exemplary illustration of perfusion MRI of a rat with left-side AKI and perfusion maps. (A) True-FISP M0 image of an ASL measurement and the corresponding perfusion map (B). (C) TWIST post-contrast agent injection image and the corresponding RBF map (D). All drawings show the same rat and the same axial slice. Differences between the kidney with AKI and the contralateral kidney are clearly visible on the MRI images as well as on the perfusion maps.
Figure 2.
Representative DCE-MRI images.
Representative DCE-MRI TWIST images at different points in time. (A) Baseline image before contrast agent injection. (B) Cortical peak contrast image approximately 40 s after bolus injection and an image (C) taken approximately 4 min later showing increased medullar contrast. Regarding the contrast uptake and its distribution, the AKI kidney can clearly be distinguished from the healthy kidney.
Figure 3.
Time course of contrast uptake in DCE-MRI.
The lower panel shows two exemplary DCE-MRI time courses of the tissue signal intensities (B), i.e. the contrast uptake in two cortical ROIs. In the upper panel (A) the position of the according ROIs is depicted. One ROI was placed in the healthy kidney (green), one in the diseased kidney (red). Please note that choice and shape of the ROIs in this figure are different from the ones drawn for the data evaluation.
Figure 4.
Histology of a native and a diseased kidney.
Histological slides (H&E, 40x) of a native kidney (A) and a kidney five days after acute injury (B). Compared to the native kidney the diseased kidney shows main hallmarks of acute renal injury like cellular swelling, necrosis and tubular dilatation. Examples for necrosis and tubular dilatation are marked with arrows and stars, respectively.
Table 1.
Cortical RBF in ml/100 g/min as estimated from ASL and DCE-MRI measurements.
Figure 5.
Comparison of renal perfusion between healthy and diseased kidneys.
Differences in renal perfusion between healthy and diseased kidneys visualised in two Bland-Altman plots. The upper plot shows the differences as measured with DCE-MRI, the lower plot shows the differences as assessed with ASL. Both mean differences are significantly different from zero as zero is not included in the limits of agreement, i.e. the dotted lines that denote 1.96 times the standard deviation of the mean.
Table 2.
Perfusion estimates of repeated ASL measurements in two animals. All values are in ml/100 g/min.
Figure 6.
Relative perfusion between healthy and diseased kidneys.
Graph of relative perfusion between AKI kidneys and healthy kidneys for each rat. The red circles represent the ratios as found with the ASL measurement. The blue squares depict the ratios as measured with DCE-MRI.
Table 3.
Ratios of cortical RBF between left and right kidneys as estimated with ASL and DCE-MRI.