Fractal analysis of renal cortical perfusion.

Abstract

Contrast-enhanced computed tomography (CT) images of canine renal cortex were analyzed to determine if the heterogeneous pixel intensity patterns met the requirements for fractal analysis and if the heterogeneity could be quantified by a fractal dimension, Df. Contrast-enhanced CT images were obtained after injection of iodipamide ethyl ester (IDE), a vascular marker, or iohexol, a freely filtered interstitial marker, into the catheterized renal artery of an anesthetized dog. Images were mounted on a graphics workstation for analysis. A computer program was written to determine the fractal dimension of the pixel-intensity pattern within selected regions. All regions of renal cortex examined met the requirements for fractal analysis. Three seconds after injection of IDE, the mean fractal dimension decreased significantly from 1.21 +/- 0.05 to 1.12 +/- 0.06 (P < .05). Although the mean fractal dimensions were not significantly different, the variation in the fractal dimension around the renal cortex was significantly different with IDE as compared with iohexol at 3 seconds (P < .05). Differences in the change in fractal dimension over time were also observed with IDE as compared with iohexol. Fractal dimension measurement provides a new means to examine the in-vivo organization of renal vascular perfusion by quantifying pixel heterogeneity in contrast-enhanced CT. This may prove useful in understanding and quantifying the pathophysiologic changes in renal disease.