Programs for assessment of spatial heterogeneity of regional organ blood flow

Regional organ blood flow (RBF) is spatially heterogeneous. Relative dispersion (standard deviation S.D./mean) is often used to assess heterogeneity of RBF. Relative dispersion is a global measure of heterogeneity and is strongly influenced by the tissue sample size making comparisons between research groups inappropriate. Spatial correlation (s.c.) of blood flow is, on the other hand, averaged local self similarity. Both parameters change oppositely secondary to interventions. Fractal dimension (D) is a scale-independent measure of spatial heterogeneity and thus facilitates comparison of data. Programs for calculation of s.c. and D have not been published. We present two portable computer programs written in C+2 for calculating s.c. and D. The programs were validated with six computer generated data sets of known heterogeneity. The results were in agreement with data from the literature: we conclude that the programs accurately calculate spatial correlation and fractal dimension of 1-, 2-, or 3-dimensional perfusion matrices.