FRACTAL ANALYSIS OF STRIATAL DOPAMINE REUPTAKE SITES

Spatial variation in regional blood flow, metabolism and receptor dens ity within the brain and in other organs is measurable even with a low spatial resolution technique such as emission tomography. It has been previously shown that the observed variance increases with increasing number of subregions in the organ/tissue studied. This resolution-dep endent variance can be described by fractal analysis. We studied stria tal dopamine re-uptake sites in 39 healthy volunteers with high-resolu tion single-photon emission tomography using iodine-123 labelled 2 bet a-carbomethoxy-3 beta-(4-iodophenyl)tropane ([I-123]beta-CIT). The mea n fractal dimension was 1.15+/-0.07. The results indicate that regiona l striatal dopamine re-uptake sites involve considerable spatial heter ogeneity which is higher than the uniform density (dimension=1.00) but much lower than complete randomness (dimension=1.50). There was a gen der difference, with females having a higher heterogeneity in both the left and the right striatum. In addition, we found striatal asymmetry (left-to-right heterogeneity ratio of 1.19+/-0.15; P<0.001), suggesti ng functional hemispheric lateralization consistent with the control o f motor behaviour and integrative functions.