IMAGING THE STRUCTURE OF THE STRIATUM - A FRACTAL APPROACH TO SPECT IMAGE INTERPRETATION

The spatial pattern of striatal dopamine transporter density in the li ving human brain was tested by duplicate SPECT scans with [I-123]PE2I, [I-123]beta-CIT or [I-123]beta-CIT-FP and striatal phantom measuremen ts. The resolution-dependent spatial variation was calculated by the f ractal analysis of SPECT images. This variation, which depends on the size of the region of interest, was described by the spatial dispersio n i.e. the standard deviation of the count densities divided by the me an density. In each sub-region, the observed and methodological disper sions were computed, and the resulting spatial dispersion was calculat ed. The methodological dispersion is caused by the imaging resolution, hood field non-uniformity, count density, scatter, reconstruction err ors and partial volume effects, whereas the spatial dispersion is base d on the cerebral heterogeneity of the dopamine transporter density. R ecognition of the normal variation in heterogeneity is important in ev aluation of the striatal dopamine transporter density between controls and patients suffering from various neuropsychiatric disorders.