Stereotaxic summation analysis of human cerebral benzodiazepine binding maps.

Summation analysis strategies are recognized throughout diverse scientific fields as powerful means of differentially enhancing experimental signals over random fluctuations (noise). Such techniques, applied to emission tomographic cerebral blood flow scans, reveal subtle alterations in neuronal activity during specific behavioral states. In the present work, we extend the principles of intersubject image summation analysis to the evaluation of emission tomographic ligand-binding studies. A general methodology is presented that may be applied to a wide variety of binding site determinations. The procedure consists of anatomic standardization of individual brains to a common stereotaxic orientation, followed by statistical analyses of group versus group or individual versus group differences. We develop and evaluate performance of our technique with the use of positron emission tomographic [11C]flumazenil scans from normal volunteers, depicting the regional cerebral distribution of benzodiazepine binding sites.