Effect of age and gender on dopamine transporter imaging with [123I]FP-CIT SPET in healthy volunteers

Dopamine transporter imaging is a valuable tool to investigate the integrity of the dopaminergic neurons. To date, several reports have shown an age-associated decline in dopamine transporters in healthy volunteers. Although animal studies suggest an effect of gender on dopamine transporter density, this gender effect has not yet been confirmed in human studies. To study the influence of age and gender on dopamine transporter imaging in healthy volunteers, we performed single-photon emission tomography imaging with [I-123]FP-CIT to quantify dopamine transporters. Forty-five healthy volunteers (23 males and 22 females) were included, ranging in age from 18 to 83 years. SPET imaging was performed 3 h after injection of +/-110 MBq [I-123]FP-CIT. An operator-independent volume of interest analysis was used for quantification of [I-123]FP-CIT binding in the striatum. The ratio of specific striatal to non-specific [I-123]FP-CIT binding was found to decrease significantly with age. Moreover, we found a high variance in [I-123]FP-CIT binding in young adults. Finally, females were found to have significantly higher [I-123]FP-CIT binding ratios than males. This effect of gender on [I-123]FP-CIT binding ratios was not related to age. The results of this study are consistent with findings from previous studies, which showed that dopamine transporter density declines with age. The intriguing finding of a higher dopamine transporter density in females than in males is in line with findings from animal studies.