Iodine-123 labelled PE2I for dopamine transporter imaging: influence of age in healthy subjects

The iodine-123 labelled selective ligand N-(3-iodoprop-2E-enyl)-2β-carbomethoxy-3β-(4-methylphenyl)nortropane ([123I]PE2I) has been developed and has been shown to be suitable for single-photon emission tomography imaging of the dopamine transporter. In this study the influence of age on ligand binding was investigated in 16 healthy males with an age range of 23– 75 years. Single-photon emission tomography (SPET) imaging was performed with a triple-headed gamma camera. A simplified reference region model, in which the input function was derived from the non-displaceable cerebellar compartment, was used to calculate the volume of distribution in the striatum. The volume of distribution was shown to decline with age (–0.4%/year; P<0.005). The results were in agreement with in vivo and in vitro findings of a decline in dopamine transporter binding with age. The findings confirm the suitability of [123I]PE2I for SPET imaging in clinical routine but emphasize the necessity of using age-matched controls in patient studies.