Iodine-123 labelled PE21 for dopamine transporter imaging:: influence of age in healthy subjects

The iodine-123 labelled selective ligand N-(3-iodoprop-2E-enyl)-beta P-carbomethoxy-3 beta-(4-methylphenyl)nortropane ([I-123]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 [I-123]PE2I for SPET imaging in clinical routine but emphasize the necessity of using age-matched controls in patient studies.