[I-123]IPT binding to the presynaptic dopamine transporter: variation of intra- and interobserver data evaluation in parkinsonian patients and controls

Imaging the presynaptic dopamine transporter with cocaine analogues and sin gle-photon emission tomography (SPET) has proven to be a potential diagnost ic tool for classifying the extent and degree of dopaminergic nerve cell lo ss. For correct interpretation of scan results, however, knowledge of the i ntra-/interobserver variation of data evaluation is mandatory. Iodine-123 l abelled N-(3-iodopropen-2-yl)-2 beta -carbomethoxy-3 beta-(chlorophenyl)tro pane ([I-123]IPT) SPET data of 10 controls and 30 parkinsonian patients wit h varying degrees of reduced IPT binding were analysed twice by an expert ( intraobserver) and once by a less experienced physician in training (intero bserver). For semiquantitative evaluation of specific IPT binding, ratios b etween total striatum, caudate and putamen and a background region were cal culated. No significant differences were observed for either the intra- or the interobserver analyses. Variation was lower in controls than in the pat ient group. Overall variation indices were below 5%. Variation in interobse rver results was only slightly higher than that in intraobserver results. T he intra-/interobserver results showed highly significant correlations (r = 0.99). The intraclass correlation was higher than 0.9 for all evaluations. Our results indicate that the specific presynaptic striatal dopamine trans porter binding assessed with IPT-SPET may be reproducibly analysed by the s ame and different observers in controls as well as in patients with varying degrees of reduced binding.