Positron emission tomography inter-scanner differences in dopamine D ₂ receptor binding measured with [¹¹C]FLB457

Objective: It is well known that the positron emission tomography (PET) system is subject to inter-scanner differences of regional radioactivity distribution. In the present study, the effect of inter-scanner difference of regional radioactivity on estimated binding potential (BP_ND) of [¹¹C]FLB457 using the simplified reference tissue model (SRTM) was investigated. Methods: Each of the 11 subjects was given two PET scans using [¹¹C]FLB457, one each with both SET-3000 GCT/X (Shimadzu) and with ECAT EXACT HR+ (Siemens/CTI). In order to assess regional differences between the two scanners, estimated BP_ND values in six volumes of interest (VOIs) by SRTM method were compared in both individual PET space and anatomical template space after anatomical normalization. Statistical voxel-by-voxel paired t test of BP_ND images between SET-3000 GCT/X and ECAT EXACT HR+ was also performed. Results: Shapes of time-activity curves of the two PET scanners were slightly different in each VOI, with estimated BP_ND values from ECAT EXACT HR+ appearing greater in the cerebral cortical regions and thalamus than that of SET-3000 GCT/X in both individual PET space and anatomical template space after anatomical normalization. Statistical voxel-by-voxel analysis showed similar tendency to BP_ND value estimation, with greater BPND values from ECAT EXACT HR+ than from SET-3000 GCT/X. Conclusions: We demonstrated the inter-scanner differences in dopamine D₂ receptor binding measured with [¹¹C]FLB457. In particular, statistically significant differences of BP_ND in certain regions were observed between two PET scanners, despite the subject groups being the same. Our results suggest that we reconsider the effect of the scanner model on the measurement of receptor binding.