The reproducibility of [11C]SCH 23390 in PET was studied in 10 normal human subjects.
Methods: The scan-to-scan variation of several measures used in PET data analysis, including the radioactivity ratio, plasma-input Logan total distribution volume (DV), plasma-input Logan DV ratio (DVR) and tissue-input Logan Bmax/Kd values, was determined.
Results: There were significant correlations among the radioactivity ratio, plasma-input DVR and tissue-input Bmax/Kd. With the cerebellum as the reference region, these three measures also had high reliability (86%-95%), high between-subject s.d. (7.7%-11.3%) and small within-subject s.d. (2.3%-3.6%), indicating that they are comparable and useful measures for the assessment of dopamine D1 receptor binding.
Conclusion: The radioactivity ratio and the tissue-input Bmax/Kd may be preferred methods for the evaluation of dopamine D1 receptor binding because these two methods do not require arterial blood sampling and metabolite analysis. Our results show that cerebellum is a reliable reference region for SCH 23390. When the Logan plasma-input function method is used in data analysis for SCH 23390, DVRs rather than total DV values should be used because of the poor reliability of the DV values and their lack of correlation with other measures. Carbon-11-SCH 23390 is thus a reliable and reproducible ligand for the study of dopamine D1 receptor binding by PET.