Objective: Recent PET studies have indicated altered presynaptic function and relation with psychotic symptoms in patients with schizophrenia. The L-[β-(11)C]DOPA uptake rate reflects the dopamine synthesis capacity (kref), whereas the nondisplaceable binding potential (BPND) of [(18)F]FE-PE2I reflects the dopamine transporter availability. Although the kref values of L-[β-(11)C]DOPA and the BPND of [(18)F]FE-PE2I can be potential markers for evaluating the severity of positive symptoms, test-retest reproducibility has not been confirmed. The purpose of this study was to investigate the test-retest reproducibility of kref values of L-[β-(11)C]DOPA and that of BPND of [(18)F]FE-PE2I in the striatum and midbrain in healthy humans.
Materials and methods: Twelve healthy male volunteers underwent two PET studies on separate days. Each PET study comprised two PET scans, one with L-[β-(11)C]DOPA and the other with [(18)F]FE-PE2I. Volumes of interest were defined for the caudate, putamen, midbrain, and thalamus. Test-retest reproducibility was assessed in terms of intrasubject variability (absolute variability) and reliability [intraclass correlation coefficient (ICC)].
Results: The absolute variability values of kref and BPND were 4.8-25.7% on average for the caudate, putamen, midbrain, and thalamus. The ICC values of the kref values of L-[β-(11)C]DOPA were 0.78, 0.71, 0.77, and 0.77 for the caudate, putamen, midbrain, and thalamus, respectively. The ICC values of the BPND of [(18)F]FE-PE2I were 0.83, 0.88, 0.71, and 0.70 for the caudate, putamen, midbrain, and thalamus, respectively.
Conclusion: We found good test-retest reproducibility for the kref values of L-[β-(11)C]DOPA and that for the BPND of [(18)F]FE-PE2I in the striatum and midbrain, indicating the reliability of clinical investigation using PET with L-[β-(11)C]DOPA and [(18)F]FE-PE2I.