Comparison of [(18)F]-FDOPA PET and [(123)I]-FP-CIT SPECT acquired in clinical practice for assessing nigrostriatal degeneration in patients with a clinically uncertain parkinsonian syndrome

PURPOSE: Two commonly used imaging techniques to aid in the diagnosis of neurodegenerative parkinsonian syndromes are dopamine transporter (DAT) imaging with [(123)I]-FP-CIT single-photon emission computed tomography (DAT-SPECT) and positron emission tomography with [(18)F]-FDOPA (FDOPA-PET). This paper provides a unique series of parkinsonian patients who received both FDOPA-PET and DAT-SPECT in routine clinical practice and compares the reported results to assess potential differences between these two imaging techniques. METHODS: We present 11 patients with a clinically uncertain parkinsonian syndrome (CUPS), who received both FDOPA-PET and DAT-SPECT. All patients received an FDOPA-PET scan and DAT-SPECT as part of routine clinical care. RESULTS: The median time between the F-DOPA-PET scan and DAT-SPECT scan was 6 months (range 0–15 months). There was a discrepancy in the reported results of the FDOPA-PET and DAT-SPECT scans in nine patients, including 7 patients whose FDOPA-PET scan was reportedly normal, whereas their DAT-SPECT scan was abnormal. CONCLUSIONS: In this case series of CUPS patients, DAT-SPECT was more often rated as abnormal than FDOPA-PET. The striatal loss of FDOPA uptake can be less pronounced than that of DAT binding in CUPS patients in early disease stages. Consequently, the interpretation of FDOPA-PET scans in CUPS can sometimes be challenging in routine practice. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13550-022-00943-6.