Normal [¹⁸F]FE-PE2I PET in Patients with Persistent Diagnostic Uncertainty after Abnormal [¹²³I]FP-CIT SPECT

In some patients with parkinsonism and abnormal dopamine transporter (DAT) imaging using [¹²³I]FP-CIT single-photon emission computed tomography (SPECT), subsequent clinical evolution does not fit well with a neurodegenerative diagnosis.

The objective was to analyze the results of positron emission tomography (PET) with the recently developed DAT radioligand [¹⁸F]FE-PE2I in patients with persistent diagnostic uncertainty despite an abnormal previous [¹²³I]FP-CIT SPECT scan.

This retrospective study included 19 patients with suspected parkinsonism and persistent diagnostic uncertainty after visually abnormal [¹²³I]FP-CIT SPECT who subsequently underwent [¹⁸F]FE-PE2I PET (time between the two scans: 3.7 ± 2.2 years). Concordance between [¹²³I]FP-CIT SPECT and [¹⁸F]FE-PE2I PET was determined after either purely visual assessment or semiquantitative analysis.

In 74% of cases with visually abnormal [¹²³I]FP-CIT SPECT, [¹⁸F]FE-PE2I PET was visually normal. After semiquantitative analysis, 63% of cases with abnormal [¹²³I]FP-CIT SPECT had normal [¹⁸F]FE-PE2I PET.

[¹⁸F]FE-PE2I PET is normal in the majority of cases, with persistent diagnostic uncertainty after abnormal [¹²³I]FP-CIT SPECT. © 2025 International Parkinson and Movement Disorder Society.