A simplified method for the diagnosis of striatal dopaminergic dysfunction using PET with a new fluorine DAT tracer, the ¹⁸F-LBT-999

Objectives: Parkinson's (PD) or Lewy body dementia characterized by a degeneration of the presynaptic dopaminergic neurons can be in vivo explored with SPECT DAT ligands. Nevertheless, as this type of exams present some drawbacks many efforts have been made to develop PET DAT radioligands either labelled with C-11 or F-18. We report here the quantitative evaluation of the presynaptic dopaminergic neurons impairment in parkinsonian patients using a new F-18 DAT ligand, the ¹⁸F-LBT-999.

Methods: Six PD patients (age: 69±7 y, Hoehn and Yahr: stage I-II) and eight 8 controls (age: 69±9y) were studied with an Ingenuity Philips tomograph. A 90-min dynamic PET followed an iv injection of ¹⁸F-LBT (3.6 MBq/kg). The binding potential (BP) using SRTM method as also the ratios obtained for a 10-min image acquired between 30 and 40 min pi were calculated in the caudate nucleus (Cd) and in the putamen (Pu) using regions of interest (ROI) defined over each T1 3D MRI. The cerebellum activity was used as reference region.

Results: In PD patients and for both striatal structures, BP and ratios were significantly decreased compared to control group (p<0.001). For PD group, the mean±SD BP values were 3.97±1.32 and 2.72±1.51, and the ratios 3.76±0.82 and 3.12±0.80, for Cd and Pu, respectively. For control group, the values were for BP 6.30±1.17 and 6.75±1.17 and for ratios 5.01±0.68 and 5.40±0.73, for Cd and Pu, respectively.

Conclusion: Our results indicate that the use of striatal ratios using a 10 minutes PET acquisition is reliable to differentiate early PD patients to controls. Moreover, the findings using ratios are in accordance with those obtained using a dynamic acquisition with a SRTM analysis of a 90-min dynamic PET scan. Research Support: This study was supported by the French National Agency for Research (‘‘Investissements d’Avenir’’ ANR-11-LABX-0018-01), IRON and by Cyclopharma Laboratories. We thank the technical and nursing staffs of CERRP, the Service de Médecine Nucléaire, CIC-IT, CHRU Tours for their assistance.