11C-β-CFT, used as the DAT radioligand for PET tracer, was synthesized at Department of Nuclear Medicine, PLA General Hospital. 11C-β-CFT was prepared by reaction of [11C] methyl triflate with the N-desmethyl precursor, nor-P-CFT (RBI, Natick, MA, USA).[8 (link)9 (link)] A high-resolution PET/CT scanner (DaTSCAN; GEMINI GXL-16, Philips, The Netherlands) was used for each patient at Nuclear Medicine Center of the Second Hospital of Armed Police Beijing Office. Anti-parkinsonism drugs must not be taken at least 12 h before PET, and DAT agonists 72 h before the PET. The head of the caudate and putamen on the two consecutive planes with best articulation were selected to be the regions of interest (ROIs) on bilateral hemispheres. The average of 11C-β-CFT concentrations of ROIs was calculated. Striatal asymmetry index (SAI) was used to describe the asymmetry of the radioactivity uptake in the bilateral striatum. SAI = (RISP − RCON)/[(RISP + RCON)/2] ×100%. RISP and RCON represent the uptake value of DAT tracer in the striatum ipsilateral or contralateral to the clinically affected body side, respectively.[7 (link)8 (link)] PD was diagnosed if SAI existed.