DDC and essential tremor: Abbreviations: A.A.D.C, aromatic L-amino acid decarboxylase; P.E.T., positron emission tomography; [18F]F-DOPA, 6-[18F]fluoro-DOPA; [18F]FMT, 6-[18F]fluoro-m-tyrosine; SPECT, single photon emission computed tomography; [11C/18F]DTBZ, [11C](+)dihydrotetrabenazine/[18F] (+)dihydrotetrabenazine; [18F]FEOBV, [18F]fluoroethoxy benzovesamicol; [11C]MeNER, (S,S)-[11C]-2-(α-(2-methoxyphenoxy) benzyl)morpholine; [11C]TMSX, 7-methyl-[11C]-(E )-8-(3,4,5-trimethoxystyryl)1,3,7- trimethylxanthine; DLB, dementia with Lewy bodies; E.T., essential tremor.