SLC6A3 and supranuclear palsy, progressive, 1: Dopamine transporter (DAT) single-photon emission tomography (SPECT) with 123I-N-omega-fluoropropyl-2-beta-carbomethoxy-3-beta (4-iodophenyl) nortropane (123I-FP-CIT) is a widely used diagnostic tool for patients with suspected parkinsonian syndromes such as Parkinson’s disease, PSP, and CBD as an in vivo marker of nigrostriatal neuron loss (Palermo and Ceravolo, 2019).