In brain scans of PD, common SPECT tracers include 123I-β-CIT [10, 11], 123I-FPCIT [12, 13], 123I-Ioflupane (DATSCAN) [6, 14, 15], and [99mTc]-TRODAT [16–18] for DAT imaging and 123I-S(-)IBZM [19, 20] for D2 receptors. The gene discussed is SLC6A3; the disease is Parkinson disease.