Single-photon emission computed tomography
Single-photon emission computed tomography (SPECT) tracers, such as123I-ioflupane (123I-FP-CIT) or123I-β-CIT, bind selectively to presynaptic dopamine transporter (DAT) and can be used to measure the density of nigrostriatal nerve terminals. The outcome of a meta-analysis suggested that DAT-SPECT is useful in the diagnosis of early PD and in differentiating PD from essential tremor and vascular parkinsonism [46]. DAT-SPECT can also be utilized to follow disease progression because striatal binding seems to correlate to different stages of disease severity [49]. Importantly, 123I-β-CIT SPECT-CT has shown translational potential as it can be used to visualize dopaminergic degeneration in experimental animal models of PD [50].123I-IBZM is an example of a radiotracer that binds to dopamine D2 receptors and can be used for SPECT imaging of postsynaptic striatal neurons [51].