Takahashi H, et al. - By comparing neuromelanin MRI and dopamine transporter SPECT, researchers searched for an optimal image biomarker to quantify the severity of Parkinson disease, characterized by dopaminergic neuron loss in the substantia nigra pars compacta leading to presynaptic nigrostriatal dopamine dysfunction. Participants in the study were 40 patients with Parkinson disease who underwent neuromelanin MRI and dopamine transporter SPECT. The authors concluded that dopaminergic neuroimaging, especially dopamine transporter SPECT, is a potentially useful imaging biomarker of Parkinson disease severity.