Reference Values for Dopamine Transporter Imaging With 99mTc-TRODAT-1 in Healthy Subjects and Parkinson’s Disease Patients

The aim of this study was to evaluate different quantitative indexes of striatum dopamine transporter density in healthy subjects and patients with PD.Sixty-seven patients, 23 healthy (8 male; 59 ± 11 years old) and 44 age-matched patients (29 male; 59 ± 7 years old), with various degrees of severity of idiopathic PD (duration of symptoms, 10 ± 6 years; Hoehn and Yahr Scale, 2.16 ± 0.65; UPDRS-3, 29.74 ± 17.79). All patients performed 99mTc-TRODAT-1 SPECT. Binding potential indexes (BPIs) of striatum and subregions, asymmetry index (AI), and putamen/caudate ratio (P/C) were calculated.Binding potential index was lower in the PD than in healthy subjects. A BPI cutoff for striatum and putamen ranging from 0.73 to 0.78 showed 95% to 100% sensitivity and 84% to 88% specificity. For the caudate nucleus, a BPI threshold of 0.8 to 0.88 revealed 100% sensitivity and 77% to 84% specificity. The BPI's respective areas under the curve ranged from 0.92 to 0.98. For AI and P/C, the area under the curve was less than 0.70. Binding potential index intraclass correlation coefficient was close to 1.0 in the intraobserver evaluation and 0.76 to 0.87 in the interobserver assessment. Intraclass correlation coefficient for AI and P/C was inferior to 0.75 in the intraobserver and interobserver evaluations.Different semiquantitative indices differentiated PD and healthy subjects and may help the differential diagnosis of other entities involving the dopaminergic system. Asymmetry index and P/C performances were lower than BPI, including their intraobserver and interobserver reliability, and therefore should be used with caution.