Comparative Nigrostriatal Dopaminergic Imaging with Iodine-123-βCIT-FP/SPECT and Fluorine-18-FDOPA/PET

SPECT imaging of the dopamine transporter is now an alternative to PET in the quantification of nigrostriatal dopaminergic function. We compared [ 123 I]βCIT-FP/SPECT and [ 18 F]FDOPA/PET in the assessment of nigrostriatal dopaminergic function in Parkinson's disease (PD) and normal aging. Methods : We studied 12 mildly affected PD patients (mean age : 61.0 ± 13.2 yr ; H&Y Stage I-II) with both [ 123 I]βCIT-FP and [ 18 F]FDOPA. Fifteen normal volunteers (mean age : 45.5 ± 22.1 yr) served as controls for both tracers. We measured the striato-occipital ratio (SOR) for both tracers at approximately 100 min postinjection. Results : We found a highly significant correlation between SOR measures obtained for both tracers (r = 0.79, p < 0.0001). In normal volunteers a significant age-related decline in striatal uptake was noted with [ 123 I]βCIT-FP (r = -0.56, p < 0.04) but not with [ 18 F]FDOPA. SOR values for both tracers discriminated PD patients from controls with comparable accuracy (F[1,25] = 52.1 and 53.0, p < 0.0001 for [ 123 I]βCIT-FP and [ 18 F]FDOPA, respectively). UPDRS motor ratings correlated with SOR values obtained by both imaging techniques (r = -0.69 and -0.60, p < 0.04 for [ 123 I]βCIT-FP and [ 18 F]FDOPA, respectively). Conclusion : These results indicate that [ 123 I]βCIT-FP/SPECT can provide quantitative descriptors of presynaptic dopaminergic function comparable to those obtained with [ 18 F]FDOPA/PET.