SPECT imaging using [123I]β-CIT and [123I]IBF in extrapyramidal diseases

Imaging of dopaminergic function is useful in the investigation of patients with Parkinson disease (iPD) and other extrapyramidal diseases. Using agents that bind to dopamine transporters ([123I]β-CIT) and receptors ([123I]IBF SPECT), we investigated SPECT in 9 healthy volunteers and 24 patients for dopamine transporters as well as 15 patients for dopamine receptors. In β-CIT SPECT studies, we examined 17 iPD patients (63.3±9.9 y/o), 3 multiple system atrophy (MSA) patients (olivopontocerebellar atrophy (OPCA) type) (64.0±8.0 y/o), 2 vascular parkinsonism (VP) patients (71.0±0.0 y/o), 1 progressive supranuclear palsy (PSP) patient (69 y/o), 1 cortico-basal degeneration (CBD) patient (50 y/o) and nine healthy controls (39.1±9.3 y/o). For IBF SPECT studies 11 iPD patients (60.6±10.9 y/o), 3 MSA patients (2 OPCA type (50.5±3.5 y/o) and 1 striatonigral degeneration (SND) type (65 y/o)) and 1 PSP patient (60 y/o) underwent SPECT scans after the injection of [123I]IBF. The specific to nonspecific striatal ratio (St/Oc-1), ratio of putaminal uptake to caudatal uptake (Pu/Ca), and asymmetry indices (AI) were estimated. β-CIT studies showed ST/Oc-1 as follows; iPD: 2.66±1.09 (n=17), VP: 5.73 and 7.39, MSA: 1.84±0.46 (n=3), PSP: 2.34, CBD: 2.16. In all extrapyramidal diseases except VP, St/Oc-1 ratios were significantly lower than those in normal volunteers (6.46±1.08) (p<0.01). Also in early-phase iPD patients (Yahr I-II), St/Oc-1 (3.16±1.49: n=4) was significantly lower than those in normal volunteers (p<0.01). In IBF studies, St/Oc-1 ratios were significantly higher in early-phase (Yahr I-II) iPD patients (1.82±0.25: n=5) than those in late-phase (Yahr III-IV) iPD patients (1.38±0.32: n=6) (p<0.05). The Pu/Ca ratios in iPD patients (1.12±0.13) and MSA (OPCA type) patients (0.95±0.05) were higher than that in MSA (SND type) patient (0.78) and were lower than that in PSP patient (1.55). In conclusion, β-CIT-SPECT is useful for the diagnosis of early-phase iPD patients and for differentiating VP from other extrapyramidal diseases. IBF-SPECT is useful for the diagnosis of the severity of iPD and has the possibility for ruling out MSA (SND type) or PSP from iPD. Both tracers are useful for investigating the pathophysiology of patients with iPD and other extrapyramidal diseases. (author)