@misc{oai:repo.qst.go.jp:00070847,
 author = {Kawaguchi, Hiroshi and Shimada, Hitoshi and Suzuki, Masayuki and Takano, Harumasa and Kershaw, Jeffrey and Suhara, Tetsuya and Ito, Hiroshi and 川口 拓之 and 島田 斉 and 鈴木 雅之 and 高野 晴成 and Ｋｅｒｓｈａｗ Ｊｅｆｆｒｅｙ and 須原 哲也 and 伊藤 浩},
 month = {Aug},
 note = {Introduction: The presynaptic function of dopaminergic neurons can be estimated from radiotracer binding to the transporter in PET [1]. In substantia nigra pars compacta (SNc), dopaminergic neurons contain the neuromelanin pigment made from oxyradical metabolites of monoamine neurotransmitters such as dopamine [2]. It has been shown that neuromelanin-related signal is measurable in vivo using the 3T MRI [3]. Both of the dopamine transporter and neuromelanin exist in the doperminergic neurons in SNc. This preliminary study reports the relationship between the binding potential (BPND) of dopamine transporters measured with [18F]FE-PE2I PET and a neuromelanin-weighted MRI ratio (NM-ratio) in human SNc.
Methods: Both the PET and MRI experiments were performed on four normal controls (NCs) and seven Parkinson's disease patients (PDs) (NCs: 63.5 plusminus 2.1, PDs: 70.1 plusminus 6.1 years old). A dynamic PET scan was performed for 90 min after intravenous injection of [18F]FE-PE2I. Neuromelanin-weighted (NMW) images were acquired with a 3T MRI scanner using a 2D fast spin echo sequence (TR/TE: 550/11 ms, resolution: 0.45 x 0.64, slice thickness: 2.5 mm). T1-weighted images were also acquired to aid spatial registration between PET and NMW images. Registration and inter-subject anatomical normalization were performed with the statistical parametric mapping software (SPM8) [4]. The BPND of dopamine transporter was calculated with a simplified reference tissue model using the cerebellum as a reference region. The anatomically normalized BPND and NMW images were averaged across subjects before regions-of-interest (ROIs) were defined on the averaged images. The NM-ratio was defined as the ratio of the signal intensities in the SNc and decussation of the superior cerebellar peduncles. The NM-ratio and BPND were averaged over the bilateral SNc ROIs. Statistical tests were performed with custom Matlab scripts. A p-value of less than 0.05 was considered significant.
Results: The NM-ratios of the NCs and PDs were 1.11 plusminus 0.03 and 1.08 plusminus  0.02, respectively (mean plusminus  SD). The BPND of the NCs and PDs were 0.40 plusminus  0.15 and 0.25 plusminus 0.05, respectively. Both parameters showed a statistically significant difference between NCs and PDs (Student's t-test, NM-ratio: p=0.036, BPND: p=0.027). The scatter plot of NM-ratios and BPND shown in the attached figure suggests that multimodal imaging with NMW MRI and [18F]FE-PE2I PET of the SNc can distinguish PDs from NCs. Pearson's correlation coefficient between NM-ratios and BPND were 0.22, -0.53 and 0.03 for all participants, NCs and PDs, respectively. There was no statistically significant correlation between the NM-ratio and BPND for any of the groups.
Conclusion: The NM-ratio may give the additional information apart from the presynaptic function measured by dopamine transporter imaging. However, the role of neuromelanin in the dopaminergic system is still controversial, and further studies are necessary., The 9th International Symposium on Functional Neuroreceptor Mapping of the Living Brain (NRM12)},
 title = {Comparison between neuromelanin-related MRI signal and dopamine transporter binding measured by PET in humans},
 year = {2012}
}