Measurement of dopamine D₂ receptors in living human brain using [¹¹C]raclopride with ultra-high specific radioactivity

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• 作者：Yota Fujimura ; Hiroshi Ito ; Hidehiko Takahashi ; Fumihiko Yasuno ; Yoko Ikoma ; Ming-Rong Zhang ; Shinichiro Nanko ; Kazutoshi Suzuki ; Tetsuya Suhara
• 关键词：[¹¹C]raclopride ; Ultra-high specific radioactivity ; Dopamine D₂ receptor ; Binding potential ; Positron emission tomography
• 刊名：Nuclear Medicine and Biology
• 出版年：2010
• 出版时间：October 2010
• 年：2010
• 卷：37
• 期：7
• 页码：831-835
• 全文大小：351 K

文摘

Introduction

High specific radioactivity is preferable in the measurement of neuroreceptor bindings with positron emission tomography (PET) because receptor occupancy by mixed cold ligand hampers the accurate estimation of receptor binding. Recently, we succeeded in synthesizing [¹¹C]raclopride, a dopamine D₂ receptor ligand, with ultra-high specific radioactivity, i.e., several thousand GBq/μmol. In the present study, we compared the [¹¹C]raclopride bindings to dopamine D₂ receptors between radioligands with ultra-high specific radioactivity and ordinary high specific radioactivity in healthy human subjects.

Methods

Two PET studies using [¹¹C]raclopride with ultra-high specific radioactivity (4302–7222 GBq/μmol) or ordinary high specific radioactivity (133-280 GBq/μmol) were performed on different days in 14 healthy men. Binding potential (BP) was calculated by the simplified reference tissue method, peak equilibrium method, and area-under-the-curve method for each region-of-interest using time-activity data in the cerebellum as a reference brain region.

Results

BP values for radioligands with ultra-high specific radioactivity and ordinary high specific radioactivity calculated by the simplified reference tissue method were 4.06±0.29 and 4.10±0.25 in the putamen, 0.44±0.07 and 0.47±0.07 in the thalamus and 0.37±0.06 and 0.38±0.06 in the temporal cortex, respectively (mean±S.D.). No significant difference in BP was observed between ultra-high specific radioactivity and ordinary high specific radioactivity in any of the brain regions.

Conclusion

BP values of [¹¹C]raclopride with ultra-high specific radioactivity did not differ from those with ordinary high specific radioactivity in the measured brain regions, including striatal and extrastriatal regions.