Molecular Neuroimaging Group, Molecular Imaging Center, National Institutes of Radiological Sciences, Inage-ku, Chiba, 263-8555, Japan.
Nucl Med Biol. 2010 Oct;37(7):831-5. doi: 10.1016/j.nucmedbio.2010.04.138.
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 [(11)C]raclopride, a dopamine D(2) receptor ligand, with ultra-high specific radioactivity, i.e., several thousand GBq/μmol. In the present study, we compared the [(11)C]raclopride bindings to dopamine D(2) receptors between radioligands with ultra-high specific radioactivity and ordinary high specific radioactivity in healthy human subjects.
Two PET studies using [(11)C]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.
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.
BP values of [(11)C]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.
正电子发射断层扫描（PET）测量神经受体结合时，高比活度是优选的，因为混合冷配体占据受体，会妨碍对受体结合的准确估计。最近，我们成功合成了超高比活度的[(11)C]raclopride，一种多巴胺 D2 受体配体，比活度达到几千 GBq/μmol。在本研究中，我们在健康受试者中比较了超高比活度和普通比活度的[(11)C]raclopride 对多巴胺 D2 受体的结合。
在不同的日子里，14 名健康男性分别进行了两次使用超高比活度（4302-7222 GBq/μmol）或普通比活度（133-280 GBq/μmol）的[(11)C]raclopride 的 PET 研究。使用小脑的时间-活性数据作为参考脑区，通过简化参考组织法、峰值平衡法和曲线下面积法计算每个感兴趣区的结合潜能（BP）。
简化参考组织法计算的超高比活度和普通比活度的放射性配体的 BP 值在纹状体分别为 4.06±0.29 和 4.10±0.25，在丘脑分别为 0.44±0.07 和 0.47±0.07，在颞叶分别为 0.37±0.06 和 0.38±0.06（均值±SD）。在任何脑区，超高比活度和普通比活度的 BP 值均无显著差异。
在测量的脑区，包括纹状体和纹状体外区域，超高比活度的[(11)C]raclopride 的 BP 值与普通比活度的[(11)C]raclopride 无差异。
