Fully automated synthesis of 11C–labeled 2β-carbomethoxy-3β-(4-fluorophenyl)tropane (11C CFT) as a dopamine transporter positron emission tomography (PET) tracer is performed with Sep-Pak purification, which cannot separate 11C CFT from nor-β-CFT and will result in the residual precursor nor-β-CFT in the final 11C CFT injection. The aim of this study is to estimate the influence of the residual precursor nor-β-CFT in the 11C CFT injection on the Parkinson disease (PD) diagnosis results.
Automated synthesis of 11C CFT was performed using the different chemical amounts (0.10, 0.20, 0.25, and 0.30 mg) of nor-β-CFT with Sep-Pak purification. According to the given different amounts of nor-β-CFT in the radiosynthesis, clinically suspected 25 PD patients were randomly divided into the following 4 groups: 0.10 mg, 0.20 mg, 0.25 mg, and 0.30 mg, which had 5, 9, 5, and 6 cases, respectively. A normal control group with 0.10 mg of nor-β-CFT included 2 volunteers. After the brain PET images of the subjects were acquired, the regions of interests of striatum and cerebellum were drawn, and the standard uptake values of these regions were calculated. Finally, comparing the 18F FDG PET and clinical diagnosis, the coincidence rates of 11C CFT PET imaging for PD patients were determined.
Given 0.25 mg of the precursor nor-β-CFT, high radiochemical yield (59.4%) and high radiochemical purity of 11C CFT were obtained using Sep-Pak purification within a short synthesis time. The 11C CFT standard uptake value ratios of striatum to cerebellum had no statistically significant difference (P > 0.05) between the 4 suspected PD groups. However, there was statistically significant difference (P < 0.05) between the suspected PD groups and the control group. Also, the coincidence rates between the PD diagnosis using 11C CFT PET imaging for different dose groups and the final clinical diagnosis result were greater than 80%, but difference between the coincidence rates was not statistically significant (P = 0.955).
A simple, rapid, and efficient automated synthesis of 11C CFT using 0.25 mg of nor-β-CFT with Sep-Pak purification is afforded, providing enough radioactivity for PD PET imaging routinely. The residual nor-β-CFT in the 11C CFT injection is not inhibit 11C CFT binding to dopamine transporter, and also has no influence on PET diagnosis results of PD.