The Optimization of the Synthesis of 2-(4-N-[C-11] methylaminophenyl)-6-hydroxybenzothiazole ([C-11] PiB) With Eckert&Ziegler Modular System

Chi-Wei Chang, Chun-Tse Hung, Wan-Jen Yang, Shih-Pei Chen, Wen-Yi Chang, Ren-Shyan Liu, Wen-Sheng Huang, Nan-Jing Peng

Published by the 2023 Annals of Nuclear Medicine and Molecular Imaging 36(2)，58-70。

Background: [C-11] Pittsburgh Compound-B (PiB) is now almost routinely used to perform clinical studies for patients in the neurological department at Taipei Veterans General Hospital positron emission tomography (PET) center. It is important to have high molar activity of [C-11] PiB when it is injected into the patients. The aim of this work was to modify an Eckert-Ziegler (EZ) modular system for the routine synthesis of [C-11] PiB to meet the demand of clinical studies. Some modifications of [C-11] PiB routine production procedures are described in detail.

Methods: The fully automated synthesis of [C-11] PiB starting from [C-11] CO_2 is reported. [C-11] methyl triflate was produced in the semi-preparative HPLC loop in EZ modular system. Methylation reactions and the final formulation were performed using the EZ modular system. Results: The radiochemical yield of [C-11] PiB was 9.66 ± 2.02% (based on [C-11] CO_2 decay uncorrected, n = 22) and the molar activity was 156.71 ± 4.56 GBq/μmol (end of synthesis) (n = 22). The radiochemical purity exceeded 99%.

Conclusions: We adopted the “loop” method and modified some procedures in the modular system. The molar activity of [C-11] PiB was getting stable and so was the total radioactivity of [C-11] PiB. Sufficient radioactivity of [C-11] PiB with high molar activity could be achieved by EZ modular system for clinical studies. The C-11-methylation reaction could be applied to other radiosynthesis of the C-11-tracer via the loop method.

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