Optimization of [11C]Choline Synthesis on the TracerMaker Module for Primary Hyperparathyroidism PET Imaging

Positron emission tomography (PET) using [11C]choline has recently gained clinical importance for localizing autonomous adenomas in primary hyperparathyroidism (PHPT), offering superior diagnostic accuracy and sensitivity compared to conventional [99mTc]sestamibi scintigraphy. To meet rising clinical demand using existing infrastructure, this study evaluated three key parameters to optimize the in-house [11C]choline synthesis on a TracerMaker module using [11C]CH4 as the radioactive precursor, which originally yielded 3.19 ± 0.69 GBq at end of synthesis (EOS). Three critical synthesis steps were systematically evaluated: (1) cyclotron irradiation time, (2) precursor (dimethylaminoethanol, DMAE) loading volume across Sep-Pak Accell CM cartridges, and (3) purification wash volumes. Extending irradiation time from 25 to 42 min produced no significant increase in EOS yield. Increased DMAE loading volumes up to 300 µL across 1–3 serially connected 130 mg sorbent cartridges doubled the EOS yield but elevated residual DMAE levels in the final product. Increased wash volumes of ethanol and water failed to improve purification efficiency; however, substituting the multi-cartridge system with a single higher-mass sorbent cartridge (360 mg) achieved effective DMAE removal while maintaining high EOS yield (6.46 ± 0.31 GBq). These findings demonstrate a practical route for [11C]choline synthesis optimization to meet the growing clinical demand for PET imaging of PHPT.