Preparation of routine automated synthesis of [11C]choline

Introduction [11C]choline is a very effective PET radiopharma-ceutical for the study of prostate cancer. To support the increasing demand for [11C]choline, several different synthetic approaches have been described in the literature, including different automated production methods using remote-controlled synthesis modules [1–4]. The most popular method uses a C18 Sep-Pak as solid support for methylation and, subsequently, a CM Sep-Pak for purification [2]. We report an optimized method for producing [11C]choline using only one CM Sep-Pak for both reaction and purification as was shown in the literature [4]. For synthesis of [11C]choline we used two modules Tracerlab FXC for preparation of methylation reagent [11C]CH3I and GPF-101 for [11C]choline synthesis. Material and Methods TracerlabFXC GE, GPF-101 Veenstra Instrument, 2-(dimethylamino)-ethanol (DMAE) ABX, Sep-Pak Light Accell Plus CM cation-exchange cartridges Waters used without conditioning, precursor 50 µL of DMAE dissolved in 25 µL of ethanol and loaded on a CM Sep-Pak. Schematic diagram of the automated system for the production of [11C]choline is given below. [11C]CH4 was produced in two standard Nitra target IBA irradiation of mixture 90 % N2/10 % H2 with 15 MeV protons using dual beam. Results and Conclusion [11C]CH4 was prepared in the targets and connected with Tracerlab FXC. [11C]CH3I was pre-pared in a loop in which allowed to react of elemental iodine at a temperature 720 oC. Con-version to [11C]CH3I usually is around 50% uncorrected activity. Activity is within the range 15–18 GBq of [11C]CH3I and time of production 10 min. Synthesis of [11C]choline is based on the reaction DMAE with [11C]CH3I on a Accell Plus CM cation-exchange column which serves both as a support for reaction and for separation of choline from DMAE by ethanol washing. The basic parameters are shown in TABLE 1. Beam current 2X 20 µA Irradiation time 30 min DMAE 50 µl Synthesis time from EOB 25 min Absolute yield without correction 6.6 GBq Radiochemical purity > 99 % Residual DMAE in product < 5 ppm Ethanol < 1000 mg/L pH 4.5–8.5 TABLE 1. Reaction parameters and result of production of [11C]choline syntheses Conclusion We have applied a simple synthesis method for [11C]choline preparation using automated commercial equipments with one column used both for reaction and separation purpose. The main advantage of using one column is lower contamination of the product [11C]choline with DMAE. When for synthesis of [11C]choline two columns C18 for synthesis and CM for separation is used, higher contamination of DMAE can be found in the product due to a release of DMAE from C18 column