Shigeki Yamazaki

Improved preparation of l-[Methyl-11C]methionine by on-line [11C]methylation

Abstract On-line [ 11 C]methylation using [ 11 C]methyl iodide has been successfully applied to the preparation of l -[methyl- 11 C]-methionine ( 11 C-Met). [ 11 C]Methyl iodide is first trapped in a short column that contains Porapak Q and l -homocysteine thiolactone coated on inert support. The column is then charged with NaOH dissolved in a mixture of ethanol and water to cause the [ 11 C]methylation. The present method can provide practically pure 11 C-Met in radiochemical yield of over 98%. The whole procedure including the sterilization of final product has been completely automated for routine PET use.

Polymer-supported catalysts for efficient on-column preparation of 2-deoxy-2-[18F]fluoro-D-glucose

Abstract Several kinds of polymer-supported quaternary salts, such as dimethylaminopyridinium or tributylphosphonium salts, have been examined for the on-column preparation of [18F]FDG. Factors affecting [18F]fluoride trapping efficiency and [18F]fluorination yield have been optimized. [18F]Fluoride was practically, quantitatively trapped from flowing water and the subsequent 18F-substitution was carried out on-column with a radiochemical yield of over 70% (EOB). The improvement in the [18F]fluorination yield was achieved by introducing a spacer alkene chain between the supporting resin molecule and the catalytic site. A resin with higher cross-linkage and lower content of catalytic sites was shown to be useful for preventing column plugging.

On-line interconversion of [15O]O2 and [15O]CO2 via metal oxide by isotopic exchange

Abstract A novel method has been developed for the on-line production of 15 O-labelled gases. The 15 O exchange reactions between O 2 and CO 2 assisted by a metal oxide catalyst were successfully applied to on-line interconversion of [ 15 O]O 2 and [ 15 O]CO 2 with Hopcalite II(CuO 40% and MnO 2 60%). The conversion reactions were optimized as to the reaction temperature, the amount of the catalyst, and the flow rate of a gas added for oxygen exchange. [ 15 O]O 2 was converted to [ 15 O]CO 2 in a 80% yield with 0.7 g of Hopcalite II and 100 mL/min of CO 2 at 500°C, and [ 15 O]CO 2 to [ 15 O]O 2 in 70% with 100 mL/min of O 2 at 650°C. The radiochemical purities of the 15 O-labelled gases converted under the optimal conditions were high enough for clinical studies using the standard dilution and inhalation procedures.

Automated injection of a radioactive sample for preparative HPLC with feedback control

Abstract The injection of a radioactive reaction mixture into a preparative HPLC column has been automated with computer control for rapid purification of routinely prepared positron emitting radiopharmaceuticals. Using pneumatic valves, a motor-driven pump and a liquid level sensor, two intelligent injection methods for the automation were compared with regard to efficient and rapid sample loading into a 2 mL loop of the 6-way valve. One, a precise but rather slow method, was demonstrated to be suitable for purification of 18 F-radiopharmaceuticals, while the other, due to its rapid operation, was more suitable for 11 C-radiopharmaceuticals. A sample volume of approx 0.5 mL can be injected onto a preparative HPLC column in over 90% efficiency with the present automated system.

Intelligent control of liquid transfer for the automated synthesis of positron emitting radiopharmaceuticals

Abstract A method for the intelligent control of liquid transfer, developed for automated synthesis of 2-deoxy-2-[18F]fluoro- d -glucose from [18F]fluoride, is described. A thermal mass flow controller coupled to a personal computer is used to monitor conditions for transferring or passing liquid through a tube or a column. Using this sensor a computer can detect completion of liquid transfer, dispense a stock solution and check the setup conditions of the system. The present feedback control can be readily adapted to other automated syntheses of positron emitting radiopharmaceuticals.