Development of additive [C-11]CO2 target system in the KOTRON-13 cyclotron and its application for [C-11]radiopharmaceutical production

作者：Moon Byung Seok; Lee Hong Jin; Lee Won Kyung; Hur Min Goo; Yang Seung Dae; Lee Byung Chul^*; Kim Sang Eun

来源：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms , 2015, 356: 1-7.

DOI：10.1016/j.nimb.2015.04.022

• Carbon-11 gas target
• [C-11]carbon dioxide
• KOTRON-13
• Cyclotron

The KOTRON-13 cyclotron, which was developed in South Korea for the production of medical radioisotopes, has the structural limitation of only one beam-output port, restricting the production of the carbon-11 isotope. In the present study, we investigate the design of a switchable target system and develop an effective carbon-11 target in the KOTRON-13 cyclotron, for combination with the fluorine-18 target. The target system was designed by introducing a sliding-type element between the fluorine-18 and carbon-11 targets, a tailor-made C-11 target and its cooling system. For the efficient production of [C-11]CO2, the desirable target shape and internal volume were determined by a Stopping and Range of Ions in Matter (SRIM) simulation program, and the target grid was modified to resist the cavity pressure during beam irradiation. We evaluated the [C-11]CO2 production while varying the material and thickness of the target foil, oxygen content of the nitrogen gas, and target loading pressure. Using sliding-type equipment including an additional gate valve and a high vacuum in a beam line, the bi-directional conversion between the fluorine-18 and carbon-11 targets was efficient regarding the accurate beam irradiation on both targets. The optimal [C-11]CO2 production for 30 min irradiation at 60 mu A (86.6 +/- 1.7 GBq in the target at EOB) was observed at a thickness of 19 mu m with HAVAR (R) material as a target foil and a target loading pressure of 24 bar with nitrogen plus 300 ppb of oxygen gas. Additionally, the coolant cavity system in the target grid and target chamber is useful to remove the heat transferred to the target body by the internal convection of water and thereby ensure the stability of the [C-11]CO2 production under a high beam current. In the application of C-11 labeled radiopharmaceuticals such as [C-11]PIB, [C-11]DASB, [C-11]PBR28, [C-11]Methionine and [C-11]Clozapine, the radiochemical yields were shown to be 25-38% (decay corrected) with over 166 GBq/mu mol of specific activity. Consequently, the additive carbon-11 target system was successfully developed in only one output port of the KOTRON-13 cyclotron and exhibited the stable production of C-11 labeled radiopharmaceuticals.

• 出版日期2015-8-1