In-target production of [ 11 C]CH 4 from a nitrogen/hydrogen gas target as a function of beam current, irradiation time, and target temperature.

Autor: Helin S; Turku PET Centre, Radiopharmaceutical Chemistry Laboratory, University of Turku, Kiinamyllynkatu 4-8, 20520, Turku, Finland., Rajander J; Turku PET Centre, Accelerator Laboratory, Åbo Akademi University, Kiinamyllynkatu 4-8, 20520, Turku, Finland., Aromaa J; Turku PET Centre, Accelerator Laboratory, Åbo Akademi University, Kiinamyllynkatu 4-8, 20520, Turku, Finland., Arponen E; Turku PET Centre, Radiopharmaceutical Chemistry Laboratory, University of Turku, Kiinamyllynkatu 4-8, 20520, Turku, Finland., Helin JS; MediCity Research Laboratory, University of Turku, Tykistökatu 6 A, 20520, Turku, Finland.; Turku PET Centre, Preclinical Imaging Laboratory, University of Turku, Tykistökatu 6 A, 20520, Turku, Finland., Solin O; Turku PET Centre, Radiopharmaceutical Chemistry Laboratory, University of Turku, Kiinamyllynkatu 4-8, 20520, Turku, Finland. olof.solin@abo.fi.; Turku PET Centre, Accelerator Laboratory, Åbo Akademi University, Kiinamyllynkatu 4-8, 20520, Turku, Finland. olof.solin@abo.fi.; Department of Chemistry, University of Turku, Henrikinkatu 2, 20500, Turku, Finland. olof.solin@abo.fi.; Turku PET Centre, Turku University Hospital, Kiinamyllynkatu 4-8, 20520, Turku, Finland. olof.solin@abo.fi.
Jazyk: angličtina
Zdroj: EJNMMI radiopharmacy and chemistry [EJNMMI Radiopharm Chem] 2024 Mar 25; Vol. 9 (1), pp. 24. Date of Electronic Publication: 2024 Mar 25.
DOI: 10.1186/s41181-024-00255-1
Abstrakt: Background: Production of [ 11 C]CH 4 from gas targets is notorious for weak performance with respect to yield, especially when using high beam currents. Post-target conversion of [ 11 C]CO 2 to [ 11 C]CH 4 is a widely used roundabout method in 11 C-radiochemistry, but the added complexity increase the challenge to control carrier carbon. Thus in-target-produced [ 11 C]CH 4 is superior with respect to molar activity. We studied the in-target production of [ 11 C]CO 2 and [ 11 C]CH 4 from nitrogen gas targets as a function of beam current, irradiation time, and target temperature.
Results: [ 11 C]CO 2 production was practically unchanged across the range of varied parameters, but the [ 11 C]CH 4 yield, presented in terms of saturation yield Y SAT ( 11 CH 4 ), had a negative correlation with beam current and a positive correlation with target chamber temperature. A formulated model equation indicates behavior where the [ 11 C]CH 4 formation follows a parabolic graph as a function of beam current. The negative square term, i.e., the yield loss, is postulated to arise from Haber-Bosch-like NH 3 formation: N 2  + 3H 2  → 2NH 3 . The studied conditions suggest that the NH 3 (liq.) would be condensed on the target chamber walls, thus depleting the hydrogen reserve needed for the conversion of nascent 11 C to [ 11 C]CH 4 .
Conclusions: [ 11 C]CH 4 production can be improved by increasing the target chamber temperature, which is presented in a mathematical formula. Our observations have implications for targetry design (geometry, gas volume and composition, pressure) and irradiation conditions, providing specific knowledge to enhance [ 11 C]CH 4 production at high beam currents. Increased [ 11 C]CH 4 radioactivity is an obvious benefit in radiosynthesis in terms of product yield and molar radioactivity.
(© 2024. The Author(s).)
Databáze: MEDLINE
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