Improved Sc-44 production in a siphon-style liquid target on a medical cyclotron.

In order to use new and promising radiometals for molecular imaging, it is important that they can be obtained as inexpensively and easily as possible. This often requires a cyclotron with solid target hardware or a radionuclide generator, which are not widely available for rarely used radionuclides. Here, we investigate the improved production of ⁴⁴ Sc with a siphon-style liquid target system and compare to our previous work with a simple liquid target. A metal salt solution with a high concentration of natural abundance Ca(NO ₃ ) ₂ (0.14 g/cm ³ ) was irradiated with a medical cyclotron (12 MeV protons; 20 μA). ⁴⁴ Sc was produced via the ^nat Ca(p,x) ⁴⁴ Sc reaction. As the pressure increase during irradiation was reduced in the siphon-style target, it was possible to irradiate with a higher proton beam current (20 μA) than with the simple liquid target system (7.9 μA). In addition, the saturation yield per μA of ⁴⁴ Sc was increased by a factor of 3.18 ± 0.05 (6.2 ± 0.1 MBq/μA with the siphon target versus 1.94 ± 0.08 MBq/μA with the simple target). This results in an overall increase in ⁴⁴ Sc activity by a factor of 11.
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