Current State of 44Ti/44Sc Radionuclide Generator Systems and Separation Chemistry

Abstract

In recent years, there has been an increased interest in 44Ti/44Sc generators as an onsite source of 44Sc for medical applications without needing a proximal cyclotron. The relatively short half-life (3.97 hours) and high positron branching ratio (94.3%) of 44Sc make it a viable candidate for positron emission tomography (PET) imaging. This review discusses current 44Ti/44Sc generator designs, focusing on their chemistry, drawbacks, post-elution processing, and relevant preclinical studies of the 44Sc for potential PET radiopharmaceuticals.

Scandium Radioisotopes—Toward New Targets and Imaging Modalities

“…Target materials with natural isotopic abundance Scandium-43 Ca(α,n) 43 Ti-> 43 Sc 96.9 12.5-17.5 240 MBq/µAh >98.9 [12] Ca(α,n) 43 Ti-> 43 Sc 96.9 34 54.8 MBq/µAh 99.7 [13] 96.9 28 102.7 MBq/µAh 99.9 [14] Scandium-44 44 Ca(p,n) 44 Scandium-47 46 Ca(n, γ) 47 Ca-> 47 Sc 5.0 2.14 GBq 99.99 [22] 47 Ti(n,p) 47 Sc 95.7 4.9 MBq 88-99 [22] Another potentially attractive pathway for the production of scandium radioisotopes is production from a generator by the decay of the parent radionuclide, which is immobilized on the solid phase and then selectively eluted on the scandium radioisotope. It replicates the concepts of technetium-99 m and gallium-68 generators commonly and successfully introduced in nuclear medicine, significantly facilitating the availability of radioisotopes in clinical applications [23]. Scandium-44 is produced as a decay product of titanium-44 formed in the reaction 45 Sc(p,2n) 44 Ti, while scandium-47 is a decay product of calcium-47 produced in 46 Ca (n,γ) 47 Ca or 48 Ca(γ,n) 47 Ca reactions.…”

“…Scandium-44 is produced as a decay product of titanium-44 formed in the reaction 45 Sc(p,2n) 44 Ti, while scandium-47 is a decay product of calcium-47 produced in 46 Ca (n,γ) 47 Ca or 48 Ca(γ,n) 47 Ca reactions. The status of generator systems for scandium-44 was recently reviewed [23]. In its current state, the concept is very interesting, but it has not been possible to create a generator that would provide enough activity for clinical applications.…”