Separation of ^44mSc/^44gSc Nuclear Isomers Based on After-Effects

Abstract

44g Sc presents a particular interest for application in nuclear medicine for positron emission tomography (PET) due to its favorable nuclear decay properties (t 1/2 = 3.97 h, E max = 1.47 MeV, branching ratio 94.3% β + ). Its nuclear isomer 44m Sc (t 1/2 = 58.61 h) decays by isomeric transition (IT) into 44g Sc, accompanied by ≈12% of conversion electron emission, which can cause a partial release of the daughter 44g Sc from the chelate complex. A 13 MeV cyclotron at TRIUMF was used to produce both 44m Sc and 44g Sc via the nat Ca(p,n) 44m,g Sc reaction. A 44m Sc/ 44g Sc generator was designed by using a Strata C-18E cartridge. After several tested systems, a successful separation method was developed using DOTATOC as a chelator, a Strata C-18E cartridge as a generator column, and an elution solution of 0.1 M NH 4 -α-HIB. The yield of the generator with the daughter 44g Sc release was equal to 9.8 ± 1.0% (or ≈80% per portion of conversion). This result shows the important role of after-effects in the design of radionuclide generators. Nuclear cross-section calculations were applied using the TALYS code to allow for the determination of the most promising alternative routes for 44m Sc production, which will enable the development of a full-scale 44m Sc/ 44g Sc radionuclide generator based on after-effects.