Scandium Radioisotopes-Toward New Targets and Imaging Modalities

Abstract

The concept of theranostics uses radioisotopes of the same or chemically similar elements to label biological ligands in a way that allows the use of diagnostic and therapeutic radiation for a combined diagnosis and treatment regimen. For scandium, radioisotopes -43 and -44 can be used as diagnostic markers, while radioisotope scandium-47 can be used in the same configuration for targeted therapy. This work presents the latest achievements in the production and processing of radioisotopes and briefly characterizes solutions aimed at increasing the availability of these radioisotopes for research and clinical practice.

Keywords: radiochemical separation; radiolabeling; radiopharmaceuticals; scandium radioisotopes; theranostics.

Figure 1

The structures of compounds mostly used in extraction chromatography for Sc separation.

Figure 2

Distribution coefficients (Kd) of some metal ions on TODGA resin as a function of HCl concentration [38].

Figure 3

Elution curves for the ⁴⁴Ca irradiated target on TODGA resin [38]. Following the first step in the elution of Ca excess, 12 mL of 1M HNO₃ was used to elute Fe and Zn. An amount of 10 mL of diluted HCl solution was used to quantitatively elute scandium.

Figure 4

Schematic diagram of scandium-44 production panel using a two-column system [45].

Figure 5

Distribution coefficients of Sc(III) and Ca(II) in UTEVA resin at different HCl concentrations [48].

Figure 6

Proposed mechanism for the separation of scandium-47 using the ZrV matrix [54].

Figure 7

Influence of HCl concentration on the values of K_d for ⁴⁴Ti/⁴⁴Sc on: (A) TEHDGA resin and (B) ZR hydroxamate resin (ZR) [27].

Figure 8

The scheme for TEVA-based ⁴⁴Ti/⁴⁴Sc generator eluate post-processing [28].