Production and separation of 43Sc for radiopharmaceutical purposes

Abstract

BackgroundThe favorable decay properties of 43Sc and 44Sc for PET make them promising candidates for future applications in nuclear medicine. An advantage 43Sc (T1/2 = 3.89 h, Eβ+ av = 476 keV [88%]) exhibits over 44Sc, however, is the absence of co-emitted high energy γ-rays. While the production and application of 44Sc has been comprehensively discussed, research concerning 43Sc is still in its infancy. This study aimed at developing two different production routes for 43Sc, based on proton irradiation of enriched 46Ti and 43Ca target material.Results 43Sc was produced via the 46Ti(p,α)43Sc and 43Ca(p,n)43Sc nuclear reactions, yielding activities of up to 225 MBq and 480 MBq, respectively. 43Sc was chemically separated from enriched metallic 46Ti (97.0%) and 43CaCO3 (57.9%) targets, using extraction chromatography. In both cases, ~90% of the final activity was eluted in a small volume of 700 μL, thereby, making it suitable for direct radiolabeling. The prepared products were of high radionuclidic purity, i.e. 98.2% 43Sc were achieved from the irradiation of 46Ti, whereas the product isolated from irradiated 43Ca consisted of 66.2% 43Sc and 33.3% 44Sc. A PET phantom study performed with 43Sc, via both nuclear reactions, revealed slightly improved resolution over 44Sc. In order to assess the chemical purity of the separated 43Sc, radiolabeling experiments were performed with DOTANOC, attaining specific activities of 5–8 MBq/nmol, respectively, with a radiochemical yield of >96%.ConclusionsIt was determined that higher 43Sc activities were accessible via the 43Ca production route, with a comparatively less complex target preparation and separation procedure. The product isolated from irradiated 46Ti, however, revealed purer 43Sc with minor radionuclidic impurities. Based on the results obtained herein, the 43Ca route features some advantages (such as higher yields and direct usage of the purchased target material) over the 46Ti path when aiming at 43Sc production on a routine basis.Electronic supplementary materialThe online version of this article (10.1186/s41181-017-0033-9) contains supplementary material, which is available to authorized users.

Radiometals for imaging and theranostics, current production, and future perspectives

“…Another option for the production of 43 Sc is the irradiation of enriched 42 Ca targets with deuterons using the 42 Ca(d,n) 43 Sc nuclear reaction; however, this method has yet to produce 43 Sc in high activities in a practical setting. The drawback of the abovementioned production routes is the fact that the availability of cyclotrons with high‐current α beams, or those with deuteron beams, is limited …”

“…One can utilize three scandium radioisotopes towards theranostic applications . 43 Sc ( T 1/2 = 3.9 h) and 44 Sc ( T 1/2 = 4.0 h) are both positron emitters and can be used for PET imaging.…”

“…PET images of Derenzo phantoms were acquired using 44 Sc from irradiated 44 Ca targets, as well as 43 Sc obtained from both 46 Ti‐ and 43 Ca‐irradiated target material . In line with the smaller positron energy of 43 Sc, the resolution was found to be the best for pure 43 Sc, followed by the 43 Sc/ 44 Sc mixture and 44 Sc.…”

“…The drawback of the abovementioned production routes is the fact that the availability of cyclotrons with high-current α beams, or those with deuteron beams, is limited. 78 Recently, the production of 43 Sc was investigated, comparing two different production routes, namely, 46 Ti(p,α) 43 Sc and 43 Ca(p,n) 43 Sc. 78 The former nuclear reaction has a low cross section and resulted in a product with modest yield after extensive irradiation of 97% enriched 46 Ti metal powder with protons at approximately 17 MeV but high radionuclidic purity (>98%).…”

“…78 Recently, the production of 43 Sc was investigated, comparing two different production routes, namely, 46 Ti(p,α) 43 Sc and 43 Ca(p,n) 43 Sc. 78 The former nuclear reaction has a low cross section and resulted in a product with modest yield after extensive irradiation of 97% enriched 46 Ti metal powder with protons at approximately 17 MeV but high radionuclidic purity (>98%). The production via the 43 Ca(p,n) 43 Sc nuclear reaction produced higher activities of 43 Sc, but the product consisted of a mixture of 43 Sc and 44 Sc at an activity ratio of 2:1 when using 57.9% enriched 43 CaCO 3 and irradiating with approximately 11 MeV protons to maximize 43 Sc production over its 44 Sc counterpart.…”