Production and Purification of Terbium-155 Using Natural Gadolinium Targets

Terbium-155 (t _1/2 = 5.32 days) is one of four medically relevant radioisotopes of terbium. It is of interest to the field as a suitable diagnostic counterpart for therapeutic radiolanthanides, as its decay scheme includes γ-rays that are suitable for single photon emission computed tomography (SPECT) imaging. Additionally, ¹⁵⁵Tb has an Auger electron (AE) yield that is viable for AE therapy. There are several direct and indirect production routes that can produce ¹⁵⁵Tb. Two possible direct routes include proton irradiation on gadolinium targets via ¹⁵⁵Gd-(p,n)¹⁵⁵Tb and ¹⁵⁶Gd-(p,2n)¹⁵⁵Tb. The ¹⁵⁵Gd-(p,n)¹⁵⁵Tb reaction is accessible at incident proton beam energies of ∼10 MeV, whereas the ¹⁵⁶Gd-(p,2n)¹⁵⁵Tb nuclear reaction requires ∼18 MeV. This study aims to investigate the production of ¹⁵⁵Tb from ^natGd through the ^natGd-(p,x) nuclear reaction, wherein both (p,n) and (p,2n) reactions were leveraged, and the purification using a three-column ion chromatography method. Using this system, recoveries of radioterbium of up to 97% were achieved in addition to high recoveries of the Gd target material, illustrating the suitability of this technique for enriched targets.