New method for production of 155Tb via 155Dy by irradiation of natGd by medium energy alpha particles

Comparative study of 155Tb production via 155Dy precursor with p, d and α beams on natural targets for medical applications

Three different reactions with the use of natural targets are investigated to produce 155Tb for medical applications from the decay of its precursor 155Dy. The TALYS code has been exploited to optimize the cross section description and to improve the agreement with the full set of available data. The study is completed by a theoretical model for the two radio-chemical separations: optimal solutions are presented for the production of high quality 155Tb samples, guaranteed by the absence of the main contaminant, 156Tb.

Co-production of 155Tb and 152Tb irradiating 155Gd / 151Eu tandem target with a medium energy α-particle beam

INTRODUCTION

Four terbium isotopes 149,152,155,161Tb emitting various types of radiation can be used for both diagnostics and therapy. 152Tb emits positrons and is ideal for PET. 155Tb is considered a promising Auger emitter and a diagnostic pair for other terbium therapeutic isotopes. Several methods for the production of 155Tb using charged particle accelerators have been proposed, but they all have significant limitations. The restricted availability of this isotope hinders its medical applications. We have proposed a new method for production of 155Tb, irradiating enriched 155Gd by alpha particles. The possibility of simultaneous production of two isotopes of terbium, 152,155Tb, was also studied for more efficient cyclotron beam use.

METHODS

Irradiation of 155Gd enriched targets and 155Gd / 151Eu tandem target with alpha-particles with an energy of 54 MeV was carried out at the U-150 cyclotron at the NRC "Kurchatov Institute". The cross sections of nuclear reactions on enr-155Gd were measured by the stack foil technique, detecting the gamma-radiation of the activation products. The separation of rare earth elements was performed by extraction chromatography with the LN Resin. 155Tb was produced via 155Dy decay.

RESULTS

The cross sections for the 155,156Tb and 155,157Dy production were measured by the irradiation of a gadolinium target enriched with the 155Gd isotope with alpha-particles in an energy range of 54 → 33 MeV. The yield of 155Dy on a thick target at 54 MeV was 130 MBq/μAh, which makes it possible to obtain 1 GBq of 155Tb in 11 hour-irradiation with 20 μA beam current. The possibility of simultaneous production of 152,155Tb by irradiation of 155Gd and 151Eu tandem target with medium-energy alpha-particles is implemented. Optimal irradiation energy ranges of alpha -particles as 54 → 42 MeV for 155Tb and 42 → 34 MeV for 152Tb were suggested. Product activity and radionuclidic purity were calculated.

Photonuclear production of medical radioisotopes 161Tb and 155Tb

The production possibility of ¹⁶¹Tb and ¹⁵⁵Tb by irradiating of natural dysprosium with gamma rays obtained by decelerating an electron beam with an energy of 55 MeV has been demonstrated experimentally. The yield of ¹⁶¹Tb was 14.4 × 10³ Bq × μA^-1 × h^-1 × cm² × g_Dy2O3^-1. Simultaneously, upon irradiation, ¹⁵⁵Dy is formed with the yield of 25 × 10³ Bq × μA^-1 × h^-1 × cm² × g_Dy2O3^-1, which leads to the formation of 1.6 × 10³ Bq × μA^-1 × h^-1 × cm² × g_Dy2O3^-1 of ¹⁵⁵Tb. It has been shown that the isolation of terbium radioisotopes from tens of mg of dysprosium target can be achieved by extraction chromatography, and final separation yield was 39%. The impurity of ¹⁶⁰Tb is 7.3% of the ¹⁶¹Tb activity at EOB.