Production of zirconium-88 via proton irradiation of metallic yttrium and preparation of target for neutron transmission measurements at DICER

A process for the production of tens to hundreds of GBq amounts of zirconium-88 (⁸⁸Zr) using proton beams on yttrium was developed. For this purpose, yttrium metal targets (≈20 g) were irradiated in a ~16 to 34 MeV proton beam at a beam current of 100-200 µA at the Los Alamos Isotope Production Facility (IPF). The ⁸⁸Zr radionuclide was produced and separated from the yttrium targets using hydroxamate resin with an elution yield of 94(5)% (1σ). Liquid DCl solution in D₂O was selected as a suitable ⁸⁸Zr sample matrix due to the high neutron transmission of deuterium compared to hydrogen and an even distribution of ⁸⁸Zr in the sample matrix. The separated ⁸⁸Zr was dissolved in DCl and 8 µL of the obtained solution was transferred to a tungsten sample can with a 1.2 mm diameter hole using a syringe and automated filling station inside a hot cell. Neutron transmission of the obtained ⁸⁸Zr sample was measured at the Device for Indirect Capture Experiments on Radionuclides (DICER).

Evaluation of nuclear reaction cross sections for optimization of production of the important non-standard positron emitting radionuclide 89Zr using proton and deuteron induced reactions on 89Y target

⁸⁹Zr (T_1/2 = 3.27 d) is an important β⁺-emitting radionuclide of zirconium used in immuno PET. The excitation functions of the ⁸⁹Y(d,2n)⁸⁹Zr and ⁸⁹Y(p,n)⁸⁹Zr reactions were analyzed to deduce the optimum conditions for the high purity production of ⁸⁹Zr. The nuclear model codes ALICE-IPPE, EMPIRE 3.2 and TALYS 1.9 were used to check the consistency and reliability of the experimental data. A polynomial fit to the chosen data for each reaction gave the excitation function, which was then used for the integral yield calculation of the product. The amount of the major radioactive impurity ⁸⁸Zr was precisely analyzed for both the proton and the deuteron induced reactions on the ⁸⁹Y target.

Calculation of 89Y(p,x)86,88,89gZr, 86g,87g,88gY, 85gSr, and 84Rb reaction cross sections based on level density

Excitation functions based on level density were calculated for proton-induced on yttrium-89 using the TALYS-1.8 code. Hence, production cross-section of the ⁸⁹Y(p,x)^86,88,89gZr, ^86g,87g,88gY, ^85gSr, and ^84gRb were computed up to 50 MeV. In this study, the constant temperature model alongside the Fermi Gas model (CGCM) was employed as a default model. For this reason, the a-parameter as an essential parameter in the Fermi Gas formula was modified to obtain the best result. Besides, the Back-shifted Fermi Gas Model (BSFGM) and the Generalized Superfluid Model (GSM) are presented to the deliberation. The outcomes of cross-sections were compared with the experimental data approaching regarding desired consequences.

Recent Advances in Zirconium-89 Chelator Development

The interest in zirconium-89 (⁸⁹Zr) as a positron-emitting radionuclide has grown considerably over the last decade due to its standardized production, long half-life of 78.2 h, favorable decay characteristics for positron emission tomography (PET) imaging and its successful use in a variety of clinical and preclinical applications. However, to be utilized effectively in PET applications it must be stably bound to a targeting ligand, and the most successfully used ⁸⁹Zr chelator is desferrioxamine B (DFO), which is commercially available as the iron chelator Desferal^®. Despite the prevalence of DFO in ⁸⁹Zr-immuno-PET applications, the development of new ligands for this radiometal is an active area of research. This review focuses on recent advances in zirconium-89 chelation chemistry and will highlight the rapidly expanding ligand classes that are under investigation as DFO alternatives.

Investigative for no-carrier-added 87m,gY production by the proton-induced on 89Y

The radioisotope ⁸⁷Y is one of the candidates for the SPECT and ⁸⁷Y/^87mSr generator due to its suitable half-life and decay properties. The proton-induced on the ⁸⁹Y target can be used for the production of ⁸⁷Y. The present perusal calculated the excitation function for the both ⁸⁹Y(p,x)^87m,gY direct reaction and decay of ⁸⁷Zr via ⁸⁹Y(p,3n)⁸⁷Zr → ^87mY → ^87gY indirect reaction using the TALYS-1.8 code. To simulation the production of ^87m,gY nuclide, the target thickness was designed based on the stopping power calculation by the SRIM-2013 code. The Monte Carlo code GEANT4 was used to simulate the transport of protons through the irradiation assembly. Then, the cumulative integral yield of the ^87m,gY has been calculated directly after the decay of ⁸⁷Zr radionuclide entirely. These results were in good agreement with the theoretical and reported experimental data. Eventually, the integral yield of the ^87m,gY was calculated by the indirect method from ⁸⁷Zr decay after separation the zirconium. This work provides the basis for theoretical appraisement of the use of no-carrier-added ⁸⁷Y as radiopharmaceutical for the purpose of medical applications.

Spot-welding solid targets for high current cyclotron irradiation

Zirconium-89 finds broad application for use in positron emission tomography. Its cyclotron production has been limited by the heat transfer from yttrium targets at high beam currents. A spot welding technique allows a three-fold increase in beam current, without affecting ⁸⁹Zr quality. An yttrium foil, welded to a jet-cooled tantalum support base accommodates a 50µA proton beam degraded to 14MeV. The resulting activity yield of 48±4 MBq/(μA∙hr) now extends the outreach of ⁸⁹Zr for a broader distribution.

Nuclear model analysis of excitation functions of proton induced reactions on ⁸⁶Sr, ⁸⁸Sr and natZr: Evaluation of production routes of ⁸⁶Y

The proton induced nuclear reactions on (86)Sr, (88)Sr and (nat)Zr were investigated for the production of (86)Y. The literature data were compared with the results of nuclear model calculations using the codes ALICE-IPPE, TALYS 1.6 and EMPIRE 3.2. The thick target yields of (86)Y were calculated from the recommended excitation functions. Analysis of radioyttrium impurities was also performed. A comparison of the various production routes showed that for medical applications of (86)Y, the reaction (86)Sr(p,n)(86)Y is the method of choice, which gives efficient yield with minimum impurities.

Experimental studies on excitation functions of the proton-induced activation reactions on yttrium

Proton-induced activation cross-sections were measured for the (89)Y(p,x)(89,88,86)Zr, (89)Y(p,x)(88,87,87 m,86)Y, (89)Y(p,x)(85,83,82)Sr and (89)Y(p,x)(84,83)Rb reactions by a stacked foil technique in the energy range 15-80 MeV which was covered by two separate measurements for 15-50 and 32-80 MeV energy range with 50 and 80 MeV incident protons. The differences between the results of two irradiations were found within 6% in the overlapping energy regions. The production yields for the long-lived products like (88)Zr, and (88)Y are significantly larger than that of (nat)Mo+p, (nat)Nb+p and (nat)Zr+p processes. The productions of the medical isotopes, (85)Sr and (83)Sr are also effective by Y+p process using an 80 MeV beam. Thick target integral yields were also deduced using the measured cross-sections. The (87)Y, (88)Y, (88)Zr and (89)Zr radionuclides have suitable yields and decay characteristics important for thin-layer activation (TLA) analysis.

Reactions of 88Sr with protons of energies7–85 MeV

Excitation functions for the (p,xn) (x = 1–5), (p,p3n), and (p,2pxn) (x = 1, 3, 4) reactions induced in 88Sr by protons of energy from 7 to 85 MeV have been measured by radiochemical methods. Cross sections for the individual isomeric species for the products of (p,2n), (p,3n), (p,4n), and (p,p3n) reactions are also presented.Excitation functions for each of the (p,2p3n) and (p,2p4n) reactions exhibit two peaks, the first of which is assigned to (p,α n) or (p,α 2n) reactions from threshold considerations. The experimental results are compared with Monte Carlo calculations using the codes of Chen et al. for the cascade stage and Dostrovsky et al. for the evaporation stage. The comparison suggests that the calculations of Chen et al. overestimate the extent of compound nucleus contribution at high energies.