Gadolinium Target Research Articles

Production and radiochemical separation of Tb-161 as a feasible beta therapeutic radioisotope from reactor irradiated Gd target

Terbium-161 (161Tb) is a promising therapeutic radionuclide that has gained significant attention in the field of nuclear medicine in recent years. 161Tb has several favorable characteristics that make it a valuable candidate for targeted radionuclide therapy. The production of No-carrier-added 161Tb was carried out by the neutron activation of natural gadolinium target in the Egyptian Second Research Reactor (ETRR-2) at a thermal neutron flux position of 1.8 × 1014 n cm-2 s-1. The radioactivities of 161Tb as well as coproduced Gd radioimpurities were computed theoretically by the MCNPX2.7.0 code and verified by actual measurements, where accepted discrepancies were obtained. The purification of 161Tb from irradiated Gd target was developed by Chelex-100 resin. The elution performance was studied using different eluents, and 0.1 M HNO3 was found to be the best medium to obtain a high separation efficiency of more than 92% in a short time. The eluted 161Tb was of high chemical, radiochemical, and radionuclidic purities, indicating its potential for effective application in radiopharmaceutical preparation.

Radiochemical separation of 161 Tb from neutron irradiated Gd target by liquid-liquid extraction technique

Abstract No-carrier-added (NCA) 161 Tb, which has advisable nuclear properties to be applied for cancer radiotherapy was produced at the Egyptian Second Research Reactor (ETRR-2) by neutron irradiation of natural gadolinium target via indirect nuclear reaction. The radiochemical separation of 161 Tb from irradiated gadolinium target was investigated based on solvent extraction technique using Cyanex 302. Several separation parameters were checked and optimized. According to the obtained results, the separation process of the investigated radioisotopes proceeds in two steps. The first step is an extraction of all of them into the organic phase in which the extraction % (98 %) was optimized at pH 4, 0.15 M of Cyanex 302 and 2.5 h extraction time. Moreover, the slope analysis method confirmed the participation of 2 mol of the organic extractant for the separation of 161 Tb from irradiated gadolinium. The second step is the separation of the 161 Tb isotope that was purified by the stripping of 159Gd with a citrate solution at pH 9, which is considered as a highly efficient and promising method for separation and purification of the two radioisotopes.

Angular distribution separation of the extreme ultraviolet emission and suprathermal ions with energy reduction

We have demonstrated angular distribution separation of the extreme ultraviolet (EUV) emission and suprathermal ions with a significant energy reduction for ions produced using dual pulse irradiation of a planar gadolinium (Gd) target. The pulse separation time between the pre-pulse and the main laser heating pulse was set at 30 ns, and the pre-plasma was irradiated at a distance of 50 μm above the target. Angular distributions of the EUV emission and the suprathermal ions were almost isotropic and followed a cos4θ distribution, respectively. The suprathermal ions were emitted normal to the target along the pre-pulse laser axis. The most probable energy of the suprathermal ions was less than 2 keV, while their maximum charge state was Gd6+ with the pre-plasma, compared to an energy of about 10 keV with a maximum charge state Gd15+ without the pre-plasma. The results suggest that the collector mirror position may be chosen to achieve a long lifetime, by avoiding damage from fast ion collisions.

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

IntroductionFour 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. MethodsIrradiation 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. ResultsThe 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.

Study of terbium production from enriched Gd targets via the reaction 155Gd(d,2n)155Tb

The terbium (Tb) family has attracted much attention in recent years thanks to the diagnostic and therapeutic applications of the quadruplet 149Tb, 152Tb, 155Tb and 161Tb. However, the scarce availability of Tb radioisotopes is one of the main reasons hindering its clinical applications. To increase its availability, this work proposes to use enriched gadolinium (Gd) targets to produce some Tb radioisotopes (149Tb, 152Tb, and 155Tb) via deuteron-induced reactions in cyclotrons. The production of the Auger and gamma emitter 155Tb was chosen as a case study because the 155Gd enrichment (92.8%) is the highest available from all Gd stable isotopes. The involved reaction is 155Gd(d,2n)155Tb. Using enriched thin Gd-containing targets, cross-sections of the reactions 155Gd(d,x)153,154,155,156Tb have been measured at the GIP ARRONAX cyclotron facility with a beam energy ranging from 8 MeV to 30 MeV. This measurement allows for estimating the production yield and the purity of 155Tb, and for determining the irradiation parameters for large production batches. A thick enriched 155Gd2O3 target has been then irradiated with an incident energy of 15.1 MeV and a beam current of 368 nA for 1 h. The production yield of 155Tb is 10.2 MBq/μA/h at End Of Bombardment (EOB) and the purity is 89% after 14 days of decay. These experimental values are consistent with estimation based on measured cross-sections. A comparison of the deuteron-induced and proton-induced production routes is also presented in this paper.

Can we reach suitable 161Tb purity for medical applications using the 160Gd(d,n) reaction?

Terbium is a chemical element that has several radioactive isotopes with suitable physical characteristics to be used in medical applications either for imaging or for therapy. This makes terbium a promising element to implement the theranostic approach. For therapeutic applications, 161Tb (T1/2 = 6.89 d) is suitable for targeted β-therapy. The main production route is through neutron capture reaction in nuclear reactors. In this work, we explored an alternative production route, the 160Gd(d,n)161Tb reaction. We have measured its production cross-section as well as those of possible co-produced contaminants, with a special focus on 160Tb (T1/2 = 72.3 d). To achieve this, cross-section measurements were made from natural gadolinium target. Production yields of 10.3 MBq/μA/h for the 161Tb and 1.5 MBq/μA/h for the 160Tb were obtained at 20 MeV. A161Tb radionuclidic purity of 86% was achieved over the 8 MeV–20 MeV energy range. The co-production of other terbium isotopes limits the interest of using higher energies. Based on the limited purity of 161Tb using the 160Gd(d,n)161Tb reaction, we conclude that it is not a production route suitable for medical applications. Although, this may be reconsidered when mass separation technique with high efficiency will be available.

Angular correlation of the two gamma rays produced in the thermal neutron capture on gadolinium-155 and gadolinium-157

Abstract The ANNRI-Gd collaboration studied in detail the single γ-ray spectrum produced from the thermal neutron capture on 155Gd and 157Gd in our previous publications. Gadolinium targets were exposed to a neutron beam provided by the Japan Spallation Neutron Source (JSNS) in J-PARC, Japan. In the present analysis, one new additional coaxial germanium crystal was used in combination with the 14 germanium crystals in the cluster detectors to study the angular correlation of the two γ rays emitted in the same neutron capture. We present for the first time angular correlation functions for two γ rays produced during the electromagnetic cascade transitions in the (n, γ) reactions on 155Gd and 157Gd. As expected, we observe mild angular correlations for the strong, but rare transitions from the resonance state to the two energy levels of known spin-parities. Contrariwise, we observe negligibly small angular correlations for arbitrary pairs of two γ rays produced in the majority of cascade transitions from the resonance state to the dense continuum states.

Anomalous electronic energy losses in protons passing through Gd thin films

We report a theoretical analysis of recent data on the unexpectedly high electronic energy loss protons in a polycrystalline gadolinium target. These results led the authors of this data to conclude that the free electron model used to analyse these results fails. In this work we provide a quantitative explanation of the experimental results, using an approach based on density functional theory within the framework of the free electron gas model. We performed semi-classical trajectory simulations (SCTS) and employ the local-density-approximation model (LDA), using an inhomogeneous electron density distribution and the polycrystalline character of Gd samples. The good agreement obtained, delineates the need of considering a realistic description of a particle trajectory and the effective electron density ‘seen’ along it, whose description remains within a FEG model.

NMB-4 - Production and radiochemical separation of terbium-155 from enriched gadolinium target material and its preliminary application in SPECT imaging

NMB-4 - Production and radiochemical separation of terbium-155 from enriched gadolinium target material and its preliminary application in SPECT imaging

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

Introduction155Tb (T1/2 = 5.32 d) is considered both as a promising Auger electron emitter and as a diagnostic pair for other therapeutic terbium radionuclides. Despite several methods for its production proposed, it remains scarcely available. Most of the methods using low-energy protons and deuterons beams result in a high content of radionuclidic impurities. High purity 155Tb can be obtained using high-energy proton beams combined with online mass separation of products, but the method remains inaccessible to most potential consumers. We have proposed an indirect method for the production of 155Tb via formation of 155Dy (T1/2 = 9.9 h), which can be implemented using medium energy alpha particles beam. MethodsGadolinium oxide targets of natural isotopic composition were irradiated by 60 MeV alpha particles beam on a U-150 cyclotron of the National Research Center “Kurchatov Institute”. The cross sections of nuclear reactions were measured by the stack foil technique, detecting the gamma radiation of the activation products. Gd, Tb, and Dy were separated by extraction chromatography using the LN Resin sorbent in nitric media. The isolated dysprosium fraction was stored for a day, and the formed 155Tb was isolated by the same method. ResultsThe cross sections for the formation of 159Gd, 153-156Tb, and 155,157Dy under irradiation by alpha particles of a gadolinium target of natural isotopic composition in the energy range 20–60 MeV have been measured. The 155Dy yield on a thick target at 60 MeV was 35 MBq/μAh, which makes it possible to obtain 1 GBq 155Tb as a result of 12-hour irradiation with a beam current of 50 μA. Extraction chromatography on LN Resin sorbent in nitric enabled quick and efficient separation of Gd, Tb, and Dy. The radiochemical yield of Dy was 95%, for Tb > 95%. The main radionuclidic impurity is 153Tb (T1/2 = 2.34 d; <5.4% of 155Tb activity). ConclusionsThe developed method allows the production of therapeutic amounts of 155Tb with acceptable radionuclidic purity without the need for isotopically enriched materials.The amount of 155Tb is sufficient for its use in Auger therapy, as well as for preclinical studies of the suitability of SPECT preparations in laboratory animals. Nevertheless, to obtain higher activities, a longer irradiation time and a higher projectile current are proposed.The 153Tb radionuclide present in the final preparation has a shorter half-life than the target radionuclide, and its hard γ-lines have a probability of emission of less than 1%, from which it can be concluded that the negative effect will not be significant. However, a product of this purity and type of contamination requires additional testing for toxicity in living organisms. The final sample also includes a certain amount of 157Tb (T1/2 = 71 a, the only γ-line 54.5 keV Iγ = 0.0084%), which will complicate the labeling conditions. Thus, more research is needed in the labeling area.It should be noted that the use of gadolinium enriched in the 155Gd or 156Gd nuclide as a target will help not only reduce the amount of impurities but also increase the yield of 155Tb.

Measurement of L-shell X-ray production cross sections in 89Y, 158Gd and 209Bi due to 0.3 MeV/u – 1.0 MeV/u 12C ions

Experimental heavy ion induced X–ray production cross sections in matter continue to be of importance for both fundamental ion-atom collision studies as well as practical applications such as in nuclear analytical techniques. This work presents results of L-shell X-ray production cross section measurements in 89Y, 158Gd and 209Bi due to 4 MeV–12 MeV 12Cq + projectile ions. Experimental data are compared with theoretical calculations based on the ECPSSR, ECPSSR + EC and ECPSSR-UA models. Data show fairly good, albeit energy dependent agreement with the different models for yttrium and gadolinium cross sections. For bismuth, all three models overestimate data by an almost constant factor of two. The effect of multiple ionization on the l-line intensity ratios is also presented for gadolinium and bismuth targets.

Theragnostics - Alternative production of terbium isotopes at the University of Birmingham using an MC40 cyclotron

In this work alternative methods for the production of terbium isotopes, and in particular 152Tb and 155Tb, have been investigated. These isotopes, which could be used for theragnostics, have been produced using an alpha and a proton beam incident on europium and gadolinium targets, respectively. The experimental results have been compared with the predicted cross-sections, calculated using TALYS and PACE4 code.

New excitation functions for proton induced reactions on natural gadolinium up to 70 MeV with focus on 149Tb production

Terbium is one of the most interesting elements for new potential theranostics applications. Indeed, the physical properties of four of its radionuclides (149Tb, 152Tb, 155Tb, 161Tb) allow their use in each main applications of nuclear medicine. 149Tb is the lowest mass alpha emitter with suitable physical properties for receptor-targeted alpha therapy (TAT), and the only one among the radiolanthanides. Currently 149Tb is only produced through spallation reactions induced by high-energy proton beam coupled with mass separation to obtain suitable purity. The aim of the present work is to investigate the production of 149Tb using commercial cyclotrons by irradiation of natural gadolinium target. New excitation functions for proton-induced nuclear reactions on natural gadolinium have been measured. Our results extend current knowledge up to 70 MeV and are in good agreement with existing data at low energy. From this new set of data, production yield estimations are calculated and discussed.

In situ functionalization of gadolinium oxide nanoparticles with polyethylene glycol (PEG) by pulsed laser ablation in a liquid medium (PLAL)

Abstract Gadolinium oxide (Gd2O3) nanoparticles with paramagnetic properties and biocompatible surfaces are promising materials for bioimaging applications. We synthesized in situ pegylated Gd2O3 (Gd2O3@PEG) nanoparticles by liquid phase pulsed laser ablation (PLAL) of a gadolinium target in a polyethylene glycol (PEG) liquid medium. We characterized their shape and morphology using transmission electron microscopy (TEM), and confirmed their crystalline structure with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) in combination with energy-dispersive X-ray spectroscopy (EDX) elemental mapping. The magnetic properties of the nanoparticles were characterized by vibrating sample magnetometry (VSM). We have found that the crystalline nanoparticles generated have a spherical shape and a narrow distribution with average diameters of 15.0, 11.6, and 6.0 nm, for PEG concentrations of 0.01, 0.05, and 0.10 mM, respectively. We verified that partially oxidized molecules of PEG are attached to the nanoparticle surface as carboxyl groups. An analysis of the magnetization of Gd2O3@PEG nanoparticles revealed highly paramagnetic properties. Consequently, PLAL forms a green synthesis of Gd2O3@PEG, opening up new opportunities for bioimaging applications.

Energy Spectrum and Charge Composition of Ions of Laser-Produced Gd and Al Plasmas

The energy spectrum and the distribution of the total charge over the ion energy are studied for plasma produced by partially coherent radiation of the neodymium glass laser with a power density of ~1013 W/cm2 in the focusing spot incident on continuous gadolinium (Gd) and aluminum(Al) plates. The spectra of plasma ions for gadolinium and aluminumtargets are presented at laser radiation energies of 2, 7, 20 J and 1 J, respectively. For the gadolinium target, an increase in the peak amplitudes in ion spectra with increasing influencing radiation energy and manifestations of higher-energy ions are observed. The difference in the ion emission for gadolinium and aluminum targets is also recorded at close radiation energies of 2 and 1 J, respectively.

Application of a novel targeting nanoparticle contrast agent combined with magnetic resonance imaging in the diagnosis of intraductal papillary mucinous neoplasm.

Intraductal papillary mucinous neoplasm (IPMN) is a severe disease with macroscopic visible mucin secretion that primarily occurs in biliary tracts or pancreatic ducts. In comparison with standard diagnostic imaging, probing the molecular abnormalities associated with the initial stages of diseases rather than imaging the end effects markedly improves the accuracy of diagnosis. In the present study, magnetic resonance imaging (MRI) in combination with the contrast agent PEGylated magnetoliposome consisting of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) and target molecules of IPMN were investigated in the diagnosis of patients with suspected IPMN. The present investigation indicated that the novel targeting nanoparticle contrast agent targeted platelet-derived growth factor receptor-β and RET, and maintained a high affinity with tumor markers located on the IPMN surface. The novel targeting nanoparticle contrast agent combined with MRI exhibited increased sensitivity in diagnosing early-stage patients with IPMN. Furthermore, image quality was improved following the use of the novel targeting nanoparticle contrast agent combined with MRI compared with standard MRI. The targeting nanoparticle contrast agent retained sufficient affinity and was present for an adequate amount of time to observe the tumor mass in papillae using MRI. Notably, the targeting nanoparticle contrast agent was metabolized at 12 h post-injection. In conclusion, these outcomes indicate that the novel targeting nanoparticle contrast agent combined with MRI improved image quality and sensitivity compared with standard MRI, which suggests that this approach may be promising for clinical detection in patients with suspected IPMN.

Separation of radioactive terbium from massive Gd targets for medical use

Methods for chemical separation of terbium from gadolinium and dysprosium have been investigated using proton activated gadolinium, as well as gadolinium–terbium mixture matrix. Terbium radioisotopes can be effectively separated from large amount (> 100 mg) gadolinium on an analytical column. In reactors inactive dysprosium also forms in the activated Gd matrix, considerably decreasing the chemical purity of the labelled radiopharmaceutical. A semi-preparative column method was therefore developed to separate terbium at the same time both from the dysprosium and the gadolinium target material.

Heavy-ion beam induced effects in enriched gadolinium target films prepared by molecular plating

A series of enriched gadolinium (Gd, Z=64) targets was prepared using the molecular plating process for nuclear physics experiments at the Cyclotron Institute at Texas A&M University. After irradiation with 48Ca and 45Sc projectiles at center-of-target energies of Ecot=3.8–4.7MeV/u, the molecular films displayed visible discoloration. The morphology of the films was examined and compared to the intact target surface. The thin films underwent a heavy-ion beam-induced density change as identified by scanning electron microscopy and α-particle energy loss measurements. The films became thinner and more homogenous, with the transformation occurring early on in the irradiation. This transformation is best described as a crystalline-to-amorphous phase transition induced by atomic displacement and destruction of structural order of the original film. The chemical composition of the thin films was surveyed using energy dispersive spectroscopy and X-ray diffraction, with the results confirming the complex chemistry of the molecular films previously noted in other publications.

Proposal for precision wavelength measurement of the Ni-like gadolinium x-ray laser formed during the interaction of a nanostructured target with an ultrashort laser beam

The wavelengths of the 3d94d [J = 0]–3d94p [J = 1] transitions of x-ray lasers in Ni-like sequence ions with nucleus charges Z ⩽ 79 are refined. The results of calculations are within the experimental error. It was found that the wavelengths of [J = 0]–4p1/2 [J = 1] and 4d3/2[J = 0]–4p3/2[J = 1] transitions in Sm34+ and Gd36+, respectively, are in the range of 6.70–6.75 nm. Exactly for this narrow range, multilayer mirrors with high reflectance are developed.The gain of the x-ray laser with λ = 6.748 nm in Gd36+ is calculated under the assumption that plasma is formed during the interaction of a nanostructured (cluster-like) gadolinium target with high-intensity pump laser radiation. The optimum plasma density, temperature, length, and pump parameters are determined to achieve the highest Gd36+ ion fraction and emission quantum yield of ~1013 photons.

Preparation of thin gadolinium samples via electrodeposition for excitation function studies

A preparation method for gadolinium targets with a thickness up to 4 mg/cm2 on aluminum supports from aqueous electrolytes was developed. These electrodeposited adhesive and mechanically stable natGd layers were used to measure excitation functions of Gd + p nuclear reactions relevant to the production of medically important 152Tb (PET) and 155Tb (SPECT) radioisotopes.