TiO2 Decorated Low-Molecular Chitosan a Microsized Adsorbent for a 68Ge/68Ga Generator System

We report column material for a ⁶⁸Ge/⁶⁸Ga generator with acid resistance and excellent adsorption and desorption capacity of ⁶⁸Ge and ⁶⁸Ga, respectively. Despite being a core element of the ⁶⁸Ge/⁶⁸Ga generator system, research on this has been insufficient. Therefore, we synthesized a low molecular chitosan-based TiO₂ (LC-TiO₂) adsorbent via a physical trapping method as a durable ⁶⁸Ge/⁶⁸Ga generator column material. The adsorption/desorption studies exhibited a higher separation factor of ⁶⁸Ge/⁶⁸Ga in the concentration range of HCl examined (0.01 M to 1.0 M). The prepared LC-TiO₂ adsorbent showed acid resistance capabilities with >93% of ⁶⁸Ga elution yield and 1.6 × 10⁻⁴% of ⁶⁸Ge breakthrough. In particular, the labeling efficiency of DOTA and NOTA, by using the generator eluted ⁶⁸Ga, was quite encouraging and confirmed to be 99.65 and 99.69%, respectively. Accordingly, the resulting behavior of LC-TiO₂ towards ⁶⁸Ge/⁶⁸Ga adsorption/desorption capacity and stability with aqueous HCl exhibited a high potential for ion-exchange solid-phase extraction for the ⁶⁸Ge/⁶⁸Ga generator column material.     

Ga2O for target, solvent extraction for radiochemical separation and SnO2for the preparation of a68Ge/68Ga generator

Summary The target for the production of⁶⁸Geconsists of a disc of gallium suboxide, Ga₂O, with a 19 mm diameter. The suboxide was primarily prepared by repeatedly mixing metallic Ga and Ga₂O₃at 700 °C. The target (2.4 g) was quite stable under a long-time irradiation with a 34 MeV proton beam at a current of ~80<span lang=EN-ZA style='font-size:12.0pt; font-family:Symbol;mso-bidi-font-family:Symbol;mso-ansi-language:EN-ZA'>mA. The dissolution of the target was performed using 12M sulphuric acid solution, assisted with the dropwise addition of 30% H₂O₂solution, and took less than 4 hours. A solvent extraction method, using a 9M H₂SO₄-0.3M HCl/CCl₄system, was employed for the radiochemical separation of⁶⁸Ge from Ga and Zn radionuclides, while 0.05M HCl was used for the back extraction of⁶⁸Ge from the organic phase. The⁶⁸Ge obtained in the dilute HCl was directly loaded onto a column containing either a hydrous tin dioxide or a crystalline tin dioxide, obtained by calcinations of the hydrous oxide at 450, 700, and 900 °C. The calcinated hydrous tin dioxide at 900 °C showed the highest crystallinity and highest⁶⁸Ga elution yield and was selected for use in the generator. The⁶⁸Ga elution from the column generator packed with 2 g of tin dioxide, using 3 ml of 1M HCl, and yielded an average of 65%. The breakthrough of⁶⁸Ge was 6.1^. 10^-4%.     

Separation of radioarsenic from irradiated germanium oxide targets for the production of <Superscript>71</Superscript>As and <Superscript>72</Superscript>As

A method for the separation of no-carrier-added arsenic radionuclides from the bulk amount of proton-irradiated GeO₂ targets as well as from coproduced radiogallium was developed. The radionuclides ⁶⁹Ge and ⁶⁷Ga produced during irradiation of GeO₂ were used as tracers for Ge and Ga in the experiments. After dissolution of the target the ratio of As(III) to As(V) was determined via thin layer chromatography (TLC). The extraction of radioarsenic by different organic solvents from acid solutions containing alkali iodide was studied and optimized. The influence of the concentration of various acids (HCl, HClO₄, HNO₃, HBr, H₂SO₄) as well as of KI was studied using cyclohexane. The optimum separation of radioarsenic was achieved using cyclohexane with 4.75 M HCl and 0.5 M KI and its back-extraction with a 0.1% H₂O₂ solution. The separation leads to high purity radioarsenic containing no radiogallium and <0.001% [⁶⁹Ge]Ge. The overall radiochemical yield is 93 ± 3%. The practical application of the optimized procedure in the production of ⁷¹As and ⁷²As is demonstrated and batch yields achieved were in the range of 75–84% of the theoretical values.     

A new68Ge/68Ga generator based on CeO2

A new⁶⁸Ge/⁶⁸Ga generator using CeO₂ as absorbent for⁶⁸Ge has been developed. Sharp elution curves were obtained by using 0.02 mol/l HCl as eluent. About 56% of⁶⁸Ga formed on the column was concentrated in 0.5 ml of eluate. Neither radioactive impurities, nor dissolved cerium were found in the eluate.     

Cyclotron production of 68Ge with a Ga2O target

Systematic information of exchange behavior of Ge(IV) and Ga(III) in varying oxalic acid (0.05M and 0.25M) and sulphuric acid (0.005M-2M range) mixtures is presented. These findings were used to develop a separation involving ⁶⁸Ge from a Ga₂O target material. A method based on acid dissolution of the target and chromatography on an anion exchange resin (Bio-Rad^Ò AG1-X8) was developed. The separated ⁶⁸Ge has high radionuclidic purity and an acceptable chemical purity.     

Reduction of <Superscript>68</Superscript>Ge activity containing liquid waste from <Superscript>68</Superscript>Ga PET chemistry in nuclear medicine and radiopharmacy by solidification

PET with ⁶⁸Ga from the TiO₂- or SnO₂- based ⁶⁸Ge/⁶⁸Ga generators is of increasing interest for PET imaging in nuclear medicine. In general, radionuclidic purity (⁶⁸Ge vs. ⁶⁸Ga activity) of the eluate of these generators varies between 0.01 and 0.001%. Liquid waste containing low amounts of ⁶⁸Ge activity is produced by eluting the ⁶⁸Ge/⁶⁸Ga generators and residues from PET chemistry. Since clearance level of ⁶⁸Ge activity in waste may not exceed 10 Bq/g, as stated by European Directive 96/29/EURATOM, our purpose was to reduce ⁶⁸Ge activity in solution from >10 kBq/g to <10 Bq/g; which implies the solution can be discarded as regular waste. Most efficient method to reduce the ⁶⁸Ge activity is by sorption of TiO₂ or Fe₂O₃ and subsequent centrifugation. The required 10 Bq per mL level of ⁶⁸Ge activity in waste was reached by Fe₂O₃ logarithmically, whereas with TiO₂ asymptotically. The procedure with Fe₂O₃ eliminates ≥90% of the ⁶⁸Ge activity per treatment. Eventually, to simplify the processing a recirculation system was used to investigate ⁶⁸Ge activity sorption on TiO₂, Fe₂O₃ or Zeolite. Zeolite was introduced for its high sorption at low pH, therefore ⁶⁸Ge activity containing waste could directly be used without further interventions. ⁶⁸Ge activity containing liquid waste at different HCl concentrations (0.05–1.0 M HCl), was recirculated at 1 mL/min. With Zeolite in the recirculation system, ⁶⁸Ge activity showed highest sorption.     

Measurement of isomeric yield ratios of the 104m,g,106m,gAg in the 45- and 55-MeV bremsstrahlung induced reactions of natural silver

The isomeric yield ratios for the ^natAg(γ,xn)^{104m,g,106m,g}Ag reactions with the end-point bremsstrahlung energies of 45- and 55-MeV have been determined by the off-line γ-ray spectrometric technique using 100 MeV electron linac at Pohang accelerator laboratory, Korea. The present data were compared with literature data in comparable compound nucleus from the ^natAg(γ,xn), ^natPd(p,xn), and ¹⁰³Rh(α,xn) reactions to examine the effects of an excitation energy and an input angular momentum. It is observed that the isomeric yield ratios of ^104,106Ag in ^natAg(γ,xn), ^natPd(p,xn) and ¹⁰³Rh(α,xn) reactions increase with the end-point bremsstrahlung energy, proton and alpha energy, which indicate the role of excitation energy. It is also found that for the similar compound nucleus at same excitation energy, the isomeric yield ratio of ^104m,gAg is higher in the ^natPd(p,xn) and ¹⁰³Rh(α,xn) reactions than those in ^natAg(γ,xn) reaction, which indicate the effect of an input angular momentum.     

Mechanism for Solvent Extraction of Lanthanides from Chloride Media by Basic Extractants

The solvent extraction of lanthanides from chloride media to an organic phase containing an anion exchanger in the chloride form is known to show low extraction percentages and small separation factors. The coordination chemistry of the lanthanides in combination with this kind of extractant is poorly understood. Previous work has mainly used solvent extraction based techniques (slope analysis, fittings of the extraction curves) to derive the extraction mechanism of lanthanides from chloride media. In this paper, EXAFS spectra, luminescence lifetimes, excitation and emission spectra, and organic phase loadings of lanthanides in dry, water-saturated and diluted Aliquat 336 chloride or Cyphos IL 101 have been measured. The data show the formation of the hydrated lanthanide ion [Ln(H₂O)_8–9]³⁺ in undiluted and diluted Aliquat 336 and the complex [LnCl₆]^3? in dry Aliquat 336. The presence of the same species [Ln(H₂O)_8–9]³⁺ in the aqueous and in the organic phase explains the small separation factors and the poor selectivities for the separation of mixtures of lanthanides. Changes in separation factors with increasing chloride concentrations can be explained by changes in stability of the lanthanide chloro complexes in the aqueous phase, in combination with the extraction of the hydrated lanthanide ion to the organic phase. Finally, it is shown that the organic phase can be loaded with 107 g·L^?1 of Nd(III) under the optimal conditions.     

A new method for the preparation of68Ga-generators following proton bombardment of gallium oxide targets

A method of preparing a⁶⁸Ge/⁶⁸Ga generator directly from an irradiated target of Ga₂O₃ is discussed, which utilises an ion exchange column containing hydrous zirconium oxide (HZO). A yield of 30–40% of⁶⁸Ga is reported with a breakthrough of⁶⁸Ge as low as one part in 10⁵. The leakage of stable zirconium from the column may be a problem for routine clinical use and this is being investigated further.     

Isomeric yield ratios of 148Pm from the natSm(γ, x) and the natNd(p,xn) reactions

The independent isomeric yield ratios of ¹⁴⁸Pm from the ^natSm(γ, x) reaction at the end-point bremsstrahlung energy of 45–64 MeV have been determined using an off-line γ-ray spectrometric technique at the 100 MeV electron linac of Pohang accelerator laboratory, Pohang, Korea. We also have determined the isomeric yield ratios of ¹⁴⁸Pm from the ^natNd(p,xn) reactions in the proton energy of 5.08–44.72 MeV by a stacked-foil activation and an off-line γ-ray spectrometric techniques at the MC-50 cyclotron of the Korean Institute of Radiological and Medical Sciences, Korea. The determined isomeric yield ratios of ¹⁴⁸Pm were compared with literature data and theoretical values estimated by the TALYS 1.4. The present data along with the similar data from literature at other energies shows that the isomeric yield ratio of ¹⁴⁸Pm increases with the excitation energy both in the ^natSm(γ, x) and the ^natNd(p, xn) reactions. The isomeric yield ratios of ¹⁴⁸Pm from the ^natNd(p, xn) reactions are always higher than those from the ^natSm(γ, x) reactions at the same excitation energy, which indicate the role of input angular momentum besides excitation energy.     

Extraction and separation of Zr,Nb and Hf by Aliquat 336 and its mixtures with TOPO from acidic thiocyanate media

Presence of thiocyanate ions results in appreciable extraction of Zr(IV) by Aliquat 336 from low aqueous HCl acidities, i.e., 0.1 to 4.5M. The variation of concentrations of HCl, thiocyanate and Aliquat 336 greatly influences the extent of extraction. Mixtures of Aliquat 336 and TOPO result in synergistic extraction of Zr and Hf from acidic thiocyanate media, the extracted species being the disolvate with TOPO. By controlled adjustment of HCl, SCN^– and Aliquat 336 concentrations, separation of Zr, Nb and Hf is possible. A maximum separation factor (D_Nb/D_Zr) of 3675 has been achieved under certain conditions.     

New cross section data on68Zn(p, 2n)67Ga andnatZn(p,xn)67Ga nuclear reactions for the development of a reference data base

Excitation functions were measured by stacked-foil technique for the⁶⁸Zn(p, 2n)⁶⁷Ga,⁶⁸Zn(p,3n)⁶⁶Ga,^natCu(p,xn)⁶²Zn,^natZn(p,xn)⁶⁷Ga,^natZn(p,xn)⁶⁶Ga,^natZn(p,px)⁶²Zn and^natZn(p,αx)⁶¹Cu nuclear reactions in the energy range from 15–35 MeV. The experimental excitation functions were compared with published data. Our present measurements not only increase the number of available cross section data points for the above reactions, but for some reactions (and in some energy regions) values are presented for the first time.     

Isomeric yield ratios in the photoproduction of 52m,gMn from natural iron using 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung

The isomeric yield ratios for the ^natFe(γ,xn1p)^52m,gMn reactions have been measured by the activation and the γ-ray spectroscopic methods at 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies. The high purity natural iron foils in disc shape were irradiated with uncollimated bremsstrahlung beams of the Pohang Accelerator Laboratory. The induced activities in the irradiated foils were measured by the high-resolution γ-ray spectrometry with a calibrated high-purity Germanium (HPGe) detector. In order to improve the accuracy of the experimental results the necessary corrections were made in the gamma activity measurements and data analysis. The obtained isomeric yield ratios for the ^natFe(γ,xn1p)^52m,gMn reactions at 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies are 0.27 ± 0.03, 0.33 ± 0.04, 0.34 ± 0.04, and 1.25 ± 0.15, respectively. The present results at 50-, 60-MeV, and 2.5-GeV bremsstrahlung energies are the first measurements. We found that the isomeric yield ratio of the ^natFe(γ,xn1p)^52m,gMn reaction depends on the incident bremsstrahlung energy and the mass difference between the product and the target nucleus when we compared the present results with other experimental data at different energies.     

A Triazacyclononane‐Based Bifunctional Phosphinate Ligand for the Preparation of Multimeric 68Ga Tracers for Positron Emission Tomography

For application in positron emission tomography (PET), PrP9 , a N,N′,N′′‐trisubstituted triazacyclononane with methyl(2‐carboxyethyl)phosphinic acid pendant arms, was developed as ⁶⁸Ga³⁺ complexing agent. The synthesis is short and inexpensive. Ga^III and Fe^III complexes of PrP9 were characterized by single‐crystal X‐ray diffraction. Stepwise protonation constants and thermodynamic stabilities of metal complexes were determined by potentiometry. The Ga^III complex possesses a high thermodynamic stability (log K_[GaL]=26.24) and a high degree of kinetic inertness. ⁶⁸Ga labeling of PrP9 is possible at ambient temperature and in a wide pH range, also at pH values as low as 1. This means that for the first time, the neat eluate of a TiO₂‐based ⁶⁸Ge/⁶⁸Ga generator (typically consisting of 0.1 M HCl) can be directly used for labeling purposes. The rate of ⁶⁸Ga activity incorporation at pH 3.3 and 20 °C is higher than for the established chelators DOTA and NOTA. Tris‐amides of PrP9 with amino acid esters were synthesized to act as models for multimeric peptide conjugates. These conjugates exhibit radiolabeling properties similar to those of unsubstituted PrP9 .     

Preparation of 68Ge/68Ga Generator with a Binary Ga/Ag Electrodepositions as Solid Target

A novel type of a binary Ga/Ag alloy electrodeposited on silver substrate as a solid target was developed. It was successfully used for the preparation of ⁶⁸Gc/⁶⁸Ga generator. The deposition was carried out in an alkali solution containing gallium, silver and certain electrolytes at controlled current and ambient temperature so that the quality of the deposits was proved to be suited for target irradiation. The yield of ⁶⁸Ge with proton bombardment on this deposits via the ⁶⁹Ga(p,2n) reaction was assessed. The chemical process for providing millicuries ⁶⁸Ge/⁶⁸Ga generator using a generic tin dioxide as an adsorbent was also established. It was revealed from long-term elution tests that approximately 60–70% of ⁶⁸Ga could be eluted from the generator column with 4 ml of 1.0M HCl per elution, and high radio- and chemical purities of the eluates were quite satisfactory for application purposes.     

Study of the cyclotron production of <Superscript>172</Superscript>Lu: an excellent radiotracer

¹⁷²Lu due to its suitable (T _1/2 = 6.7 days) and high detection sensitivity, is used as a radiotracer in different fields. ¹⁷²Lu appears to be suitable as a long-lived rare-earth tracer for compound labelling and biodistribution studies. In the present study, excitation functions via ¹⁷²Yb(p,n)¹⁷²Lu, ^natYb(p,xn)¹⁷²Lu, ¹⁷²Yb(d,2n)¹⁷²Lu and ^natYb(d,xn)¹⁷²Lu reactions were calculated by ALICE/91, ALICE/ASH and TALYS-1.2 codes. Deposition of ^natYb₂O₃ on Cu substrate was carried out via sedimentation method for the production of ¹⁷²Lu. Cementation separation process and liquid–liquid extraction (LLX) of no-carrier-added (nca) radiolutetium from irradiated ytterbium(III)oxide target hydrochloric solution was described using Na(Hg) amalgam, α-hydroxyisobutyric acid (α-HIB) and di-(2-ethylhexyl)phosphoric acid (HDEHP).     

Atmospheric depositional fluxes of cosmogenic <Superscript>32</Superscript>P, <Superscript>33</Superscript>P and <Superscript>7</Superscript>Be in the Sevastopol region

⁹⁰Y was separated from ⁹⁰Sr using an extraction chromatographic resin consisting of 4, 4′(5′)-bis-t-butylcyclohexano-18-crown-6 (DtBuCH₁₈C₆), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide (C₂mimNTf₂), and a polymer (Amberlite XAD-7). Ionic liquid was introduced into the column to improve the separation efficiency. The column showed an excellent performance for the separation of Y from Sr. After the separation, the ratio of ⁹⁰Sr/⁹⁰Y was <2.0 × 10^?5; the column was recycled for >18 times. This study provides preliminary results on columns to produce ⁹⁰Y with a high purity in radiopharmaceuticals.     

Investigation of production routes for the 161Ho Auger-electron emitting radiolanthanide, a candidate for therapy

The radiolanthanide ¹⁶¹Ho (2.48 h) is a promising Auger-electron emitter for internal radiotherapy that can be produced with particle accelerators. The excitation functions of the ^natDy(p,xn)¹⁶¹Ho and ^natDy(d,x)¹⁶¹Ho reactions were measured up to 40 and 50 MeV respectively by using the stacked foil activation method and γ-ray spectrometry. The experimental data were compared with results of the TALYS code available in the TENDL 2011 library [1]. The main parameters of different production routes are discussed.     

Intensification of gadolinium(III) separation by effective utilization of nanoliquids in supported liquid membrane using Aliquat 336 as carrier

A supported nanoliquid membrane was developed to improve the separation of rare metal ion gadolinium (Gd) from nitrate solution medium. The nanoliquid membrane was prepared by dispersion of nanoparticles in organic phase and Aliquat 336 was applied as the carrier. TiO₂ and SiO₂ as hydrophobic and hydrophilic nanoparticles were effectively incorporated in the supported liquid membrane (SLM) system and the effect of size, concentration, and type of nanoparticle in the SLM were evaluated. A membrane phase of 0.015 M Aliquat-336 in kerosene and 0.04 wt% of SiO₂ with the size of 15 nm was found to have the highest permeability coefficient of 12.57?×?10^?5 m/s and enhanced the permeability coefficient by 28.2%. Hydrophobicity and hydrophilicity of the nanoparticles were observed to have remarkable effects on the permeation of the SLM system and concluded that the hydrophobic nanoparticle was more desirable. Results showed that the solid supported pore’s blockage and aggregation of nanoparticles could bring adverse effects at a high nanoparticle concentration at this SLM configuration. The stability tests were conducted over ten cycles of separation and the supported nanoliquid membrane had slight reduction of permeation during the test.     

Production of high specific activity <Superscript>68</Superscript>Ge at Brookhaven National Laboratory

Summary Germanium-68 is produced at the Brookhaven Linac Isotope Producer (BLIP) by irradiating ^natGa targets with ~45 MeV protons. Typical irradiation yields are 17.4 GBq (470 mCi) from a 4 week irradiation (0.52 MBq/µAh). Germanium-68 is recovered from the target by extraction into 4N HCl and 30% H₂O₂. Further purification is achieved by extraction into carbon tetrachloride and back-extraction into H₂O. Recovery yields are greater than 85%, with greater than 99% radiopurity, and activity concentrations are greater than 3.15 GBq/ml (85 mCi/ml). The final pH of the product solution, which is 0.03M diethylenetriaminepentaacetate (DTPA), can now be adjusted to user specifications.