Large-scale production of 88Y and 88Zr/88Y generators: A proof of concept study for a 70 MeV H- cyclotron.

The large-scale production of 88Y with proton-induced reactions has been investigated from the perspective of new generation 70 MeV H- cyclotrons. Tandem target configurations are presented for both the direct production of 88Y as well as for producing 88Zr/88Y generators. Based on the relevant excitation functions, physical yields have been derived for 88Y production with Y2O3/SrCO3 tandem targets and 88Zr production with Zr/Y2O3 tandem targets. Yields are presented for optimized targets (i.e. optimum yield) as well as for balanced thermal loads on the individual targets. Liquid 88Zr/88Y generators have been produced using both natural Zr and Nb target materials, the former for dedicated productions and the latter as a byproduct by processing spent irradiated Nb capsules which normally would constitute radioactive waste. These stock solutions, which contain both the target material and 88Zr precursor, are retained virtually unchanged after processing except for the removal of 88Y on AG MP-50 macroporous cation-exchange resin. Methods are presented for the preparation of Nb stock solutions in hydrofluoric acid and Zr stock solutions in sulphuric acid. It is shown that multi-Ci productions of 88Y are feasible at a 70 MeV cyclotron facility, suitable for the needs of fracking applications. In addition, 88Zr/88Y generators can provide 88Y with very high specific activity, suitable for labelling of biomolecules. LA-UR-20-24305.

The use of selective volatization in the separation of 68Ge from irradiated Ga targets.

Cyclotron-produced (68)Ge can be separated from its Ga target material by dissolving the target in aqua regia and collecting the volatile (68)Ge in a solution containing 1.0M NaOH and 2% Na2SO3. The solution is then acidified with HF before being loaded onto a column containing AG MP-1 anion exchange resin. The column is rinsed with dilute HF to remove any remaining impurities, before eluting the desired product with 0.1M HCl. A radiochemically pure product is obtained.

The production of (88)Y in the proton bombardment of (nat)Sr: New excitation and separation studies.

The cyclotron production of (88)Y at iThemba LABS is performed via the reaction (88)Sr(p,n)(88)Y. The yields obtained were inconsistent with nuclear data obtained from the literature and the excitation function of the nuclear reaction was re-measured, using a differentiation of thick-target production rate measurements. Ion exchange chromatographic methods are described to separate (88)Y from (nat)Sr target material using AG MP-1 resin and AG 50W-X4 resins, respectively.

Ion exchange separation of strontium and rubidium on Dowex 50W-X8, using the complexation properties of EDTA and DCTA.

A chromatographic method for separation of strontium from rubidium, using the unique alkaline-earth metal complexation ability of the carboxylic acids EDTA and DCTA is proposed. The method was developed in order to improve the effectiveness of (87)Sr/(86)Sr isotope studies with ICP-QMS. Due to the isobaric overlap of (87)Rb with (87)Sr, strontium needs to be separated from rubidium prior to sample analysis with ICP-QMS. The method involves the retention of strontium, calcium, magnesium, and rubidium on Dowex 50W-X8 resin in its NH(4)(+) form, followed by elution of the divalent cations as metal EDTA or DCTA complexes. Because divalent cations have different EDTA and DCTA complex formation constants, it is possible to separate them under the correct conditions. Neither EDTA nor DCTA form complexes with alkali metals, thus rubidium remains retained by the column and is later eluted using HNO(3). Both EDTA and DCTA elution methods were tested with different concentrations of the elements to determine the effect of increased concentration on separation efficiency. The EDTA elution procedure was proved to be effective in separating strontium from both calcium and rubidium, while the DCTA method was found to be even more effective, because strontium is separated from all the elements involved in this study.

Yield and purity of 82Sr produced via the natRb(p,xn) 82Sr process.

The recently reported cross-section data for the production of 82Sr via the natRb(p,xn) 82Sr process were evaluated. For the natRb(p,xn) 85Sr process, cross-sections were measured experimentally over the proton energy range of 25-45 MeV, a region where very few data existed. An evaluation of the recently published data on the formation of 85Sr was then also performed. From the recommended data curves, the integral yields of the desired radionuclide 82Sr and the impurity 85Sr were calculated. Yields were also determined experimentally over several energy ranges using thick natRbCl targets. The experimental and calculated yields were found to be in agreement within 15%. These integral tests add confidence to the evaluated cross-section data. For the production of 82Sr, an incident proton energy of 60 MeV or above is recommended; the 85Sr impurity then corresponds to <20%.

Comments on the feasibility of 61Cu production by proton irradiation of (nat)Zn on a medical cyclotron.

Feasibility of 61Cu production in high radionuclidic purity form via (nat)Zn(p,x) 61Cu nuclear process is discussed. Based on the experimentally available cross-sections of the (nat)Zn(p,x) 61Cu, (nat)Zn(p,x) 60Cu and (nat)Zn(p,x) 64Cu nuclear processes the usefulness of the (nat)Zn(p,x) 61Cu process for high-scale production is questionable in the 22 --> 12 MeV energy range.

Formation of short-lived positron emitters in reactions of protons of energies up to 200 MeV with the target elements carbon, nitrogen and oxygen.

Excitation functions were measured by the stacked-foil technique for proton induced reactions on carbon, nitrogen and oxygen leading to the formation of the short-lived positron emitters (11)C (T(1/2) = 20.38 min) and (13)N (T(1/2) = 9.96 min). The energy region covered extended up to 200 MeV. The product activity was measured non-destructively via gamma-ray spectrometry. A careful decay curve analysis of the positron annihilation radiation was invariably performed. The experimental results were compared with theoretical data obtained using the modified hybrid nuclear model code ALICE-IPPE for intermediate energies. The agreement was found to be generally satisfactory. The data are of importance in proton therapy.

Excitation functions of 85Rb(p,xn)(85m,g,83,82,81)Sr reactions up to 100 MeV: integral tests of cross section data, comparison of production routes of 83Sr and thick target yield of 82Sr.

The beta+ emitter 83Sr (T(1/2) = 32.4 h, Ebeta+ = 1.23 MeV, Ibeta+ = 24%) is a potentially useful radionuclide for therapy planning prior to the use of the beta+ emitter 89Sr (T(1/2) = 50.5 d). In order to investigate its production possibility, cross section measurements on the 85Rb(p,xn)-reactions, leading to the formation of the isotopes (85m,g)Sr, 83Sr, 82Sr and 81Sr, were carried out using the stacked-foil technique. In a few cases, the products were separated via high-performance liquid chromatography. For 82Sr, both gamma-ray and X-ray spectrometry were applied; in other cases only gamma-ray spectrometry was used. From the measured excitation functions, the expected yields were calculated. For the energy range Ep = 37 --> 30 MeV the 83Sr yield amounts to 160 MBq/microA h and the level of the 85gSr (T(1,2) = 64.9 d) and 82Sr (T(1/2) = 25.5 d) impurities to <0.25%. In integral tests involving yield measurements radiostrontium was chemically separated and its radioactivity determined. The experimental production data agreed within 10% with those deduced from the excitation functions. The results of the 85Rb(p,3n)83Sr reaction were compared with the data on the production of 83Sr via the 82Kr(3He,2n)-process. In the energy range E3Hc = 18 --> 10 MeV the theoretical yield of 83Sr amounts to 5 MBq/microA h and the 82Sr impurity to about 0.2%. The method of choice for the production of 83Sr is thus the 85Rb(p,3n)-process, provided a 40 MeV cyclotron is available. During this study some supplementary information on the yield and purity of 82Sr was also obtained.

Excitation functions of 125Te(p, xn)-reactions from their respective thresholds up to 100 MeV with special reference to the production of 124I.

Excitation functions of the nuclear reactions 125Te(p, xn) (119,120m, 120g, 121,122,123,124,125)I were measured for the first time from their respective thresholds up to 100 MeV using the stacked-foil technique. Thin samples were prepared by electrolytic deposition of 98.3% enriched 125Te on Ti-backing. In addition to experimental studies, excitation functions were calculated by the modified hybrid model code ALICE-IPPE. The experimental and theoretical data generally showed good agreement. From the measured cross section data, integral yields of (123,124,125)I were calculated. The energy range Ep 21 --> 15 MeV appears to be very suitable for the production of the medically interesting radionuclide 124I (T(1/2) = 4.18 d; I(beta)+ = 25%). The thick target yield of 124I amounts to 81 MBq/microA h and the level of 125I-impurity to 0.9%. The 125Te(p,2n)124I reaction gives 124I yield about four times higher than the commonly used 124Te(p,n)124I and 124Te(d,2n)124I reactions. The proposed production energy range is too high for small cyclotrons but large quantities of 124I can be produced with medium-sized commercial machines.

Cyclotron production of 67Ga(III) with a tandem natGe-natZn target.

Production of 67Ga(III) at the National Accelerator Centre is by proton bombardment of a natZn target, and uses 15-20 h of cyclotron beam time per production. A study was undertaken to use a tandem natGe-natZn target to produce the same amount of 67Ga, but using less beam time (7-8 h). 67Ga(III) was separated from the tandem target material by a method based on acid dissolution of the target and chromatography on an organic polymer resin (Amberchrom CG-71cd) containing no ion exchange groups. The separated 67Ga(III) has high radionuclidic purity and complies with the British and US Pharmacopoeia requirements for chemical purity.

Implementation of a Tc-99m and Ce-139 scanning line source for attenuation correction in SPECT using a dual opposing detector scintillation camera.

Image degradation during single photon emission computed tomography (SPECT) due to attenuation and Compton scatter of photons can cause clinical image artifacts and will also result in inaccurate quantitative data. Therefore attenuation correction methods recently received wide interest. Transmission imaging can be performed to obtain the attenuation coefficients of a nonhomogeneous attenuating medium accurately. The aim of this study was firstly to evaluate the imaging characteristics of the scanning line source assembly. The results obtained with Tc-99m and Ce-139 were compared. Secondly the calculated attenuation coefficients were compared with known values from literature, using Tc-99m and Ce-139 as transmission sources. Lastly the method of acquiring simultaneous transmission and emission data was investigated. This study shows that an attenuation coefficient map can be obtained using a scanning line source for transmission imaging with a dual opposing detector camera. The imaging characteristics of Tc-99m and Ce-139 as transmission sources are similar. The resolution obtained with the Ce-139 line source was poorer than that obtained with the Tc-99m line source. A linear relationship was found between CT numbers and attenuation coefficients for transmission images using both Tc-99m and Ce-139 line sources. The attenuation coefficient value for water was underestimated by 1% using the Tc-99m transmission source and underestimated by 10% using Ce-139 as transmission source. This underestimation of attenuation coefficient values was also obtained in the human study. A myocardial perfusion study processed without and with attenuation correction clearly demonstrated the effect of the attenuation correction in the inferior myocardial region. The potential of using a scanning line source as transmission source with a dual opposing detector camera has been demonstrated in this study. The transmission source, Ce-139 was successfully introduced in this investigation for simultaneous acquisition of transmission and emission data.

Distribution coefficients and ion exchange behaviour of some elements with Purolite S-950 in hydrochloric acid.

Equilibrium distribution coefficients, K(d), are presented for some elements in hydrochloric acid using the phosphonated polystyrene ion exchange resin Purolite S-950. A few possible separations using this resin are demonstrated by elution curves and separations of synthetic mixtures of some elements (Ru, Rh, Mo, I, Li, Te, Si, Y).

Behaviour of Mo, Al, As, Cs, Sn, Sb, Pd, Rh, Ru, Ge, Se and Te on the macroporous resin AG MP-1 in alkaline medium.

The behaviour of Mo and some other elements on Ag MP-1 in alkaline medium was investigated. Equilibrium distribution coefficients, K(d), are presented for Mo on the anion exchangers AG 1-X2, AG 1-X4, AG 1-X8 and AG MP-1, and for some elements on AG MP-1 in alkaline medium. An anion exchange chromatographic separation of Mo from some of these elements is described and some results obtained with this method are reported.

Separation of (203)Pb by ion-exchange chromatography on chelex 100 after production of (203)Pb by the Pb(p, xn)(203)Bi--> EC.beta+ (203)Pb nuclear reaction.

Bismuth radioisotopes, produced by 50-MeV proton bombardment of a lead target in a cyclotron, are separated from the lead target material by ion-exchange chromatography on a column containing 5.0 ml of Chelex 100. After a decay period of 24 hr, the (203)Pb formed in situ is eluted from the column and then separated from (200)Tl and (201)Tl on a second ion-exchange column containing 0.5 ml of Chelex 100. Separations are sharp and carrier-free (203)Pb is obtained.

Indirect spectrophotometric determination of BIDA, DISIDA, DTPA and MDP in labelled compounds.

N-(4-(n-butyl)-acetanilide)iminodiacetic acid (BIDA), N-(2,6-diisopropylacetanilide)iminodiacetic acid (DISIDA), diethylenetriaminepentaacetic acid (DTPA) and methylene diphosphonic acid (MDP) are used in labelling kits. The contents of BIDA, DISIDA or MDP of the 99mTc-labelled compounds can be determined (indirectly) spectrophotometrically with copper, eriochrome cyaanine R (ECC) and dodecylethyldimethylammonium bromide (DEDA) in a sodium barbital buffered system at pH 8.5. The calibration curves obey Beer's Law from 0 to 40 micrograms/25 mL for BIDA and DISIDA, 0 to 60 micrograms/25 mL for DTPA and 0 to 100 micrograms/10 mL for MDP.

Separation of trace amounts of indium, gallium and aluminium from each other by cation-exchange chromatography on AG50-X4 resin.

Traces and minor amounts of indium, gallium and aluminium can be separated from gram amounts of thallium and from each other by cation-exchange chromatography on a column containing as little as 2 g of AG50W-X4, a cation-exchange resin with low cross-linking. An elution sequence of 0.1 M HBr in 40% acetone [for Tl(III)], 0.2M HBr in 80% acetone for In, 0.3M HCl in 90% acetone for Ga and 3M aqueous HCl for Al is used. The separations are very sharp and even 10-mug amounts of In, Ga and Al in synthetic mixtures are recovered quantitatively, with a standard deviation of 0.3 mug. The separation factors between neighbouring ions are extremely large (> 5000).

Separation of iron-52 from chromium cyclotron targets on the 2% cross-linked anion-exchange resin AG1-X2 in hydrochloric acid.

Iron-52 can be separated from solutions of chromium cyclotron targets by eluting chromium, copper and radioactive impurities with 9.0M hydrochloric acid from a column containing 1.0 g of AG1-X2 anion-exchange resin. Iron-52 is retained and can then be eluted with 6.0M hydrochloric acid containing 0.05M hydrogen iodide or 0.05M sodium iodide. The separations are sharp and quantitative. Less than 2 microg of chromium will remain with the iron-52, from 2.0 g originally present.

Separation of lead-203 from cyclotron-bombarded thallium targets by ion-exchange chromatography.

A simple method is presented for the separation of lead-203 from copper-backed thallium cyclotron targets. The procedure involves cation-exchange chromatography in hydrochloric acid and hydrochloric acid-acetone mixtures. Further purification involves anion-exchange chromatography in nitric acid-hydrobromic acid mixtures. A cation-exchange column containing 3.0 g of resin can handle as much as 15 g of thallium and 160 mg of copper. An anion-exchange column containing 3.0 g of resin can separate lead from up to 200 mg of thallium and 10 mg of copper. Separations are extremely sharp and less than 0.1 mug of thallium and less than 0.1 mug of copper remain in the lead-203 fraction.

Comparative study of the masking effect of various complexans in the spectrophotometric determination of uranium with arsenazo III and chlorophosphonazo III.

Results are presented for the masking of 35 elements with the complexans DTPA, EGTA and TTHA in the spectrophotometric determination of uranium(VI) with Arsenazo III at pH 1.8 +/- 0.2 and with Chlorophosphonazo III at pH 1.1 +/- 0.2. The complexans EDTA and DCTA were found to be less suitable because at low pH they tended to precipitate. DTPA is shown to be especially attractive for masking other elements in the determination of uranium(VI) at low pH.

Selective separation of indium from zinc, lead, gallium and many other elements by cation-exchange chromatography in hydrohalic acid-acetone medium.

Indium can be separated from Zn, Pb(II), Ga, Ca, Be, Mg, Ti(IV), Mn(II), Fe(III), Al, U(VI), Na, Ni(II) and Co(II) by selective elution with 0.50M hydrochloric acid in 30% aqueous acetone from a column of AG50W-X8 cation-exchange resin, all the other elements being retained by the column. Lithium is included in the elements retained by the column when 0.35M hydrochloric acid in 45% aqueous acetone is used for eluting indium, but the elution of indium is slightly retarded. Ba, Sr, Zr, Hf, Th, Sc, Y, La and the lanthanides, Rb and Cs should also be retained according to their distribution coefficients. Cd, Bi(III), Au(III), Pt(IV), Pd(II), Rh(III), Mo(VI) and W(VI) can be eluted with 0.20M hydrobromic acid in 50% aqueous acetone before the elution of indium, and Ir(III), Ir(IV), As(III), As(V), Se(IV), Tl(III), Hg(II), Ge(IV), Sb(III) and Sb(V), though not investigated in detail, should accompany these elements. Relevant distribution coefficients and elution curves and results for analyses of synthetic mixtures of indium with other elements are presented.