The current knowledge of the half-lives (T.sub.1/2) of several radiolanthanides is either affected by a high uncertainty or is still awaiting confirmation. The scientific information deriving from ...this imprecise T.sub.1/2 data has a significant impact on a variety of research fields, e.g., astrophysics, fundamental nuclear sciences, and nuclear energy and safety. The main reason for these shortcomings in the nuclear databases is the limited availability of suitable sample material together with the difficulties in performing accurate activity measurements with low uncertainties. In reaction to the urgent need to improve the current nuclear databases, the long-term project "ERAWAST" (Exotic Radionuclides from Accelerator Waste for Science and Technology) was launched at Paul Scherrer Institute (PSI). In this context, we present a wet radiochemical separation procedure for the extraction and purification of dysprosium (Dy), terbium (Tb), gadolinium (Gd), and samarium (Sm) fractions from highly radioactive tantalum specimens, in order to obtain .sup.154 Dy, .sup.157-158 Tb, .sup.148,150 Gd, and .sup.146 Sm samples, needed for T.sub.1/2 determination studies. Ion-exchange chromatography was successfully applied for the separation of individual lanthanides. All separations were conducted in aqueous phase. The separation process was monitored via gamma-spectrometry using suitable radioactive tracers. Both the purity and the quantification of the desired radiolanthanides were assessed by inductively coupled plasma mass spectrometry. Test experiments revealed that, prior to the Dy, Tb, Gd, and Sm separation, the removal of hafnium, lutetium, and barium from the irradiated tantalum material was necessary to minimize the overall dose rate exposure (in the mSv/h range), as well to obtain pure lanthanide fractions. With the herein proposed separation method, exotic .sup.154 Dy, .sup.157-158 Tb, .sup.148,150 Gd, and .sup.146 Sm radionuclides were obtained in sufficient amounts and purity for the preparation of samples for envisaged half-life measurements. During the separation process, fractions containing holmium, europium, and promethium radionuclides were collected and stored for further use.
Sixty years after the discovery of
Dy, the half-life of this pure alpha-emitter was re-measured.
Dy was radiochemically separated from proton-irradiated tantalum samples. Sector field- and ...multicollector-inductively coupled plasma mass spectrometry were used to determine the amount of
Dy retrieved. The disintegration rate of the radio-lanthanide was measured by means of α-spectrometry. The half-life value was determined as (1.40 ± 0.08)∙10
y, with an uncertainty reduced by a factor of ~ 10 compared to the currently adopted value of (3.0 ± 1.5)∙10
y. This precise half-life value is useful for the the correct testing and evaluation of p-process nucleosynthetic models using
Dy as a seed nucleus or as a reaction product, as well as for the safe disposal of irradiated target material from accelerator driven facilities. As a first application of the half-life value determined in this work, the excitation functions for the production of
Dy in proton-irradiated Ta, Pb, and W targets were re-evaluated, which are now in agreement with theoretical calculations.
In the present study, SibuDAB, an albumin-binding PSMA ligand, was investigated in combination with actinium-225 and the data were compared with those of
AcAc-PSMA-617. In vitro,
AcAc-SibuDAB and
...AcAc-PSMA-617 showed similar tumor cell uptake and PSMA-binding affinities as their
Lu-labeled counterparts. The in vitro binding to serum albumin in mouse and human blood plasma, respectively, was 2.8-fold and 1.4-fold increased for
AcAc-SibuDAB as compared to
LuLu-SibuDAB. In vivo, this characteristic was reflected by the longer retention of
AcAc-SibuDAB in the blood than previously seen for
LuLu-SibuDAB. Similar to
AcAc-PSMA-617,
AcAc-SibuDAB was well tolerated at 30 kBq per mouse. Differences in blood cell counts were observed between treated mice and untreated controls, but no major variations were observed between values obtained for
AcAc-SibuDAB and
AcAc-PSMA-617.
AcAc-SibuDAB was considerably more effective to treat PSMA-positive tumor xenografts than
AcAc-PSMA-617. Only 5 kBq per mouse were sufficient to eradicate the tumors, whereas tumor regrowth was observed for mice treated with 5 kBq
AcAc-PSMA-617 and only one out of six mice survived until the end of the study. The enhanced therapeutic efficacy of
AcAc-SibuDAB as compared to that of
AcAc-PSMA-617 and reasonable safety data qualify this novel radioligand as a candidate for targeted α-therapy of prostate cancer.
UO2 samples doped with 6, 11, 22 mol% lanthanum were examined before and after air oxidation. To verify the formation of uranium–lanthanum‐mixed oxide solid solutions, powder X‐ray diffraction (XRD) ...analyses of the crystalline phases in the materials were carried out. The presence of oxygen vacancies in the La‐doped UO2 samples was identified by Raman spectrometry. It was evidenced by changes induced in the Raman spectra by air oxidation. This latter was carried out either by increasing the Raman laser power or by thermally treating the samples at 500 K for 370 h. In addition, oxidation behavior differences of pure and La‐doped UO2 samples were reported by comparing XRD and Raman results of the samples before and after air oxidation. It was shown that the concentration of the M4O9 (M: U, La) phase increased with increasing content of La, whereas inhibition for the formation of M3O8 phase was observed.
Copper radioisotopes are generally employed for cancer imaging and therapy when firmly coordinated via a chelating agent coupled to a tumor-seeking vector. However, the biologically triggered ...Cu2+-Cu+ redox switching may constrain the in vivo integrity of the resulting complex, leading to demetallation processes. This unsought pathway is expected to be hindered by chelators bearing N, O, and S donors which appropriately complements the borderline-hard and soft nature of Cu2+ and Cu+. In this work, the labelling performances of a series of S-rich polyazamacrocyclic chelators with 64CuCu2+ and the stability of the 64CuCu-complexes thereof were evaluated. Among the chelators considered, the best results were obtained with 1,7-bis 2-(methylsulfanyl)ethyl-4,10,diacetic acid-1,4,7,10-tetraazacyclododecane (DO2A2S). DO2A2S was labelled at high molar activities in mild reaction conditions, and its 64CuCu2+ complex showed excellent integrity in human serum over 24 h. Biodistribution studies in BALB/c nude mice performed with 64CuCu(DO2A2S) revealed a behavior similar to other 64CuCu-labelled cyclen derivatives characterized by high liver and kidney uptake, which could either be ascribed to transchelation phenomena or metabolic processing of the intact complex.
44Sc is a promising radionuclide for positron emission tomography (PET) in nuclear medicine. As a part of the implementation of a production site for 44Sc, precise knowledge of the activity of the ...product is necessary. At the Paul Scherrer Institute (PSI) and the University of Bern (UniBE), 44Sc is produced by enriched 44CaO-target irradiation with a cyclotron. The two sites use different techniques for activity measurement, namely a dose calibrator at the PSI and a gamma-ray spectrometry system at UniBE and PSI. In this work, the 44Sc was produced at the PSI, and samples of the product were prepared in dedicated containers for onsite measurements at PSI, UniBE, and the Institute of Radiation Physics (IRA) in Lausanne for precise activity measurement using primary techniques and for the calibration of the reference ionization chambers. An accuracy of 1% was obtained for the activity measurement, allowing for a precise calibration of the dose calibrator and gamma-ray spectrometry of the two production sites. Each production site now has the capability of measuring 44Sc activity with an accuracy of 2%.
In this study, Raman spectroscopy technique was implemented to characterize un-irradiated MIMAS (MIcronized - MASter blend) MOX fuel samples with average 7 wt.% Pu content and different damage ...levels, 13 years after fabrication, one year after thermal recovery and soon after annealing, respectively. The impacts of local Pu content, deviation from stoichiometry and self-radiation damage on Raman spectrum of the studied MIMAS MOX samples were assessed. MIMAS MOX fuel has three different phases Pu-rich agglomerate, coating phase and uranium matrix. In order to distinguish these phases, Raman results were associated with Pu content measurements performed by Electron Microprobe Analysis. Raman results show that T2g frequency significantly shifts from 445 to 453 cm−1 for Pu contents increasing from 0.2 to 25 wt.%. These data are satisfactorily consistent with the calculations obtained with Gruneisen parameters. It was concluded that the position of the T2g band is mainly controlled by Pu content and self-radiation damage. Deviation from stoichiometry does not have a significant influence on T2g band position. Self-radiation damage leads to a shift of T2g band towards lower frequency (∼1–2 cm−1 for the UO2 matrix of damaged sample). However, this shift is difficult to quantify for the coating phase and Pu agglomerates given the dispersion of high Pu concentrations. In addition, 525 cm−1 band, which was attributed to sub-stoichiometric structural defects, is presented for the first time for the self-radiation damaged MOX sample. Thanks to the different oxidation resistance of each phase, it was shown that laser induced oxidation could be alternatively used to identify the phases. It is demonstrated that micro-Raman spectroscopy is an efficient technique for the characterization of heterogeneous MOX samples, due to its low spatial resolution.
Background
161
Tb draws an increasing interest in nuclear medicine for therapeutic applications. More than 99% of the emitted gamma and X-rays of
161
Tb have an energy below 100 keV. Consequently, ...precise activity measurement of
161
Tb becomes inaccurate with radionuclide dose calibrators when using inappropriate containers or calibration factors to account for the attenuation of this low energy radiation. To evaluate the ionization chamber response, the sample activity must be well known. This can be performed using standards traceable to the Système International de Référence, which is briefly described as well as the method to standardize the radionuclides.
Methods
In this study, the response of an ionization chamber using different container types and volumes was assessed using
161
Tb. The containers were filled with a standardized activity solution of
161
Tb and measured with a dedicated ionization chamber, providing an accurate response. The results were compared with standardized solutions of high-energy gamma-emitting radionuclides such as
137
Cs,
60
Co,
133
Ba and
57
Co.
Results
For the glass vial type with an irregular glass thickness, the
161
Tb measurements gave a deviation of 4.5% between two vials of the same type. The other glass vial types have a much more regular thickness and no discrepancy was observed in the response of the ionization chamber for these type of vials. Measurements with a plastic Eppendorf tube showed stable response, with greater sensitivity than the glass vials.
Conclusion
Ionization chamber measurements for low-energy gamma emitters (< 100 keV), show deviation depending on the container type used. Therefore, a careful selection of the container type must be done for activity assessment of
161
Tb using radionuclide dose calibrators. In conclusion, it was highlighted that appropriate calibration factors must be used for each container geometry when measuring
161
Tb and, more generally, for low-energy gamma emitters.
Purpose
The co-stimulatory molecules CD80 and CD86 are upregulated on activated antigen-presenting cells (APC). We investigated whether local APC activation, induced by subcutaneous (s.c.) ...inoculation of lipopolysaccharides (LPS), can be imaged by positron emission tomography (PET) with CD80/CD86-targeting
64
Cu-labelled abatacept.
Procedures
Mice were inoculated s.c. with extracellular-matrix gel containing either LPS or vehicle (PBS). Immune cell populations were analysed by flow cytometry and marker expression by RT-qPCR.
64
Cu-NODAGA-abatacept distribution was analysed using PET/CT and
ex vivo
biodistribution.
Results
The number of CD80
+
and CD86
+
immune cells at the LPS inoculation site significantly increased a few days after inoculation. CD68 and CD86 expression were higher at the LPS than the PBS inoculation site, and CD80 was only increased at the LPS inoculation site. CTLA-4 was highest 10 days after LPS inoculation, when CD80/CD86 decreased again. A few days after inoculation,
64
Cu-NODAGA-abatacept distribution to the inoculation site was significantly higher for LPS than PBS (4.2-fold). Co-administration of unlabelled abatacept or human immunoglobulin reduced tracer uptake. The latter reduced the number of CD86
+
immune cells at the LPS inoculation site.
Conclusions
CD80 and CD86 are upregulated in an LPS-induced local inflammation, indicating invasion of activated APCs.
64
Cu-NODAGA-abatacept PET allowed following APC activation over time.
The biosorption of lanthanum and cerium by leaves powder of
Platanus orientalis was separately determined at varying experimental conditions using a batch technique. The effects of initial pH, ...contact time, initial metal ion concentration and temperature were investigated. The Langmuir and Freundlich isotherms were applied to represent the adsorption process. Langmuir isotherm fits the experimental data quite well. The Langmuir monolayer capacity of the sorbent is 28.65mg g
−
1
and 32.05mg g
−
1
for La and Ce(III), respectively. Thermodynamic parameters such as standard enthalpy (ΔH°), entropy (ΔS°) and free energy (ΔG°) were calculated from the slope and intercept of the plots of l
nK
d versus 1/
T. The results indicated that sorption was endothermic and spontaneous in nature. The work reveals that powdered leaf of
Platanus orientalis is a good choice as a biosorbent for the recovery of lanthanum and cerium from aqueous solution.
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