[en] We show that use of the radionuclide ⁵⁶Co for calibration of the full energy peak efficiency, ε, of a coaxial HPGe detector, in addition to the commonly employed set of activity standards (¹³³Ba, ²⁴¹Am, ¹⁵²Eu, ⁵⁷Co, ¹³⁷Cs, ⁸⁸Y, ⁶⁵Zn), affects significantly the ε values in the high energy region. This change resulted in substantial improvement of the accuracy of Ca determination by k₀-INAA via the ⁴⁹Ca radionuclide, which emits predominantly the 3084 keV photons, as demonstrated by Ca results in NIST SRMs 1547 Peach Leaves, 1633b constituent elements in coal fly ash, and 2711 Montana II Soil. (author)

[en] Objectives: Nimotuzumab (h-R3) is a humanized monoclonal antibody (mAb) which recognizes the external domain of the epidermal growth factor receptor (EGFR) with high specificity. It was demonstrated that h-R3 has a unique clinical profile for immunotherapy of adult gliomas and pediatric pontine gliomas. The aim of this work was to evaluate the conjugate ¹⁷⁷Lu-h-R3 as a potential radioimmunoconjugate for radioimmunotherapy (RIT) of tumors overexpressing EGFR. Methods: h-R3 was modified with the macrocylcic ligand S-2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (p-SCN-Bn-DOTA) and the acyclic ligand S-2-(4-Isothiocyanatobenzyl)-diethylenetriamine pentaacetic acid (p-SCN-Bn-DTPA); the immunoconjugates were labeled with no-carried added ¹⁷⁷Lu. Specificity and affinity were tested using radioimmunoassays in a cell line overexpressing EGFR. Biodistribution in mice, healthy or bearing A431 epithelial carcinoma xenografts, was performed for 11 days. Tumor uptake, the influence of the nature of the chelate and the way of administration were studied. Absorbed dose in tumor and selected organs was calculated using the OLINDA/EXM software; the data from the animals was extrapolated to humans. Results: ¹⁷⁷Lu-h-R3 conjugates were obtained with specific activity up to 915 MBq/mg without significant loss of immunoreactivity. The binding of ¹⁷⁷Lu-h-R3 conjugates to A431 cells showed to be EGFR specific, and the affinity was similar to native h-R3. Tumor uptake reached a maximum value of 22.4±3.1 %ID/g at 72 h and remained ∼20% ID/g over 1 week. Locoregional application showed better tumor/nontumor ratios than intravenous application. Conclusions: ¹⁷⁷Lu-h-R3 should be considered for further evaluations as a potential radiopharmaceutical for RIT of tumors overexpressing EGFR.

[en] In experiments searching for rare events, like the neutrinoless double beta decay, background knowledge and reduction is essential. For SNO+, the follow up of the Sudbury Neutrino Observatory experiment, the investigated transition is ¹⁵⁰Nd → ¹⁵⁰Sm with an estimated half-life for the 0 ν-channel of T_1/2 ∼ 10²⁵ years. SNO+ is a liquid scintillator based detector with a total mass of 780 tons. In order to study the mentioned transition, the detector will be loaded with 0.3 % natural neodymium. Even with the desired amount of 131 kg of ¹⁵⁰Nd in SNO+, only few decays are expected. Their observation and the measured half-life would not only give an answer on the effective neutrino mass, but also to other important questions in modern neutrino physics. Long-living radioisotopes, induced by cosmogenic activation on natural Nd, contribute to the background in SNO+ and are investigated at TU Dresden. Proton activation measurements for determining the excitation functions for different isotopes in the energy range of 10 to 30 MeV were done in 2010/2011 while in 2012 the lower and higher energies were investigated. The procedure and the latest results are presented.

[en] A new simplified approach for the preparation of ²¹¹At-labelled compounds is presented. The labelling procedure is carried out entirely in a Teflon capillary which also serves as a cryotrap. Two organic astatine compounds were synthesized by this method: 5-[²¹¹At]astato-2'-deoxyuridine (AUdR) and N-succinimidyl-4-[²¹¹At]astatobenzoate (SAB), starting from their respective stannylated precursors. The first reaction was performed in aqueous solution and the latter in an organic solvent using Iodogen as the oxidant in both cases. Overall radiochemical yields were approximately 75% for AUdR and approximately 70% for SAB

[en] The SNO+ (Sudbury Neutrino Observatory Plus Scintillator) experiment, located 6000 m.w.e. underground, is planning to search for the neutrinoless double beta decay of ¹⁵⁰Nd. The expected half-life is of the order of 10²⁵ years which requires extremely low background levels. At TU Dresden the production of long-living isotopes by cosmic ray exposure of Neodymium on the Earth's surface is studied. These produced isotopes can be a source of background radiation during the measurement phase of SNO+ and need to be well-known. Most of the cross-sections have not been measured, yet. We performed a Neodymium proton irradiation experiment at Rez near Prague (Czech Republic) to measure production cross sections of various radioisotopes. The experimental procedure is described briefly and first results for the excitation functions are presented.

[en] Cross-sections for the proton induced reactions on natural molybdenum leading to ^93mTc, ^93m+gTc, ⁹⁴Tc, ^94mTc, ⁹⁵Tc, ^95mTc, ^96m+gTc, ^99mTc, ⁹⁰Mo, ^93mMo, ⁹⁹Mo, ^90m+gNb, ^92mNb, ⁹⁵Nb and ^89m+gZr were measured in the proton energy range 8.4-37.1 MeV on the cyclotron U-120M at the Institute of Nuclear Physics AS CR. Special attention was paid to excitation functions and thick target yields for the formation of ^95mTc, a suitable tracer for ⁹⁹Tc, of ^96m+gTc, which was proposed as a proton beam monitor, and of ^99mTc and ⁹⁹Mo, the most widespread radionuclide generator pair in nuclear medicine. If appropriate, obtained data are compared with the heretofore published cross-sections.

[en] The isomer ^83mKr with its half-life of 1.83 h is an ideal calibration source for a liquid noble gas dark matter experiment like the XENON project. For such a low counting experiment the possibility that traces of the much longer living mother isotop ⁸³Rb (t_1/2 = 86.2 d) contaminate the detector must be avoided. In this work the ⁸³Rb release of a 1.8 MBq strong ⁸³Rb source embedded in zeolite spheres has been investigated by searching for the characteristic ⁸³Rb γ lines with the ultra-sensitive germanium detector Gator at LNGS after collecting a possible ⁸³Rb release in a cryogenic trap for about 10 days. No signal has been found. The corresponding upper limit for the ⁸³Rb release of 200μBq means, that such a ⁸³Rb source as ^83mKr generator can be used at the XENON project as well as for the KATRIN experiment. % without the danger of contaminating the detector with ⁸³Rb. The germanium detector also allowed to set upper limits on the possible release of the isotopes ⁸⁴Rb and ⁸⁶Rb, which were produced during the ⁸³Rb production at the Rez cyclotron to some amount.

[en] Cross-sections for the deuteron-induced reactions on natural molybdenum leading to ^93mTc, ^93m+gTc, ⁹⁴Tc, ^94mTc, ⁹⁵Tc, ^95mTc, ^96m+gTc, ^99mTc, ⁹⁹Mo, ¹⁰¹Mo, ^90m+gNb, ^92mNb, ⁹⁵Nb and ^89m+gZr were measured in the energy range 3.0-19.6 MeV on the cyclotron U-120 M in the Institute of Nuclear Physics AS CR. Special attention was paid to excitation functions and thick target yields for the formation of ^95mTc, a suitable tracer for ⁹⁹Tc, of ^96m+gTc, which might be used as a beam monitor, and of ^99mTc and ⁹⁹Mo, the most widespread radionuclide generator pair in nuclear medicine. If appropriate, obtained data are compared with the heretofore published cross-sections.

[en] Drug delivery systems based on thermoresponsive polymers might serve as suitable carriers for local radiotherapy. We have, therefore, designed and synthesized a radioiodine-labellable thermoresponsive polymer. The polymer was synthesized by copolymerization of N-isopropylacrylamide with N-methacryloyl tyrosinamide in tetrahydrofuran, and then labelled by ¹³¹I. The solution of this labelled polymer in dimethylsulfoxide (4.4 MBq/ml; 1.8 wt% polymer) was applied to femoral muscle of male Balb/C mice (50 μl per animal). The biodistribution and excretion of radioactivity was followed in 2 h and 1, 7, 14, 28 and 42 d post injection (n=6 per time point). As expected, the labelled polymer was left on the application site (ca 90% 2 h post injection), decreasing slowly to ca 80% within 14 d. At 28 d post injection, ca 70% of the injected activity was still found on the application site, decreasing to ca 60% at 42 d. No organ-specific accumulation of the radioactivity released from the application site, including thyroid, was observed. Majority of the released radioactivity was excreted via urine and faeces. This preliminary study suggests that thermoresponsive polymers could be used as an effective delivery system for localized radiotherapy.

[en] The alpha emitter ²¹¹At is a prospective radionuclide for the therapy of smaller tumours and metastases. However, the chemical properties of ²¹¹At together with the fact that it is available only in trace amounts, makes the labelling of prospective astatine carriers rather complicated. In this context we have studied a new class of possible astatine carriers-nanoparticle systems, which tend to concentrate themselves in some types of tumours by means of the EPR effect. Additionally, such nanoparticles have the advantage that they may be chemically modified by the attachment of a tumour-seeking agent, and also directly applied to the target site. In order to reach high labelling yields, and in order to protect the nanoparticles from rapid degradation by the immune system, silver-containing particles covalently coated by poly(ethylene oxide) were developed and tested. The effect of the different reducing and oxidizing agents on the labelling yield was also determined. It was found that labelling yields were almost quantitative and well reproducible under reducing conditions, while under oxidizing conditions they dropped to ca. 50%. In the absence of any reducing or oxidizing agent, the labelling yields were randomly distributed between a range of 50% and 97%. The labelled nanoparticles were stable even in a large surplus of competing chloride ions