Efficient Production of High Specific Activity Thulium-167 at Paul Scherrer Institute and CERN-MEDICIS

Thulium-167 is a promising radionuclide for nuclear medicine applications with potential use for both diagnosis and therapy (“theragnostics”) in disseminated tumor cells and small metastases, due to suitable gamma-line as well as conversion/Auger electron energies. However, adequate delivery methods are yet to be developed and accompanying radiobiological effects to be investigated, demanding the availability of 167Tm in appropriate activities and quality. We report herein on the production of radionuclidically pure 167Tm from proton-irradiated natural erbium oxide targets at a cyclotron and subsequent ion beam mass separation at the CERN-MEDICIS facility, with a particular focus on the process efficiency. Development of the mass separation process with studies on stable 169Tm yielded 65 and 60% for pure and erbium-excess samples. An enhancement factor of thulium ion beam over that of erbium of up to several 104 was shown by utilizing laser resonance ionization and exploiting differences in their vapor pressures. Three 167Tm samples produced at the IP2 irradiation station, receiving 22.8 MeV protons from Injector II at Paul Scherrer Institute (PSI), were mass separated with collected radionuclide efficiencies between 11 and 20%. Ion beam sputtering from the collection foils was identified as a limiting factor. In-situ gamma-measurements showed that up to 45% separation efficiency could be fully collected if these limits are overcome. Comparative analyses show possible neighboring mass suppression factors of more than 1,000, and overall 167Tm/Er purity increase in the same range. Both the actual achieved collection and separation efficiencies present the highest values for the mass separation of external radionuclide sources at MEDICIS to date.

Analysis of radon and radium content in springs of the city of Ekaterinburg and its outskirts

Despite development of central water supply systems, springs still remain to be important sources of drinking water. In this work, the study of water quality in springs of Yekaterinburg city and its settlements was performed with the attention to radiological factor. Activity concentrations of radium-226 were determined in water of 20 springs. Methods. Determination of the radon-222 activities of was performed using gamma-spectrometry vis the equilibrium bismuth-214 gamma line. To determine radium-226, 5-liter water samples were taken, the radium was preconcentrated on a T-5 sorbent; then radium was separated on a thinlayer MnO2-PE sorbent followed by measurement on an alpha spectrometer. Results. In the vast majority of cases, activity concentrations of radium-226 were lower than the detection limit (0.3 Bq/L); the maximal activity concentration of 1.03 ± 0.27 was found that corresponded to the internal dose of 0.21 ± 0.05 μSv/y due to daily consumption of this water. No correlations were found between content of radium-226 and concentrations of radon-222, uranium-238 and alkaline earth ions. At the period of 09.2020 – 06.2021, monitoring of radon activity was performed in seven springs with previously found high radon content. Significant seasonal variations of radon activity were found; for some springs the difference between the minimal and the maximal activity reached 3. In the most cases, increase of radon activity occurred in water during winter that can be explained by both an increase of radon solubility in cold water and a decrease of flowrate.

Methodology of 63Cu(n,2n)62Cu Reaction Rate Measurement

This paper presents the measurement of the spectrum-averaged cross section (SACS) of 63Cu(n,2n)62Cu reaction in 252Cf spontaneous fission neutron spectrum. The SACS in the 252Cf spectrum was chosen as a validation tool since 252Cf is the only standard neutron field and 62Cu isotope is not easy to measure by gamma spectroscopy since the gamma line of interest is an annihilation peak, which is also produced by 64Cu isotope. Fortunately, contributions to the annihilation peak from these isotopes can be distinguished due to the very different half-lives. SACS was inferred from the experimental reaction rate. The SACS in the 252Cf spontaneous fission neutron field for the 63Cu(n,2n)62Cu reaction was determined as equal to (0.1763 ± 0.0077 mb). This value agrees with value (0.183 ± 0.007) × 10−3 b within uncertainty presented by W. Mannhart. However, it differs by 12.7% from IRDFF-II value, which is equal to (0.19874 ± 8.954 10−3) × 10−3 b. Furthermore, reasonable agreement is not achieved with ENDF/B-VIII.0, JEFF-3.3, CENDL-3.1, ROSFOND-2010, nor JENDL-4.0 nuclear data libraries.

Research and Selection of Prospective Materials for Activation Dosimetry of Intense Bremsstrahlung Radiation

Radiation technologies based on the use of powerful electron beams and gamma radiation are closely related to the need for dosimetry of these beams. Dosimetry based on the use of the inelastic gamma-ray scattering reaction on a number of nuclei with the formation of isomers with different half-lives and energies of radiation quanta is very successful for these purposes. An example of this application in dosimetry is the 115In (γ,γ')115mIn reaction, which results in the formation of the 115mIn isomer, having a gamma line with an energy of 336.24 keV and a half-life of 4.5 hours. There was a successful application of this technique in dosimetry in solving certain practical problems (irradiation complexes based on 60Co source- cobalt “guns”). In this work, it is shown that the use of In detectors for dosimetry of gamma-radiation with a wide energy spectrum (bremsstrahlung) is associated with significant uncertainty in measuring the equivalent dose of the gamma spectrum with an upper limit of 10 MeV. This uncertainty is due to the relatively high threshold of the aforementioned reaction of 1.08 MeV. The quantitative contribution to the total radiation flux of the region of the gamma spectrum below the threshold (γ,γ') of the reaction on the In nucleus was determined and it was shown that, depending on the direction of radiation, there is an systematic error in measuring the equivalent dose, reaching 20-60%. Investigated and proposed for use alternative materials detectors, allowing reducing the systematic error in measuring the equivalent dose to 2-3%, which is quite acceptable for practical use.

Liver Radioembolization: a New Chapter in Russian Oncology

Recent years have seen an increase in the number of patients with malignant tumours of the liver. In this context, new treatment methods are being actively introduced into practice, one of which is liver radioembolization utilizing microspheres embedded with yttrium-90 (90Y).Aim. To review literature data on the history of radioembolization and its application for liver tumours.Key findings. Annually, over 200 thousand patients with inoperable primary liver cancer and over 270 thousand patients with inoperable metastatic liver cancer are registered globally, for whom radioembolization is considered as the most suitable treatment method. 90Y is a pure beta emitter without its own gamma line, which is characterized by a small average particle path in the tissue of 2.5 mm (the maximum level is 11 mm), a maximum beta particle energy of 2.27 MeV (average energy of 0.937 MeV) and a half-life of 64.1 hours. Clinical research into microspheres containing 90Y has been actively conducted since 1977 all over the world. However, it was only in 2004 that the US FDA authorized the clinical use of glass microspheres containing 90Y for the treatment of hepatocellular cancer and liver colorectal cancer metastases. Until recently, radioembolization has not been applied in Russia. In 2018, the joint efforts of the A. Tsyb Medical Radiological Research Centre (MRRC) — branch of the National Medical Research Radiological Centre and BEBIG LLC resulted in the production of Russian microspheres containing yttrium-90, which were subsequently introduced into routine clinical practice. The first liver embolization in Russia using microspheres containing domestic yttrium-90 (BEBIG LLC) to a patient with hepatocellular cancer was carried out by V.V. Kucherov and A.P. Petrosyan at the A. Tsyb RMMC on April, 25 in 2019.Conclusion. The production of microspheres containing 90Y in Russia, as well as a technical improvement of the procedure, will facilitate the introduction of liver radioembolization into the routine management of patients with malignant liver tumours.

Detection of background thermal neutrons in a modified low-background germanium gamma-ray spectrometer

The paper presents the detection of background neutrons using the 558.4 keV gamma line emitted from excited 114Cd nuclei after neutron induced processes. Stable cadmium and 60 L water moderator were placed inside low background shield of high purity germanium (HPGe) based spectrometer. The method was applied to study diurnal mean variation of background neutron flux. For this purpose 1 h gamma background spectra of modified HPGe spectrometer were collected subsequently for 50.5 days and then summed in 24-h-cycle. Results for the 558.4 keV line are presented along with those of main background lines. The total gamma-ray spectrum was also analysed and results are presented and discussed. No cyclic structure was noticed for all examited lines but 2223 keV, for which some day-night effect is suggested to exist. Test of another moderator made of 108 kg of graphite was done, but the results obtained with water are more promising.

Comparison of MC Geant4 simulation with the measurements of gamma photons produced by neutrons

In this work, we have focused on results of measurements of the hydrogen line 2223 keV and compared them with the results of Geant4 simulations. The paraffin containing hydrogen was irradiated by neutrons produced by the weak AmBe source. Produced gammas were measured with the germanium detector. The experimental setup was placed inside a carbon chamber which provided the shielding from the external neutrons. The measurements were performed for different amounts of paraffin. The processes playing a role in the description of our measurements are transport and moderation of neutrons, production of gamma rays in neutron-hydrogen interactions, transport and detection of gamma rays. It has been shown that the correctly carried out Monte Carlo simulations reproduced the measured values of the intensity of the observed gamma line 2223 keV from the neutron capture on hydrogen. The absorption of gamma rays is also described correctly. This has been shown in comparing the measurements of gamma line 322 keV from [Formula: see text]Pb with the simulations.

Optimization of Shielding- Collimator Parameters for ING-27 Neutron Generator Using MCNP5

Neutron generators are now used in various fields. They produce only fast neutrons; D-D neutron generator produces 2.45 MeV neutrons and D-T produces 14.1 MeV neutrons. In order to optimize shielding-collimator parameters to achieve higher neutron flux at the investigated sample (The signal) with lower neutron and gamma rays flux at the area of the detectors, design iterations are widely used. This work was applied to ROMASHA setup, TANGRA project, FLNP, Joint Institute for Nuclear Research. The studied parameters were; (1) shielding-collimator material, (2) Distance between the shielding-collimator assembly first plate and center of the neutron beam, and (3) thickness of collimator sheets. MCNP5 was used to simulate ROMASHA setup after it was validated on the experimental results of irradiation of Carbon-12 sample for one hour to detect its 4.44 MeV characteristic gamma line. The ratio between the signal and total neutron flux that enters each detector was calculated and plotted, concluding that the optimum shielding-collimator assembly is Tungsten of 5 cm thickness for each plate, and a distance of 2.3 cm. Also, the ratio between the signal and total gamma rays flux was calculated and plotted for each detector, leading to the previous conclusion but the distance was 1 cm.

Polynomial spectrum of gamma ray from dark matter

In this paper, we present some general features of gamma-ray spectra from dark matter (DM). We find that the spectrum with sharp features could appear in a wide class of DM models and mimic the gamma line signals. If all other physical degrees of freedom are heavy or effectively decoupled, the resulting gamma ray from DM decay or annihilation would generally have polynomial-type spectra or power-law with positive index. We illustrate our findings in a model-independent framework with generic kinematic analysis. Similar results can also apply for cosmic ray or neutrino cases.