Various studies, including morpho-taxonomic identifications, have indicated that commercial spirulina cultures (Limnospira spp.) can be contaminated by other cyanobacteria without establishing a connection with the potential presence of cyanotoxins. The taxonomy and nomenclature of cyanobacteria has changed significantly since the usage of phylogenetic methods and reclassification could lead to confusion in the designation of taxa previously identified as toxin producers. It therefore appears necessary to characterize the cyanosphere of commercial spirulina cultures in the light of these recent developments. In a collection of six spirulina cultivars used in commercial biomass production, we detected a recurrent dominant cyanobacterial contaminant using 16S rRNA gene amplicon sequencing. Further, Next-Generation Sequencing as well as genetic and morphological characterization pointed towards the genus Sodalinema. A comprehensive analysis of five Sodalinema available genomes as well as our novel metagenome-assembled genome did not reveal any genes involved in the synthesis of cyanotoxins, which suggested that this contaminant is harmless. Still, to avoid valuable biomass related financial loss, we took advantage of spirulina capacity to utilize various forms of nitrogen to set up a procedure to control the proliferation of Sodalinema sp. Finally, a glimpse into heterotrophic contamination of those cultivars indicated that the bacterial composition is very diverse but still several phyla appeared to be very common in open-pond cultivation of spirulina in the Mediterranean region.
The β--emitter 161Tb is emerging as a promising radionuclide for radiopharmaceutical therapy because of its increased yield of low-energy electrons compared with 177Lu. This results in an increased localized absorbed dose, potentially influencing nephrotoxicity with 161Tb. Because of the excretion and reabsorption in specific kidney tissues of radiopharmaceuticals, substructure-level dosimetry is of interest for improving understanding of radiation-induced kidney damage in radiopharmaceutical therapy. This study investigated the renal dosimetry of [161Tb]Tb-DOTATATE and [177Lu]Lu-DOTATATE in C57BL6/Jjr mice using 2 different dosimetry frameworks. Methods: Detailed biodistribution data were assessed at 5 time points postinjection (15 min, 1 h, 4 or 4.5 h, 24 h, and 72 h). The activity in different nephron substructures was determined by γ-counting of the entire kidney and quantitative digital autoradiography acquisition of kidney sections. Tissue-level activity was distributed between nephron substructures. Simplistic dosimetry assuming uniform absorbed dose distribution was compared with nephron-substructure-level dosimetry based on a multinephron computational model. Results: Both radiopharmaceuticals exhibited similar pharmacokinetics, with rapid renal clearance and peak uptake at 15 min postinjection. 161Tb resulted in a significantly increased absorbed dose heterogeneity across nephron substructures compared with 177Lu. Absorbed doses to proximal tubules were on average 71% higher than to glomeruli for 161Tb and 28% higher for 177Lu. Simplistic whole-kidney dosimetry underestimated proximal tubule absorbed doses by up to 35% for 161Tb and 24% for 177Lu and over- or underestimated glomerular absorbed doses, particularly for 161Tb. The highest absorbed doses were observed in the juxtamedullary nephrons for both radionuclides, reflecting their distinct morphology. Conclusion: Nephron-substructure-level dosimetry revealed substantial absorbed dose heterogeneity for both radiopharmaceuticals, which is not considered with simplistic whole-organ dosimetry. Small-scale dosimetry enables identification of possible dose-limiting nephron substructures, informing future nephroprotective strategies and improving the translational evaluation of novel radioligands.
BACKGROUND:Intensity modulated proton therapy (IMPT) is the preferred option during pregnancy, as it reduces out-of-field doses compared to photon techniques. A physical pregnancy phantom was validated for in-field proton dosimetry and used to assess fetal dose across four IMPT plans. METHODS:The 18-week pregnancy Tena phantom was composed of bone, soft tissue, and lung substitutes. Proton relative stopping power (RSP) for Tena tissues was measured and compared with treatment planning system (TPS) and Monte Carlo (MC) calculations. Experimental TPS dose verification was performed using gamma index (GI). Fetal dose was measured for IMPT of glioma, Hodgkin lymphoma without (HL) and with a range shifter (HL-RS), and submandibular gland (neck) cancer using a Timepix and bubble detectors. RESULTS:Differences between TPS-assigned and MC-simulated relative to the measured RSP values were up to -7.4 %. GI(3 %/3 mm) values were above 93.38 %. The neutron dose equivalent in the fetus position ranged between 2.5 and 49.4 µSv/Gy(RBE) for glioma and HL-RS plans, respectively. The HL plan reduced neutron dose equivalent to 15.8 µSv/Gy(RBE), while for the neck 20 µSv/Gy(RBE) was measured. Neutrons were dominant with ∼ 80 % contribution to the total dose equivalent. A summed fetal dose was calculated considering the prescribed dose per treatment and ranged between 0.17 mSv and 1.89 mSv for glioma and HL-RS, respectively. CONCLUSIONS:The Tena phantom is suitable for proton dosimetry and enables accurate TPS calculations. The use of a range shifter increased the fetal dose by more than threefold. Fetal doses for all IMPT plans remained below 2 mSv.
In this study, both heterogeneous and homogeneous oxalate precipitation method, as well as hydroxidecarbonate precipitation, were employed to produce ThO2 powders with distinct morphologies- platelets, cubes, and nanoparticles. These powders were compacted and sintered at 2023 K (1750 degrees C) under an oxygen potential of -420 kJ mol-1 for 1 h and 10 h. This approach enabled a systematic investigation of the influence of morphology on packing behavior, densification kinetics, and the resulting microstructure, which were characterized using XRD, SEM, BET surface area analysis, He pycnometry, and immersion density measurements. All powders achieved high final densities (>95 % of the theoretical density) after 10 h of sintering, underscoring their potential for nuclear fuel-related applications. For porous ThO2 materials intended for low-temperature ISOL target applications, the oxalate-derived powders, particularly those precipitated at room temperature, provided a promising balance between low sinterability and process scalability.
Background: Improvement in radiation protection practice may be achieved by acquisition of reliable and accurate dosimetry data. Use of dosimeters with known properties provides insight into their performance in real radiation fields encountered in radiation monitoring practice. Aim: Performance evaluation in a wide range of radiation conditions provides insight into dosimeter behaviour, providing input for revision, update and harmonization of IEC type testing standards. Methods: A total of 32 active dosimeters were investigated, of which 26 are used for area workplace, and 6 for individual monitoring. Dosimeter performance was evaluated against the IEC 60846-1:2009 standard for portable workplace and environmental meters and monitors and the IEC 61526:2024 standard for active personal dosimeters in a wide range of photon energies, angles of incidence and dose equivalent rates. Performance was examined beyond the minimum rated range: 33.3 keV-1.25 MeV photon energy; (0 degrees; +/- 75 degrees) angle of incidence for personal dosimeters and (0 degrees; +/- 120 degrees with 180 degrees) for area dosimeters; 3 mu Sv h-1-7 Sv h-1 dose rate range. In addition, dosimeter short-term stability and overload properties were investigated. Results: State-of-the-art and commonly used dosimeters complied with the standard defined limits of variation with respect to the manufacturer stated specifications. Some dosimeters had significantly lower variations in terms of relative response than the current standard stated requirements. Conclusion: Potential update of the relevant IEC type testing standards was considered, with the possibility of introducing two distinct dosimeter classes, one of which would comply with reduced limits of variation.
