Distribution Of Radioactivity Research Articles

Effect of sampling face velocity on the ultrafine particle surface collection efficiency of a cellulose membrane filter and a cellulose-glass fiber filter for environmental airborne radioactivity monitoring.

Surface collection efficiency (SCE) of a cellulose membrane filter (CMF) and a cellulose-glass fiber filter used in environmental monitoring for alpha-emitting radionuclides from nuclear facilities and natural radioactivity sources was evaluated for particles in the size range of 0.03-0.1μm at different levels of face velocity. The SCE of the CMF was higher than that of the cellulose-glass fiber filter, and only the membrane filter showed the dependence of SCE on the particle size at higher face velocity. The use of the CMF at higher face velocity in environmental radioactivity monitoring leads to measurements of the background alpha spectrum with more degradation under the changing particle size condition in the atmosphere. Consequently, that fact needs to be taken into account, along with the expected particle size distribution and concentration of the airborne radioactivity being sampled, when selecting a face velocity to achieve the best possible detection limit.

Unexpected uncertainty in the use of simple sample machining technique for gamma-spectrometry.

Elementary processing techniques such as cutting or grinding of foodstuffs are deemed adequate, particularly in the context of post-nuclear accidental situations, ensuring expeditious and effective testing for the gamma-ray spectrometry. Nevertheless, it is worth acknowledging that this straightforward procedure may predispose itself to appreciable variances in the detection efficiency of gamma-ray spectrometry, primarily attributable to the heterogeneity of the radioactivity distribution within the sample container, thereby incurring unexpected discrepancies or uncertainties. To investigate this impact, the precision of the actual sample measurements was scrutinised through statistical analysis.

Detection of lipid radicals generated via cerebral ischemia/reperfusion injury using a radiolabeled nitroxide probe

Reactive oxygen species generated via reperfusion cause lipid damage and induce lipid peroxidation, leading to cerebral ischemia/reperfusion injury and exacerbation of cerebral infarction. Lipid radicals are key molecules generated during lipid peroxidation. Therefore, understanding the spatiotemporal behavior of lipid radicals is important to improve the therapeutic outcomes of cerebral infarction. However, the behaviors of lipid radicals in the brain remain unclear. In this study, we aimed to evaluate the distribution of radioactivity in a transient middle cerebral artery occlusion (tMCAO) model using lipid radical detection probe [125I]1 to assess the behaviors of lipid radicals after cerebral ischemia/reperfusion. The tMCAO model administered [125I]1 exhibited significant differences in the timing and location of radioactivity accumulation between the ischemic and non-ischemic regions. Liquid chromatography/mass spectrometry analysis identified the lipid radical adducts formed by the reaction of 1 with the lipid radicals generated after reperfusion. More adducts were detected in the ischemic region samples than in the non-ischemic region samples. Therefore, 1 successfully detected the lipid radicals generated after cerebral ischemia/reperfusion. Overall, this study demonstrates the potential of nuclear medical imaging using radiolabeled 1 to detect the lipid radicals generated after cerebral ischemia/reperfusion. Our approach can aid in the development of new therapeutic agents scavenging lipid radicals after cerebral reperfusion by facilitating the determination of therapeutic efficacy and optimal administration period.

Potential of digital autoradiography for characterization of uranium materials

This study evaluates the capabilities of a commercial digital autoradiography set-up in characterizing the spatial distribution of radioactivity in U-bearing materials. Two different imaging plates (IPs) from various manufacturers, as well as three read-out granularities (25 µm, 50 µm, and 100 µm) of a high-resolution IP scanner, were tested. A custom software, developed using Python, was used for processing of the image raw data obtained from the IP scanner. The software extracted 25 intensity profiles from each autoradiographic image, allowing for a detailed analysis of the data. By applying various mathematical fitting functions, important metrics such as edge width, amplitude of the flat top, and central core width of the intensity profiles were determined. This provided valuable insights into the interaction between the U samples and IPs, particularly for samples of different geometry and thickness. Comparisons were made between samples embedded in epoxy resin or modelling clay and non-embedded U specimens. The results highlighted the superior performance of epoxy embedding in the characterization of U-bearing materials. The variation in signal intensity between runs for individual samples reached up to 20 %, showing consistent behavior across all samples in each measurement. This suggests that the inconsistency in signal response during repetitive analysis is likely due to the IP scanner rather than the IP itself. By using the analytical method of global spatial autocorrelation (Moran’s I), we were able to effectively detect enrichment inhomogeneity within low enriched UO2 pellets. The Moran’s I value quantified the levels of inhomogeneity, providing a numerical measure that was not visually apparent from the digital autoradiographic image.

Novel β-amyloid PET Imaging Study of [18F]92 in Patients with Cognitive Decline.

[18F]-4-((E)-(((E)-4-(2-(2-(2-Fluoroethoxy)ethoxy)ethoxy)benzylidene)-hydrazono)methyl)-N-methylaniline ([18F]92) is a novel positron emission tomography (PET) tracer previously reported to exhibit high binding affinity to aggregated β-amyloid (Aβ). This study aims to report a fully automated radiosynthesis procedure for [18F]92, explore its radioactive distribution in the brains of healthy subjects, and investigate its potential application value in the early diagnosis of Alzheimer's disease (AD). The fully automated radiosynthesis of [18F]92 was performed on the AllinOne module. Thirty one participants were recruited for this study. Dynamic [18F]92 PET imaging was conducted over 0-90 min period to assess time-activity curves (TAC) and standardized uptake value ratio (SUVR) curves in cognitively normal (CN) subjects. All participants were visually classified as either positive (+) or negative (-). Semiquantitative analyses of [18F]92 were performed by calculating SUVRs in different regions of interest. Furthermore, the study analyzed the relationships between global SUVR and plasma AD biomarkers, including Aβ42, Aβ40, P-tau181, and T-tau. The automated radiosynthesis of [18F]92 was completed within 50 min, yielding a radiochemical purity of greater than 95% and a radiochemical yield of 36 ± 3% (nondecay-corrected). Among the participants, 15 were estimated as Aβ (-) and 16 as Aβ (+). TACs indicated that [18F]92 rapidly crossed the blood-brain barrier within 10 min, followed by a rapid decrease, which then slowed down in the last 50-90 min. SUVR curves revealed that SUVR values stabilized around 60-70 min after injection and reached an equilibrium between 70 and 90 min, primarily in the cerebral cortex. SUVRs of Aβ (+) participants were significantly higher than those of Aβ (-) individuals within the cerebral cortex. In addition, Aβ42 and the Aβ42/Aβ40 ratio exhibited negative correlations with global SUVR, while plasma P-tau181 and the P-tau181/T-tau ratio displayed positive correlations with global SUVR. [18F]92 exhibits excellent pharmacokinetic properties in the human brain and can be synthesized automatically on a large scale. [18F]92 is a promising and reliable radiotracer for estimating Aβ pathology accumulation, providing valuable assistance in AD diagnosis and guiding clinical trials of therapeutic drugs.

Investigation of intra-fractionated range guided adaptive proton therapy: I. On-line PET imaging and range measurement

Objective. Develop a prototype on-line positron emission tomography (PET) scanner and evaluate its capability of on-line imaging and intra-fractionated proton-induced radioactivity range measurement. Approach. Each detector consists of 32 × 32 array of 2 × 2 × 30 mm3 Lutetium–Yttrium Oxyorthosilicate scintillators with single-scintillator-end readout through a 20 × 20 array of 3 × 3 mm2 Silicon Photomultipliers. The PET can be configurated with a full-ring of 20 detectors for conventional PET imaging or a partial-ring of 18 detectors for on-line imaging and range measurement. All detector-level readout and processing electronics are attached to the backside of the system gantry and their output signals are transferred to a field-programable-gate-array based system electronics and data acquisition that can be placed 2 m away from the gantry. The PET imaging performance and radioactivity range measurement capability were evaluated by both the offline study that placed a radioactive source with known intensity and distribution within a phantom and the online study that irradiated a phantom with proton beams under different radiation and imaging conditions. Main results. The PET has 32 cm diameter and 6.5 cm axial length field-of-view (FOV), ∼2.3–5.0 mm spatial resolution within FOV, 3% sensitivity at the FOV center, 18%–30% energy resolution, and ∼9 ns coincidence time resolution. The offline study shows the PET can determine the shift of distal falloff edge position of a known radioactivity distribution with the accuracy of 0.3 ± 0.3 mm even without attenuation and scatter corrections, and online study shows the PET can measure the shift of proton-induced positron radioactive range with the accuracy of 0.6 ± 0.3 mm from the data acquired with a short-acquisition (60 s) and low-dose (5 MU) proton radiation to a human head phantom. Significance. This study demonstrated the capability of intra-fractionated PET imaging and radioactivity range measurement and will enable the investigation on the feasibility of intra-fractionated, range-shift compensated adaptive proton therapy.

Imageable Radioembolization Microspheres for Treatment of Unresectable Hepatocellular Carcinoma: Interim Results from a First-in-Human Trial

PurposeTo determine 6-month interim safety, effectiveness, and multimodal imageability of imageable glass microsphere yttrium-90 (90Y) radioembolization for unresectable hepatocellular carcinoma (HCC) in a first-in-human trial. Materials and MethodsImageable microspheres (Eye90 Microspheres; ABK Biomedical, Halifax, Nova Scotia, Canada), a U.S. Food and Drug Administration (FDA) Breakthrough-Designated Device consisting of glass radiopaque 90Y microspheres visible on computed tomography (CT) and single photon emission CT (SPECT), were used to treat 6 subjects with unresectable HCC. Patients underwent selective (≤2 segments) treatment in a prospective open-label pilot trial. Key inclusion criteria included liver-only HCC, performance status ≤1, total lesion diameter ≤9 cm, and Child-Pugh A status. Prospective partition dosimetry was utilized. Safety (measured by Common Terminology Criteria for Adverse Events [CTCAE] v5), multimodal imageability on CT and SPECT, and 3- and 6-month imaging response by modified Response Evaluation Criteria in Solid Tumors on magnetic resonance (MR) imaging were evaluated. ResultsSeven tumors in 6 subjects were treated and followed to 180 days. Administration success was 100%. Microsphere distribution measured by radiopacity on CT correlated with SPECT. Ninety-day target lesion complete response (CR) was observed in 3 of 6 subjects (50%) and partial response (PR) in 2 (33.3%). At 180 days, target lesion CR was maintained in 3 subjects (50%) and PR in 1 (16.7%). Two subjects could not be reassessed, having undergone intervening chemoembolization. All subjects reported adverse events (AEs), and 5 reported AEs related to treatment. There were no treatment-related Grade ≥3 AEs. ConclusionsRadioembolization using imageable microspheres was safe and effective in 6 subjects with unresectable HCC at 6-month interim analysis. Microsphere distribution by radiopacity on CT correlated with radioactivity distribution by SPECT, providing previously unavailable CT-based tumor targeting information.

Evaluating and Comparing Human Perceptions of Streets in Two Megacities by Integrating Street-View Images, Deep Learning, and Space Syntax

Street quality plays a crucial role in promoting urban development. There is still no consensus on how to quantify human street quality perception on a large scale or explore the relationship between street quality and street composition elements. This study investigates a new approach for evaluating and comparing street quality perception and accessibility in Shanghai and Chengdu, two megacities with distinct geographic characteristics, using street-view images, deep learning, and space syntax. The result indicates significant differences in street quality perception between Shanghai and Chengdu. In Chengdu, there is a curvilinear distribution of the highest positive perceptions along the riverfront space and a radioactive spatial distribution of the highest negative perceptions along the ring road and main roads. Shanghai displays a fragmented cross-aggregation and polycentric distribution of the streets with the highest positive and negative perceptions. Thus, it is reasonable to hypothesize that street quality perception closely correlates with the urban planning and construction process of streets. Moreover, we used multiple linear regression to explain the relationship between street quality perception and street elements. The results show that buildings in Shanghai and trees, pavement, and grass in Chengdu were positively associated with positive perceptions. Walls in both Shanghai and Chengdu show a consistent positive correlation with negative perceptions and a consistent negative correlation with other positive perceptions, and are most likely to contribute to the perception of low street quality. Ceilings were positively associated with negative perceptions in Shanghai but are not the major street elements in Chengdu, while the grass is the opposite of the above results. Our research can provide a cost-effective and rapid solution for large-scale, highly detailed urban street quality perception assessments to inform human-scale urban planning.

Distribution of natural radioactivity in different geological formations and their environmental risk assessment in Malaysia

Labuan, Miri, Kundasang and Raub regions of Malaysia have very different geological formations and settings that could result in different levels of natural radioactivity. Hence, this study determines the influence of different geological formations on radioactivity in these locations using field measurements, petrology and geochemistry. A total of 141 gamma dose rates and 227 beta flux measurements were collected using Polimaster survey meters (PM1405) in these four regions. The gamma dose rate values range from 0.37 to 0.05 µSv/h with a mean value of 0.11 µSv/h. Beta flux values range from 3.46 to 0.12 CPS with a mean value of 0.57 CPS. Mineralogy and elemental composition of the different rock types were analysed using thin-section petrography, XRD, ICP and pXRF methods. Felsic igneous rocks such as syenite and granite have higher natural radioactivity and contain more radionuclide-bearing minerals such as apatite, zircon, allanite, K-feldspar, titanite, muscovite and biotite. Metamorphic rocks have the second highest natural radioactivity and contain fewer radioactive minerals. The natural radioactivity of sedimentary rocks mostly depends on their clay content. The gamma dose rate maps show that igneous and metamorphic regions around Raub have higher radioactivity compared to the sedimentary-dominated regions around Miri and Labuan. Annual effective dose (AED) and excess lifetime cancer risk (ELCR) were calculated to evaluate the potential health risk for inhabitants of these regions. Labuan and Miri are considered to be safe zones with respect to natural radioactivity as the results show little to no risk for the public, compared with the Raub region, which is medium to high risk.

ETFC-01: a dual-labeled chelate-bridged tracer for SSTR2-positive tumors.

Integrating radioactive and optical imaging techniques can facilitate the prognosis and surgical guidance for cancer patients. Using a single dual-labeled tracer ensures consistency in both imaging modalities. However, developing such molecule is challenging due to the need to preserve the biochemical properties of the tracer while introducing bulky labeling moieties. In our study, we designed a trifunctional chelate that facilitates the coupling of the targeting vector and fluorescent dye at opposite sites to avoid undesired steric hindrance effects. The synthesis of the trifunctional chelate N3-Py-DOTAGA-(tBu)3 (7) involved a five-step synthetic route, followed by conjugation to the linear peptidyl-resin 8 through solid-phase synthesis. After deprotection and cyclization, the near-infrared fluorescent dye sulfo-Cy.5 was introduced using copper free click chemistry, resulting in eTFC-01. Subsequently, eTFC-01 was labeled with [111In]InCl3. In vitro assessments of eTFC-01 binding, uptake, and internalization were conducted in SSTR2-transfected U2OS cells. Ex-vivo biodistribution and fluorescence imaging were performed in H69-tumor bearing mice. eTFC-01 demonstrated a two-fold higher IC50 value for SSTR2 compared to the gold standard DOTA-TATE. Labeling of eTFC-01 with [111In]InCl3 gave a high radiochemical yield and purity. The uptake of [111In]In-eTFC-01 in U2OS.SSTR2 cells was two-fold lower than the uptake of [111In]In-DOTA-TATE, consistent with the binding affinity. Tumor uptake in H69-xenografted mice was lower for [111In]In-eTFC-01 at all-time points compared to [111In]In-DOTA-TATE. Prolonged blood circulation led to increased accumulation of [111In]In-eTFC-01 in highly vascularized tissues, such as lungs, skin, and heart. Fluorescence measurements in different organs correlated with the radioactive signal distribution. The successful synthesis and coupling of the trifunctional chelate to the peptide and fluorescent dye support the potential of this synthetic approach to generate dual labeled tracers. While promising in vitro, the in vivo results obtained with [111In]In-eTFC-01 suggest the need for adjustments to enhance tracer distribution.

Evaluation of 68Ga-PSMA-11 PET/CT: a Phase 1 clinical study in Japanese patients with primary, recurrent, or suspected recurrent prostate cancer

BackgroundProstate-specific membrane antigen (PSMA)-targeted radiopharmaceuticals allow whole-body imaging to detect prostate cancer (PC). Positron emission tomography imaging using gallium-68 (68Ga)-PSMA-11 has been shown to have a favorable safety and tolerability profile and high diagnostic performance. The study evaluates the safety and pharmacokinetics of 68Ga-PSMA-11 in Japanese patients with primary, recurrent, or suspected recurrent prostate cancer.MethodsThis single arm study enrolled Japanese patients with primary PC (n = 3), suspected recurrent PC following radical prostatectomy (n = 4), or suspected recurrent PC following radical radiotherapy (n = 3). All patients received a single intravenous dose of 68Ga-PSMA-11 2.0 MBq/kg (±10%) followed by PSMA PET imaging and safety and pharmacokinetic evaluations. Based on the blood concentrations of 68Ga-PSMA-11 and the radioactivity distribution rate in each organ/tissue, the absorbed doses in major organs/tissues and the whole-body effective dose were calculated by the Medical Internal Radiation Dose method.ResultsTen patients were enrolled. Mean age was 73.3 ± 4.8 years, and median prostate-specific antigen was 8.250 ng/mL. Five patients (50%) experienced a total of 6 adverse events, and no grade ≥ 2 adverse events or serious adverse events were reported. No clinically significant changes in vital signs, haematology parameters, or blood chemistry or ECG abnormalities were observed. The estimated whole body effective dose of 68Ga-PSMA-11 (mean ± standard deviation) was 2.524 × 10–2 ± 2.546 × 10–3 mSv/MBq. Time to maximum concentration (1.16 × 10–4 ± 1.3 × 10–5% ID/mL) in whole blood was 2.15 ± 0.33 min.Conclusions68Ga-PSMA-11 has a favourable safety and tolerability profile in Japanese patients with primary, recurrent, or suspected recurrent prostate cancer, which is comparable to previous observations in other populations.

Machine learning‐based evaluation technology of 3D spatial distribution of residual radioactivity in large‐scale radioactive structures

During the decommissioning of nuclear and particle accelerator facilities, a considerable amount of large-scale radioactive waste may be generated. Accurately defining the activation level of the waste is crucial for proper disposal. However, directly measuring the internal radioactivity distribution poses challenges. This study introduced a novel technology employing machine learning to assess the internal radioactivity distribution based on external measurements. Random radioactivity distribution within a structure were established, and the photon spectrum measured by detectors from outside the structure was simulated using the FLUKA Monte-Carlo code. Through training with spectrum data corresponding to various radioactivity distributions, an evaluation model for radioactivity using simulated data was developed by above Monte-Carlo simulation. Convolutional Neural Network and Transformer methods were utilized to establish the evaluation model. The machine learning construction involves 5425 simulation datasets, and 603 datasets, which were used to obtain the evaluated results. Preprocessing was applied to the datasets, but the evaluation model using raw spectrum data showed the best evaluation results. The estimation of the intensity and shape of the radioactivity distribution inside the structure was achieved with a relative error of 10%. Additionally, the evaluation based on the constructed model takes only a few seconds to complete the process.

Realistic estimation framework of radioactive release distributions into the environment during nuclear power plant accidents

Since the level 2 PSA of OPR-1000 was the requirement for regulatory purposes, Cs-137 release estimation was contained as the Nuclear Safety Act of ROK in which the Cs-137 release frequency exceeding 100 TBq was determined to happen less than 1.0E-6 per year after the Fukushima Daiichi Accident. However, Cs-137 release estimation from the conventional level 2 PSA of OPR-1000 provided uncertainty due to dominant accident sequence consideration. Thus, this study aimed to develop systematic methods through the overall framework to quantify realistic uncertainty concerns of radioactive material release using sensitivity and uncertainty analysis methods and apply them to OPR-1000. This framework helped to quantify confidential value for the Cs-137 release under the BEPU approach using both parametric and non-parametric methods to cover both realistic and conservative points. Uncertainty propagation analysis showed the unexpected uncertainty increase of Cs-137 release exceeding 100 TBq. The non-parametric uncertainty analysis provided higher conservative concerns for safety than the realistic concerns in terms of economics when compared with the parametric uncertainty analysis. Wilks’ uncertainty analysis showed the importance to consider conservative Cs-137 release in order to reach the higher safety need. Sensitivity analysis showed reasonable relationships between engineering safety parameters with the Cs-137 release.

Radioactive Mineral Distribution on Tin Placer Deposits of Southeast Asia Tin Belt Granite in Bangka Island

Bangka Island is an area rich in primary and secondary tin deposits. Tin deposits are formed around the contact between granite and older rocks, while secondary tin deposits are formed in the modern channels and paleochannels. Many previous researchers have researched radioactive minerals in primary tin deposits and modern channel deposits, but research on radioactive minerals in paleo channel deposits has never been carried out. The characterization of radioactive minerals in paleo channel deposits was done in this study to determine the potency of radioactive minerals in secondary tin deposits by comparing the content of radioactive minerals in paleochannels with modern channels and tin mine tailing deposits. The data used were mineralogical data and radioactivity data, along with the uranium and thorium content of the rocks from several previous studies. Data showed significant mineral content differences in paleo channel, modern channel, and tin mine tailings deposits. Mineral (monazite and zircon) content in tin mine tailing deposits was the highest. Source rocks for the radioactive minerals monazite and zircon are predicted to be the granitic rocks or tourmaline quartz veins of primary tin deposits. The radioactivity value of rocks in the paleo channel is relatively the same as the modern channel, ranging from 20 to 150 c/s. Uranium content in paleo channel is the same as modern channel deposits, ranging from 10 to 15 ppm eU. The thorium content of the rocks in the paleo channel ranges from 1 to 60 ppm eTh, while in the modern channel, it ranges from 1 to 45 ppm eTh. The radioactivity value and uranium content of the rocks are less effective for determining potential areas of radioactive minerals in placer tin deposits. In contrast, data on thorium content are quite effective for determining potential areas of radioactive minerals in placer tin deposits.

Spatial distribution of 137Cs; 40K, 226Ra, 232Th in soils of Monchegorsk city (Murmansk region)

The purpose of the study was to establish the patterns of spatial distribution of radioactivity of technogenic 137Cs and natural radionuclides 232Th, 226Ra, 40K in urban soils of Monchegorsk. Location and time of the study. Soil samples, were collected in summer 2018 in the Monchegorsk city, Murmansk region, Russia. To study the specific activity of radiocesium and natural radionuclides, soil samples were taken from topsoil (0-5 cm) at 82 sites, including 68 sites within the city territory (urban soils) and 14 sites beyond the city limits in the subtorch areas strongly affected by the Severonickel factory. Similar studies of urban soils in Monchegorsk had not been carried out previously. Methods. During expeditionary work and laboratory research, soil, radiological, and mathematical and statistical methods were used. When carrying out gamma spectrometric measurements, radionuclides 137Cs, 226Ra, 232Th and 40K were determined on a low-background semiconductor gamma spectrometer ORTEC (USA) based on a high-purity coaxial germanium detector GEM10P4–70 (HPGe) with a SBS-75 pulse signal processor and Gamma-software. The resolution of the gamma spectrometer along the 1.33 MeV line (60Co) was 1.75 keV, and the relative efficiency was 15%. Calibration and quality control of gamma spectrometric measurements was carried out using volumetric activity measurements with 1-L Marinelli vessels of different densities (RITVERZ, Russia-Germany). Main results. The values of specific activity of radionuclides in soil samples were as following: in the technogenic 137Cs up to 31.3 Bq/kg and in the subtorch soils up to 63.4 Bq/kg. Specific activity of natural radionuclides in urban soils reached to 14.2 Bq/kg for 226Ra, whereas in the subtorch soils it reached 21.6 Bq/kg. The specific activity of 232Th in urban soils reached 18.3 Bq/kg, with 17 Bq/kg registered for the subtorch soils. As for 40K, its specific activity reached 498 Bq/kg in the urban soils and 317 Bq/kg. Conclusion. The gamma survey of the Monchegorsk territory did not reveal any anomaly in radiation. The dose rate of gamma radiation in the city does not exceed 0.074 μSv/hour, which is less than the values elsewhere in Russia, ranging from 0.04 to 0.20 μSv/hour. The obtained data about specific activity of technogenic 137Cs and natural radionuclides 232Th, 226Ra, 40K in the Monchegorsk soils are typical for the Murmansk region.

Multiplexing Autoradiography.

Autoradiography, the direct imaging of radioactive distribution in tissue sections, is a powerful technique that has several key advantages for the validation of PET radiotracers. Using autoradiography, we can localize radiotracer uptake to neighbours of cells, and when multiplexed with additional radiotracers, fluorescent probes, or in situ tissue analysis, autoradiography can help to characterize the mechanism of radiotracer uptake and assess functional heterogeneity in tissue. In this chapter, the author outlines the basic ex vivo autoradiography protocol and shows how it can be multiplexed using dual radionuclides 18F and 14C. They also highlight where autoradiography can be combined with other technologies to provide synergistic information for interrogating spatial biology.

Radioactivity distributions and biohazard assessment of coastal marine environments of niger-delta, Nigeria

Radioactivity distributions and biohazard assessment of coastal marine environments of niger-delta, Nigeria

Development and application of a fully automatic multi-function cassette module Mortenon M1 for radiopharmaceutical synthesis.

Functions of existing automatic module systems for synthesis of radiopharmaceuticals mainly focus on the radiolabeling of small molecules. There are few modules which have achieved full-automatic radiolabeling of non-metallic and metallic nuclides on small molecules, peptides, and antibody drugs. This study aimed to develop and test a full-automatic multifunctional module system for the safe, stable, and efficient production of radiopharmaceuticals. According to characteristics of labeling process of radioactive drugs, using UG and Solidworks softwares, full-automatic cassette-based synthesis module system Mortenon M1 for synthesis of radiopharmaceuticals with various radionuclides, was designed and tested. Mortenon M1 has at least three significant highlights: the cassettes are disposable, and there is no need of manual cleaning; the synthesis method program is flexible and can be edited freely by users according to special needs; this module system is suitable for radiolabeling of both small-molecule and macromolecular drugs, with potentially various radionuclides including 18F, 64Cu, 68Ga, 89Zr, 177Lu, etc. By program control methods for certain drugs, Mortenon M1 was used for radiolabeling of both small-molecule drugs such as [68Ga]-FAPI-46 and macromolecular drugs such as [89Zr]-TROP2 antibody. Quality control assays for product purity were performed with radio-iTLC and radio-HPLC, and the radiotracers were confirmed for application in microPET imaging in xenograft tumor-bearing mouse models. Functional tests for Mortenon M1 module system were conducted, with [68Ga]-FAPI-46 and [89Zr]-TROP2 antibody as goal synthetic products, and it displayed that with the cassette modules, the preset goals could be achieved successfully. The radiolabeling synthesis yield was good ([68Ga]-FAPI-46, 70.63% ± 2.85%, n = 10; [89Zr]-TROP2, 82.31% ± 3.92%, n = 10), and the radiochemical purity via radio-iTLC assay of the radiolabeled products was above 99% after purification. MicroPET imaging results showed that the radiolabeled tracers had reasonable radioactive distribution in MDA-MB-231 and SNU-620 xenograft tumor-bearing mice, and the tumor targeted radiouptake was satisfactory for diagnosis. This study demonstrated that the full-automatic module system Mortenon M1 is efficient for radiolabeling synthesis of both small-molecule and macromolecular substrates. It may be helpful to reduce radiation exposure for safety, provide qualified radiolabeled products and reliable PET diagnosis, and ensure stable production and supply of radiopharmaceuticals.

Relationship between stable cesium concentration and body size of Japanese flounder Paralichthys olivaceus and the effect of a size-dependent shift in diet.

To understand the relationship between the radioactive cesium (Cs) concentration in muscle of Japanese flounder Paralichthys olivaceus and the species' biological characteristics (size, sex, and age) under conditions of ecological equilibrium (i.e., distributed among ecosystem components over sufficient time, and with nearly constant ratios of Cs concentration in organisms to the concentration in water) as existed before the accident at the Fukushima Dai-ichi Nuclear Power Station (FDNPS), Japan, in 2011, we examined stable Cs, as it is thought to exist in equilibrium in the environment and behave similarly to radioactive Cs in aquatic animals. The concentration of stable Cs in 241 P. olivaceus (range 216-782 mm total length [TL]) collected in Sendai Bay, approximately 90 km north of the FDNPS, in June-July 2015 was expressed as an exponential function with size as an independent variable; the results show the concentration of stable Cs doubled with an increase in TL of 442 mm. Next, to evaluate the cause of the size-dependent change in stable Cs concentration, we examined 909 individuals (200-770 mm TL) collected in September 2013-July 2015 to determine their feeding habit based on size. Analysis of the frequency of occurrence of prey organisms in stomach contents showed that sand lance Ammodytes japonicus (55-180 mm standard length [SL]) was the most consistently consumed across size classes. Analysis on a wet-mass basis showed that A. japonicus and anchovy Engraulis japonicus (65-130 mm SL) were the main food of P. olivaceus sized 200-599 mm TL, whereas chub mackerel Scomber japonicus (120-230 mm SL) and two species of flatfishes (180-205 mm SL) were abundant in the diet of P. olivaceus sized ≥600 mm TL. All these prey items were presumed to have similar concentrations of stable Cs. Based on the above, the effect of diet on the relationship between stable Cs in muscle and fish size was considered negligible. That the diet of P. olivaceus largely did not change with size was also confirmed by C and N stable isotope ratios in P. olivaceus and their prey species. Therefore, the Cs-size relationship is probably determined by changes in the balance between the rate of Cs intake from food and seawater and the excretion rate during growth, both of which change as functions of body mass. Values of stable Cs concentrations among environmental components and animals appear to be a valid indicator for understanding the radioactive Cs distribution in the marine environment and aquatic animals under the equilibrium state, as existed before the 2011 nuclear accident.

Method for predicting lifetime of ion exchange resin in PWR primary loop based on nuclide distribution measurement

Ion exchange resins are commonly utilized for water treatment in pressurized water reactors' primary loop. These resins have the ability to adsorb radioactive cations present in the primary loop coolant, leading to a purification effect. However, the resin becomes radioactive post-purification and cannot be regenerated, thus requiring regular replacement. As the process of resin replacement exposes personnel to radiation, it is crucial to enhance the resin's utilization. This paper aims to investigate a non-destructive testing method for evaluating the lifetime of resin in pressurized water reactor purification units. It also aims to offer guidance for safe resin replacement. The resin is contained in a column (commonly referred to as ion exchange columns) and consumed from top to bottom, with radioactivity decreasing in intensity from top to bottom. The study utilizes the longitudinal radioactivity distribution characteristics of ionic resins to build a gamma-ray detection system with high resistance to interlayer interference and good longitudinal resolution. In this study, a two-stage resin column was utilized to capture common fission product nuclides and corrosion-activated nuclides, such as 60Co, 137Cs, 54Mn, and 124Sb, from the effluent of a pressurized water reactor. The distribution of these nuclides was measured using this device. The results indicate that the activity levels of 60Co, 137Cs, and 54Mn reached their peak in the column before rapidly declining. The height of the resin layer corresponding to the highest activity level of each nuclide varied, indicating the resin's adsorption selectivity. After processing an additional 10 tons of wastewater, a second measurement was taken which showed that the failure range of the resin expanded downwards as the treated water volume increased. The entire distribution curve of the nuclides within the exchange column also shifted upwards and to the right. By comparing the first and second observations, we discovered that the bottom part of the resin will fail when the activity of the most penetrating nuclide in the wastewater surpasses a specific threshold. This research suggests a novel approach to predicting the lifetime of resin, which generalizes the trend of radionuclide intensity inside the ion exchange column.