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Radioguidance that makes use of β-emitting radionuclides is gaining in popularity and could have potential to strengthen the range of existing radioguidance techniques. While there is a strong tendency to develop new PET radiotracers, due to favorable imaging characteristics and the success of theranostics research, there are practical challenges that need to be overcome when considering use of β-emitters for surgical radioguidance. In this position paper, the EANM identifies the possibilities and challenges that relate to the successful implementation of β-emitters in surgical guidance, covering aspects related to instrumentation, radiation protection, and modes of implementation. [ABSTRACT FROM AUTHOR]

Microfluidic technology is a highly efficient technique used in positron emission tomography (PET) radiochemical synthesis. This approach enables the precise control of reactant flows and reaction conditions, leading to improved yields and reduced synthesis time. The synthesis of two radiotracers, L-[11C]methionine and [11C]choline, was performed, using a microfluidic cassette and an iMiDEVTM module by employing a dose-on-demand approach for the synthesis process. We focused on optimizing the precursor amounts and radiosynthesis on the microfluidic cassette. L-[11C]methionine and [11C]choline were synthesized using a microreactor filled with a suitable resin for the radiochemical reaction. Trapping of the [11C]methyl iodide, its reaction, and solid-phase extraction purification were performed on a microreactor, achieving radiochemical yields of >80% for L-[11C]methionine and >60% for [11C]choline (n = 3). The total synthesis time for both the radiotracers was approximately 20 min. All quality control tests complied with the European Pharmacopeia standards. The dose-on-demand model allows for real-time adaptation to patient schedules, making it suitable for preclinical and clinical settings. Precursor optimization enhanced the cost efficiency without compromising the yield. The importance of dose-on-demand synthesis and optimized precursor utilization to produce L-[11C]methionine and [11C]choline was emphasized in this study. The results demonstrated the feasibility of dose-on-demand adaptations for clinical applications with reduced precursor quantities and high radiochemical yields. [ABSTRACT FROM AUTHOR]

The diagnosis and understanding of pain is challenging in clinical practice. Assessing pain relies heavily on self-reporting by patients, rendering it inherently subjective. Traditional clinical imaging methods such as computed tomography and magnetic resonance imaging can only detect anatomical abnormalities, offering limited sensitivity and specificity in identifying pain-causing conditions. Radiotracers play a vital role in molecular imaging that aims to identify abnormal biological processes at the cellular level, even in apparently normal anatomical structures. Therefore, molecular imaging is an important area of research as a prospective diagnostic modality for pain-causing pathophysiology. We present a mini review of the current knowledge base regarding radiotracers for identification of pain in vivo. We also describe radiocaine, a novel positron emission tomography imaging agent for sodium channels that has shown great potential for identifying/labeling pain-producing nerves and producing an objectively measurable pain intensity signal. [ABSTRACT FROM AUTHOR]

Immune checkpoint inhibitor therapy targeting the PD-1/PD-L1 axis in cancer patients, is a promising oncological treatment. However, the number of non-responders remains high, causing a burden for the patient and the healthcare system. Consequently, a diagnostic tool to predict treatment outcomes would help with patient stratification. Molecular imaging provides said diagnostic tool by offering a whole-body quantitative assessment of PD-L1 expression, hence supporting therapy decisions. Four PD-L1 radioligand candidates containing a linker-chelator system for radiometalation, along with three hydrophilizing units—one sulfonic and two phosphonic acids—were synthesized. After labeling with 64Cu, log D7.4 values of less than −3.03 were determined and proteolytic stability confirmed over 94% intact compound after 48 h. Binding affinity was determined using two different assays, revealing high affinities up to 13 nM. µPET/CT imaging was performed in tumor-bearing mice to investigate PD-L1-specific tumor uptake and the pharmacokinetic profile of radioligands. These results yielded an unexpected in vivo distribution, such as low tumor uptake in PD-L1 positive tumors, high liver uptake, and accumulation in bone/bone marrow and potentially synovial spaces. These effects are likely caused by Ca2+-affinity and/or binding to macrophages. Despite phosphonic acids providing high water solubility, their incorporation must be carefully considered to avoid compromising the pharmacokinetic behavior of radioligands. [ABSTRACT FROM AUTHOR]

This publication presents the application of radiotracers in the characterization of industrial flotation circuits. Two examples are showcased: the detection of feed flow rate imbalances and the characterization of particle size segregation in automatic mineral-cutting machines. The feed pulp distribution was determined from the mean residence times. Particle size segregation was measured by sampling the cutting machines (≅ 25 grams samples) using coarse, intermediate, and fine-sized radiotracer particles. Radiotracers were injected into the feed streams and measured at various points of the circuit using nuclear instruments, allowing for non-invasive and real time detection. Results show that in the rougher flotation stage, the feed flow is distributed almost evenly in lines 2 and 3 (approximately 38% of the flow goes to each line) and to a lesser extent towards line 4 (approximately 24%). In lines 1 and 2 of the scavenger stage, a higher percentage of the flow goes towards line 1 (approximately 59%) and a lower percentage towards line 2 (41%). Line 6 of the rougher flotation is the fastest of the circuit (shortest residence time). In addition, the inlet mineral-cutting machine of the rougher stage segregates particles with a bias for fine sizes (11.4 % more fine-sized particles than coarse ones). This work is an example of how radiotracer technology can be applied to improve metal production and processes. Radiotracers provide reliable information to be used in combination with other metallurgical data to properly assess flotation circuits. [ABSTRACT FROM AUTHOR]

This review describes the basic principles of radiometal-theranostics and its dawn based on the development of the positron-emitting 86Y and 86Y-labeled radiopharmaceuticals to quantify biodistribution and dosimetry of 90Y-labeled analogue therapeutics. The nuclear and inorganic development of 86Y (including nuclear and cross section data, irradiation, radiochemical separation and recovery) led to preclinical and clinical evaluation of 86Y-labeled citrate and EDTMP complexes and yielded organ radiation doses in terms of mGy/MBq 90Y. The approach was extended to [86/90Y]Y-DOTA-TOC, yielding again yielded organ radiation doses in terms of mGy/MBq 90Y. The review further discusses the consequences of this early development in terms of further radiometals that were used (68Ga, 177Lu etc.), more chelators that were developed, new biological targets that were addressed (SSTR, PSMA, FAP, etc.) and subsequent generations of radiometal-theranostics that resulted out of that. [ABSTRACT FROM AUTHOR]

The application of [18F]-fluorodeoxyglucose ([18F]FDG) as a radiotracer to detect sites of inflammation (either due to bacterial infection or primary inflammation) has led to exploring the role of PET in visualizing bacteria directly at sites of infection. However, the results from such efforts are controversial and inconclusive so far. We aimed to assess the limitations of PET as an effective modality in the diagnosis of bacterial infections. Inflammation due to bacterial infections can be visualized by using [18F]FDG-PET. However, the non-specificity of [18F]FDG makes it undesirable to visualize bacteria as the underlying cause of inflammation. Hence, more specific radiotracers that possibly bind to or accumulate in bacteria-specific receptors or enzymes are being explored. Several radiotracers, including 2-deoxy-2-[18F]fluorosorbitol ([18F]FDS), 6-[18F]-fluoromaltose, [11C]para-aminobenzoic acid ([11C]PABA), radiolabeled trimethoprim (11C-TMP) and its analog fluoropropyl-trimethoprim (18F-FPTMP), other radiolabeled sugars, and antimicrobial drugs have been used to image microorganisms. Unfortunately, no progress has been made in translating the results to routine human use; feasibility and other factors have constrained their success in clinical settings. In the current article, we discuss the limitations of direct bacterial visualization with PET tracers, but emphasize the important role of [18F]FDG-PET as the only option for detecting evidence of infection. [ABSTRACT FROM AUTHOR]

With the emergence of positron emission tomography (PET) in the late 1970s, psychiatry had access to a tool capable of non‐invasive assessment of human brain function. Early applications in psychiatry focused on identifying characteristic brain blood flow and metabolic derangements using radiotracers such as [15O]H2O and [18F]FDG. Despite the success of these techniques, it became apparent that more specific probes were needed to understand the neurochemical bases of psychiatric disorders. The first neurochemical PET imaging probes targeted sites of action of neuroleptic (dopamine D2 receptors) and psychoactive (serotonin receptors) drugs. Based on the centrality of monoamine dysfunction in psychiatric disorders and the measured success of monoamine‐enhancing drugs in treating them, the next 30 years witnessed the development of an armamentarium of PET radiopharmaceuticals and imaging methodologies for studying monoamines. Continued development of monoamine‐enhancing drugs over this time however was less successful, realizing only modest gains in efficacy and tolerability. As patent protection for many widely prescribed and profitable psychiatric drugs lapsed, drug development pipelines shifted away from monoamines in search of novel targets with the promises of improved efficacy, or abandoned altogether. Over this period, PET radiopharmaceutical development activities closely paralleled drug development priorities resulting in the development of new PET imaging agents for non‐monoamine targets. Part one of this review will briefly survey novel PET imaging targets with relevance to the field of psychiatry, which include the metabotropic glutamate receptor type 5 (mGluR5), purinergic P2X7 receptor, type 1 cannabinoid receptor (CB1), phosphodiesterase 10A (PDE10A), and describe radiotracers developed for these and other targets that have matured to human subject investigations. Current limitations of the targets and techniques will also be discussed. [ABSTRACT FROM AUTHOR]

Atmospheric radioxenon analyses conducted under the Comprehensive Test Ban Treaty Organization (CTBTO) necessitates the collection of air samples to quantify 135Xe, an indicator for nuclear explosions and reactor operations. Analytical instrument calibration for these analyses requires high quality, monoisotopic reference standards that are typically short lived, and therefore must be produced and shipped promptly to monitoring stations worldwide. The work described here outlines two methods to produce highly enriched 135Xe by irradiating stable monoisotopic targets by (1) neutron capture (n, ɣ) on monoisotopic 134Xe and (2) high energy photon irradiation (ɣ, n) of monoisotopic 136Xe. The targets were prepared by electromagnetic isotope separation of natural xenon. Results from each process were compared for 135Xe yield and purity. [ABSTRACT FROM AUTHOR]

The excellent features of non‐invasive molecular imaging, its progressive technology (real‐time, whole‐body imaging and quantification), and global impact by a growing infrastructure for positron emission tomography (PET) scanners are encouraging prospects to investigate new concepts, which could transform clinical care of complex infectious diseases. Researchers are aiming towards the extension beyond the routinely available radiopharmaceuticals and are looking for more effective tools that interact directly with causative pathogens. We reviewed and critically evaluated (challenges or pitfalls) antibiotic‐derived PET radiopharmaceutical development efforts aimed at infection imaging. We considered both radiotracer development for infection imaging and radio‐antibiotic PET imaging supplementing other tools for pharmacologic drug characterization; overall, a total of 20 original PET radiotracers derived from eleven approved antibiotics. [ABSTRACT FROM AUTHOR]

We hereby propose the use of stable, biocompatible, and uniformly sized polymeric micelles as high-radiotracer-payload carriers at region-of-interest with negligible background activity due to no or low offsite radiolysis. We modified glycol chitosan (GC) polymer with varying levels of palmitoylation (P) and quaternization (Q). Quaternary ammonium palmitoyl glycol chitosan (GCPQ) with a Q:P ratio of 9:35 (Q9P35GC) offers >99% biocompatibility at 10 mg mL−1. Q9P35GC micelles exhibit >99% 99mTechnetium (99mTc) radiolabeling via the stannous chloride reduction method without heat. The 99mTc-Q9P35GC micelles (65 ± 3 nm) exhibit >98% 6 h serum stability at 37 °C and 7 day of radiochemical stability at 25 °C. HepG2 cells show a higher uptake of FITC-Q9P35GC than Q13P15GC and Q20P15GC. The in vivo 24 h organ cumulated activity (MBq h) order follows: liver (234.4) > kidneys (60.95) > GIT (0.73) > spleen (88.84). The liver to organ ratio remains higher than 2.4, rendering a better contrast in the liver. The radiotracer uptake decreases significantly in fibrotic vs. normal liver, whereas a blocking study with excess Q9P35GC significantly decreases the radiotracer uptake in a healthy vs. fibrotic liver. FITC-Q9P35GC shows in vivo hepato-specific uptake. Radiotracer liver uptake profile follows reversible binding kinetics with data fitting to two-tissue compartmental (2T), and graphical Ichise multilinear analysis (MA2) with lower AIC and higher R2 values, respectively. The study concludes that 99mTc-Q9P35GC can be a robust radiotracer for noninvasive hepatocyte function assessment and diagnosis of liver fibrosis. Furthermore, its multifunctional properties enable it to be a promising platform for nanotheranostic applications. [ABSTRACT FROM AUTHOR]

5-Chloro-2-methyl-4-isothiazolin-3-one (CMIT) and 2-methyl-4-isothiazolin-3-one (MIT) used as preservatives in various products, including humidifier disinfectants, presents substantial health hazards. This research delves into the toxicological assessments of CMIT/MIT in the respiratory system using animal models. Through the synthesis of radiolabeled [14C]CMIT and [14C]MIT, we investigated the biological uptake and in vivo behaviors of CMIT/MIT in the respiratory tissues following intratracheal exposure. Quantitative whole-body autoradiography (QWBA) revealed significant persistence of CMIT/MIT in lung tissue. In addition, radio high-performance liquid chromatography (radio-HPLC) with tandem mass spectrometry (LC-MS/MS) was employed for metabolite profiling and identification. Notably, around 28% of the radiolabel was retained in tissue after the extraction step, suggesting covalent binding of CMIT/MIT and their metabolites with pulmonary biomolecules. This observation demonstrates the propensity of the electrophilic isothiazolinone ring in CMIT/MIT to undergo chemical interactions with biothiols in proteins and enzymes, fostering irreversible alterations of biomolecules. Such accumulations of transformations could result in direct toxicity at both cellular and organ levels. Additionally, the detection of metabolites, including a MIT dimer conjugated with glutathione (GSH), as analyzed by mass spectrometry indicates the possible reduction of cellular GSH levels and subsequent oxidative stress. This investigation offers an in-depth insight into the toxic mechanisms of CMIT/MIT, underlying their capability to engage in complex formations with biomacromolecules and induce pronounced respiratory toxicity. These results highlight the imperative for stringent safety assessments of these chemicals, advocating for improved public health and safety measures in the use of chemicals. [Display omitted] • The radiolabeled CMIT and MIT were synthesized using radioactive carbon (14C). • The SUV of CMIT/MIT in lung was determined to be 6.01 after 0.083 h post exposure. • In the analysis of metabolites, the parent structures of CMIT/MIT were not observed. • Some metabolites were found to be conjugated with glutathione. • Approximately 28% of the radiolabel was bound to pulmonary biomolecules. [ABSTRACT FROM AUTHOR]

Purpose: Imaging of PARP expression has emerged as valuable strategy for prediction of tumor malignancy. While [18F]PARPi and [18F]FTT are already in clinical translation, both suffer from mainly hepatobiliary clearance hampering their use for detection of abdominal lesions, e.g., liver metastases. Our novel radiotracer [18F]FPyPARP aims to bridge this gap with a higher renal clearance and an easily translatable synthesis route for potential clinical application. Methods: We developed a less lipophilic variant of [18F]PARPi by exchange of the fluorobenzoyl residue with a fluoronicotinoyl group and automated the radiosyntheses of the three radiotracers. We then conducted a comparative side-by-side study of [18F]PARPi, [18F]FPyPARP, and [18F]FTT in NOD.CB17-Prkdcscid/J mice bearing HCC1937 xenografts to assess xenograft uptake and pharmacokinetics focusing on excretion pathways. Results: Together with decent uptake of all three radiotracers in the xenografts (tumor-to-blood ratios 3.41 ± 0.83, 3.99 ± 0.99, and 2.46 ± 0.35, respectively, for [18F]PARPi, [18F]FPyPARP, and [18F]FTT), a partial shift from hepatobiliary to renal clearance of [18F]FPyPARP was observed, whereas [18F]PARPi and [18F]FTT show almost exclusive hepatobiliary clearance. Conclusion: These findings imply that [18F]FPyPARP is an alternative to [18F]PARPi and [18F]FTT for PET imaging of PARP enzymes. [ABSTRACT FROM AUTHOR]

Advancements in brain imaging techniques have emerged as a significant tool in detecting Alzheimer's disease (AD) progression. The complicated cascade of AD progression can be detected using radio imaging, especially with Positron emission tomography (PET). The review focus on recently introduced investigational PET tracers targeting neurofibrillary tau aggregates found typically in AD. Herein, we also address the use of different PET tracers and the clinical implementation of established and newer generation tracers. This review also intends to discuss the importance of several PET radiotracers and challenges in PET imaging. • PET tracers play an important role in understanding AD progression. • Molecular PET tracers are a helpful tool to assess neuronal circuits. • PET tracers can be used to detect the alteration of toxic proteoforms in AD. • Engineering PET tracers would allow better adaptation in the early diagnosis of AD. [ABSTRACT FROM AUTHOR]

Evolving scientific evidence has begun to point towards hyperphosphorylated tau as a major neurotoxic component in the pathophysiological development of many major neurodegenerative conditions. In response to a need for accurate and reliable diagnosis and disease monitoring in clinical and trial settings, there has been great effort put into the development of tau radiotracers. While first-generation and second-generation radiotracers have provided a basis for assessing tau, concerns of inadequate specificity and selectivity have continued to motivate further study of these radiotracers and the development of novel radiopharmaceuticals. Given the prospective scientific and clinical value of a valid tau radiotracer, the molecular neuroimaging community must be aware of the most recent developments in the realm of tau radiotracer development. This brief review article will critically overview the most established tau radiotracers and, most importantly, concentrate on the progress of more recently developed tau radiotracers. [ABSTRACT FROM AUTHOR]

Atherosclerosis is a well-known disease leading to cardiovascular events, including myocardial infarction and ischemic stroke. These conditions lead to a high mortality rate, which explains the interest in their prevention, early detection, and treatment. Molecular imaging is able to shed light on the basic pathophysiological processes, such as inflammation, that cause the progression and instability of plaque. The most common radiotracers used in clinical practice can detect increased energy metabolism (FDG), macrophage number (somatostatin receptor imaging), the intensity of cell proliferation in the area (labeled choline), and microcalcifications (fluoride imaging). These radiopharmaceuticals, especially FDG and labeled sodium fluoride, can predict cardiovascular events. The limitations of molecular imaging in atherosclerosis include low uptake of highly specific tracers, possible overlap with other diseases of the vessel wall, and specific features of certain tracers’ physiological distribution. A common protocol for patient preparation, data acquisition, and quantification is needed in the area of atherosclerosis imaging research. [ABSTRACT FROM AUTHOR]

Purpose: Many radiotracers are currently available for the detection of recurrent prostate cancer (rPC), yet many have not been compared head-to-head in comparative imaging studies. There is therefore an unmet need for evidence synthesis to guide evidence-based decisions in the selection of radiotracers. The objective of this study was therefore to assess the detection rate of various radiotracers for the rPC. Methods: The PUBMED, EMBASE, and the EU and NIH trials databases were searched without date or language restriction for comparative imaging tracers for 13 radiotracers of principal interest. Key search terms included 18F-PSMA-1007, 18F-DCPFyl, 68Ga-PSMA-11, 18F-PSMA-11, 68Ga-PSMA-I&T, 68Ga-THP-PSMA, 64Cu-PSMA-617, 18F-JK-PSMA-7, 18F-Fluciclovine, 18F-FABC, 18F-Choline, 11C-Choline, and 68Ga-RM2. Studies reporting comparative imaging data in humans in rPC were selected. Single armed studies and matched pair analyses were excluded. Twelve studies with eight radiotracers were eligible for inclusion. Two independent reviewers screened all studies (using the PRISMA-NMA statement) for inclusion criteria, extracted data, and assessed risk of bias (using the QUADAS-2 tool). A network meta-analysis was performed using Markov-Chain Monte Carlo Bayesian analysis to obtain estimated detection rate odds ratios for each tracer combination. Results: A majority of studies were judged to be at risk of publication bias. With the exception of 18F-PSMA-1007, little difference in terms of detection rate was revealed between the three most commonly used PSMA-radiotracers (68Ga-PSMA-11, 18F-PSMA-1007, 18F-DCFPyl), which in turn showed clear superiority to choline and fluciclovine using the derived network. Conclusion: Differences in patient-level detection rates were observed between PSMA- and choline-radiotracers. However, there is currently insufficient evidence to favour one of the four routinely used PSMA-radioligands (PSMA-11, PSMA-1007, PSMA-I&T, and DCFPyl) over another owing to the limited evidence base and risk of publication bias revealed by our systematic review. A further limitation was lack of reporting on diagnostic accuracy, which might favour radiotracers with low specificity in an analysis restricted only to detection rate. The NMA derived can be used to inform the design of future clinical trials and highlight areas where current evidence is weak. [ABSTRACT FROM AUTHOR]

Single and binary titanium and silicon xerogels were prepared to evaluate and compare their sorption performance with commercial sorbents (Al2O3 and TiO2) used for the 99Mo/99mTc separation, under neutral pH and room temperature conditions. Molybdenum sorption capacities were determined by batch equilibrium systems using Mo(VI) solutions labelled with 99Mo radiotracer. Ti-xerogel showed the highest 99Mo distribution coefficient and sorption capacity, while Si-xerogel exerted null affinity. Binary xerogels and reference sorbents showed similar capacities. Additionally, Ti-xerogel, after a heating process, drastically decreased its sorption capacity. Finally, a molybdenum sorption mechanism was studied. [ABSTRACT FROM AUTHOR]

Radioactive sealed sources and radiotracer techniques are used to diagnose industrial process units. This work introduces a workspace to simulate four sealed sources and radiotracer applications, namely, gamma scanning of distillation columns, gamma scanning of pipes, gamma transmission tomography, and radiotracer flow rate measurements. The workspace was created in Geant4 Application for Tomographic Emission (GATE) simulation toolkit and was called Industrial Radioisotope Applications Virtual Laboratory. The flexibility of GATE and the fact that it is an open-source software render it advantageous to radioisotope technology practitioners, educators, and students. The comparison of the simulation results with experimental results that are available in the literature showed the effectiveness of the virtual laboratory. [ABSTRACT FROM AUTHOR]

The chlordecone (CLD) and the β-hexachlorocyclohexane (β-HCH) are persistent organic pollutants with a great environmental stability that cause severe affectations to health. The concentration of these pesticides in the environment is low, which represent a problem for their determination, even for the modern analytical methods. The labeling of these compounds with an iodine radioisotope for their use as radiotracers is a potential solution to this problem. The present work studies the interaction of 1-iodochlordecone (I-CLD) and β-1-iodo-pentachlorocyclohexane (I-β-HCH) with cyclodextrins (CDs), during the formation of molecular inclusion complexes pesticide@CDs. The methodology of multiple minima hypersurfaces, quantic calculations based on density functional theory and a topologic study of electronic density were used to corroborate the stability of I-CLD@CDs and I-β-HCH@CDs complexes. Three main types of guest-host complexes in relation to the occlusion grade were observed: with total occlusion, with partial occlusion and external interaction without occlusion. The more stable complexes are obtained when the γ-CD is the host molecule. The formed complexes with radiolabelled pollutants are analogous with the ones reported in previous works. These results confirm the utility of these complexes for the removal of organochlorine pesticides from polluted water and, also, demonstrate the possibility of using the I-CLD and the I-β-HCH as possible radiotracers for these pollutants in further studies with environmental proposes. [ABSTRACT FROM AUTHOR]

The historical anthropogenic impact on sediments from the Basque Mud Patch (southern Bay of Biscay) is explored using a multidisciplinary approach including the analysis of natural (210Pb) and artificial (137Cs, 239/240Pu) radiotracers, major elements (Al, Mn), metals (Zn, Pb, Cu, Cr), Pb isotopic ratios, and foraminiferal and pollen contents. The study of three short cores (19–46 cm), despite being hindered by the effects of biomixing, allow the calculation of a sedimentation rate of 1 ± 0.1 mm yr−1. Distribution with depth of Al-normalised concentrations of metals reflects an increasing trend since 1880 CE, related to the industrialization of the Basque coastal area. According to the Sediment Quality Guidelines applied, contents of Zn and Pb appear as a potential cause of concern, given that they exceed the values from which adverse biological effects can be occasionally expected. However, foraminiferal assemblages do not show recognizable changes along the cores following increasing trace metal concentrations. Finally, pollen results reveal an increasing trend of coniferous taxa and a parallel reduction of authochthonous Deciduous Quercus , probably as a consequence of reforestation works. Data obtained confirm that effects of coastal anthropogenic activities extend to the adjacent shelf, where muddy deposits are likely to act as a trap for contaminants. [ABSTRACT FROM AUTHOR]

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Herein, we report the development of an 18F‐labeled, activity‐based small‐molecule probe targeting the cancer‐associated serine hydrolase NCEH1. We undertook a focused medicinal chemistry campaign to simultaneously preserve potent and specific NCEH1 labeling in live cells and animals, while permitting facile 18F radionuclide incorporation required for PET imaging. The resulting molecule, [18F]JW199, labels active NCEH1 in live cells at nanomolar concentrations and greater than 1000‐fold selectivity relative to other serine hydrolases. [18F]JW199 displays rapid, NCEH1‐dependent accumulation in mouse tissues. Finally, we demonstrate that [18F]JW199 labels aggressive cancer tumor cells in vivo, which uncovered localized NCEH1 activity at the leading edge of triple‐negative breast cancer tumors, suggesting roles for NCEH1 in tumor aggressiveness and metastasis. [ABSTRACT FROM AUTHOR]

Bifunctional HBED chelators are hexadentate complexing ligands (chelators) that tightly coordinate to trivalent gallium and, additionally, are able to bind to bioactive molecules. In nuclear medicine, HBED-based radiopharmaceuticals are used as powerful radiotracers for tumor imaging. Among variants of bifunctional HBED chelators, HBED-CC is the most well-known; it possesses two terminal carboxylic acid groups that are able to undergo bioconjugation by amide-bond formation. However, to permit bioconjugation through click coupling, we previously modified the structure of HBED-CC and introduced HBED-NN chelator bearing two azide functions. We have now combined the conjugation capabilities of HBED-CC and HBED-NN chelators in one molecule and have created HBED-NC, which possesses both azide and carboxylic acid groups. The advantage of HBED-NC is that it provides options for constructing either monomeric or heterodimeric radiolabeling precursors. This work describes the synthesis of HBED-NC by either of two pathways. [ABSTRACT FROM AUTHOR]

68Ga-labeled cyclic RGD dimers and trimer were evaluated as PET radiotracers. It was found that the linker group had little impact on α v β 3 binding affinity of RGD dimers, which share similar α v β 3 binding affinity with the RGD trimer despite of their different multiplicity. Biodistribution properties of 68Ga radiotracers depend on RGD peptides and radiometal chelates. Among the 68Ga radiotracers evaluated, 68Ga-I2P-RGD 2 has the best tumor uptake with good tumor-to-background ratios, and is a good PET radiotracer for imaging gliomas. • Three new 68Ga radiotracers were prepared and evaluated as radiotracers for glioma imaging. • NOTA-Galacto-RGD 2 , NOTA-I2P-RGD 2 and NOTA-4P-RGD 3 share similar α v β 3 binding affinity. • 68Ga-I2P-RGD 2 has higher tumor uptake than 68Ga-Galacto-RGD 2 and 68Ga-4P-RGD 3. • The blocking experiment shows that the tumor uptake of 68Ga radiotracers is α v β 3 –specific. [ABSTRACT FROM AUTHOR]

Abstract Plastic pollution is ubiquitous in aquatic environments and its potential impacts to wildlife and humans present a growing global concern. Despite recent efforts in understanding environmental impacts associated with plastic pollution, considerable uncertainties still exist regarding the true risks of nano- and micro-sized plastics (<5 mm). The challenges faced in this field largely relate to the methodological and analytical limitations associated with studying plastic debris at low (environmentally relevant) concentrations. The present paper highlights how radiotracing techniques that are commonly applied to trace the fate and behaviour of chemicals and particles in various systems, can contribute towards addressing several important and outstanding questions in environmental plastic pollution research. Specifically, we discuss the use of radiolabeled microplastics and/or chemicals for 1) determining sorption/desorption kinetics of a range of contaminants to different types of plastics under varying conditions, 2) understanding the influence of microplastics on contaminant and nutrient bioaccumulation in aquatic organisms, and 3) assessing biokinetics, biodistribution, trophic transfer and potential biological impacts of microplastic at realistic concentrations. Radiotracer techniques are uniquely suited for this research because of their sensitivity, accuracy and capacity to measure relevant parameters over time. Obtaining precise and timely information on the fate of plastic particles and co-contaminants in wildlife has widespread applications towards effective monitoring programmes and environmental management strategies. Highlights • Global plastic pollution poses potential risks to aquatic wildlife and humans. • Several fundamental research questions remain to be addressed in this field. • Radiotracer techniques are highly sensitive and capable of real-time analysis in vivo. • We outline how radiotracers can contribute towards environmental plastics research. • Radiolabeled microplastics and chemicals can benefit bioaccumulation and contaminant transfer studies. [ABSTRACT FROM AUTHOR]

A novel, rapid, and automated loop method for the synthesis of [ 11 C]nicotine was developed and optimized. The method involves, a reaction of the precursor, ( + ) nornicotine or (-) nornicotine, with a gas-phase produced [ 11 C]CH 3 I in an 800 µL loop at 75 °C for 5 min followed by a semi-preparatory Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC) purification. The optimized synthesis and purification process was complete in < 30 min and produced [ 11 C]nicotine with > 99.9% Radiochemical Purity (RCP), no [ 11 C]CH 3 I, no ( + ) nornicotine, 105 mCi/µmole specific activity, 7.0 – 7.2 pH, and 16.6% ethanol. The current method can be optimized, to reduce the ethanol content (<10%), and can be translated to a cGMP production of [ 11 C]nicotine for human clinical trials. [ABSTRACT FROM AUTHOR]

Eckernförde Bay in the Baltic Sea is well-known for the pockmarks areas which are located in the centre and off the southern shore-line of the bay emanating groundwater in a non-continuous but episodic way. Mobile underwater in situ gamma-ray spectroscopy is exploited proving that both 214 Bi and 40 K are efficient radiotracers for localization of seepage areas whenever either sediment is in mixture with the emanating fluid or resuspension of surface sediment occurs as a side effect of the fluid emanation. [ABSTRACT FROM AUTHOR]

The application of the radiometric method with the use of radiotracers for the investigation of membrane fouling was tested. The radiotracer method allows for a more complete control of membrane modules’ performance, which may contribute to a longer working time due to the reduction of a frequency and an intensity of a periodic cleaning. The experiments were carried out with the crossflow membrane module equipped with flat-sheet ultrafiltration membranes made of polyether sulfone. A suspension of the bentonite labeled by the radioactive isotope of lanthanum – 140La was used as a feed solution. The influence of process parameters such as cross-flow velocity and pressure as well as feed concentration on the rate of membrane blocking indicated by the change in the specific radioactivity of deposit formed on the membrane surface was tested. The performed studies demonstrated that radiometric method enabled to estimate the thickness of the cake layer deposited on the membrane during the filtration process. It was noticed that thickness of the bentonite layer formed on the membrane surface increased with the increasing concentration of the feed solution and decreased with the increasing flow velocity and applied pressure. Experiments also showed the ability of applied method for in situ determination of both kinetics of the deposit formation on the membrane as well as the permeability of the deposit layer and its resistance. [ABSTRACT FROM AUTHOR]

The biological activity influence on the mangrove sediment capacity to remove 65Zn and 109Cd from tidal water was evaluated in a site chronically polluted. Benthic Activity Indexes (BAI), corresponding to relative estimates of biological impact on radiotracer accumulation, were higher for 109Cd (~ 38%) than for 65Zn (~ 10%) in the top centimetre of sediment. However, BAI exceeded 96% for deeper sediment layers. This apparent decrease in radiotracer diffusion into deep sediments through biological activity inhibition is stronger than reported for much less polluted mangrove nearby, suggesting that benthic organisms tolerant of chronic metal pollution may affect metal sorption mechanisms. [ABSTRACT FROM AUTHOR]

A series of vasopressin receptor V 1a ligands have been synthesized for positron emission tomography (PET) imaging. The lead compound (1 S, 5 R )- 1 ( (4-(1H-indol-3-yl)-3-methoxyphenyl) ((1 S ,5R)-1,3,3-trimethyl-6-azabicyclo[3.2.1]octan-6-yl)methanone ) and its F-ethyl analog 6c exhibited the best combination of high binding affinity and optimal lipophilicity within the series. (1 S, 5 R )- 1 was radiolabeled with 11 C for PET studies. [ 11 CH 3 ](1 S, 5 R )- 1 readily entered the mouse (4.7% ID/g tissue) and prairie vole brains (∼2% ID/g tissue) and specifically (30–34%) labeled V 1a receptor. The common animal anesthetic Propofol significantly blocked the brain uptake of [ 11 CH 3 ](1 S, 5 R )- 1 in the mouse brain, whereas anesthetics Ketamine and Saffan increased the uptake variability. Future PET imaging studies with V 1a radiotracers in non-human primates should be performed in awake animals or using anesthetics that do not affect the V 1a receptor. [ABSTRACT FROM AUTHOR]

Bubble column reactors are widely used for gas-liquid operations and most often are fitted with vertical internals for appropriate heat transfer. Apart from these applications, cylindrical vessels with concentrically installed vertical tube bundles find major use in boiling water reactors. Most often, heat removal takes place in boiling water reactors by phase change of the flowing water, which results in a complex, axially developing and highly dynamic two-phase flow pattern. Though the hydrodynamics in a bubble column with vertical internals have been addressed in few publications, the characteristics of liquid phase mixing and turbulence over a wide range of operating conditions and dense configuration of the internals have not been reported thus far. The present communication addresses the hydrodynamic characteristics in bubble column equipped with dense internals over a wide range of superficial gas and liquid velocities. Experiments were performed using the air-water system in a 120 mm I.D. bubble column with, and without internals, by varying the percent cross-sectional area covered by the internals. A non-invasive Radioactive Particle Tracking (RPT) method has been employed for estimating the hydrodynamic parameters and mixing characteristics have also been investigated using residence time distribution (RTD) studies with radiotracers. The experimental results obtained in this work indicates that the configuration of the heat exchanger internals, superficial gas, and liquid velocities have a strong effect on liquid phase hydrodynamics and mixing characteristics. [ABSTRACT FROM AUTHOR]

Introduction The production of 18 F-radiotracers using continuous flow microfluidics is under-utilized due to perceived equipment limitations. We describe the dose-on-demand principle, whereby the back-to-back production of multiple, diverse 18 F-radiotracers can be prepared on the same day, on the same microfluidic system using the same batch of [ 18 F]fluoride, the same microreactor, the same HPLC column and SPE cartridge to obtain a useful production yield. Methods [ 18 F]MEL050, [ 18 F]Fallypride and [ 18 F]PBR111 were radiolabeled with [ 18 F]fluoride using the Advion NanoTek Microfluidic Synthesis System. The outlet of the microreactor was connected to an automated HPLC injector and following the collection of the product, SPE reformulation produced the 18 F-radiotracer in <10% ethanolic saline. A thorough automated cleaning procedure was implemented to ensure no cross-contamination between radiotracer synthesis. Results The complete productions for [ 18 F]MEL050 and [ 18 F]Fallypride were performed at total flow rates of 20 μL/min, resulting in 40 ± 13% and 25 ± 13% RCY respectively. [ 18 F]PBR111 was performed at 200 μL/min to obtain 27 ± 8% RCY. Molar activities for each 18 F-radiotracer were >100 GBq/μmol and radiochemical purities were >97%, implying that the cleaning procedure was effective. Conclusions Using the same initial solution of [ 18 F]fluoride, microreactor, HPLC column and SPE cartridge, three diverse 18 F-radiotracers could be produced in yields sufficient for preclinical studies in a back-to-back fashion using a microfluidic system with no detectable cross-contamination. [ABSTRACT FROM AUTHOR]

In last years, sensitive hydrogels have become a breakthrough in ophthalmic pharmaceutical technology aimed at developing new strategies to increase the residence time of active substances. In a previous paper, we qualitatively demonstrated the capacity of a new ion sensitive hydrogel to increase the residence time. Nevertheless, the clearance of the gel from the ocular surface was not quantifiable with the used methodology. The aim of the present work was to use a well-established approach based on scintigraphy to quantitatively estimate the residence time of the previously proposed hydrogel. The rat corneal residence time of a topic ophthalmic formulation containing gellan gum and kappa carragenan (0.82% w/v) labeled with 99mTc-DTPA radiotracer was evaluated and compared with the residence of an aqueous solution. Ophthalmic safety studies such as eye irritation or passage through the cornea were also carried out. After 1.5 h of contact, 77% of the hydrogel remained in the ocular surface, presenting kinetics of disappearance one-phase decay and a half time of 262 min. We conclude that the novel ophthalmic hydrogel developed with kappa carrageenan and gellan gum remains for long periods of time on the corneal surface, presenting a drop that fits an exponential decay. [ABSTRACT FROM AUTHOR]

The aim of this study is to develop cerebral radiotracers for central nervous system receptors imaging. The synthesis, characterization and biological evaluation of two aryl piperazine Tc-radiocomplexes based on the piano stool motif [CpM(CO)] (Cp = cyclopentadienyl, M = Tc/Re) is reported. The Tc-radiocomplexes were obtained quickly (time < 5 min) with high radiochemical yields. The Tc-radiocomplexes characterized by high performance liquid chromatography comparison with the rhenium surrogates have both a suitable lipophilicity and are able to cross the blood brain barrier with 0.43 ± 0.05 and 1.96 ± 0.06% ID/g of brain uptake, at 10 min post injection. [ABSTRACT FROM AUTHOR]

A simple and rapid nonradioactive iodide labeling/radiolabeling method for peptides, using an inexpensive oxidizing agent such as sodium hypochlorite and a cyclic peptide, cRGDyK (cyclo Arg-Gly-Asp-d-Tyr-Lys), was developed in this work. Labeling reaction was optimized by conducting experiments under variable ratios of the reagents, the reaction times, and the pH. The study demonstrated that radiolabeling of the cyclic peptide was fast and pH independent. Monoiodinated and di-iodinated cRGDyK were formed under all conditions and varied with the ratio of the reagents and the reaction time. Total percent of the iodinated cRGDyK (monoiodinated and di-iodinated cRGDyK) varied between 44 and 100 depending on the reaction conditions. Excess cyclic peptide over equal molar ratio of sodium iodide and sodium hypochlorite yielded in predominant amounts of monoiodinated cRGDyK, ie, >60% under 2:1:1 ratio and ~88% under 5:1:1 ratio of cRGDyK:sodium iodide:sodium hypochlorite. [ABSTRACT FROM AUTHOR]

Numerous field studies highlighted the capacities of marine sponges to bioaccumulate trace elements and assessed their potential as biomonitors of the marine environment. Experimental works demonstrated that dissolved metals and radionuclides can be taken up directly by sponge tissues but, to the best of our knowledge, little is known on the contribution of the dietary pathway through the consumption of contaminated bacteria considered as one of the trophic source in sponge diet. Objectives of this work are to study trophic transfer of radiotracers 110m Ag, 241 Am, 109 Cd, 57 Co, 134 Cs, 54 Mn and 65 Zn from the marine bacteria Pseudomonas stutzeri to the Mediterranean sponges Aplysina cavernicola and Ircinia oros. P. stutzeri efficiently bioaccumulated trace elements in our culture experimental conditions with CF comprised between 10 5 and 10 7 after 48 h of growth in radiolabeled medium. When fed with these radiolabelled bacteria, A. cavernicola took up around 60% of radiotracers accumulated in trophic source except 134 Cs for which only 8% has been transferred from bacteria to sponge. Contrasting to this, I. oros retained only 7% of 110m Ag, 109 Cd and 65 Zn counted in bacteria, but retained 2-fold longer accumulated metals in its tissues. The sponge inter-specific differences of accumulation and depuration following a trophic exposure are discussed with respect to the structure and the clearance capacities of each species. [ABSTRACT FROM AUTHOR]

Ploidy affects the amount of DNA per cell. Because phosphorus (P) is required for building DNA, polyploids should have higher P content and be more sensitive to dietary P limitation. Such differences could be due to some combination of differential incorporation and excretion of P. We tested these predictions using diploids and polyploids of the zooplankter Daphnia pulex. After manipulating the P content of natural seston, we fed it to diploids and polyploids and quantified growth and %P. Although neither growth nor %P differed significantly with ploidy, polyploids tended to grow faster on P-spiked seston. Laboratory experiments on four genotypes using Scenedesmus algae cultured under low (LoP) and high (HiP) phosphorus supplies revealed significant P treatment by ploidy interactions in both growth and %P, with polyploids growing faster in HiP, and containing more P in LoP. Radiotracer assays revealed that polyploids incorporated significantly more 33P and excreted significantly less 33P compared with diploids. Ploidy-specific P use could interact with environmental P supply to affect the fitness of genotypes differing in ploidy level. Further, these results indicate unique ecological functions (i.e. P recycling) of lineages differing in ploidy level that should be generally applicable to taxa that have undergone whole-genome duplications. [ABSTRACT FROM AUTHOR]

The relationship between the particulate matter in the atmosphere of Malaga and the origin of air masses with special attention to African intrusions was analyzed. The concentrations of PM10 and the activities of some radionuclides ( 7 Be and 210 Pb) as tracers of these intrusions are discussed. The origin of these radiotracers is completely different. 210 Pb is a good tracer of air masses traveling close to the ground and come from inland areas. On the other hand, the production of 7 Be is very low in the vicinity of the Earth's surface, and increases with altitude, making it a great tracer of stratospheric air masses in the troposphere. Studies of radionuclide activities in aerosol particles provide a means for evaluating the integrated effects of transport and meteorology on the atmospheric loadings of substances with different sources. Measurements of aerosol mass concentration and specific activities of 7 Be and 210 Pb in aerosols at Malaga (36° 43′ 40″ N; 4° 28′ 8″ W) for the period 2009–2011 were used to obtain the relationships between radionuclide activities and airflow patterns by comparing the data grouped by air mass trajectory. The average concentration values of 7 Be and 210 Pb over the 3-year period have been found to be 5.05 and 0.55 mBq m −3 , respectively, with mean aerosol mass concentration of 53.6 μg m −3 . Taking into account the outbreaks of the daily values limits of PM10 in the study period (2009–2011), the origin of air masses is studied to explain three different situations of both radionuclides 7 Be and 210 Pb: 1) high concentrations of 7 Be and low concentrations of 210 Pb; 2) high concentrations of 210 Pb and low concentrations of 7 Be and 3) high concentrations of 7 Be and 210 Pb. [ABSTRACT FROM AUTHOR]

[11C]Methylation ( t1/2 = 20.4 min) is a main labeling strategy for the development of PET (positron emission tomography) radiotracers. A straight radiomethylation of amines with cyclotron-produced 11CO2 has been developed to obtain various radiolabeled compounds with good radiochemical yields. This strategy is a new approach to simplifying radiolabeling processes and transpositions onto automatic synthesizers and has been applied to the synthesis of radiolabeled drugs and a PET radiotracer used in the study of Alzheimer's disease. [ABSTRACT FROM AUTHOR]

The lack of specificity of traditional cytotoxic drugs has triggered the development of anticancer agents that selectively address specific molecular targets. An intrinsic property of these specialized drugs is their limited applicability for specific patient subgroups. Consequently, the generation of information about tumor characteristics is the key to exploit the potential of these drugs. Currently, cancer stratification relies on three approaches: Gene expression analysis and cancer proteomics, immunohistochemistry and molecular imaging. In order to enable the precise localization of functionally expressed targets, molecular imaging combines highly selective biomarkers and intense signal sources. Thus, cancer stratification and localization are performed simultaneously. Many cancer types are characterized by altered receptor expression, such as somatostatin receptors, folate receptors or Her2 (human epidermal growth factor receptor 2). Similar correlations are also known for a multitude of transporters, such as glucose transporters, amino acid transporters or hNIS (human sodium iodide symporter), as well as cell specific proteins, such as the prostate specific membrane antigen, integrins, and CD20. This review provides a comprehensive description of the methods, targets and agents used in molecular imaging, to outline their application for cancer stratification. Emphasis is placed on radiotracers which are used to identify altered expression patterns of cancer associated markers. [ABSTRACT FROM AUTHOR]

Introduction In this study two 111 In-labeled dimeric cyclic RGD peptides, 111 In(DOTA-Galacto-RGD 2 ) and 111 In(DOTA-3P-RGD 2 ), were evaluated as radiotracers for breast tumor imaging. The objective was to evaluate the impact of SAA, PEG 2 and 1,2,3-triazole linkers as compare to PEG 4 on the tumor uptake and excretion kinetics of 111 In radiotracers. Methods DOTA-Galacto-RGD 2 was prepared by conjugation of Galacto-RGD 2 with DOTA-OSu in the presence of diisopropylethylamine. Its integrin α v β 3 binding affinity was determined using a whole-cell displacement assay against 125 I-echistatin bound to U87MG glioma cells, and was compared with those of c(RGDfK), DOTA-3P-RGD 2 and DOTA-3P-RGK 2 (a nonsense peptide conjugate with “scrambled” RGK sequences). 111 In(DOTA-Galacto-RGD 2 ) and 111 In(DOTA-3P-RGD 2 ) were prepared and evaluated for their tumor-targeting capability and biodistribution properties in athymic nude mice bearing MDA-MB-435 breast tumor xenografts. Planar imaging studies were performed to demonstrate the utility of 111 In(DOTA-Galacto-RGD 2 ) and 111 In(DOTA-3P-RGD 2 ) for breast tumor imaging. Results IC 50 values of DOTA-Galacto-RGD 2 , DOTA-3P-RGD 2 , and DOTA-3P-RGK 2 were calculated to be 27 ± 2, 29 ± 4, 596 ± 48 nM, respectively. The tumor uptake values of 111 In(DOTA-Galacto-RGD 2 ) (6.79 ± 0.98, 6.56 ± 0.56, 4.17 ± 0.61 and 1.09 ± 0.13 %ID/g at 1, 4, 24 and 72 hours p.i., respectively) were almost identical to those of 111 In(DOTA-3P-RGD 2 ) (6.17 ± 1.65, 5.94 ± 0.84, 3.40 ± 0.50 and 0.99 ± 0.20 %ID/g, respectively). 111 In(DOTA-Galacto-RGD 2 ) had a faster clearance from blood and muscle than 111 In(DOTA-3P-RGD 2 ), leading to higher tumor/blood and tumor/muscle ratios. 111 In(DOTA-3P-RGD 2 ) had lower liver uptake and better tumor/liver ratios than 111 In(DOTA-Galacto-RGD 2 ). The tumor uptake of 111 In(DOTA-Galacto-RGD 2 ) and 111 In(DOTA-3P-RGD 2 ) was both integrin α v β 3 and RGD-specific. Imaging data suggest that 111 In(DOTA-Galacto-RGD 2 ) and 111 In(DOTA-3P-RGD 2 ) are useful as radiotracers for imaging integrin α v β 3 -positive breast tumors. Conclusion The results from this study suggest that replacing PEG 4 linkers between two RGD moieties with a pair of SAA, PEG 2 and 1,2,3-triazole groups has little impact on integrin α v β 3 binding affinity and tumor uptake of 111 In-labeled dimeric cyclic RGD peptides. Despite the subtle differences in their excretion kinetics from noncancerous tissues, 111 In(DOTA-Galacto-RGD 2 ) and 111 In(DOTA-3P-RGD 2 ) are useful radiotracers for imaging integrin α v β 3 -positive breast tumors. [ABSTRACT FROM AUTHOR]

This paper presents a study on the fouling of ceramic microfiltration (MF) membrane. Such membranes are often used in the treatment of liquid radioactive waste. In the investigation of the phenomenon of fouling, a radiotracer method with a short-lived lanthanum isotope (140La) is applied. The effect of the molecular weight (MW) of the complexing agent, used to bind the radionuclides in the MF-enhanced process, was studied in radiotracer experiments. Poly(acrylic acid) with a MW of 30 kDa, 100 kDa and 250 kDa is used as the complexing agent. The distribution of particles with different MWs at various positions along the membrane module is examined. The test results show that the particles with the lowest MW (i.e. 30 kDa) blocks the membranes the quickest, causing the greatest decrease in the permeate flux. However, the amount of deposit formed on the membrane, which is reflected by the level of radioactivity measured, is the lowest in this case. This indicates the existence of different membrane blocking mechanisms, which depend on the size of the particles contained in the filtered medium. [Display omitted] • Fouling of membranes used for LRW treatment was studied by the radiotracer method. • The polyacrylic acid (PAA) with different MWs was used as a model fouling agent. • The effect of MW of PAA on particles distribution along the membrane was examined. • The PAA molecules with the lowest MW blocked the membrane surface the fastest. • Different mechanisms of fouling can occur depending on the MW of PAA. [ABSTRACT FROM AUTHOR]

The objective of this study was to develop a kit formulation for [99mTcN(mpo)(PNP5)]+ (MPO = 2-mercaptopyridine oxide), (99mTcN-MPO) to support its clinical evaluations as a SPECT radiotracer. Radiolabeling studies were performed using three different formulations (two-vial formulation and single-vial formulations with/without SnCl2) to explore the factors influencing radiochemical purity (RCP) of 99mTcN-MPO. We found that the most important factor affecting the RCP of 99mTcN-MPO was the purity of PNP5. 99mTcN-MPO was prepared >98% RCP (n = 20) using the two-vial formulation. For single-vial formulations with/without SnCl2, β-cyclodextrin (β-CD) is particularly useful as a stabilizer for PNP5. The RCP of 99mTcN-MPO was 95-98% using β-CD, but its RCP was only 90-93% with γ-cyclodextrin (γ-CD). It seems that PNP5 fits better into the inner cavity of β-CD, which forms more stable inclusion complex than γ-CD in the single-vial formulations. The results from biodistribution and imaging studies in Sprague-Dawley rats clearly demonstrated biological equivalence of three different formulations. Single photon-emission computed tomography data suggested that high quality images could be obtained at 0-30-min post-injection without significant interference from the liver radioactivity. Considering the ease for 99mTc-labeling and high RCP of 99mTcN-MPO, the non-SnCl2 single-vial formulation is an attractive choice for future clinical studies. [ABSTRACT FROM AUTHOR]

An overview of the modified radiotracer based diffusion studies carried out at IGISOL is provided. The experimental procedures are briefly described followed by examples involving IGISOL as the key facility. In this respect the studies related to silicon-germanium (Si 1 − xGe x) alloys and on the related diffusion systematics are summarized. Another group of examples is related to mobility determination of lead isotopes in glass for verifying retrospective radon measurements. Finally an outlook to future possibilities related to employing radiotracers in solid state research is provided. [ABSTRACT FROM AUTHOR]

Mangrove sediment cores sampled from Sepetiba Bay (SE Brazil) were covered with tidal water spiked with Se, Cr and Co to evaluate the removal efficiency of these radiotracers by underlying sediments. Variable time-evolution trends were observed along 115 h experiments, with significant differences between removal efficiencies of all radiotracers observed only after 70 h (Cr > Co > Se). After an event of Co release back to overlying water, there was a general trend of lower Co removal than observed for other radiotracers during the period from 20 to 54 h. After this event, alternated periods of higher Co and higher Se removal trends were observed, attributed to behavioural differences expected for such anionic and cationic radiotracers. While Se and Cr showed uniform time-evolution curves, as typically found in the literature for most radiotracers, Co removal rates presented oscillations, probably due to sensitivity to changes in redox conditions within underlying sediments. Results evidenced the role of mangrove sediments as trace element sinks, which have implications for coastal water quality and for possible uses of such sediments in wastewater treatment systems. [ABSTRACT FROM AUTHOR]

Abstract: In Nuclear Medicine, radioiodine, in various chemical forms, is a key tracer used in diagnostic practices and/or therapy. Medical professionals may incorporate radioactive iodine during the preparation of the dose to be administered to the patient. In radioactive iodine therapy doses ranging from 3.7 to 7.4GBq per patient are employed. Thus, aiming at reducing the risk of occupational contamination, we developed a low cost filter to be installed at the exit of the exhaust system (where doses of radioiodine are handled within fume hoods, and new filters will be installed at their exit), using domestic technology. The effectiveness of radioactive iodine retention by silver impregnated silica [10%] crystals and natural activated carbon was verified using radiotracer techniques. The results showed that natural activated carbon and silver impregnated silica are effective for I2 capture with large or small amounts of substrate but the use of activated carbon is restricted due to its low flash point (423K). Besides, when poisoned by organic solvents, this flash point may become lower, causing explosions if absorbing large amounts of nitrates. To hold the CH3I gas, it was necessary to use natural activated carbon since it was not absorbed by SiO2+Ag crystals. We concluded that, for an exhaust flow range of (145±2)m3/h, a double stage filter using SiO2+Ag in the first stage and natural activated carbon in the second stage is sufficient to meet radiological safety requirements. [Copyright &y& Elsevier]

Isotopes have played an important role in chemistry, biology, and medicine. For the last three decades, we have focused on the use of organoboron compounds as precursors to isotopically labeled physiologically active reagents. During that period, we have successfully developed methods for incorporating short- and long-lived isotopes of carbon, nitrogen, oxygen, and the halogens using a variety of reactive organoboron precursors. In addition, labeling strategies employing polymer-supported organoboron derivatives were developed. In this report, we present a short overview focused on the evolution of radiolabeling techniques based on boron chemistry. [ABSTRACT FROM AUTHOR]

Microcosm experiments on the behaviour of Se, Cr and Co were carried out with mangrove sediments from Sepetiba Bay, Brazil. Three 8-cm length sediment cores were covered with tidal water spiked with Se, Cr and Co to evaluate its behaviour within the sediments. Two cores retained almost all activities (99-100 %) within the uppermost centimetre layer, while the third core presented a deeper penetration of all radiotracers, displaying a second activity peak at the 3-4-cm depth interval, which evidenced benthic fauna bioturbation influence. This influence extended the diffusion into depths in which mangrove rhizosphere can retain the elements, suggesting increased retention efficiency. This mechanism of retention enhancement was proposed in addition to previous conceptual models describing trace elements behaviour in mangrove sediments. Increased bioturbation and rhizosphere development will probably increase this effect, while mangrove plant cover losses may promote a less efficient retention of elements recently diffused from tidal water. [ABSTRACT FROM AUTHOR]