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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]

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]

Radioactive Particle Tracking (RPT) is a non-invasive measurement technique used to reconstruct the Lagrangian particle field inside a fluid flow. This technique tracks the trajectories followed by radioactive particles that move along the fluid, and it is based on the counts registered by radiation detectors that are placed strategically around the boundaries of the system. The aim of this paper is to develop a low-budget RPT system proposed by the Departamento de Ciencias Nucleares of the Escuela Politécnica Nacional and to generate a GEANT4 model of it for optimizing its design. This system is based on the usage of the minimum amount of radiation detectors required to track a tracer and on the innovative idea of calibrating them with moving particles. To achieve this, energy and efficiency calibrations were performed with a single NaI detector, and their results were compared with the results generated with a GEANT4 model simulation. As a result of this comparison, another methodology was proposed to add the effects of the electronic detector chain in the simulated results by a Detection Correction Factor (DCF) without further C++ coding in GEANT4. Next, the NaI detector was calibrated for moving particles. For this purpose, a single NaI was used in different experiments to analyze the influence of particle velocity, data acquisition systems, and radiation detector position along the x-axis, y-axis, and z-axis. Finally, these experiments were simulated in GEANT4 to improve the digital models. Particle positions were reconstructed based on the generation of Trajectory Spectrum (TS) which gives a specific count rate for each particle position as it moves on the x-axis. The magnitude and shape of TS were compared with DCF corrected simulated data and experimental results. This comparison showed that the variation of detector position along the x-axis changed the shape of TS, while the variation of the location along the y-axis and z-axis reduced the sensitivity of the detector. The existence of an effective zone of the detector location was identified. At this zone, the TS shows high changes in the count rate for low changes of particle position. Based on the overhead of the TS, it was demonstrated that this RPT system must employ at least 3 detectors to have capabilities to predict particle positions. • Trajectory Spectra are used to predict particle position in a proposed RPT system. • Trajectory Spectra have flat and effective zones that can be used to track a particle. • An RPT system needs several detectors to have redundant information. • Reducing the detector number is one feasible way to make low-cost RPT 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]

Abstract: The possibility of application of fluorescein and radioactive 99mTc as tracers for determination of residence time distribution of liquid phase and for diagnosing hydrodynamic conditions in apparatuses for membrane separation was studied. Two different ultrafiltration systems with diverse arrangement of liquid flow: the apparatus with helical flow generated by the movable element (inner cylinder) and the tubular module with cross flow filtration, were tested by the RTD technique. The tracer studies were supplemented with modelling. The optimal conditions enabling to handle the plug flow-like structure in the helical apparatus were determined. The minimum of dimensionless variance (vard) was obtained at P=0.765bar, Q R =121.88l/h and Ω=2887.5rpm. In spite of higher linear velocities attained in the tubular cross-flow module, the flow structure in the helical apparatus was more similar to the ideal plug flow pattern that was demonstrated by higher Peclet numbers and lower values of the dimensionless variance. Application of movable part and Couette–Taylor flow in the membrane apparatus may balance the advantages coming from high flow rates applied in cross-flow filtration systems minimising formation of the deposit on the membrane surface and reducing membrane fouling. [Copyright &y& Elsevier]

Abstract: Carbon-11-labeled tricyclic necroptosis inhibitors were first designed and synthesized as new potential PET agents for imaging of tumor necrosis factor α (TNF-α). The target tracers were prepared by O-[11C]methylation of their corresponding precursors using [11C]CH3OTf under basic conditions and isolated by a simplified SPE method in 50–60% radiochemical yields based on [11C]CO2 and decay corrected to end of bombardment (EOB). The overall synthesis time from EOB was 15–20min, the radiochemical purity was >99%, and the specific activity at end of synthesis (EOS) was 111–185GBq/μmol. [ABSTRACT FROM AUTHOR]

Abstract: Carbon-11-labeled tariquidar derivatives were first designed and synthesized as new PET agents for imaging of breast cancer resistance protein. The target tracers were prepared by O-[11C]methylation of their corresponding acid precursors using [11C]CH3OTf under basic conditions and isolated by a simplified solid-phase extraction (SPE) method in 50–60% radiochemical yields based on [11C]CO2 and decay corrected to end of bombardment (EOB). The overall synthesis time from EOB was 15–20min, the radiochemical purity was >99%, and the specific activity at end of synthesis (EOS) was 111–185GBq/μmol. [Copyright &y& Elsevier]

Abstract: Carbon-11-labeled piperidine ring of N-[ω-(6-methoxynaphthalen-1-yl)alkyl] derivatives were first designed and synthesized as new selective PET σ 1 receptor probes. The target tracers were prepared by O-[11C]methylation of their corresponding phenolic hydroxyl precursors using [11C]CH3OTf under basic conditions and isolated by a simplified SPE method in 40–50% radiochemical yields based on [11C]CO2 and decay corrected to EOB. The overall synthesis time from EOB was 15–20min, the radiochemical purity was >99%, and the specific activity at EOS was 111–185GBq/μmol. [Copyright &y& Elsevier]

Abstract: Carbon-11-labeled 4-aryl-4H-chromenes, 2-amino-7-(dimethylamino)-4-(3-[11C]methoxy-5-methoxyphenyl)-4H-chromene-3-carbonitrile ([11C]6a), 2-amino-4-(3-bromo-4-[11C]methoxy-5-methoxyphenyl)-7-(dimethylamino)-4H-chromene-3-carbonitrile ([11C]6c), 2-amino-4-(3-[11C]methoxy-5-methoxyphenyl)-4,7-dihydropyrano[2,3-e]indole-3-carbonitrile ([11C]6d), 2-amino-4-(3-bromo-4-[11C]methoxy-5-methoxyphenyl)-4,7-dihydropyrano[2,3-e]indole-3-carbonitrile ([11C]6f), 2-amino-4-(3-[11C]methoxy-5-methoxyphenyl)-4,9-dihydropyrano[3,2-g]indole-3-carbonitrile ([11C]6g), 2-amino-4-(3-bromo-4-[11C]methoxy-5-methoxyphenyl)-4,9-dihydropyrano[3,2-g]indole-3-carbonitrile ([11C]6i), 2-amino-4-(3-[11C]methoxy-5-methoxyphenyl)-7-methyl-4,7-dihydropyrano[2,3-e]indole-3-carbonitrile ([11C]6j) and 2-amino-4-(3-bromo-4-[11C]methoxy-5-methoxyphenyl)-7-methyl-4,7-dihydropyrano[2,3-e]indole-3-carbonitrile ([11C]6l), were prepared by O-[11C]methylation of their corresponding precursors using [11C]CH3OTf under basic conditions and isolated by a simplified solid-phase extraction (SPE) method in 30–50% radiochemical yields based on [11C]CO2 and decay corrected to end of bombardment (EOB). The overall synthesis time from EOB was 15–20min, the radiochemical purity was >99%, and the specific activity at end of synthesis (EOS) was 111–185GBq/μmol. [Copyright &y& Elsevier]