Size Distribution Of Radioactive Particles Research Articles

Preparation of 68 Ga-Mg-Ca-phytate colloid and its evaluation as a liver imaging agent.

The objective of this study was to investigate the radiosynthesis of 68 Ga-Mg-Ca-phytate colloid and then characterise the formulation for radiochemical purity (RCP), radioactive particle size distribution, and biodistribution in normal rats. This radiocolloid was prepared by mixing an aqueous solution of phytic acid, 68 Ga3+ ions, a dispersant, Mg2+ and Ca2+ ions, and then heating the contents at 100°C for 5minutes. After cooling the vial to 5°C, the solution was basified to pH5 and stored in the cold. The resulting product contained 92±3% RCP 68 Ga-colloidal particles and a low level (8±3%) of soluble 68 Ga-Mg-Ca-phytate. Particle size experiments defined the radioactive particle population was 6±4% <20nm, 90±6% 20 to 200nm, and 4% were >200nm in diameter. Intravenous injection of the 68 Ga-colloid dispersion to rats resulted in 93% uptake by the liver plus spleen, 1% lungs, 1% total blood, and 6% in the carcass after 20minutes. This optimal formulation remained stable at 5°C for 1½hours in vitro, and it resulted in the same biodistribution as the formulation prepared at t=0hours. The preclinical data so far indicate that 68 Ga-Mg-Ca-colloid has excellent potential as a liver imaging agent.

68 Ga-Ca-phytate particles: A potential lung perfusion agent of synthetic origin prepared in a cold kit format.

The objective of this study was to investigate the radiosynthesis of 68 Ga-Ca-phytate particles and then characterize the formulation for radiochemical purity, radioactive particle size distribution, and biodistribution in normal rats. This radiotracer was prepared using a commercial phytate cold kit after reconstitution with saline, 68 Ga-chloride generator eluent, calcium chloride, and air, then heating at 100°C for 30minutes to achieve 99% radiochemical purity of 68 Ga-particles that were 21% 3-5μm, 8% 5-15μm, and 71% >15μm in diameter. This optimal formulation was stable for 2hours at room temperature. Intravenous administration of 68 Ga-particles in rats resulted in an uptake of 93% in the lungs, 4% in the liver plus spleen, and 3% in the carcass after 20minutes. Two-thirds of the carcass activity was radioactive blood, likely to be 68 Ga-transferrin. The positron emission tomography image was superior than the 99m Tc-MAA image because it displayed high lung uptake against a low background. Low uptake by the liver, spleen did not interfere with the diagnostic quality, and faint activity in the submandibular (salivary) glands was due to 68 Ga-transferrin. The preclinical data so far indicate that 68 Ga-Ca-phytate particles have good potential as a lung perfusion imaging agent.

The influence of particle size distribution on dose conversion factors for radon progeny in the underground excavations of hard coal mine

In Polish underground mines, hazards caused by enhanced natural radioactivity occur. The sources of radiation exposure are short-lived radon decay products, mine waters containing radium 226Ra and 228Ra and the radioactive sediments that can precipitate out of these waters. For miners, the greatest exposure is usually due to short-lived radon decay products. The risk assessment is based on the measurement of the total potential alpha energy concentration (PAEC) and the evaluation of the related dose by using the dose conversion factor as recommended by relevant legal requirements. This paper presents the results of measurements of particle size distributions of ambient aerosols in an underground hard coal mine, the assessment of the radioactive particle size distribution of the short-lived radon decay products and the corresponding values of dose conversion factors. The measurements of the ambient airborne particle size distribution were performed in the range from a few nanometers to about 20 μm. The study therefore included practically the whole class of respirable particles. The results showed that the high concentration of ultrafine and fine aerosols measured can significantly affect the value of the dose conversion factors, and consequently the corresponding committed effective dose, to which the miners can be exposed.

A study of radiogallium aqueous chemistry: in vitro and in vivo characterisation of (67) Ga-hydrolysed-stannous fluoride particles.

The objective of this study was to explore the aqueous chemistry of gallium using (67) Ga-chloride starting material, by radiolabelling hydrolysed(h)-stannous fluoride particles and then characterising the optimal formulation for radiochemical purity (RCP) and radioactive particle size distribution in vitro. The pilot reactions determined stannous fluoride was added to (67) Ga-acetate under nitrogen and then heated at 100 °C for 20 min to achieve ≥95% RCP and (67) Ga-particles were >3 µm in diameter. A high radioactive concentration of (67) Ga-h-SnF2 particles could be prepared similarly in ≥97% RCP with 74% as 3-5 µm and 26% >5 µm in diameter. The latter formulation had larger particles than (99m) Tc-h-SnF2 colloid (96% of 1-3 µm), and it resulted in a rat biodistribution of 41% in the lungs, 41% in the liver plus spleen and 18% in the carcass at 20 min after injection. The carcass activity was attributed to bone marrow and some (67) Ga-transferrin formed in blood. Isolated mixed human leucocytes were radiolabelled with (67) Ga-h-SnF2 particles in 100% efficiency, and the (67) Ga-cells did not release soluble (67) Ga(3+) at room temperature over 3 h. The (67) Ga-h-SnF2 particle formulation could find a use in labelling leucocyte cells for in vivo homing studies when delayed animal imaging is required.

Size distribution of radioactive particles collected at Tokai, Japan 6 days after the nuclear accident

Airborne radioactive particles released by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in 2011 were collected with a cascade low-pressure impactor at the Japan Atomic Energy Agency (JAEA) in Tokai, Japan, 114 km south of the FDNPP. Size-fractionated samples were collected twice, in the periods of March 17–April 1, 2011, and May 9–13, 2011. These size-fractionated samplings were carried out in the earliest days at a short distance from the FDNPP. Radioactivity of short-lived nuclides (several ten days of half-life) was determined as well as 134Cs and 137Cs. The elemental composition of size-fractionated samples was also measured. In the first collection, the activity median aerodynamic diameter (AMAD) of 129mTe, 140Ba, 134Cs, 136Cs and 137Cs was 1.5–1.6 μm, while the diameter of 131I was 0.45 μm. The diameters of 134Cs and 137Cs in the second collection were expressed as three peaks at <0.5 μm, 0.94 μm, and 7.8 μm. The 134Cs/137Cs ratio of the first collection was 1.02 in total, but the ratio in the fine fractions was 0.91. A distribution map of 134Cs/137Cs – 136Cs/137Cs ratios was helpful in understanding the change of radioactive Cs composition. The Cs composition of size fractions <0.43 μm and the composition in the 1.1–2.1 μm range (including the AMAD of 1.5–1.6 μm) were similar to the calculated compositions of fuels in the reactors No. 1 and No. 3 at the FDNPP using the ORIGEN-II code. The Cs composition collected in May, 2011 was similar to the calculation results of reactor No. 2 fuel composition. The change of Cs composition implies that the radioactive Cs was released from the three reactors at the FDNPP via different processes.

A potential lung perfusion imaging agent of synthetic origin

Abstract99mTc‐labelled macroaggregated albumin (MAA) is the radiopharmaceutical routinely used for perfusion lung scans. However MAA formulations contain excipients of biological origin, that may potentially cause allergic hypersensitivity in patients. The aim of this study was to prepare a non‐biological lung imaging agent, with physiological uptake based on a mechanism of colloid localisation in the pulmonary vasculature. To a frozen stannous fluoride cold kit (RAH Radiopharmacy) was added 99mTc‐pertechnetate (⩽2 GBq) in saline (1–4 ml), and the radioactive contents were mixed by rotation (40 rpm) in a syringe at room temperature for 30–180 min. The preparative conditions were varied to control particle growth by: the addition of metal ions, halide ions, or oxidants; different mixing times; and temperatures. The 99mTc products were analysed for % radiolabelling efficiency (RE), radioactive particle size distribution (RPSD), qualitative and quantitative rat biodistribution studies. Results indicated that all radioactive particles were formed with &gt;99% RE, and 1–47% were &gt;8 µm. The optimum radiotracer formulation containing the highest proportion of the largest particles, was prepared by mixing SnF2 and 99mTc‐pertechnetate with a low [Na+] at room temperature for 50 min. Results from the quantitative organ assays gave 88±1% tracer in the lungs, and less than 10% in the liver and spleen. The images showed excellent, uniform lung uptake with minimal interference from liver and spleen to the lower regions of right and left lobes. In conclusion, the synthetic radiopharmaceutical 99mTc–tin fluoride colloid can be prepared with a large particle size, from a commercially available cold kit in a simple and practical manner, and it has good potential for use as a perfusion imaging agent in lung scans. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Physico-chemical characterisation of99mTc-tin fluoride colloid agent used for labelling white cells

99mTc–tin fluoride colloid is an agent used to label leucocytes, for the imaging and diagnosis of inflammatory conditions including Crohn's disease. Despite previous investigations, this radiolabelling agent is still poorly characterised. The aim of this work was to examine the process of formation and stability of 99mTc–tin fluoride colloid using mass spectrometry, membrane filtration and atomic absorption spectrophotometric techniques. Tin-oxide bonds in tin clusters were identified in the stannous fluoride reagent vial by mass spectrometry. From radioactive particle size distribution experiments, the facile disruption of radiocolloid particles with excess oxygen gas contrasted to the partial hydrolysis of Sn(II) during the formation process. Under the standard conditions, 10% of particles were determined as 1–3 µm, and this population coordinated 96% of the 99mTc added. Colloid particle formation and the reduction of 99mTc-pertechnetate is discussed. Sodium fluoride may optimise 1–3 µm radioactive particle size, by regulating particle growth. 99mTc–tin fluoride colloid is affected by positive or negative charge, as either Al, Mo ions or solid membranes, resulting in either coagulation and/or deflocculation of the particles. Copyright © 2006 John Wiley & Sons, Ltd.

Variations in radionuclide concentrations and size distribution of radioactive particles from the Chinese nuclear weapon test of October 16, 1980

Debris from Chinese twenty-sixth nuclear explosion test (October 16, 1980) was collected by a high volume air sampler equipped with five-stage cascade impactors at the ground level in Fukuoka, Japan. The variations of radionuclide concentrations were measured for a period of about ten months following the test. The fallout seemed to be injected into the lower stratosphere as well as the troposphere because the effect persisted for about eight months until June 1981. The141Ce/95Zr and141Ce/144Ce of the particles smaller than 1.1 μm were relatively constant in spite of different collection periods. However, in the particle range larger than 1.1 μm, depletion of141Ce atom was observed and it was greater in the larger particles, but it reached gradually a constant value as time passed. This variation pattern was explained by the time difference between particle formation and detonation and the height of the fireball when the particles were formed.

The size distribution of radioactive particles from nuclear weapon tests and their transport in the atmosphere

The size distribution of radioactive particles from nuclear weapon tests and their transport in the atmosphere

The size distribution of radioactive particles from nuclear weapon tests and their transport in the atmosphere

In 1964–1965 in the Moscow region radioactive particle size distribution was studied in the ground layer of the atmosphere and in December, 1964, measurements were carried out at 5–6 km as well. Four kinds of radioactive aerosol size distribution variations were observed. In the troposphere at 5–6 km radioactive particles were on the average smaller than in the ground layer. The mean diameter of particles-carriers of Cs137 at 5–6 km was greater than that of particles-carriers of Ce144. This difference was smoothed in the samples, taken at the ground surface. Analysis of literature data on variations of ratios of various isotope concentrations was made. It shows that radioactive particle size distribution significantly effects the transport of these particles in the atmosphere, especially in the higher layers of the stratosphere and in the mesosphere. DOI: 10.1111/j.2153-3490.1966.tb00260.x