International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes最新文献

Because of the widespread use of 2-deoxy-2-[¹⁸F]fluoro-d-glucose (FDG) prepared by the “Julich” method or its variants it was decided necessary to determine the major chemical impurities present in the final product. An analytical system for quantifying FDG was developed using pulsed amperometry after separation by high-performance anion exchange chromatography. With this system a heretofore unidentified impurity, 2-deoxy-2-chloro-d-glucose (ClDG, ca 20–2000 μg; typically < 100 μg), was found in our preparation and in those from other laboratories using the “Julich” method. ClDG arises from Cl⁻ ion displacement during the labeling procedure where Cl⁻ ion comes from several sources, and Cl⁻ ion displacement from the HCl used in the hydrolysis step. FDG mass was present in the same preparations at a level of ca 1–40 μg. Other major chemical constituents were glucose (ca 1–6 mg) and mannose (ca 10–18 μg). Glycerol, arising from sterilizing filters, was also detected in most preparations.

Although ClDG is a chemical impurity which has not been detected previously in nca FDG preparations, its biochemical and pharmacological properties are similar to FDG and 2-deoxy-d-glucose. Thus it is unlikely that the presence of small quantities of ClDG found in typical FDG preparations (ca 100 μg) would have adverse pharmacological or toxicological consequences that would limit continued application of this radiopharmaceutical in basic and clinical studies.

The energy transfer rate parameter K₃ and the quenching rate parameter K_7b are determined in a liquid scintillator system consisting of 2,5-di-[5-tertbutyl-2-benzoxazolyl)-thiophene (BBOT) as solute, toluene as solvent and bromobenzene as external solvent quencher in three different media; neat toluene (TN), dilute mixture 1:9 by volume fraction to toluene to cyclohexane (TC) and toluene to liquid paraffin (TP), in the temperature range 20°–70°C (viscosity range 0.35–39.0 cp). The results are discussed in terms of the role of diffusion, migration and long-range dipole-dipole interaction of Forster type in these three systems.

Measurements of coincidences between conversion electrons of the 88 keV transition in the ¹²³Te^m decay and subsequent 159 keV quanta have been made with a 4πβ-γ coincidence system equipped with a pressurized proportional counter (PPC) in the beta channel. With ¹²³Te^m sources prepared for activity determination, a detection probability for conversion electrons, ϵ, very close to ϵ = 1 was achieved. The following data have been derived from the slope of a polynomial fit to n_βn_γ/n_c vs (1 − ϵ)/ϵ by varying ϵ by discrimination and taking into account the γ sensitivity of the PPC (n_β, n_γ, n_c are the counting rates in the β, γ and coincidence channel): the total conversion coefficient of the 159 keV transition α_t = 0.1895(13), the γ-ray emission probability of the 159 keV photons p = 0.8407(9). These data agree with the theoretically calculated values, and with less accurate values determined experimentally by other authors.

The reduction of nitrate to nitrite is studied by the transfer of energy stored in γ-irradiated NaCl crystals to aqueous ammonium nitrate solution. The G(NO₂⁻) values are evaluated under varying conditions of energy transfer from γ-irradiated NaCl crystals. Similarly, the G(NO₂⁻) value for direct radiolysis of 0.1 M aqueous ammonium nitrate solution is determined. The efficiency of energy transfer is the ratio of the G-values of the two pathways. The efficiency is 60% at low doses. It is explained on the basis of two processes. The first process depends upon the extent to which the energy can be stored in irradiated NaCl crystals, while the second process of energy transfer is governed by various parameters which limit the yield of nitrite.

Basic characteristics of different batches of Radix RN15® dosimeter, a commercially available undyed polymethylmethacrylate dosimeter, was studied for its application to process control of radiation sterilization. Radix has relatively small deviation of thickness, optical absorption spectrum, and optical density values before irradiation. The response curves, in terms of net optical density per unit thickness (ΔOD/mm) as a function of absorbed dose, D_PMMA, are nearly linear up to 15 kGy and become sublinear at higher doses. Scattering of dose response in 5 dosimeter replicates is ± 1% (1 σ). The dose-response slope at 25 kGy while held at irradiation temperatures in the range 0–60°C, relative to those under 25°C, increases with temperature up to 40°C, the maximum point, and decreases at higher temperatures. Over the temperature range of 10–50°C, the variation with temperature of evaluated dose derived from the calibration curve at 25°C is less than 5% when using a dose rate of 6 kGy/h. At lower dose rates (e.g. 0.7 kGy/h) the irradiation temperature dependence is negligible over this temperature range. The temperature dependence at 40 kGy is less severe than that at 25 kGy. The post-irradiation stability of dose response is less than 5% for more than 100 h after 25 kGy irradiation and storage at 0–35°C. The change in optical density of unirradiated dosimeters 3 years after manufacturing is negligible when the dosimeters are stored at controlled laboratory conditions of temperature (25°C) and relative humidity (40%). The 3-year-old dosimeters by irradiation to a dose of 25 kGy show about 2% lower response than that at 25 kGy at the beginning of the 3-year period.

Isotope separation with using light induced drift (LID) is discussed. Two basic theoretical characteristics of the method are deduced. I, separation simultaneously with an arbitrary high enrichment and without significant losses; 2, high separation productivity up to 100 μg/h. These characteristics are sufficient and very convenient for the separation of expensive radioactive isotopes and isomers for applications in medicine and science. The first experimental separation of the radioactive isotopes (^22,24Na) using the LID effect is reported.

The adsorption behaviour of Ba(II) on titanium(IV) oxide in an aqueous solution was studied by means of batch technique as a function of Ba(II) concentration, temperature and solution pH using Ba-140 as radiotracer. The results show that adsorption is essentially complete in ca 2 h and that the steady state values of adsorption at various concentrations agree well with the classical Freundlich isotherm and follow first order kinetics. The pH and temperature of the solution markedly affect the extent of adsorption. The nature and mechanism of adsorption are discussed.

Unlike neutrons or gamma-rays, charged particles readily lose energy when they penetrate matter; thus, the main difficulty in its calculation is, perhaps, the complication introduced in its mathematical treatment. In our experiments, determination of ¹³C in breath test samples by proton-induced gamma-ray emission, interesting regularities were found that allowed drastic simplification in the theoretical treatment of the problem, and led to the derivation from first principles of a simple, sufficiently accurate basic equation which proved reliable for the determination of the isotopic abundance ratio ${}^{13}\text{C}{}^{12}\text{C}$ by low-energy proton bombardment of biological samples with simultaneous prompt gamma spectrometry.