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

A commercially available, thin, dyed-plastic film (mean thickness 30 μm) having a transparent green color, changes color progressively to brown shades and then to a deep red shade upon irradiation at successively higher values of absorbed dose (gamma radiation) in the range 8–60 kGy. The analysis for dosimetry is made with spectrophotometric measurements (at visible light wavelengths) of pre-irradiation absorbance, A₀, and radiation-induced absorbance, A_i. Either the wavelength of the maximum of the absorption band that bleaches upon irradiation (γ = 425 nm) or the wavelengths of the maxima of the two overlapping radiation-induced absorption bands (γ = 525 or 556 nm) are used to make these measurements. The most reproducible calibration consists of the ratio, $\text{A}{}_{\mathrm{<mtext>i</mtext>}}\text{A}{}_0$, at a given wavelength, as a function of the absorbed dose. The new film dosimeter is flexible, rugged, and relatively stable at temperatures between −80°C and +50°C, and in daylight. The radiation-induced color, in terms of the absorbance, A_i, at selected wavelengths, is unstable for about two days subsequent to irradiation, after which the values of $\text{A}{}_{\mathrm{<mtext>i</mtext>}}\text{A}{}_0$ remain stable for at least several months, even under illumination with white fluorescent or indirect daylight. The film color is unstable at high temperatures (60°C and above). The film sensitivity to gamma radiation increases gradually with rise in irradiation temperature up to 50°C and then decreases sharply at temperatures above 60°C. There is only slight variation of response with change in relative humidity during irradiation.

The intensities of K x- and γ-rays emitted following the decays of ⁹⁹Mo and ¹¹¹Ag have been measured with better precision using four well calibrated semiconductor detectors. These intensity results have been further used to deduce the photon emission probabilities of various γ-transitions deexciting these radionuclides. The 158.9 and 162.5 keV γ-rays have been identified and placed through coincidence evidence to be in the level scheme of ⁹⁹Tc while 11 γ-rays, proposed in the earlier investigations of ⁹⁹Mo decay, have been discarded. This rules out the possibility of the existence of levels at 163, 727, 762 and 1082 keV. The intensities for K x-rays emitted following the decay of ¹¹¹Ag are reported for the first time.

A series of preparations of (3-$\text{N-}\text{[}{}^{11}\text{C]methyl)spiperone}$ in several basis conditions by means of an automated system incorporating an “on-line” methylation is reported. The radiochemical yield was observed to be strongly affected by the water content. For all the preparations the reaction temperature was 80°C and the reaction time 5 min. The influence of these two parameters on the radiochemical yield for the synthesis utilizing methanolic tetrabutylammonium hydroxide has been briefly examined.

The feeding pattern of the superdeformed band in ¹⁴⁸Gd has been found to remain essentially the same, using the ¹²²Sn (³⁰Si, Xn) ^152-xGd reaction, by varying the energy of the incident ³⁰Si between 150 and 166 MeV in steps of around 5 MeV, leading to different input angular momenta and excitation energies in the compound nuclear system. This similarity as well as the relative yields of the superdeformed states as a function of beam energy may be understood in terms of the nuclear level density dependence on deformation and the onset of fission. In addition, it has been shown that, at beam energies, the selection of high-energy gamma-rays does not enhance the yield of the superdeformed states.

An isotopic exchange method was used to label lipiodol with ¹³¹I. The labelling efficiency was > 92.5%, and the radiochemical purity of [¹³¹I]lipiodol was above 98% as determined by ITLC. The influencing factors e.g. the heating temperature, reaction time, pH and storage conditions were studied and the optimum conditions were determined.

In a pilot study injecting [¹³¹I]lipiodol for the treatment of hepatoma, about 70% of hepatoma patients had a response to the treatment with a reduction of α-fetoprotein and decrease of hepatoma sizes. The overall median survival was 9 months (range 2–17 months).

We have developed an improved ⁶²Cu-generator system based on a small (25 mm × 5 mm) ion exchange column which allows the instant production of ⁶²Cu-PTSM ready for injection.

The generator column can rapidly be eluted with a high yield in a volume of 1 mL to afford an eluate with largely acceptable radionuclidic purity. Collection of the eluate in a labelling kit which contains the PTSM ligand in an appropriate buffer allows to obtain in less than 30 s a highly pure ⁶²Cu-PTSM preparation that can be injected intravenously.

Zirconium-desferal was prepared and analysed by TLC, NMR and u.v.-spectroscopy. The stoichiometry of the complex was found to be 1:1. Chelation of desferal, coupled to resin, with ⁸⁸Zr appeared to be fast and almost quantitative in various buffer systems in a broad pH-range (4–7). A high in vitro stability of the zirconium-desferal complex was observed; less than 0.2% zirconium was lost within 24 h in plasma-solutions.

A reliable remote water target loading system has been designed and fabricated around the operation of a single pneumatic syringe dispenser that accesses one of two water reservoirs, filling one or more targets depending on the system configuration. For multiple radionuclide configuration, reservoirs are filled with ¹⁸O-enriched water for [¹⁸F]fluoride production, and natural abundance water for [¹³N]nitrate and [¹³N]nitrite production. When actuated, the system withdraws a calibrated volume of water from a selected reservoir, and automatically dispenses that charge through a short transfer line to the appropriate target. A second actuation then forces the dispenser to purge itself of residual water by dispensing a charge of helium gas through the same line thus completing the transfer of water to the target volume. Direct liquid level sensing inside the target, utilizing the specific resistance response of water, signals the operator that the target is loaded. For single radionuclide configuration, one or both reservoirs can be used with the same type of water, while dispensing is directed to a single target.