In response to the CIPM MRA, and to improve radioactivity measurements in the face of advancing technologies, the CIPM's consultative committee on ionizing radiation developed a strategic approach to the realization and validation of measurement traceability for radionuclide metrology. As a consequence, measurement institutions throughout the world have devoted no small effort to establish radionuclide metrology capabilities, supported by active quality management systems and validated through prioritized participation in international comparisons, providing a varied stakeholder community with measurement confidence.
Most of the existing methods for obtaining the frequency factors make use of the trap depth (activation energy) making some assumptions about the order of the kinetics. This causes inconsistencies in the reported values of trapping parameters due that the values of the activation energy obtained by different methods differ appreciably among them. Then, it is necessary to use a method independent of the trap depth making use of the isothermal luminescence decay (ILD) method.The trapping parameters associated with the prominent glow peak of BeO (280 °C) are reported using ILD method. As a check, the trap parameters are also calculated by glow curve shape (Chen's) method after isolating the prominent glow peak by thermal cleaning technique. Our results show a very good agreement between the trapping parameters calculated by the two methods. ILD method was used for determining the trapping parameters of BeO. Results obtained applying this method are in good agreement with those obtained using other methods, except in the value of the frequency factor.
As reported at the ICRM 2011, it was discovered that the source holder used for calibrations in the NIST 4πγ ionization chamber (IC) was not stable. This has affected a large number of half-life measurement results previously reported and used in compilations of nuclear data. Corrections have been made on all of the half-life data based on the assumption that the changes to the ionization chamber response were gradual. The corrections are energy dependent and therefore radionuclide specific. This presentation will review our results and present the recommended changes in half-life values and/or uncertainties.
The characterization of a liquid scintillator incorporating an aqueous solution of enriched lithium chloride to produce a scintillator with 0.40% 6Li is presented, including the performance of the scintillator in terms of its optical properties and neutron response. The scintillator was incorporated into a fast neutron spectrometer, and the light output spectra from 2.5MeV, 14.1MeV, and 252Cf neutrons were measured using capture-gated coincidence techniques. The spectrometer was operated without coincidence to perform thermal neutron measurements. Possible improvements in spectrometer performance are discussed.
The orally active platinum anti-tumour complex JM216[bis-acetatoamminedichlorocyclohexylamineplatinum(IV)] is at present in stage II clinical trials. A procedure for synthesising the complex labelled with 191Pt or 188Pt at the platinum centre has been developed. The purity (shown by HPLC) is 98% and the specific activity (0.3-0.4 Ci/kg) is enough for in vivo and in vitro studies.
The 11C-labelled β-adrenergic receptor ligands atenolol 1, metoprolol 2 and propranolol 3 have been synthesized by an N-alkylation reaction using [2-11C]isopropyl iodide. The labelled isopropyl iodide was prepared in a one-pot reactor system from [11C]carbon dioxide and obtained in 40% radiochemical yield within 14 min reaction time. The total reaction times for compounds 1–3, counted from the start of the isopropyl iodide synthesis and including purification were 45–55 min. The products were obtained in 5–15% radiochemical yields and with radiochemical purities higher than 98%. The specific activity ranged from 0.4 to 4 GBq/μmol. In a typical experiment starting with 4 GBq around 75 MBq of product was obtained.
The production and radiochemical separation of 55Co from deuteron irradiation of enriched 54Fe target is described. Methods used for the recovery and reuse of the target material (54Fe) are also described. The yield of 55Co at 12 MeV incident deuteron energy is 1.7 mCi per μAh at end of bombardment and the contamination with 57Co is 0.016%. The 55Co produced is chelated to bleomycin and used for tumour imaging with a positron emission tomographic camera based on multi-wire proportional chamber detectors.
An automated system for the production of 11C-labeled radiopharmaceuticals, using 11C-CH3I as a precursor, has been developed. The whole procedure, including irradiation, production of 11C-CH3I, synthesis of the labeled molecule and isolation of the final product is controlled by a microprocessor. Between 30 and 80 mCi of 5 different radiopharmaceuticals are produced routinely with this system.
Titanium (Ti) doped LiF:Ti thermoluminescent crystals were prepared and their dosimetric properties were studied. They showed different thermoluminescence sensitivies with increasing amounts of Ti dopings, reaching maximum for 400 ppm in LiF. In the glow curves of all samples, two peaks at 140°C and 210°C were observed. The stability of the traps connected with these peaks were studied for a period of one month. Dose-response and energy dependence properties of the stable 210°C peak were investigated between dose ranges of 200 mR and 200 R and 50 mR and 100 R for 137Cs γ rays and x-rays respectively. Dose-response curves were found to be linear in these ranges. The energy dependence was 1.7% between 33 and 662 keV when the thermoluminescent responses were normalized to 137Cs γ rays. It is suggested that LiF:Ti (400 ppm) may be used as a personnel dosimeter.
Measured and parametrised values of the attenuation coefficients of bone and several bone standards are presented for the photon energies 33, 75, 145, 279 and 662 keV. The values are compared, inadequacies are highlighted and possible new formulations are discussed.
A comparison of the calculated absolute full-energy peak efficiencies of CdTe and NaI detectors, i.e. the ratio of the number of counts under the full-energy peak (FEP) to the number of photons at the same energy emitted by the source, is made for six different detectors and three source sizes. The CdTe and NaI detectors are assumed to be of equal volume. The calculations are performed in the photon energy region 15-2000 keV using water, muscle and blood as source media.
The dependence of track etch rate on the energy-loss, dE/dx of 126C, 168O and 2010Ne-ions with an energy 9.1 MeV/N is shown. The bulk etch rate, Vb and track etch rate, Vt are determined for different temperatures. It is observed that both Vt and V=Vt/Vb depends on dE/dx as well as on etch bath temperature. The maximum etched track lengths of different ions agree with the theoretical ranges to better than 2%. The sensitivity of this plastic detector can be adjusted by altering the etch bath temperature.
The DNA ligand Hoechst 33258 has been iodinated with carrier-free [125I]iodide by the lactoperoxidase method. The product was separated from other iodination products and the uniodinated compound by preparative thin layer chromatography. 125I-labelled Hoechst 33258 is useful as a probe with DNA molecules of defined sequence since the decay of the 125I atom results in the induction of a double-strand break, the location of which can be detected by DNA-sequencing techniques.
Distribution and chemical states of iron and cobalt in water hyacinths cultivated with a nutrient solution containing either 57Fe and 59Fe or 57Co were studied by tracer technique and Mössbauer spectroscopy. Both iron and cobalt were found to accumulate mainly in the root. Chemical states of iron and cobalt in the root are discussed on the basis of their Mössbauer absorption and emission spectra.
A study on the measurements of proton current density profiles determined by the scattering process in natural krypton gas resulted in the development of a quantitative autoradiographic technique for the determination of a proton induced activity distribution on a Cu foil. Application of this technique showed that a 24 MeV, 1 μA proton beam with a FWHM of 7.3 mm was enlarged to a beam with a FWHM of about 43.5 mm for a target length of 50 cm and a Kr gas pressure of 400 kPa. For a comparison the target was also filled with Xe gas resulting in a larger FWHM value than for krypton under the same experimental conditions.
3-(2-[131I]iodobenzoyl)estradiol-17 β (1), 3-(2-[131I]iodobenzoyl)estrone (2) and 17 β-(2-[131I]iodobenzoyl)estradiol (3) have been prepared by bromine-iodine exchange followed by preparative HPLC in radiochemical yields greater than 70% (isolated). The specific activities were greater than 200 Ci/mmol. Tissue distribution studies in DMBA-induced tumor bearing rats showed a rapid clearance via the kidneys and poor accumulation in the target tissues. The relative binding affinities to the estrogen receptor were estimated as 3.5% 1, 1.7% 2 and 0.05% 3 of the affinity of estradiol (100%).
A facility for in vivo prompt γ activation analysis using moderate neutrn beams from 0.1 W mobile nuclear reactor is described. The low-power nuclear reactor provides total neutron flux of 3.3 × 104n cm−2 s−1 on the surface of a vertical beam tube to which a liquid phantom is positioned. The capability of such a partial-body irradiation facility is demonstrated by measuring trace amounts of toxic cadmium in kidney. The detection limit of Cd in kidney for a skin dose of 1.66 mSv (166 mrem) is 1.34 mg under 500 s irradiation. This facility therefore combines the advantages of mobility with sensitivity of detection of a toxic element under low neutron and γ doses.
The remotely controlled on-line production with a cyclotron of 15O2 and C15O2 for routine medical use is described. The radiochemical purities have been determined and compared with literature data. The impurities formed during irradiation can be removed with appropriate traps. The toxic gases ozone, nitrogen dioxide and carbon monoxide are formed in the target at concentration levels above the “Threshold Limit Value”. Therefore a chemical quality control procedure has been developed. A copper oxide-iron oxide trap was found to improve the radiochemical and chemical purity of the C15O2.
