[en] A Neutron Activation Analysis (NAA) program using absolute counting and a new method of determination of the thermal and epithermal flux has been developed. Only two standards (Fe and Ru) are needed, and only the weight of the Fe must be known accurately. The program runs in a computer with 16K memory. The program is primarily designed for the nondestructive quantitative analysis of impurities at the μg/g--ng/g level in silicon or other high purity matrices which do not themselves remain very radioactive long after end of irradiation. Otherwise removal of dominant activities prior to counting is necessary. Accuracy for isotopes with well-established nuclear constants is better than 10%. All features of the program are designed to enable the user to co-irradiate and evaluate a large number of samples per activation run in order to keep the irradiation and analysis cost per sample as low as possible

No abstract available

[en] The natural abundance of iron-58 was determined by irradiation of an iron oxide (Fe₂O₃) sample highly enriched in ⁵⁸Fe and of a sample of natural pure iron foil. Comparison was measured of the resulting ⁵⁹Fe photopeak intensities. The resulting percentage, 0.283 +- 0.01, was used to calculate a new value of 1.33 b for the thermal cross section of ⁵⁸Fe

[en] The accuracy of multielement quantitative determinations by parametric neutron activation analysis using Fe--Ru flux monitors is compared with that obtained by relative measurements using Standard Reference Materials (SRMs) from NBS. Agreement is good. Isotopes with a large ratio of resonance integral/thermal cross section require empirical correction factors. Deviation of the resonance flux in the reactor reflectors from a 1/E distribution appears responsible for at least part of the necessary corrections. The correction factors were found invariant from reactor to reactor. Molybdenum and certain rare earths can be determined by parametric counting in the presence of comparable amounts of uranium; interference by fission products is eliminated by calculations including the fission yields. 7 tables

[en] The chemical similarity of technetium and rhenium has created much interest in the nuclear medicine field to make a 'matched pair' of radiopharmaceuticals for radioimmuno- diagnosis and therapy. Clinical trials with the ⁹⁹mTc-DD-3B6/22 Fab' has shown promise in the diagnosis of ovarian cancer. The design of the analogous therapeutic agent with rhenium-188 (155 keV γ 15 % abundant, β E_max 2.1 MeV, T 1/2 17 h) is under investigation. The present study describes the approach taken for direct radiolabelling of the DD-3B6/22 Fab' with carrier-free ¹⁸⁸Re and its biological evaluation in balb/c and nude mice. The effect of temperature, pH and antibody concentration on the amount and rate of transchelation was also evaluated. The final product had a specific activity of 35 mCi/mg with an immunoreactive fraction of 77%. Stability of the product was assessed under various conditions: temperature, presence and absence of an inert atmosphere and presence of ascorbic acid (stabilised). Pharmacokinetics of the final product was evaluated in balb/c and nude mice transplanted with both D-dimer (+Ve) and Glycine (-Ve) beads. Results show that ¹⁸⁸Re DD-3B6/22 Fab' clears rapidly from the blood (α = 2.4 hr, β = 3.5 hr) and is excreted through the renal system. Localisation to subcutaneous antigen beads shows specific uptake to the D-dimer (antigen) beads was achieved within 6 h (0.23% ID) and was maintained for 24 hour post injection. Specificity to antigen implants was 5:1 (P <0.001) when compared to non-specific bead implants. These results correlate well with those obtained for the ^99m Tc DD-3B6/22 Fab' in mice. The radiolabelling procedures are congenial for therapeutic levels and hence the authors believe that the ¹⁸⁸Re DD-3B6/22 Fab' has some potential for use in treatment of ovarian cancer

[en] This study involves a high yielding synthesis of a novel di-amino-phenol substituted EDTA (DAHA-EDTA) ligand and its radiolabelling chemistry with ⁶⁴Cu produced at the National Medical Cyclotron (NMC). High activity levels (up to 59.2 GBq EOB) of ⁶⁴Cu is co-produced during the production of ⁶⁷Ga from enriched ⁶⁸Zn. Waste eluent from the NMC ⁶⁷Ga production was evaporated to dryness and found to contain by products such as ⁵⁷Ni, ⁵⁷Co, ⁶⁴Cu, ⁶⁷Cu and ⁵⁵Co. A new method involving low acid concentration aqueous/organic mixtures with an anion exchange (AG 1-X8, BioRad) have been used to isolate the carrier-free ⁶⁴Cu. The specific activity of the ⁶⁴Cu (5 x 10¹⁴ Bq/g) was found to be higher than that produce by Australian radioisotopes (ARI). The synthesis of the ligand involves the refluxing of EDTA anhydride in the presence of 4-nitro-2-amino-phenol in acetonitrile to produce the di-nitro derivative (DNHA- EDTA) in > 95% yield. The DNHA-EDTA is then reduced in the presence of activated palladium charcoal with sodium borohydride under an inert atmosphere at room temperature. The reaction mixture was acidified and the catalyst removed to obtain the final product, DAHA-EDTA. Labelling of proteins (B72.3, DD-3B6/22 and streptavidin) has been achieved with the DAHA-EDTA ligand. The reaction mixture is left to incubate for 1 h at 37 deg C and radiolabelled protein is then isolated using size exclusion chromatography

[en] The large and expanding field of modern high technology based upon silicon and its compounds is ideally suited for INAA using parametric counting, since neither the silicon nor the impurities present in almost infinite dilution give rise to self-shielding effects. Parametric counting, however, requires a fast and convenient method for determining the thermal, resonance, and fast neutron fluxes during irradiation. The resonance flux should be measured close to 5 eV, because most of the analytically important isotopes with large Irho/sigmasub(0) values have their resonance energies in the 1-15 eV region, and because the resonance flux in a commercial reactor does not follow the theoretical 1/E distribution in energy. It is shown in this paper that the resonance flux as measured with the 'zirconium method' is practically identical to the resonance flux obtained from cadmium ratio measurements on gold. In addition, the zirconium monitor also yields the thermal and fast fluxes, and has several practical advantages, especially for longer irradiations. (author)

[en] The LAMMA spectra of electron irradiated organic molecules show a decrease of the intensive mass peaks with increasing charge density. This decrease can be attributed to a progressive cross-linking in the irradiated films. The cross-linked structure does not further result in characteristic peaks of the LAMMA spectra. The charge densities necessary for a decrease of the peak intensities in the LAMMA spectrum correspond to charge densities of equal order necessary for a fading of the electron diffraction intensity. (orig.)

[en] In this paper electron-irradiated films of organic molecules (leucine as an alipathic and tetracene as an aromatic compound) are studied by laser microprobe mass analysis 1. to get information about fragmentation and cross-linking processes of the organic molecules 1. to get information about the fragmentation and cross-linking processes of the organic molecules as secondary processes of radiation damage, and 2. to demonstrate that an electron pre-irradiation changes the LAMMA spectra and that an observation of organic specimens in a transmission or scanning electron microscope before LAMMA experiments should be avoided. (orig.)

[en] Iodine-131, ⁹⁰Y and ⁶⁴Cu are three radionuclides identified to have potential in radioimmunotherapy (RIT) applications Iodine-131 has been used extensively in RIT because it is readily available, inexpensive, and it chemistry for radiolabelling is relatively easy. However its high gamma emission (365 keV 81 %) together with its long half life (8 d) causes an undesirable high whole body radiation dose to the patient and creates problems associated with the hospitalisation of the patient and radiation exposure to the radiopharmacy and medical staff. Yttrium-90 has a high energy beta that has a long range in tissue (12 mm), hence it is considered( best for the treatment of large tumours (I - 2 cm). However, with the absence of an imaginable γ emission, imaging and dosimetry calculations must be calculated with the analogous ¹¹¹In labelled product. Poor stability of ⁹⁰Y labelled antibodies may result in a dose to the patient's bone marrow, due to normal accreditation of free ⁹⁰Y. Copper-64 has a 12.7 h half life and emits positrons that offer the advantage of use in Positron Emission Tomography (PET). The greater resolution of PET allows more accurate monitoring ol tissue uptake and optimum use for therapy. Copper-64 β max energy of 0.58 MeV (37 %) is slightly lower, though comparable to ¹³¹I, and hence could be expected to administer similar therapeutic effect. Now that high specific activity ⁶⁴Cu is readily available at the National Medical Cyclotron, it was thought useful to assess the potential of this radionuclide in RIT. A series oi radioimmunoconjugates of B72.3 antibody incorporating ¹²³I, ¹¹¹In and ⁶⁴Cu were prepared and their biodistribution in nude mice bearing colorectal tumours evaluated. This data was used to estimate the dosimetry of the analogous ¹³¹I, ⁹⁰Y, and ⁶⁴Cu products in humans assuming similar pharmacokinetics in both species. A comparison of the therapeutic dose to the target and nontarget sites was made and consideration given to the most appropriate regime for optimum patient management