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

It was indicated that ⁵⁵Fe (EC decay, half-life: 2.7 y) is the most abundant radioisotope in the residual activities formed in hardware composed of iron and steel at high energy accelerator facilities. Its approximate activity could be evaluated on the basis of an integrated neutron flux measured by an activation method using a copper threshold detector. Both a low energy photon spectroscopy and a liquid scintillation counting method were confirmed to be applicable to ⁵⁵Fe measurement with high sensitivity.

New polymer-based materials have been evaluated in an effort to improve nitrogen-13 production with medical cyclotrons. A series of poly(styrene/divinylbenzene) derivatives have been synthesized and then pyrolysed to yield carbonized beads. Preliminary cyclotron studies indicate that pure ¹³N-labelled ammonia is produced upon irradiation of these materials.

An inexpensive target system for the production and on-line extraction of no carrier-added radioisotopes of bromine is described. The suitability of ⁷⁷Br as a probe for time-differential perturbed angular correlation studies is discussed.

Several target compounds and different purification procedures are compared for reactor production of [¹⁸F]fluoride by means of the ⁶Li(n,α)³H; ¹⁶O(t,n)¹⁸F reaction sequence. Best results are obtained using moist Li₂CO₃ as target, followed by aqueous dissolution using a cation exchange resin and purification by adsorption on a small alumina column with dilute ammonium hydroxide as eluent.

Three monoclonal antibodies (mAb) directed against the human ovarian adenocarcinoma cell line HEY, were substituted with maleimide and covalently bonded to thiolated streptavidin. The conjugates were separated from unreacted reagents by successive affinity chromatography on protein A—Sepharose and iminobiotin columns. Purified conjugates consisted of an immunoglobulin (Ig) monomer bound to a streptavidin tetramer through a covalent bond between the Ig molecule and one of the streptavidin subunits. The conjugates were able to specifically target [¹¹¹In]biocytin to HEY cells in vitro in the presence of human serum and ascitic fluid from ovarian cancer patients.

The method of accelerator mass spectrometry is applied to measurements of concentrations of the long-lived volatile fission product ¹²⁹I ($\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 1.6 × 10}{}^7$ a) in the primary heat transport (PHT) system and irradiated fuel bay (IFB) of a commercial nuclear power reactor. Concentrations of (8.1 ± 1.1) × 10¹²¹²⁹I atoms per gram and between 10¹¹ and 10¹³¹²⁹I atoms/L were measured in an ion-exchange resin and in the heavy water (PHT) system, respectively. The corresponding value for the IFB system water samples was 5–6 × 10¹²¹²⁹I atoms/L. These measurements, based on very small size samples (of the order of 0.5 mL) emphasize the advantage of the present method where a simple chemical process for the iodine extraction enables a direct measurement of the ¹²⁹I atom content of the samples. In view of the physical and chemical properties of iodine and their important implications in the environment, the method is likely to find even wider applications for the monitoring of ¹²⁹I and the study of long-range nuclear waste storage.

A new radioiodination reagent, 3-iodophenylisothiocyanate (3-IPI) has been developed for coupling to monoclonal antibodies. The starting material, 3-tri-n-butylstannylphenylisothiocyanate was prepared via a reaction of hexabutylditin with 3-bromoaniline, followed by treatment with thiophosgene with an overall yield of 72%. The radioiodination of this tin precursor with Na[¹²⁵I]I/iodogen in chloroform gave 3-[¹²⁵I]IPI in 23–55% radiochemical yield and 81–99.6% radiochemical purity. Purification of the impure product by high pressure liquid chromatography increased the radiochemical purity of the product up to 99%. These results suggest that 3-IPI may be a useful ligand for radioiodination and coupling to a variety of monoclonal antibodies.

Thick-target production rates of ⁵⁵Fe produced in the proton bombardment of Mn, Co and Ni were investigated from threshold up to 100 MeV. Impurity levels of the only radiocontaminant of importance, ⁵⁹Fe, were also considered. It is shown that the optimum production rate at energies above ∼ 35 MeV will be achieved by utilizing a tandem Mn/Ni target. Theoretical calculations performed with the computer code ALICE/85/300 were found to be in good agreement with the measured ⁵⁵Fe thick-target production-rate curves.

Thin- and thick-target yields for the production of ^34mCl (31.99 min; β + 53%; IT 47%) with high-energy protons on natural isotopic chlorine targets were measured in the 67.5–20.0 MeV energy range. The total cross section for the reactions ³⁵Cl(p,pn) (Q = -12.8 MeV) and ³⁷Cl(p,p3n) (Q = -31.7 MeV) was measured. The total cross section peaked at 30 MeV with a value of 108±14.6 (13.5%) mbarn. The ^34mCl cumulative yield reached 591±80 (13.5%) mCi/μAh with a 67.5-MeV proton beam exiting at 20 MeV. The potential to produce ^34mCl for research and radiopharmaceutical syntheses is discussed based upon current accelerator capabilities. Other aspects of the potential use of ^34mCl (i.e. radionuclidic, radiochemical purities, specific activities) are also discussed.