Pre-clinical evaluation of 188W/188Re biomedical generator

Kamioki, H; Mirzadeh, S; Lamcrecht, RM

Pre-clinical evaluation of 188W/188Re biomedical generator

Date

1983-10

Authors

Kamioki, H

Mirzadeh, S

Lamcrecht, RM

Publisher

Kyoto University

Abstract

In order to assess the performance of clinical scale generators, a 13.5 mCi generator has been prepared and evaluated for 188Re Re yield and elution profile, and 188W breakthrough using various reagents. The generator is alumina-based and eluted on a bi-weekly schedule. The results for a five-week evaluation period are presented. To address the problem of low specific volume (1), the normally used saline solution (as eluent) was replaced by reagents which could be easily destroyed by gentle evaporation from acidic solution (e.g. NH4CI and NH4NO3). Tungsten-188 with a specific activity of ~5 mCi/mg and activity concentration of ~13.5 mCi/ml in 0.1 M NaOH was purchased from ORNL. The generator column (13x21 mm) was fabricated with a coarse glass frit support at the bottom and held 750 mg of alumina (80-120 mesh, pre-equilibrated with 0.01 _M_ HNO3). One ml of the 188W stock solution (~3 mg) was titrated with 1 M HNO3 until pH 2-3 was obtained. The mixture was loaded on the column and 188Re was typically eluted with 4x10 ml portions of various eluents. At the end of each elution, the generator was equilibrated with 10 ml of the next eluent and then was purged dry. This was to reduce the effects of radiolysis which has been shown to result in erratic yield. The 10-ml eluents were collected directly in 10-ml injection vials and the activity of 188Re was measured without further dilution with a calibrated ionisation chamber. After about 2 weeks of decay to insure the equilibrium, the samples were recounted at the surface of a Ge(Li) detector and the breakthrough of 188W was evaluated from the intensity of the 155 keV y-ray of 188Re. The yield and elution profile of 188Re for various reagents are shown in Fig. 1 and 2, respectively. Within 9 elutions, the yield of 188Re decreased from 80% to 70%. As shown in Figure 2, replacement of Na+ ion with H+ or NH4+ ions in the eluent had no observable effect on the 188Re elution behaviour. Consistent with previously reported results obtained from a 1 mCi generator (2), the optimum concentration of cations for sharp elution of Re (in the 1st 10 ml of eluent) is about 0.05 M. Concentrations below this optimal value resulted in an increase in retention time as well as an increase in the FWHM of elution curve (2,3). No effect was observed due to replacement of the CI counter ions with N03 ions (Re in nitrate solutions could be further purified and concentrated in an anion exchange column) (2).

Description

Physical copy held by ANSTO Library at DDC: 616.07575/115.

Keywords

Clinical trials, Biomedical radiography, Reagents, Beta decay, Dilution, Rhenium 188, Tungsten 188, Ammonium chlorides, Ammonium nitrates

Citation

Kamioki, H., Mirzadeh, S., & Lambrecht, R. M. (1983). Pre-clinical evaluation of 188W/188Re biomedical generator. Paper presented to the Tenth International Symposium on Radiopharmaceutical Chemistry, Kyoto University (October 25-28, 1983), (pp. 279-281). Kyoto, Japan : Kyoto University.