Development of a titanium tungstate-based 188W/188Re gel generator using tungsten of natural isotopic abundance

Investigation on preparation and properties of gel type 188W/188Re generator

As one of the most important integrated nuclides for diagnosis and treatment in recent years, rhenium-188 (188Re) has a broad scope in the clinical application. Due to the specific properties of such radionuclide, it was mainly provided by the chromatographic 188W-188Re generators. There is no doubt that the application of 188Re in the treatment of various diseases depended on the development of 188W-188Re generator. Considering the high standards of such technology on radioactive activity of 188W and impurity content, a 188W-188Re generator filled with the zirconium tungstate gel has been prepared in this work. The effects of molar ratio of chemical agents, pH, reaction temperature, drying methods, rinsing methods and other conditions on the synthesis of gel particles have been studied. Furthermore, a variety of characterization techniques were used to observe the macro-/micro-morphology and chemical structure of gel particles. It can be concluded that vacuum freeze-dried method could significantly increase the specific surface area, pore size and tungsten content of gel particle. In order to decrease the content of 188W in the elute, a handful of acidic alumina was filled in the bottom of our 188W-188Re generator, an elution and purification integrated-generator was formed. During the first five processes, the nuclear purity of 188Re solution was above 99.99%, the radiochemical purity was approximately 99.5%, the pH value was 5.0-7.0 and the average elution efficiency reached up to 82.7%. In addition, the leakage rate of 188W was low as 1.60 × 10-6, and the peak of elute curve was located at 2 mL without the trailing phenomenon. This work lays a solid foundation for the domestic demand of daughter nuclide 188Re, further makes an outstanding contribution to the application of the radiation therapy technology and the protection of people's health.

Preparation and characterization of zirconium silico188W-tungstate as a base material for 188W/188Re generator

Zr:W:Si. The optimum gel was prepared using the molar ratio 1:1:7 at pH 8. The ZrSiW gel was investigated by FTIR, XRD, thermal analysis (TGA and DTA), FESEM, XRF, and NAA. Then, XRF and NAA techniques were used to estimate the proportion of the constituents of the gel according to the molecular formula [ZrO₂(Si(WO₄)₂)16H₂O]. ¹⁸⁸W/¹⁸⁸Re generator was prepared based on the selected ZrSi¹⁸⁸W gel, which gives the highest tungsten content (393.3 mg W/g gel) with 75 ± 3% elution yield of ¹⁸⁸Re. Quality control was studied on the ¹⁸⁸Re to make sure its validity for clinical applications.

Development of an electrochemical 188W/188Re generator as a technique for separation and purification of 188Re in radiopharmaceutical applications

In this study, a simple electrochemical procedure adaptable for using low specific activity ¹⁸⁸W for separation and purification of ¹⁸⁸Re from ¹⁸⁸W to obtain no carrier added (NCA) ¹⁸⁸Re is developed. The electrochemical parameters were optimized to maximize the ¹⁸⁸Re electrodeposition yield with minimal ¹⁸⁸W contamination. Two cycle electrolysis procedure was developed. The first electrochemical cell was used for separation of ¹⁸⁸Re and in the second electrochemical cell, separation and purification of ¹⁸⁸Re with >90% deposition yield of ¹⁸⁸Re and minimal contamination of ¹⁸⁸W (<10^-4%) was achieved. The overall electrodeposition yield of ¹⁸⁸Re was >90% with >99% radionuclidic purity and >99% radiochemical purity suitable for radiopharmaceutical applications. Furthermore, the performance of the generator remained consistent during a period of 69 days, one half-life of ¹⁸⁸W, when the electrochemical separation procedure was performed frequently, at least once in 5 days.

An overview of radioisotope separation technologies for development of 188W/188Re radionuclide generators providing 188Re to meet future research and clinical demands

Separation technologies for ¹⁸⁸W/¹⁸⁸Re radionuclide generators.

188W/188Re Generator System and Its Therapeutic Applications

The188Re radioisotope represents a useful radioisotope for the preparation of radiopharmaceuticals for therapeutic applications, particularly because of its favorable nuclear properties. The nuclide decay pattern is through the emission of a principle beta particle having 2.12 MeV maximum energy, which is enough to penetrate and destroy abnormal tissues, and principle gamma rays (Eγ=155 keV), which can efficiently be used for imaging and calculations of radiation dose.188Re may be conveniently produced by188W/188Re generator systems. The challenges related to the double neutron capture reaction route to provide only modest yield of the parent188W radionuclide indeed have been one of the major issues about the use of188Re in nuclear medicine. Since the specific activity of188W used in the generator is relatively low (<185 GBq/g), the elutedRe188O4-can have a low radioactive concentration, often ineffective for radiopharmaceutical preparation. However, several efficient postelution concentration techniques have been developed, which yield clinically usefulRe188O4-solutions. This review summarizes the technologies developed for the preparation of188W/188Re generators, postelution concentration of the188Re perrhenate eluate, and a brief discussion of new chemical strategies available for the very high yield preparation of188Re radiopharmaceuticals.

Concentration of 99mTc-pertechnetate and 188Re-perrhenate

The radioactive concentrations of 99mTc/188Re from their generators are dependent upon the specific activity of 99Mo/188W, which dictates the bed size of the alumina/gel column and the volume of physiological saline needed as eluent. Because of the high content of inactive molybdenum/tungsten in neutron irradiated MoO3/WO3, large columns containing alumina/gel are needed to produce chromatographic 99Mo → 99mTc/188W → 188Re generators. This results in large elution volumes containing relatively high 99Mo/188W contents and low concentrations of 99mTc/188Re. The decrease in radioactive concentration, or specific volume, places a limitation on some of the clinical procedures. We report post elution concentration of 99mTc/188Re using in house prepared silver cation exchange and alumina column. The high bolus volumes (10 − 60 ml saline) can conveniently be concentrated in 1 ml of saline. This approach also works very effectively to yield high specific volume solutions of 99mTc-pertechnetate from a fission 99Mo loaded alumina generator towards the end of its normal working life.