Concentration of 99mTc-pertechnetate and 188Re-perrhenate

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.

188Re(V) Nitrido Radiopharmaceuticals for Radionuclide Therapy

The favorable nuclear properties of rhenium-188 for therapeutic application are described, together with new methods for the preparation of high yield and stable ¹⁸⁸Re radiopharmaceuticals characterized by the presence of the nitride rhenium core in their final chemical structure. ¹⁸⁸Re is readily available from an ¹⁸⁸W/¹⁸⁸Re generator system and a parallelism between the general synthetic procedures applied for the preparation of nitride technetium-99m and rhenium-188 theranostics radiopharmaceuticals is reported. Although some differences between the chemical characteristics of the two metallic nitrido fragments are highlighted, it is apparent that the same general procedures developed for the labelling of biologically active molecules with technetium-99m can be applied to rhenium-188 with minor modification. The availability of these chemical strategies, that allow the obtainment, in very high yield and in physiological condition, of ¹⁸⁸Re radiopharmaceuticals, gives a new attractive prospective to employ this radionuclide for therapeutic 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.

Development of radiochemistry in Pakistan – 1960 to 2010

With the inception of Pakistan Atomic Energy Commission (PAEC) in 1956, peaceful uses of atomic energy commenced for the benefit of scientific community as well as masses of Pakistan. Radiochemistry played a vital role right from the beginning. The research and development in this field accelerated soon after the criticality of the first research reactor named as Pakistan Research Reactor (PARR- 1) at the Pakistan Institute of Nuclear Science and Technology (PINSTECH), Islamabad. The first radioisotope produced at PARR-1 for application in nuclear medicine was 131I. Later on, many other radioisotopes were prepared and radiopharmaceuticals were synthesised for their use in industry and hospitals. Besides providing pure radioactive tracers for nuclear medicine, radiochemistry also enhanced the detection limit of impurities at all stages of nuclear fuel cycle for power generation. In 1983, research in the field of nuclear data measurement began. The main aim was to identify suitable conditions for the production of radionuclides for cancer diagnostics, treatment and therapy. With the establishment of a second research reactor (PARR-2) at PINSTECH, research in neutron activation analysis, radioisotope production and separation studies gained more momentum and many research articles were published. Solvent extraction, adsorption and ion-exchange were the main routes of separation in those studies. Separation of heavy metals and treatment of waste generated in a nuclear power plant are other important aspects related to environmental restoration and nuclear waste management, where radiochemistry is required. In future, work in radiochemistry will be continued on similar lines to develop novel radiopharmaceuticals, identify indigenous schemes for nuclear waste management and work out intelligent procedures for material characterization for benefit to mankind, especially the people of Pakistan.

Preparation and evaluation of hydrous titanium oxide as a high affinity adsorbent for molybdenum (99Mo) and its potential for use in 99mTc generators

Hydrous titanium oxide was prepared and its affinity as an adsorbent for molybdenum ( 99Mo) and its potential for use in 99mTc generators were evaluated. Adsorption behavior of molybdate on hydrous titanium oxide was studied at boiling water bath temperature (∼100 °C) using radiotracer technique. Various parameters affecting the adsorption of molybdenum, such as pH, amount of molybdenum, incubation period etc. , were determined. Technetium-99m generators were prepared by adsorbing low specific activity Molybdenum-99 (∼230 mg) on 1 g hydrous titanium oxide. Elutions were carried out with normal saline. Performance of the generators, such as 99Mo breakthrough, titanium content, pH, elution profile, radiochemical purity and labeling efficiency of kits, was checked.

Lead (Pb) column for concentration of 99mTc-pertechnetate

Because of the high content of inactive molybdenum in neutron irradiated MoO3, large columns containing alumina or gel are needed to produce chromatographic 99Mo→99mTc generator. This results in large elution volumes containing relatively high 99Mo breakthrough and low concentrations of 99mTcO4 -. The decrease in specific volume of 99mTc places a limitation on reconstitution of some kits for 99mTc radiopharmaceuticals applied in diagnostic nuclear medicine. Hence concentration technique is mandatory for effective utilization of (n,γ) produced 99Mo/99mTc generators at the start of its life whereas in case of fission 99Mo/99mTc generator the technique may be quite useful at the end of first week of its life. We report post elution concentration of 99mTc using in house prepared Pb column. The high bolus volumes (10–60 ml saline) can conveniently be concentrated in ∼1 ml of saline.

Extraction of medically interesting 188Re-perrhenate in methyl ethyl ketone for concentration purposes

The high bolus volumes (20–40mL) of the generator-produced Rhenium-188 require post elution concentration of the eluate for the preparation of a dissolved β− source and radiopharmaceuticals labeled with Re-188 for radiotherapy. Solvent extraction of 188Re in methyl ethyl ketone was studied. With the increase of organic phase volume, extraction of 188Re was enhanced while mixing time of aqueous and organic phases did not show any significant effect on the extractability of 188Re in the organic phase. Almost 80% of 188Re was extracted in methyl ethyl ketone at a volume ratio of 1:2 for aqueous and organic phases. By evaporation/distillation of methyl ethyl ketone, 188Re was concentrated and dissolved in the desired volume of physiological saline.

Sodium sulfate as an eluant for concentrated solution of pertechnetate

Fission molybdenum-99 based technetium-99m chromatography generators are the most widely employed generator systems in the field of diagnostic nuclear medicine. In the first week these generators provide high specific volume activity Na99mTcO4, but in the second week the radioactive concentration of the eluate (99mTc) becomes 17% of that at the beginning of the first week. Low specific volume activity limits the clinical procedures (e.g. 99mTc-DTPA for lung ventilation scanning, 99mTc-sestamibi for myocardial perfusion studies, 99mTc-ECD for brain imaging and 99mTc-red cells for testicles) that can be performed at the beginning of the second week. To overcome such limitations sodium sulfate was used as an eluant, which provides>80% of 99mTc radioactivity in 2 ml solution, while 0.9% NaCl provides only 40-45% 99mTc in first 2 ml solution.