Preparation and evaluation of a hydrous tin(IV) oxide 82Sr/82Rb medical generator system for continuous elution

Preparation and Surface Characterization of Cerium Dioxide for Separation of 68Ge/68Ga and Other Medicinal Radionuclides

The overall need for the preparation of new medicinal radionuclides has led to the fast development of new sorption materials, extraction agents, and separation methods. Inorganic ion exchangers, mainly hydrous oxides, are the most widely used materials for the separation of medicinal radionuclides. One of the materials that has been studied for a long time is cerium dioxide, a competitive sorption material for the broadly used titanium dioxide. In this study, cerium dioxide was prepared through calcination of ceric nitrate and fully characterized using X-ray powder diffraction (XRPD), infrared spectrometry (FT-IR), scanning and transmission electron microscopy (SEM and TEM), thermogravimetric and differential thermal analysis (TG and DTA), dynamic light scattering (DLS), and analysis of surface area. In order to estimate the sorption mechanism and capacity of the prepared material, characterization of surface functional groups was carried out using acid-base titration and mathematical modeling. Subsequently, the sorption capacity of the prepared material for germanium was measured. It can be stated that the prepared material is prone to exchange anionic species in a wider range of pH than titanium dioxide. This characteristic makes the material superior as a matrix in 68Ge/68Ga radionuclide generators, and its suitability should be further studied in batch, kinetic, and column experiments.

The thermal release of scandium from titanium metal – a simple way to produce pure 44Sc for PET application

The radionuclide-generator based access to radiopharmaceutical isotopes represents a valuable alternative to directly produced isotopes at particle accelerators or nuclear reactors. The 44Ti based generator is of increasing interest for the delivery of PET-radiopharmaceutical isotopes used for imaging. The product of this generator 44Sc represents with its 3.97 h half-life and 94.3% positron branching [1] a very promising candidate for labeling PET radiopharmaceuticals. The long half-life of 58.9±0.3 y [2] of the 44Ti assures a constant and long lasting production of the daughter nuclide.

Here we present a gas phase separation method of scandium from titanium via thermal release in vacuum. Titanium foils were irradiated with 40Ar to produce scandium in multi-nucleon transfer reactions. Another production reaction used was the irradiation of titanium by neutrons from the SINQ neutron source at the Paul Scherrer Institute (PSI).

The titanium metal foils containing 44mSc and 46Sc were heated up for time periods of 15 and 60 min to temperatures between 900 °C and 1500 °C in vacuum. Thus, release properties of scandium from titanium under these conditions were studied. The released scandium was collected on tantalum foils and could be rinsed of with concentrated nitric acid resulting in carrier free scandium nitrate solutions. From the experimental results optimum release conditions are suggested.

New ion exchange materials for use in a 82Sr/82Rb generator

82Rb is a short-lived positron-emitting isotope (T1/2 = 75 s) that is increasingly being used in positron emission tomography for the evaluation of myocardial perfusion. The short half-life of 82Rb results in rapid decay of the administered radioactivity allowing repeat scans to be performed after a relatively short time interval. The 82Rb is available from a 82Sr/82Rb generator in which the 82Sr parent is immobilized on an ion exchange column and 82Rb eluted when required. Consequently, suitable ion exchangers for use in a generator must have a very high affinity for strontium and a negligible affinity for rubidium, allowing the pure 82Rb to be safely and efficiently eluted in high yields. This study evaluated a number of strontium-selective ion exchange materials using batch experiments and identified sodium nonatitanate as the best material for use in a 82Sr/82Rb generator.

Manufacture of strontium-82/rubidium-82 generators and quality control of rubidium-82 chloride for myocardial perfusion imaging in patients using positron emission tomography

We describe a protocol to manufacture 82Sr/82Rb generators and 82RbCl for myocardial imaging with PET. The generators are manufactured in 3 stages: (1) preparation of a tin oxide column, (2) leak test of the generator column and (3) loading of the generator with 82Sr. The generators produced sterile and non-pyrogenic 82RbCl for i.v. injection. No significant 82Sr/85Sr breakthroughs were observed after elution with 20 1 of saline. The automated system delivered human doses of 82RbCl accurately.

Reinvestigation of a physiological eluate of the 52Fe/52mMn generator

We have achieved a significant step forward in the potential application of 52mMn2+ (T1/2 = 0.35 h, beta + = 97%) as a myocardial imaging agent with positron emission tomography (PET) by the introduction of a 5% (physiological) glucose solution as an eluent for the 52Fe/52mMn generator. Our experiments have demonstrated the favourable properties of a glucose solution with minimal breakthrough (< 0.3%) of 52Fe and yields of up to 90% 52mMn2+. Although it has been shown that lower 52Fe breakthrough is attainable using other eluents, due to the short half life of 52Fe (8.27 h) breakthrough up to 1% would not appear to significantly alter the efficacy of the 52mMn eluted with this 5% glucose solution. The primary advantage of this approach lies in its convenience of application, in that a 5% glucose solution may be administered directly into patients thereby circumventing the major problem of non-injectable eluates previously associated with this generator.

The continuing important role of radionuclide generator systems for nuclear medicine

In this review, the continuing importance and status of development of radionuclide generator systems for nuclear medicine are discussed. Radioisotope costs and availability are two important factors, and both nuclear reactors and accelerator facilities are required for production of the parent radioisotopes. Radionuclide generator research is currently focused on the development of generators which provide radioisotopes for positron emission tomography (PET) applications and daughter radioisotopes for various therapeutic applications which decay primarily by particle emission. Generator research continues to be influenced by developments and requirements of complementary technologies, such as the increasing availability of PET. In addition, the availability of a wide spectrum of tumor-specific antibodies, fragments, and peptides for radioimmunodiagnosis and radioimmunotherapy has stimulated the need for generator-derived radioisotopes. The advantages of treatment of arthritis of the synovial joints with radioactive particles (radiation synovectomy) may be expected to be of increasing importance as the elderly population increases, and many of these agents are prepared using generator-derived radioisotopes such as yttrium-90 and rhenium-188. Therapeutic use of the "in vivo generator" is a new approach, where the less radiotoxic parent radioisotope is used to prepare tissue-specific therapeutic agents. Following in vivo site localization, decay of the parent provides the daughter for therapy at the target site. The principal foundation of most diagnostic agents will continue to require technetium-99m from the molybdenum-99/technetium-99m ("Moly") generator. With the limited availability of nuclear reactors and facilities necessary for production and processing of fission 99mTc and the significant issues and problems associated with radioactive waste processing, however, the possibility of utilizing lower specific activity 99Mo produced from neutron activation of enriched 98Mo may become practical in the future.

Use of the 82Sr/82Rb generator in clinical PET studies

The use of the 82Sr/82Rb generator in clinical positron emission tomography (PET) studies of myocardial perfusion has been described. An infusion pump is used to deliver the short-lived 82Rb from the generator to the patient. Various characteristics of the generator and the infusion system are described. The 82Rb yield was 69.8 +/- 13.3% and the 82Sr breakthrough was always less than the limit of 0.02 microCi/mCi 82Rb. The yield of 82Rb increased with the flow rate and the potency of the generator. Patients with coronary artery disease were studied for myocardial perfusion abnormalities by the 82Rb PET technique and images of excellent diagnostic quality were obtained.

Automated production of potassium-38 for the study of myocardial perfusion using positron emission tomography

The 35Cl(alpha, n)38K nuclear reaction was developed for the routine cyclotron production of repeated multimillicurie batches of 38K for dynamic studies of regional tissue perfusion with positron emission tomography. The objective is to make this isotope available as an alternative to the use of [13N]NH3 and 82Rb for the investigation of flow in experimental and clinical use. A sodium chloride powder target mounted on a water-cooled nickel backing is bombarded with 26 MeV helium-4 ions at a maximum beam current of 25 microA. The target is remotely disconnected from the bombardment port, transported to a hot cell and entirely processed by a computer-controlled system within a total time of less than 4 min. The final pyrogen-free isotonic and sterile solution of 38K has a radionuclidic purity of more than 99.99%. A typical yield of 19 +/- 2 mCi of 38K is obtained at the end of a 30 min bombardment at 10 microA. The production rate at saturation can therefore be estimated to 2.05 +/- 0.2 mCi/microA.