99Mo-99mTc Generators Research Articles

Exposure dose estimation considering a molybdenum generator fall accident

Radiopharmaceuticals with high radioactivity are used in the field of nuclear medicine. Moreover, understanding the exposure dose of radiation workers and the air dose in radioisotope preparation rooms is essential. In particular, evaluating exposure dose assuming an accident to reduce radiation exposure as much as possible and respond to the accident is paramount. Thus, we evaluated a case study where 1.34 GBq 99Mo–99mTc generator used in our hospital fell, and evaluated exposure doses. The results of the considered drop accident of a commercially available generator indicated a possibility of radiation exposure equivalent to several months of normal work exposure, even though the possibility of radiation exposure to the extent that deterministic biological effects appear is low. Therefore, more attention must be paid to managing radiopharmaceuticals with high radioactivity, such as generators, to reduce the anxiety of radiation workers in the hospital and respond rapidly to accidents. Furthermore, the study findings should be used for staff training during normal times to avoid unnecessary radiation exposure.

A compact solvent extraction based 99Mo/99mTc generator for hospital radiopharmacy

A compact and portable 99Mo-99 mTc generator based on solvent-extraction, mimic to the conventional 99Mo-99 mTc alumina column generator is much-needed commodity for use in hospital radiopharmacy setup. The present study includes the development of a portable, simple and low cost 99Mo/99 mTc-generator based on MEK solvent extraction technique to obtain a very high concentration of no-carrier added (nca) 99 mTc solution, where low specific activity 99Mo source is obtained through 98Mo(n, γ)99Mo reaction in a research reactor. The unit is intended for operation under the conditions of medical radiological laboratories. Technical trials showed that the mean time of preparation of sodium [99mTc] pertechnetate radiopharmaceutical did not exceed 15 min. The quality and yield of 99 mTc-pertechnetate is upto the mark for formulation of radiopharmaceuticals.

Molybdenum transmutation via 98Mo samples using bismuth/lead neutron moderators

99mTc is the usual medical isotope for imaging in nuclear medicine. The use of accelerators to produce 99Mo is an alternative to nuclear reactors. Here, the neutron production from a new neutron source is investigated to achieve a proper production yield. The induced neutron was simulated from 30 MeV protons on a beryllium target. The Adiabatic Resonance Crossing (ARC) method was evaluated using lead and bismuth moderators, and lead(II) fluoride reflector around a moderator region. The flux and energy of the aggregated neutrons within different regions of the proposed activator were estimated by the MCNPX code. The epithermal flux in the reflector region was greater than that in the moderator region, since the maximum amount was estimated to be when the bismuth moderator was employed. The outcomes demonstrated that the production yield of 99Mo improved using the bismuth material, whereas the 98Mo sample at a distance from the target showed a greater amount by 5.03E + 5 MBq through a 0.1 cm sample thickness. When the sample was positioned in the reflector region, the obtained yield increased taking advantage by the more accumulated flux in the epithermal range. The ARC method can replace conventional reactor-based prototypes of the 99Mo-99mTc generator, or complement them, because it is safe and more accessible.

Current status of nuclear cardiology practice in Latin America and the Caribbean

The burden of cardiovascular diseases (CVDs) in the world is ever growing. They represent the first cause of death worldwide and in Latin America. Nuclear cardiology has a well-established role in the management of patient with CVDs and is being increasingly integrated into the healthcare systems in the region. However, there remains variability as to the infrastructure available across the countries, in terms of existing technology, radiopharmaceuticals, and human resources. The approximate number of gamma (γ) cameras in the region is 1348, with an average of 2.25 per million population; Argentina and Brazil having the largest number. Nearly 80% of the existing cameras are single-photon emission tomography (SPECT), of which 8% are hybrid SPECT-CT systems. Positron emission tomography technology is steadily increasing, and currently, there is an average of 0.25 scanners per million inhabitants, indicating that there is a potential to expand the capacities in order to cover the needs. Four countries have nuclear reactors for research purposes, which allow the production of technetium-99 m (Argentina, Chile, Mexico and Peru), while four (Argentina, Brazil, Cuba, and Mexico) assemble 99Mo-99mTc generators. As for the nuclear cardiology studies, about 80% of studies performed are gated SPECT myocardial perfusion imaging; less than 10% are multi-gated acquisition (mainly for evaluation of cardiac toxicity in cancer patients), and the other 10% correspond to other types of studies, such as viability detection, and adrenergic innervation studies with 123I-MIBG. Physical stress is preferred, when possible, based on the clinical condition of the patient. Regarding human resources, there is an average of 1.1 physicians and 1.3 technologists per γ camera, with 0.1 medical physicists and 0.1 radiopharmacists per center in the region. The future of nuclear cardiology in Latin America and the Caribbean is encouraging, with great potential and possibilities for growth. National, regional, and international cooperation including support from scientific societies and organizations such as International Atomic Energy Agency, American Society of Nuclear Cardiology, and Latin American Association of Biology and Nuclear Medicine Societies, as well as governmental commitment are key factors for the development of the specialty. A multimodality approach in cardiac imaging will contribute to a better management of patients with CVDs.

Increased renal parenchymal retention of 99mTc-MDP (hot kidneys) in two patients of Hepatocellular Cancer: one with and other without osseous metastases

Background: Hepatocellular cancer (HCC) is the fifth-leading cancer in men worldwide. Here we present two HCC patients who showed high diffuse renal parenchymal retention of 99mTc MDP on bone scan. Cases presentation: Bone scan with 99mTc MDP was performed on two known HCC patients, which showed skeletal metastases in one and absent in the other case. Their kidneys showed high renal parenchymal retention of tracer with kidneys looking much HOT than adjacent bones. The differential diagnosis of hot kidneys include nephrocalcinosis, hypercalcemia, hyperparathyroidism, chemotherapy, sickle cell disease, acute renal injury, recent radiotherapy and aluminum breakthrough of 99Mo-99mTc generator. Our patients did not fit in any of these. Hot kidneys in patient with liver cirrhosis have been reported due to hepatorenal syndrome. Although chronic liver parenchymal disease was present in the background of HCC, but our patients were not having hepatorenal syndrome (normal renal function tests). Quality control of generator and MDP vials used showed absence of any aluminum breakthrough and labeling efficiency was greater than 95% respectively. So, the exact cause of hot kidneys in these cases cannot be ascertained and some altered metabolism in liver and hemodynamic changes in body due to HCC might be the cause. Conclusion: High diffuse renal parenchymal retention of 99mTc MDP might be seen on bone scan in HCC cases. Its clinical significance is unknown and needs further research to find out its exact mechanism and cause.

Current Status of Nuclear Medicine Practice in Latin America and the Caribbean.

The practice of nuclear medicine (NM) in the Latin American and Caribbean region has experienced important growth in the last decade. However, there is great heterogeneity among countries regarding the availability of technology and human resources. According to data collected through June 2014 by the International Atomic Energy Agency (IAEA), the total number of γ cameras in the region is 1,231, with an average of 2.16 per million inhabitants. Over 90% of the equipment is SPECT cameras; 7.6% of which have hybrid technology. There are 161 operating PET or PET/CT cameras in 12 member states, representing a rate of 0.3 per million people. Most NM centers belong to the private health system and are in capitals or major cities. Only 4 countries have the capability of assembling 99Mo-99mTc generators, and 2 countries produce 99mTc from nuclear reactors. Cold kits are produced in some countries, and therapeutic agents are mostly imported from outside the region. There are 35 operative cyclotrons. In relation to human resources: there is 1 physician per γ camera, 1.6 technologists per γ camera, 0.1 medical physicist per center, and approximately 0.1 radiochemist or radiopharmacist per center. Nearly 94% of the procedures are diagnostic. PET studies represent about 4% of the total. The future of NM in the Latin American and Caribbean region is promising, with great potential and possibilities. Some of the most important factors driving the region toward greater homogeneity in the availability and application of NM, and bridging the gaps between countries, are clinician awareness of the importance of NM in managing diseases prevalent in the region, increased building of capacity, continuous and strong support from international organizations such as the IAEA through national and regional projects, and strong public-private partnerships and government commitment.

OPTIMIZATION OF 99MO MEASUREMENT IN 99MTC ELUATE SAMPLES USING A SCINTILLATION DETECTION SYSTEM

During elution of 99Mo-99mTc generators used in nuclear medicine, 99Mo might be extracted becoming a radionuclidic impurity. According to the International Atomic Energy Agency, the activity ratio between 99Mo and 99mTc in the eluate, at the moment of administration to the patient, should not exceed 0.015%. The aim of this work is to optimize a methodology to determine 99Mo activity in 99mTc eluates. Efficiency curves were obtained using a NaI(Tl)8"×4" scintillation detector. The methodology was validated by measuring a standard solution of 99Mo. It was concluded that the technique is sensitive to detect 99Mo in 99mTc eluates at levels below international limits.

An Alumina Based 99Mo–99mTc Generator to Produce 99mTc in Organic Medium Suitable for Industrial Radiotracer Applications

An industrial chromatographic 99Mo–99mTc generator has been developed with the aid of chromatographic alumina to obtain 99mTc in a non-aqueous medium. This generator system takes advantage of tributyl phosphate to extract 99mTc selectively with appreciable yield and in high radiochemical and radionuclidic purity. This facile, versatile and efficient approach provides 99mTc at industrial sites in a medium soluble in hydrocarbon solvents, for radiotracer applications.

Polymer Embedded Nanocrystalline Titania Sorbent for 99Mo-99mTc Generator

A new sorbent material, polymer embedded nano crystalline titania (Titanium Polymer-TiP) has been developed, from titanium (IV) chloride and isopropyl alcohol, for the adsorption of 99Mo, which is a precursor to 99mTc, a workhorse in radio-pharmaceuticals. The infrared absorption spectra of the TiP showed peaks corresponding to Ti-O groups. X-ray diffraction pattern of the adsorbent corresponded to rutile TiO2. The surface area of this polymer was 30 m2/g with an average pore size of 40 nm. The average crystallite size of TiO2, embedded in polymer, was found to be 5 nm. TEM micrograph of the adsorbent revealed the network of polymer with dispersed titania phase. Potential of this adsorbent for the preparation of 99Mo-99mTc generator has been explored. 99Mo could be adsorbed on to the adsorbent column containing TiP at pH 1 from which 99mTC could be eluted with normal (0.9%) saline solution with an elution yield of approximately 80%. The quality of the 99mTcO4 obtained was in accordance with the international specifications applicable for radiopharmaceutical use. A process demonstration run was carried out with 1.1 GBq (30 mCi) 99Mo activity level making use of the above adsorbent and consistent results were obtained over a period of one week, which is generally the shelf life of 99MO-99mTC generator.

Study of gels of molybdenum with cerium in the preparation of generators of 99Mo - 99mTc

99mTc has ideal nuclear properties for organ imaging in nuclear medicine, and it is obtained from the 99Mo-99mTc generator. Four different types of generators are available: chromatographic that uses 99Mo from fission of uranium; MEK solvent extraction; Tc2O7 sublimation; gel chromatographic. This work presents the preparation of gel generators of molybdenum with cerium and characterization of the gels: mass ratio between molybdenum and cerium, structure, size of particles and elution percentage of 99mTc after irradiating the gels. Eight gels were prepared at the same temperature of 50 ºC with concentrations of NaOH of 2 and 4 mol/L, mass ratio of 0.31 and 0.38 and final pH of 3.5 and 4.5. The analysis of the results proved that these gels are not adequate for preparation of the generators of 99Mo-99mTc, since the elution percentages are low, when compared with the gel of molybdenum with zirconium.

Determination of 99Mo contamination in a nuclear medicine patient submitted to a diagnostic procedure with 99mTc

99mTc is a radionuclide widely used for imaging diagnosis in nuclear medicine. In Brazil it is obtained by elution from 99Mo-99mTc generators supplied by the Nuclear Energy Research Institute (IPEN). The elution is carried out in radiopharmacy laboratories located in hospitals and clinics. Depending of the quality of the generator and conditions of use during the elution process, 99Mo can be extracted from the column of the generator, becoming a radionuclidic impurity of the eluate used for the obtention of the radiopharmaceutical to be administered to the patient. 99Mo emits high-energy photons and beta particles and its presence degrades the quality of the image and unnecessarily increases the radiation dose delivered to the patient. An in-vivo measurement technique was developed to verify the occurrence of internal contamination by 99Mo in nuclear medicine patients. Direct measurements were made in a volunteer who underwent myocardial scintigraphy with 99mTc-sestamibi. The results indicated the presence of internal contamination of the patien by 99Mot. The activity was tracked for several days, and an assessment of the radiation dose from the contaminant 99Mo was made.

Post-elution concentration of 99mTcO4− by a single anion exchanger column: I: Feasibility of extending the useful life of column chromatographic 99mTc generator

99mTc eluate in 0.7/0.35M acetic acid and in 1:1v/v 0.7M acetic acid: 0.025M ammonium acetate (30–40ml) was conveniently concentrated by passing through a small column of a readily available weak anion exchanger, DEAE cellulose, (200mg, 6×8mm) and subsequent elution with 3ml normal saline, with greater than 90% recovery. The quality of pertechnetate thus obtained and its compatibility for preparing 99mTc compounds were satisfactory. This method was successfully applied to the alumina column chromatographic generator produced in-house and to a commercial 99Mo–99mTc generator after extensive clinical use. Potential for much higher concentration factors with compacted anion exchanger cartridges as well as applicability for 188W–188Re generator are discussed.

Fission Neutron Spectrum Averaged Cross Sections of some Threshold Reactions on Molybdenum: Estimation of Radioactive Impurities in (n, γ)-Produced 99Mo-99mTc Generator System

Fission Neutron Spectrum Averaged Cross Sections of some Threshold Reactions on Molybdenum: Estimation of Radioactive Impurities in (n, γ)-Produced ⁹⁹Mo-^99mTc Generator System

Rapid and sensitive method for the determination of aluminium in 99Mo 99mTc generator eluates

Aluminium in eluates of 99mTc generators can be determined spectrophotometrically or compared visually with a standard solution to determine whether the aluminium content is greater than, equal to, or less than a specified concentration. Eriochrome cyanine R and hexadecylpiridium chloride are used to develop the colour in an ethylenediamine buffered system at pH 7.3

Determination of residual activities in 99mTc generators and 81mKr generators

The residual activities present in spent 99Mo-99mTc generators and 81Rb-81mKr generators were determined from a view point of the disposal of radiopharmaceuticals. The results showed that seven kinds of residual nuclides such as 95Zr-95Nb, 103Ru, 90Sr, etc. were found in 99mTc generators with maximum level of 740 Bq/3.7 GBq (0.02 muCi/100 mCi) at one year after the reference date. In 81mKr generators one year old, six nuclides such as 57Co, 83Rb, 84Rb and others remained and these activities were less than 3.7 kBq/370 MBq (0.1 muCi/10 mCi). On the basis of these data, the disposal of 99mTc generators and 81mKr generators is discussed.

Some remarks on 99Mo-99mTc generator kinetics.

Attention is drawn to some erroneous and incomplete pieces of information on 99Mo-99mTc generator kinetics published in the literature. The assumption that 99mTc is eluted completely from the generator leads to the incorrect 99TmTc activity-time curve plotted in some papers. It is shown that the time at which 99mTc activity in the generator reaches the maximum value depends on the efficiency of 99mTc separation. The expression derived on by authors allows the prediction of 99mTc activity available in the second separation performed several hours after the previous separation.

Residual activity of Tc-generators.

Owing to contamination by long-lived radio-isotopes, the residual activity of an old 99Mo-99mTc generator may be large enough to prevent its disposal. The long-lived impurities of one generator were determined by energy spectrum and half-life measurements. In this generator 46Sc, 51Cr, 60 Co, 92mNb, 95Nb and 124Sb nuclides were found. Only the half-life of 60Co exceeds 3 months, thus a moderately long storage of the generator reduces the activity, and its disposal is then safe.

Assay of radioactive impurity in 99mTc-pertechnetate eluted from 99Mo-99mTc generator (author's transl)

Assay of radioactive impurity in 99mTc-pertechnetate eluted from 99Mo-99mTc generator (author's transl)

Results of regular study on radionuclidic purity of 99mTc obtained from 99Mo-99mTc generators

A total of 39 99mTc eluates obtained from 9 99Mo--99mTc generators delivered by The Radiochemical Centre Amersham during one year was studied with regard to their radionuclide purity. Using a Ge(Li) spectrometer the contaminants 60Co, 103Ru, 131I, 134Cs, 140Ba, 140La and 188Re were found in 99mTc-eluates with average levels ranging from 2.9 X 10(-3) to 2.8 X 10(-1) per cent of 99mTc activity. The additional total body absorbed dose caused by these contaminants, as calculated from their average content in 99mTc eluates, was less than 1% of the dose due to 99mTc pertechnetate.

Ruthenium Radioisotopes as Contaminants in Eluates from 99Mo-99mTc Generators

The measurement of the 106Ru content in 99mTc eluates from 99Mo-99mTc generators is difficult because of the proximity of the 103Ru and 106Ru gamma-ray spectral peaks and the low 106Ru content. 106Ru causes a relatively high whole-body dose, similarly as known contaminants 60Co, 134Cs, 140Ba and some others. Assuming that ruthenium is eliminated from the body with the biological half-life 7.3 days (according to ICRP) the additional absorbed dose caused by 106Ru does not exceed, with regard to the low content of this nuclide, the dose due to 103Ru. The results are given of the preliminary experiment in animals with the aim to determine the biological behaviour of ruthenium radioisotopes after the administration of the 99mTc eluate containing these contaminants.