Radionuclides In Nuclear Medicine Research Articles

Mausolates: Large-Cavity Chelates with Potential as Delivery Vehicles in Nuclear Medicine.

A new type of diborate clathrochelate (cage) ligand featuring nine inwardly pointing nitrogen donors that form a large, rigid cavity, termed a mausolate, is presented. The cavity size and high denticity make this an attractive delivery vehicle for large radionuclides in nuclear medicine. Metal mausolate complexes are stable to air and water (neutral pH) and display extremely high thermal stability (>400 °C). Lanthanide uptake by the mausolate ligand occurs rapidly in solution at room temperature and once complexed, the lanthanide ions are not displaced by a 250-fold excess of a competitive lanthanide salt over more than one week.

Study on (n,p) reactions of 58Ni, 99Tc, 99Ru, 131Xe, 133Cs and 186Os radioisotopes used in medicine

In the last decade, nuclear medicine appears to be a good choice of medicine. 58Co, 99Mo, 99Tc, 99Re, 133Xe and 186Re are very important radionuclides for nuclear medicine. In this study, the excitation functions of 58Ni (n, p) 58Co, 99Tc (n, p) 99Mo, 99Ru (n, p) 99Tc, 131Xe (n, p) 131I, 133Cs (n, p) 133Xe and 186Os (n, p) 186Re nuclear reactions were calculated at neutron energies between 1 and 20 MeV using TALYS 1.95 and EMPIRE 3.2 nuclear codes. Furthermore, the cross sections were calculated with the empirical formula derived in our past study at 14–15 MeV. The obtained results were compared with the measured values in EXFOR library, and with the evaluated data of (JENDL-4.0/HE, JEFF-3.3, TENDL-2019, ENDF/B-VIII.0, IRDFF-II, JENDL/ImPACT-18). The results are in good agreement with those of the evaluated data libraries and experimental results and indicates that these radioisotopes can be produced by smaller cyclotrons.

How Efficient Are Monte Carlo Calculations Together With the Q-System to Determine Radioactive Transport Limits? Case Study on Medical Radionuclides.

The development of the so-called theranostics approach, in which imaging information are used to define a personalized therapeutic strategy, is driving the increasing use of radionuclides in nuclear medicine. They are artificially produced either in nuclear reactors, charged particle accelerators, or using radionuclide generators. Each method leads to radioisotopes with different characteristics and then clinical utility. In the first two cases they are extracted from stable or radioactive target bombarded with a particle beam. After extraction/purification of the target, the radionuclides, either implanted on solid or in liquid form, needs to be transported to a centralized production site, a radiopharmacy or an hospital. The transport of needed radioactive material must obey strict rules. For a radionuclide, a limit in activity that it is possible to transport has been established for each type of allowed packages. For type A package these limits are called A1 (for special form sources, i.e., certified perfectly sealed and encapsulated sources) and A2 (for non-special form sources). However, these limits can be easily reached if the activity to transport is high or if the radionuclide of interest is a “non–conventional” one. Indeed, for many radionuclides, there are no available/tabulated A1 and A2 and, in these cases, a very conservative set of values is imposed. This is in particular the case for some of the non-conventional radionuclide of interest in medicine (as for example Tb-149 or Tb-161). The non-tabulated values, and in general the A1/A2 limit, can be evaluated following the so-called Q-system and using Monte Carlo calculations. In the present work, we have used the MCNPX Monte Carlo code to evaluate dose rate values in different exposure scenarios. This has allowed us to determine A1/A2 coefficients for several non-conventional radionuclides of interest for medical applications. The developed technique can be extended easily to other radionuclides and can be adapted in case of changes in regulatory rules.

Production of neutron deficient rare earth radionuclides by heavy ion activation

Abstract The attempts to produce neutron deficient radioisotopes of rare Earth elements by heavy ion activation are discussed in this review. The heavy ion induced reaction products have large atomic number difference with that of the target; therefore, radiochemical separation of no-carrier-added radio-lanthanides from the target matrix becomes easier. Heavy ion induced reactions also allow the production of rare Earth radionuclides from non-rare Earth target by tailor-made target-projectile combinations, and in those cases, radiochemical separations become even more easier. In general, the cross sections of heavy ion induced reactions are less than those of light charged particle induced reactions. However, some of the heavy ion induced reactions have comparable cross sections with those of light ion induced reactions. The range of heavy ions is also much smaller in the target matrix than that of lighter charged particles. These points hinder application of heavy ion induced reactions to produce radionuclides for nuclear medicine.

Yields of Photo-Proton Reactions on Nuclei of Nickel and Separation of Cobalt Isotopes from Irradiated Targets.

Nowadays, cobalt isotopes 55Co, 57Co, and 58mCo are considered to be promising radionuclides in nuclear medicine, with 55Co receiving the most attention as an isotope for diagnostics by positron emission tomography. One of the current research directions is dedicated to its production using electron accelerators (via photonuclear method). In our work, the yields of nuclear reactions occurring during the irradiation of natNi and 60Ni by bremsstrahlung photons with energy up to 55 MeV were determined. A method of fast and simple cobalt isotopes separation from irradiated targets using extraction chromatography was developed.

Development of implantation substrates for the collection of radionuclides of medical interest produced via ISOL technique at INFN-LNL

Accelerator-based techniques with electromagnetic mass separation are considered among the most innovative and promising strategies to produce non-conventional radionuclides for nuclear medicine. Such approach was successfully used at CERN, where the dedicated MEDICIS facility was built, and at TRIUMF, where the ISAC radioactive beam facility was used to produce unconventional α-emitters. In such framework, the Legnaro National Laboratories of the Italian Institute of Nuclear Physics (INFN-LNL) proposed the ISOLPHARM project (ISOL technique for radioPHARMaceuticals), which will exploit radionuclides producible with the SPES (Selective Production of Exotic Species) ISOL (Isotope Separation On-Line) facility to develop novel radiopharmaceuticals. The ISOL technique utilizes the irradiation with a primary beam of particles/nuclei of a production target where radionuclides are produced. A radioactive ion beam is subsequently extracted from the production target unit, and transported up to an analyzing magnet, where non-isobaric contaminants are filtered out. The so-obtained purified radioactive beam is dumped onto an implantation substrate, referred as collection target. Then, the desired nuclides can be chemically harvested from the collected isobars, and the isotopically pure atom collection can be employed to radiolabel high specific activity radiopharmaceuticals. Metallic deposition targets in the form of coated metal foils were mostly used at TRIUMF and CERN. At ISOLPHARM, a different approach is under investigation which foresees the use of soluble cold-pressed collection targets, possibly facilitating the chemical purification process of the collected radionuclides. In this study, the production and characterization of some of the ISOLPHARM collection targets is presented, in particular, soluble salts (NaCl and NaNO3) and organic materials widely used for pharmaceutical tablets production are considered. All such materials proved to be potentially suitable as collection targets, since solid samples were easily produced and resulted compatible with the vacuum conditions required for the ion implantation process. Furthermore, some of the selected substrates were used for proof-of-concept deposition tests with stable silver, to prove their suitability as ISOLPHARM deposition substrates for silver-111, a promising candidate for radiotherapy. Such tests highlighted possible scenarios useful for the development of new alternative materials, as the use of insoluble organic targets.

Radiochemical separation of 224Ra from 232U and 228Th sources for 224Ra/212Pb/212Bi generator

The application of diagnostic and therapeutic radionuclides in nuclear medicine has grown significantly and has translated into the increased interest in radionuclide generators and their development. 224Ra and its shorter-lived daughters, 212Pb and 212Bi, are very interesting radionuclides from Targeted Alpha Therapy point of view for treatment of small cancers or metastatic forms. The purpose of the present work was to develop a simple generator for rapid elution of carrier-free 224Ra from 232U or 228Th sources by radiochemical separation based on extraction chromatography with the utilization of a home-made material. The bis(2-ethylhexyl) hydrogen phosphate (HDEHP) extractant was immobilized on polytetrafluroethylene (PTFE) grains and its ability to selectively adsorb 232U and 228Th, with simultaneous high elution recovery of 224Ra, was checked over few years. The 224Ra was quantitatively eluted with small volume (3–5 mL) of 0.1 M HNO3 with low breakthrough (<0.005%) and was used for further milking of 212Bi and 212Pb from DOWEX 50WX12 by 0.75 M and 2.0 M HCl, respectively. The elaborated here methods allowed high recovery of 224Ra, 212Pb and 212Bi radionuclides and their application in radiolabeling of various biomolecules.

Evaluation of the nuclear reaction cross sections via proton induced reactions on 72Ge and 76Se to produce 72As: A potential entrant for the theranostic pairs

Theranostic applications of radiopharmaceuticals have revolutionized present era specially, dealing with cancer diseases. Increase in the uses of radionuclides in nuclear medicine has resulted in the demands of optimized new radionuclides to be produced focussing on the economy, simplicity and maximum yield. Two radionuclides of arsenic offer a well agreed theranostic systems namely 77As and 72As. Some arsenic radionuclides are capable of positron-emission, with range of hour to weeks half-lives and have potential to be used for nuclear medicine. Present work will elucidate the production of 72As on Germanium and Selenium via proton induced nuclear reactions. The experimental results obtained by several nuclear reactions were analyzed. The results of nuclear model codes namely ALICE-IPPE, EMPIRE-3.2.3 and TALYS-1.9 are compared with the experimental cross sections to generate recommended cross section data. Recommended excitation functions are used to compute the thick target yields (TTY) of 72As. Assessment of radionuclidic impurities are also studied and comparison of several radionuclidic impurities is done. To produce 72As,72Ge (p, n)72As, 73Ge (p, 2n)72As, 74Ge (p, 3n)72As and 76Se (p, x)72As reactions in different energy ranges are discussed. We have identified 72Ge (p, n)72As reaction; gives pre-eminent yield with least impurities mark it as feasible entrant to be applied in Positron Emission Tomography (PET) and theranostic applications.

SRIM and FLUKA simulation for target design

ABSTRACTThe increasing demand for radionuclides in nuclear medicine requires optimised production strategies. This study investigates whether any strategy is able to predict radionuclide production yields with simulations using the Monte Carlo code FLUKA. In further studies on the nuclear reaction 89Y(p,n)89Zr FLUKA results are compared with experimental data. In general, there is good agreement between both. Discrepancies typically can be explained by experimental details and problems.

Medically-derived radionuclides levels in seven heterogeneous urban wastewater treatment plants: The role of operating conditions and catchment area

In nuclear medicine radionuclides are administered to patients both for diagnosis or treatment. Subsequently, the excreta from patients, enriched in radionuclides, enter the sewerage networks and reach wastewater treatment plants (TPs). Characterization of inflow wastewaters, sewage effluents and sewage sludges in the seven different urban WWTPs in the Barcelona Metropolitan Area (BMA) has been done and 131I, 99mTc, 111In, 67Ga and 123I concentrations were determined by gamma-spectroscopy. In order to explain the diversity of nuclear medicine short-lived radionuclide concentrations found in the BMA, mean sewage sludge ages and wastewater hydraulic retention times were determined, NM services located and patient management guidelines described. Results were found to vary greatly among the different TPs in inflow wastewaters, sewage effluents and sewage sludges. 131I and 99mTc activity concentrations showed the highest values in most of the inflow wastewaters, sewage effluents and sewage sludges. In the integrated analysis of the present findings, a large-sized TP (320,000 m3/d) from the BMA urban wastewater treatment system shows higher levels and detection frequencies of medically-derived radionuclides. The maximums detected in the sludges from this TP, are partly explained by the relatively low sewage sludge ages. Furthermore, inflow wastewater hydraulic retention times and sludge ages in the TPs are long enough for decay of the short-lived nuclear medicine radionuclides studied (t1/2 ≤ 8d) in such a way that TPs work as abatement systems and decrease the levels of radioactivity both in the effluent and in the final sludge. An integrated analysis of 7 TPs from the same system has been carried out to go further into the dynamics of medically-derived radionuclides in it.

Ensuring effective and sustainable radionuclide delivery and its impact on the development of nuclear medicine in the developing world with special reference to Nigeria.

Recent activities of Boko Haram, a local extremist group in Nigeria, raise concerns about a nuclear terrorist attack. Whereas nuclear medicine (NM) relies on the timely delivery of radioactive sources, a robust security structure that assures public safety is the backbone for its beneficial use. NM radionuclides have short half-lives and carry an insignificant risk for acts of terrorism. Yet, their importation and delivery in Nigeria receive undue scrutiny in a bid to implement a strict nuclear security regime. These actions prevent timely delivery of radionuclides with direct consequences on quality and economic viability of nuclear medicine. There have been no accounts of terrorist acts accomplished with NM radionuclides. Thus, it is important the NM community question the current approach that has contributed to the loss of NM services in Nigeria and proposes a more logical strategy for securing their supply. We also highlight the need for developing local pragmatic solutions when implementing global recommendations in developing countries.

A study on the excitation functions of 60,62Ni(α,n), 60,61Ni(α,2n), 58,64Ni(α,p), natNi(α,x) reactions

The prediction of nuclear cross-section data is crucial, especially in the absence of experimental data or in the difficulty of these experimental data. Nickel (Ni) is an important material in fusion and fission reactor technologies, the production of radionuclides in nuclear medicine, and many other fields. In this study, the excitation functions for 60,62Ni(α,n), 60,61Ni(α,2n), 58,64Ni(α,p), and natNi(α,x) reactions have been investigated by using pre-equilibrium reaction models. The calculations of the excitation functions for the reactions are used with the geometry-dependent hybrid model in ALICE/ASH code and the two-component exciton model in TALYS 1.8 code. The obtained results are compared to each other, and the experimental data are taken from the EXFOR database.

Micro-dosimetry calculation of Auger-electron-emitting radionuclides mostly used in nuclear medicine using GEANT4-DNA

A large number of nuclear medicine radionuclides are Auger-electron-emitters and internal conversion electrons which can transmit significant doses to the patient during diagnosis. Therefore, the dosimetry of these radioisotopes is necessary for the evaluation of their biological effects and their use for treatment and targeted-radiotherapy.In this study, dosimetry calculation of a number of widely used radioisotopes in nuclear medicine was performed on a cellular scale using Geant4-DNA simulation.S-values of some of the diagnostic radioisotopes, including 123I, 125I, 99mTc, 67Ga, 201Tl, and 111In, were evaluated in a homogeneous spherical geometry model with unit density in which the cell and nucleus were concentric. The results revealed that S-values of these diagnostic radioisotopes were mainly greater than S-values of the radioisotope 131I, which emits β-particles; they were lower but can be compared with 211At (emitter of alpha particles) in the cellular scale. It shows better the importance of dosimetry calculation of diagnostic Auger-electron-emitting radioisotope in a cellular scale and their applicability in treatment. It should be noted that the S-values obtained out of the Geant4-DNA simulation are in line with the values of the other codes and the MIRD technique.

Presence of artificial radionuclides in samples from potable water and wastewater treatment plants

Human activity, such as the operation of nuclear power plants (NPPs) and the use of radionuclides in nuclear medicine, results in the presence of artificial radionuclides in surface waters, which may even reach potable water treatment plants (PWTPs) and wastewater treatment plants (WWTPs).In this study, water and sludge samples from a PWTP are radiologically monitored. The incoming water of the plant is influenced by the presence of an NPP upstream. Two WWTPs receiving wastewater from medical centres and other origins are also studied. As a result, 131I, 60Co and 137Cs have been determined in the dewatered sludge samples from the PWTP, while 131I, 99mTc, 67Ga and 111In were detected in the sludge samples from the WWTPs. The radionuclide activities in the influent water from the WWTPs studied were lower than the minimum detectable activity values. Therefore, on the basis of our results, the analysis of sludge samples is very useful as it enables the concentration of any radionuclides that may be present in the incoming water.Lastly, as higher activity of 131I was detected in the samples studied, the total effective dose was assessed for WWTP workers, as they handle dewatered sludge containing this radionuclide. It can be concluded that there is no risk in terms of total exposure.

Use of IAEA Radiation Dose Criteria to Assess the Need for Internal Radiation Dosimetry in Nuclear Medicine Practices

&lt;p&gt;The IAEA Safety Guide RS-G-1.2 recommends that occupational radiation monitoring should be implemented whenever it is likely that committed effective doses from annual intakes of radionuclides would exceed1mSv. This study presents the analysis of IAEA methodology for the evaluation of the need for the implementation of an internal monitoring program; considering that it should be carried out whenever the potential internal exposure of incorporation leads to a value of annual committed effective dose equal or higher than 1 m Sv. The IAEA criteria applied to commonly used radionuclides in nuclear medicine, taking into consideration usual manipulated unsealed radioactive sources and handling conditions. It is concluded that the handling of unsealed radioactive sources presents the risk of internal radiation exposure to the workers, requiring the implementation of an internal dosimetry program by the concerned Nuclear Medicine Institutes/Centers. &lt;/p&gt;&lt;p&gt;Bangladesh J. Nuclear Med. 20(1): 51-55, January 2017 &lt;/p&gt;

A preliminary study for the production of high specific activity radionuclides for nuclear medicine obtained with the isotope separation on line technique

Radiopharmaceuticals represent a fundamental tool for nuclear medicine procedures, both for diagnostic and therapeutic purposes. The present work aims to explore the Isotope Separation On-Line (ISOL) technique for the production of carrier-free radionuclides for nuclear medicine at SPES, a nuclear physics facility under construction at INFN-LNL. Stable ion beams of strontium, yttrium and iodine were produced using the SPES test bench (Front-End) to simulate the production of 89Sr, 90Y, 125I and 131I and collected with good efficiency on suitable targets.

Dose rate constants for the quantity Hp(3) for frequently used radionuclides in nuclear medicine

According to recent studies, the human eye lens is more sensitive to ionising radiation than previously assumed. Therefore, the dose limit for personnel occupationally exposed to ionising radiation will be lowered from currently 150 mSv to 20 mSv per year. Currently, no data base for a reliable estimation of the dose to the lens of the eye is available for nuclear medicine. Furthermore, the dose is usually not monitored. The aim of this work was to determine dose rate constants for the quantity Hp(3), which is supposed to estimate the dose to the lens of the eye. For this, Hp(3)-dosemeters were fixed to an Alderson Phantom at different positions. The dosemeters were exposed to radiation from nuclides typically used in nuclear medicine in their geometries analog to their application in nuclear medicine, e.g. syringe or vial. The results show that the handling of high-energy beta (i.e. electron or positron) emitters may lead to a relevant dose to the lens of the eye. For low-energy beta emitters and gamma emitters, an exceeding of the lowered dose limit seems to be unlikely.

Impact of radiation protection means on the dose to the lens of the eye while handling radionuclides in nuclear medicine

The human eye lens appears to be more radiosensitive than previously assumed. The reduction of the limit for the dose to the lens of the eye to 20 mSv per year has been passed in the current Euratom Directives (2013).Therefore, in this work the impact of laboratory glasses and X-ray protective goggles was investigated and reciprocal attenuation factors (i.e. transmission factors) for different nuclides (Tc-99m, I-131, Y-90, F-18 and Ga-68) were determined. The radionuclides in typical geometry (syringe, applicator) were positioned at a distance of 50 cm to the eyes of four Alderson-Head-Phantoms. Different dosemeters measuring Hp(3) respective Hp(0.07) were fixed to the eyes of the phantoms, either behind the glasses or without any protection means, respectively.The mean reciprocal attenuation factors were determined to be between unity for F-18 and I-131 using laboratory glasses (no attenuation effect) and < 0.01 for Y-90 using X-ray protective goggles. All other results were between these extremes. It has been shown, that prospective doses to the lens of the eye can be reduced significantly by using appropriate radiation protection means, especially for those dose-relevant beta radiation emitting nuclides such as Y-90.

Is there an interest to use deuteron beams to produce non-conventional radionuclides?

With the recent interest on the theranostic approach, there has been a renewed interest for alternative radionuclides in nuclear medicine. They can be produced using common production routes, i.e., using protons accelerated by biomedical cyclotrons or neutrons produced in research reactors. However, in some cases, it can be more valuable to use deuterons as projectiles. In the case of Cu-64, smaller quantities of the expensive target material, Ni-64, are used with deuterons as compared with protons for the same produced activity. For the Sc-44m/Sc-44g generator, deuterons afford a higher Sc-44m production yield than with protons. Finally, in the case of Re-186g, deuterons lead to a production yield five times higher than protons. These three examples show that it is of interest to consider not only protons or neutrons but also deuterons to produce alternative radionuclides.

Therapeutic radionuclides in nuclear medicine: current and future prospects.

The potential use of radionuclides in therapy has been recognized for many decades. A number of radionuclides, such as iodine-131 ((131)I), phosphorous-32 ((32)P), strontium-90 ((90)Sr), and yttrium-90 ((90)Y), have been used successfully for the treatment of many benign and malignant disorders. Recently, the rapid growth of this branch of nuclear medicine has been stimulated by the introduction of a number of new radionuclides and radiopharmaceuticals for the treatment of metastatic bone pain and neuroendocrine and other malignant or non-malignant tumours. Today, the field of radionuclide therapy is enjoying an exciting phase and is poised for greater growth and development in the coming years. For example, in Asia, the high prevalence of thyroid and liver diseases has prompted many novel developments and clinical trials using targeted radionuclide therapy. This paper reviews the characteristics and clinical applications of the commonly available therapeutic radionuclides, as well as the problems and issues involved in translating novel radionuclides into clinical therapies.