Nuclear data for medical radionuclides

Ion beam activation of natCu, natTi, natNi and measurement of product formation cross sections at low energy (<10 MeV)

In this study we investigated the production cross sections of natCu(p, x)63,65Zn, natTi(p, x)48V, natNi(p, x)55Co,61Cu and natCu(α, x)66,67,68Ga, natTi(α, x)49,51Cr, natNi(α, x)63,65Zn reactions in the low energy range using the foil activation technique. The samples were activated in vacuum at 5 MV tandem (Pelletron) accelerator installed at National Centre for Physics (NCP), Islamabad, Pakistan. The reaction products were identified with the help of off-line gamma ray spectroscopy system connected with Genie 2000 software. The data analysis revealed the production of different radioisotopes that have valuable importance in monitoring charged-particle beams and medical applications. The measured results were verified by comparing them with earlier evaluated data as well as with the theoretical values given in the TENDL-library based on TALYS-1.9 code calculations.

Status of the decay data for medical radionuclides: existing and potential diagnostic γ emitters, diagnostic β+ emitters and therapeutic radioisotopes

Recommended half-lives and specific well-defined emission energies and absolute emission probabilities are important input parameters that should be well-defined to assist in ensuring the diagnostic and therapeutic efficacy of individual radionuclides when applied in the field of nuclear medicine. Bearing in mind the nature of these requirements, approximately one hundred radionuclides have been considered and re-assessed as to whether their decay data are either adequately quantified, or require further in-depth measurements to improve their existing status and merit full re-evaluations of their decay schemes. The primary aim of such a review is to provide sufficient information on the existing and future requirements for such atomic and nuclear data.

The role of chemistry in accelerator-based production and separation of radionuclides as basis for radiolabelled compounds for medical applications

Radiochemical separations used in large scale routine production of diagnostic and therapeutic radionuclides at a particle accelerator for patient care are briefly outlined. The role of chemistry at various stages of development of a production route of a novel radionuclide, namely nuclear data measurement, high-current targetry, chemical processing and quality control of the product, is discussed in detail. Special attention is paid to production of non-standard positron emitters (e.g. 44gSc, 64Cu, 68Ga, etc.) at a cyclotron and novel therapeutic radionuclides (e.g. 67Cu, 225Ac, etc.) at an accelerator. Some typical examples of radiochemical methods involved are presented.

An overview of nuclear data standardisation work for accelerator-based production of medical radionuclides in Pakistan

The standardisation of nuclear reaction cross section data is an integral part of optimisation of production routes of medical radionuclides. The production cross sections are available for the reactor and cyclotron produced radionuclides to be used for diagnostics or therapeutic procedures. The types of nuclear data needed, and the sources of their availability are summarized. The method of standardisation of charged-particle data is briefly described. A historical overview of research work in Pakistan in this direction is given. Examples of a few medically important radionuclides, such as 64Cu, 86Y, 89Zr, 103Pd, 186Re, etc., whose data were standardised and evaluated are highlighted. Calculated thick target yields from the recommended data are given. Some new directions in the nuclear data research are outlined.

Highly Efficient Micro-Scale Liquid-Liquid In-Flow Extraction of 99mTc from Molybdenum

The trend to achieve even more compact-sized systems is leading to the development of micro-scale reactors (lab-on-chip) in the field of radiochemical separation and radiopharmaceutical production. Technetium-99m extraction from both high and low specific activity molybdenum could be simply performed by MEK-driven solvent extraction if it were not for unpractical automation. The aim of this work is to develop a solvent extraction and separation process of technetium from molybdenum in a micro-scale in-flow chemistry regime with the aid of a capillary loop and a membrane-based separator, respectively. The developed system is able to extract and separate quantitatively and selectively (91.0 ± 1.8% decay corrected) the [^99mTc]TcO₄Na in about 20 min, by using a ZAIPUT separator device. In conclusion, we demonstrated for the first time in our knowledge the high efficiency of a MEK-based solvent extraction process of ^99mTc from a molybdenum-based liquid phased in an in-flow micro-scale regime.

Expanding PET-applications in life sciences with positron-emitters beyond fluorine-18

Positron-emission-tomography (PET) has become an indispensable diagnostic tool in modern nuclear medicine. Its outstanding molecular imaging features allow repetitive studies on one individual and with high sensitivity, though no interference. Rather few positron-emitters with near favourable physical properties, i.e. carbon-11 and fluorine-18, furnished most studies in the beginning, preferably if covalently bound as isotopic label of small molecules. With the advancement of PET-devices the scope of in vivo research in life sciences and especially that of medical applications expanded, and other than "standard" PET-nuclides received increasing significance, like the radiometals copper-64 and gallium-68. Especially during the last decades, positron-emitters of other chemical elements have gotten into the focus of interest, concomitant with the technical advancements in imaging and radionuclide production. With known nuclear imaging properties and main production methods of emerging positron-emitters their usefulness for medical application is promising and even proven for several ones already. Unfortunate decay properties could be corrected for, and β⁺-emitters, especially with a longer half-life, provided new possibilities for application where slower processes are of importance. Further on, (bio)chemical features of positron-emitters of other elements, among there many metals, not only expanded the field of classical clinical investigations, but also opened up new fields of application. Appropriately labelled peptides, proteins and nanoparticles lend itself as newer probes for PET-imaging, e.g. in theragnostic or PET/MR hybrid imaging. Furthermore, the potential of non-destructive in-vivo imaging with positron-emission-tomography directs the view on further areas of life sciences. Thus, exploiting the excellent methodology for basic research on molecular biochemical functions and processes is increasingly encouraged as well in areas outside of health, such as plant and environmental sciences.

Preliminary evaluation of the production of non-carrier added 111Ag as core of a therapeutic radiopharmaceutical in the framework of ISOLPHARM_Ag experiment

Research in the field of radiopharmaceuticals is increasingly promoted by the widespread and growing interest in applying nuclear medicine procedures in both disease diagnosis and treatment. The production of radionuclides of medical interest is however a challenging issue. Along with the conventional techniques other innovative approaches are being investigated and, among those, the ISOLPHARM project is being developed at INFN-LNL (Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali di Legnaro). Such technique foresees the employment of the SPES ISOL facility to produce isobarically pure Radioactive Ion Beams (RIBs), obtained thanks to electromagnetic mass separation and collected on appropriate substrates. The latter are successively recovered and dissolved, allowing thus the chemical separation and harvesting of the nuclides of interest, free from any isotopic contaminant. Although ISOLPHARM can be potentially employed for most of the routinely used medical radioisotopes, its innovation potential is better expressed considering its capability to provide carrier free unconventional nuclides, difficult to produce with state-of-art techniques, such as ¹¹¹Ag, a β^- emitter potentially interesting for therapeutic applications. Thus, in the framework of ISOLPHARM, INFN supported a two-years experiment, called ISOLPHARM_Ag, aimed at evaluating the feasibility of the production of a¹¹¹Ag labelled radiopharmaceutical. The ISOL production yields are estimated by computing intensive Monte Carlo codes, that require an appropriate custom Information Technology infrastructure. The presented work is focused on the first part of the production chain including the capability to extract, ionize, and collect stable Ag beams with SPES technologies. MC calculations were used to estimate the expected ¹¹¹Ag in-target yields, whereas experiments with stable Ag were performed to test the ionization, transport and collection of Ag beams.

225Ac/213Bi generator based on inorganic sorbents

A scheme of an “inverse” generator based on an inorganic sorbent (annealed zirconium and yttrium mixture oxides) has been proposed and tested. The generator demonstrated high yield of the 213Bi product (up to 97 % in 0.5 mL of eluate), high degree of purification from the actinium isotopes (up to 10−2 % of initial 225Ac in 3 M NaNO3 solution), as well as the products of 227Ac decay, and low radiation impact on the sorbent. Application of circulating approach to the sorption of 213Bi provides decreasing processing time to 5 min at higher yield of the product.

Radiochemical aspects of alpha emitting radionuclides for medical application

The use of α-emitting radionuclides in targeted alpha therapy (TAT) holds great potential for treatment of human diseases, such as cancer, due to the short pathlength and high potency of the α particle, which can localize damage to targeted cells while minimizing effects to healthy surrounding tissues. In this review several potential α-emitting radionuclides having emission properties applicable to TAT are discussed from a radiochemical point of view. Overviews of production, radiochemical separation and chelation aspects relative to developing TAT radiopharmaceuticals are provided for the α-emitting radionuclides (and their generator systems) 211At, 224Ra/212Pb/212Bi, 225Ac/213Bi, 227Th/223Ra, 230U/226Th, 149Tb and 255Fm.

Therapeutic Radiometals: Worldwide Scientific Literature Trend Analysis (2008⁻2018)

Academic journals have published a large number of papers in the therapeutic nuclear medicine (NM) research field in the last 10 years. Despite this, a literature analysis has never before been made to point out the research interest in therapeutic radionuclides (RNs). For this reason, the present study aims specifically to analyze the research output on therapeutic radiometals from 2008 to 2018, with intent to quantify and identify global trends in scientific literature and emphasize the interdisciplinary nature of this research field. The data search targeted conventional (¹³¹I, ⁹⁰Y, ¹⁷⁷Lu, ¹⁸⁸Re, ¹⁸⁶Re, ¹⁵³Sm, ⁸⁹Sr, ¹⁸⁶Er) and emergent (⁶⁷Cu, ⁴⁷Sc, ²²³Ra, ¹⁶⁶Ho, ¹⁶¹Tb, ¹⁴⁹Tb, ²¹²Pb/²¹²Bi, ²²⁵Ac, ²¹³Bi, ²¹¹At, ^117mSn) RNs. Starting from this time frame, authors have analyzed and interpreted this scientific trend quantitatively first, and qualitatively after.

In-house cyclotron production of high-purity Tc-99m and Tc-99m radiopharmaceuticals

In the last years, the technology for producing the important medical radionuclide technetium-99m by cyclotrons has become sufficiently mature to justify its introduction as an alternative source of the starting precursor [^99mTc][TcO₄]^- ubiquitously employed for the production of ^99mTc-radiopharmaceuticals in hospitals. These technologies make use almost exclusively of the nuclear reaction ¹⁰⁰Mo(p,2n)^99mTc that allows direct production of Tc-99m. In this study, it is conjectured that this alternative production route will not replace the current supply chain based on the distribution of ⁹⁹Mo/^99mTc generators, but could become a convenient emergency source of Tc-99m only for in-house hospitals equipped with a conventional, low-energy, medical cyclotron. On this ground, an outline of the essential steps that should be implemented for setting up a hospital radiopharmacy aimed at the occasional production of Tc-99m by a small cyclotron is discussed. These include (1) target production, (2) irradiation conditions, (3) separation/purification procedures, (4) terminal sterilization, (5) quality control, and (6) Mo-100 recovery. To address these issues, a comprehensive technology for cyclotron-production of Tc-99m, developed at the Legnaro National Laboratories of the Italian National Institute of Nuclear Physics (LNL-INFN), will be used as a reference example.

Development of novel radionuclides for medical applications

Medical radionuclide production technology is well established. There is, however, a constant need for further development of radionuclides. The present efforts are mainly devoted to nonstandard positron emitters (eg, ⁶⁴ Cu, ⁸⁶ Y, ¹²⁴ I, and ⁷³ Se) and novel therapeutic radionuclides emitting low-range β^- particles (eg, ⁶⁷ Cu and ¹⁸⁶ Re), conversion or Auger electrons (eg, ^117m Sn and ⁷⁷ Br), and α particles (eg, ²²⁵ Ac). A brief account of various aspects of development work (ie, nuclear data, targetry, chemical processing, and quality control) is given. For each radionuclide under consideration, the status of technology for clinical scale production is discussed. The increasing need of intermediate-energy multiple-particle accelerating cyclotrons is pointed out.

Nuclear model analysis of excitation functions of α-particle induced reactions on In and Cd up to 60MeV with relevance to the production of high specific activity 117mSn

Excitation functions were calculated for the α-particle induced reactions ¹¹⁵In(α,x)^117mSn, ¹¹⁴Cd(α,n)^117mSn, ¹¹⁶Cd(α,3n)^117mSn and ^natCd(α,x)^117mSn to analyse the production of the medically important ^117mSn (T_½ = 13.6 d). For calculations three nuclear model codes (i.e. TALYS, EMPIRE and ALICE-IPPE) were used and the results were compared with the available experimental data. For the most important reaction, ¹¹⁶Cd(α,3n)^117mSn, evaluated data are presented. The yield and radionuclidic purity of ^117mSn from each reaction are discussed.

Measurements of excitation functions of α-particle induced reactions on natNi: possibility of production of the medical isotopes 61Cu and 67Cu

Excitation functions of the natNi(α,x)60,61Cu and 64Ni(α,p)67Cu reactions were measured using the stacked-foil activation technique. The experimental data achieved were compared with literature data as well as with nuclear model calculations performed using the code TALYS-1.8. Integral yields from the respective thresholds to 44 MeV were deduced from the measured excitation curves. The >99% pure 61Cu can be produced using the energy window of Eα=20→7 MeV, the yield amounting to 116 MBq/μAh. After a 2 h cooling time, the short-lived 60Cu (T1/2=23 min) impurity will be reduced to <0.1%. Due to low isotopic abundance of 64Ni, the enriched 64Ni target would be needed for the production of 67Cu via the (α,p) reaction. The cost would, however, be very high. In a few cases, particularly above 24 MeV, we have given new data points. In general, our measurements have strengthened the database.

Recent achievements in Tc-99m radiopharmaceutical direct production by medical cyclotrons

^99mTc is the most commonly used radionuclide in the field of diagnostic imaging, a noninvasive method intended to diagnose a disease, assess the disease state and monitor the effects of treatments. Annually, the use of ^99mTc, covers about 85% of nuclear medicine applications. This isotope releases gamma rays at about the same wavelength as conventional X-ray diagnostic equipment, and owing to its short half-life (t_½ = 6 h) is ideal for diagnostic nuclear imaging. A patient can be injected with a small amount of ^99mTc and within 24 h almost 94% of the injected radionuclide would have decayed and left the body, limiting the patient's radiation exposure. ^99mTc is usually supplied to hospitals through a ⁹⁹Mo/^99mTc radionuclide generator system where it is produced from the β decay of the parent nuclide ⁹⁹Mo (t_½ = 66 h), which is produced in nuclear reactors via neutron fission. Recently, the interruption of the global supply chain of reactor-produced ⁹⁹Mo, has forced the scientific community to investigate alternative production routes for ^99mTc. One solution was to consider cyclotron-based methods as potential replacement of reactor-based technology and the nuclear reaction ¹⁰⁰Mo(p,2n)^99mTc emerged as the most worthwhile approach. This review reports some achievements about ^99mTc produced by medical cyclotrons. In particular, the available technologies for target design, the most efficient extraction and separation procedure developed for the purification of ^99mTc from the irradiated targets, the preparation of high purity ^99mTc radiopharmaceuticals and the first clinical studies carried out with cyclotron produced ^99mTc are described.

Cross section measurement of alpha particle induced nuclear reactions on natural cadmium up to 52MeV

Cross sections of alpha particle induced nuclear reactions have been measured on thin natural cadmium targets foils in the energy range from 11 to 51.2MeV. This work was a part of our systematic study on excitation functions of light ion induced nuclear reactions on different target materials. Regarding the cross sections, the alpha induced reactions are not deeply enough investigated. Some of the produced isotopes are of medical interest, others have application in research and industry. The radioisotope ^117mSn is a very important theranostic (therapeutic + diagnostic) radioisotope, so special care was taken to the results for that isotope. The well-established stacked foil technique followed by gamma-spectrometry with HPGe gamma spectrometers were used. The target and monitor foils in the stack were commercial high purity metal foils. From the irradiated targets ^117mSn, ¹¹³Sn, ¹¹⁰Sn, ^117m,gIn, ^116mIn, ^115mIn, ^114mIn, ^113mIn, ¹¹¹In, ^110m,gIn, ^109mIn, ^108m,gIn, ^115gCd and ^111mCd were identified and their excitation functions were derived. The results were compared with the data of the previous measurements from the literature and with the results of the theoretical nuclear reaction model code calculations TALYS 1.8 (TENDL-2015) and EMPIRE 3.2 (Malta). From the cross section curves thick target yields were calculated and compared with the available literature data.

Nuclear data for production and medical application of radionuclides: Present status and future needs

INTRODUCTION

The significance of nuclear data in the choice and medical application of a radionuclide is considered: the decay data determine its suitability for organ imaging or internal therapy and the reaction cross section data allow optimisation of its production route. A brief discussion of reaction cross sections and yields is given.

STANDARD RADIONUCLIDES

The standard SPECT, PET and therapeutic radionuclides are enumerated and their decay and production data are considered. The status of nuclear data is generally good. Some existing discrepancies are outlined. A few promising alternative production routes of ^99mTc and ⁶⁸Ga are discussed.

RESEARCH-ORIENTED RADIONUCLIDES

The increasing significance of non-standard positron emitters in organ imaging and of low-energy highly-ionizing radiation emitters in internal therapy is discussed, their nuclear data are considered and a brief review of their status is presented. Some other related nuclear data issues are also mentioned.

PRODUCTION OF RADIONUCLIDES USING NEWER TECHNOLOGIES

The data needs arising from new directions in radionuclide applications (multimode imaging, theranostic approach, radionanoparticles, etc.) are considered. The future needs of data associated with possible utilization of newer irradiation technologies (intermediate energy cyclotron, high-intensity photon accelerator, spallation neutron source, etc.) are outlined.

CONCLUSION

Except for a few small discrepancies, the available nuclear data are sufficient for routine production and application of radionuclides. Considerable data needs exist for developing novel radionuclides for applications. The developing future technologies for radionuclide production will demand further data-related activities.