A novel method for n.c.a.64Cu production by the64Zn(d, 2p)64Cu reaction and dual ion-exchange column chromatography

Prospects for the production of radioisotopes and radiobioconjugates for theranostics

The development of diagnostic methods in medicine as well as the progress in the synthesis of biologically active compounds allows the use of selected radioisotopes for the simultaneous diagnosis and treatment of diseases, especially cancerous ones, in patients. This approach is called theranostic. This review article includes chemical and physical characterization of chosen theranostic radioisotopes and their compounds that are or could be useful in nuclear medicine.

64Cu production by 14 MeV neutron beam

64Cu is an emerging radionuclide of great interest in personalized nuclear medicine. It is produced by a cyclotron via the reaction 64Ni(p,n)64Cu. This production method increased during the last decades, because small biomedical cyclotrons can be easily installed close to the nuclear medicine department of a hospital. As a matter of fact, 64Ni is a very expensive target material. For this reason, an alternative 64Cu production method was investigated at ENEA by using the quasi-monochromatic 14 MeV fusion neutron beam made available at the Frascati Neutron Generator (FNG) located at the ENEA – Frascati Research Center. In particular, two nuclear reactions were studied: 65Cu(n,2n)64Cu and 64Zn(n,p)64Cu. The radiochemical analysis of the activated samples was performed at the ENEA-NMLNWM laboratory located in ENEA-Casaccia Research Center. The activity measurements were carried out at the ENEA-INMRI, located in the ENEA-Casaccia Research Center, with high metrological level conditions and by assuring their traceability to the 64Cu primary activity standard here developed and maintained. A prediction of the 64Cu production by means of the high-brilliance 14 MeV neutron source named Sorgentina is also discussed.

A simple and robust method for radiochemical separation of no-carrier-added 64Cu produced in a research reactor for radiopharmaceutical preparation

Copper-64 is an excellent theranostic radiometal that is gaining renewed attention of the clinical community in the recent times. In order to meet the increasing demand of this radiometal, we have demonstrated the viability of its production via ⁶⁴Zn (n,p) ⁶⁴Cu reaction in a nuclear reactor. A semi-automated radiochemical separation module based on selective extraction of ⁶⁴Cu as dithizonate complex was developed. The maximum available activity at the end of irradiation was ~ 700 MBq. The overall yield of ⁶⁴Cu after the separation process was >85% and it could be obtained with ~12 GBq/μg specific activity, >99.9% radionuclidic purity and >98% radiochemical purity. The separated ⁶⁴Cu could be utilized for preparation of a wide variety of radiopharmaceuticals.

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.

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.

The copper radioisotopes: a systematic review with special interest to 64Cu

Copper (Cu) is an important trace element in humans; it plays a role as a cofactor for numerous enzymes and other proteins crucial for respiration, iron transport, metabolism, cell growth, and hemostasis. Natural copper comprises two stable isotopes, (63)Cu and (65)Cu, and 5 principal radioisotopes for molecular imaging applications ((60)Cu, (61)Cu, (62)Cu, and (64)Cu) and in vivo targeted radiation therapy ((64)Cu and (67)Cu). The two potential ways to produce Cu radioisotopes concern the use of the cyclotron or the reactor. A noncopper target is used to produce noncarrier-added Cu thanks to a chemical separation from the target material using ion exchange chromatography achieving a high amount of radioactivity with the lowest possible amount of nonradioactive isotopes. In recent years, Cu isotopes have been linked to antibodies, proteins, peptides, and nanoparticles for preclinical and clinical research; pathological conditions that influence Cu metabolism such as Menkes syndrome, Wilson disease, inflammation, tumor growth, metastasis, angiogenesis, and drug resistance have been studied. We aim to discuss all Cu radioisotopes application focusing on (64)Cu and in particular its form (64)CuCl2 that seems to be the most promising for its half-life, radiation emissions, and stability with chelators, allowing several applications in oncological and nononcological fields.

The present and future of medical radionuclide production

Medical radionuclide production technology is well established. Both reactors and cyclotrons are utilized for production; the positron emitters, however, are produced exclusively using cyclotrons. A brief survey of the production methods of most commonly used diagnostic and therapeutic radionuclides is given. The emerging radionuclides are considered in more detail. They comprise novel positron emitters and therapeutic radionuclides emitting low-range electrons and α-particles. The possible alternative production routes of a few established radionuclides, like 68Ga and 99mTc, are discussed. The status of standardisation of production data of the commonly used as well as of some emerging radionuclides is briefly mentioned. Some notions on anticipated future trends in the production and application of radionuclides are considered.

New trends in nuclear data research for medical radionuclide production

Nuclear reaction cross section data are of great significance in optimisation of production routes of radionuclides. This article deals with some newer aspects of data research related to production of both standard and novel radionuclides. The recent work to standardise the known data is discussed and new measurements with regard to further optimisation of production routes of some commonly used radionuclides are mentioned. Attempts to increase the specific activity of some reactor-produced radionuclides through the use of charged-particle induced reactions are outlined. The jeopardy in the supply of99mTcviaa fission-produced99Mo/99mTc generator is considered and its possible direct production at a cyclotron is briefly discussed. Regarding the novel radionuclides, development work is presently focussed on non-standard positron emitters for diagnosis and on low-range highly ionising radiation emitters for internal radiotherapy. Recent nuclear reaction cross section measurements related to the production of the two types of radionuclides are briefly reviewed and some anticipated trends in nuclear data research are considered.

Preparation of 67Cu via deuteron irradiation of 70Zn

A method for preparation of 67Cu based on deuteron irradiation of enriched 70Zn is presented. Cross-sections for 67Cu formation were determined by the stacked foil technique for deuteron energies in the range from 10 to 20 MeV for the first time. Irradiations of 70Zn foils were followed by radiochemical separation of 67Cu from the target material and co-produced radionuclidic impurities. The maximum cross-section value of 25.5 ± 2.2 mb was reached at 19 MeV. The integral yield in the energy window of 20 → 10 MeV on 95% enriched 70Zn is estimated at 4.2 MBq/μA h (110 μCi/μA h) or 375 MBq/μA (10 mCi/μA) at saturation.

Update on 67Cu half-life

The half-life of 67Cu was newly determined by measurement of its 185 keV γ-ray (48.7%) over the period of 13 d (approx. 5 × T 1/2). 67Cu was prepared by deuteron irradiation of enriched 70Zn targets. The 67Cu half-life value which resulted from five independent measurements is estimated to be 61.81(22) h.

Paving the way to personalized medicine: production of some theragnostic radionuclides at Brookhaven National Laboratory

This paper introduces a relatively novel paradigm that involves specific individual radionuclides or radionuclide pairs that have emissions that allow pre-therapy low-dose imaging plus higher-dose therapy in the same patient. We have made an attempt to sort out and organize a number of such theragnostic radionuclides and radionuclide pairs that may potentially bring us closer to the age-long dream of personalized medicine for performing tailored low-dose molecular imaging (SPECT/CT or PET/CT) to provide the necessary pre-therapy information on biodistribution, dosimetry, the limiting or critical organ or tissue, and the maximum tolerated dose (MTD), etc. If the imaging results then warrant it, it would be possible to perform higher-dose targeted molecular therapy in the same patient with the same radiopharmaceutical. A major problem that remains yet to be fully resolved is the lack of availability, in sufficient quantities, of a majority of the best candidate theragnostic radionuclides in a no-carrier-added (NCA) form. A brief description of the recently developed new or modified methods at BNL for the production of four theragnostic radionuclides, whose nuclear, physical, and chemical characteristics seem to show great promise for personalized cancer therapy are described.

Development of novel positron emitters for medical applications: nuclear and radiochemical aspects

In molecular imaging, the importance of novel longer lived positron emitters, also termed as non-standard or innovative PET radionuclides, has been constantly increasing, especially because they allow studies on slow metabolic processes and in some cases furnish the possibility of quantification of radiation dose in internal radiotherapy. Considerable efforts have been invested worldwide and about 25 positron emitters have been developed. Those efforts relate to interdisciplinary studies dealing with basic nuclear data, high current charged particle irradiation, efficient radiochemical separation and quality control of the desired radionuclide, and recovery of the enriched target material for reuse. In this review all those aspects are briefly discussed, with particular reference to three radionuclides, namely 64Cu, 124I and 86Y, which are presently in great demand. For each radionuclide several nuclear routes were investigated but the ( p,n) reaction on an enriched target isotope was found to be the best for use at a small-sized cyclotron. Some other positron emitting radionuclides, such as 55Co, 76Br, 89Zr, 82mRb, 94mTc, 120I, etc., were also produced via the low-energy (p,n), (p,α) or (d,n) reaction. On the other hand, the production of radionuclides 52Fe, 73Se, 83Sr, etc. using intermediate energy (p,xn) or (d,xn) reactions needs special consideration, the nuclear data and chemical processing methods being of key importance. In a few special cases, a high intensity 3He- or α-particle beam could be an added advantage. The production of some potentially interesting positron emitters via generator systems, for example 44Ti/44Sc, 72Se/72As and 140N d/140Pr is considered. The significance of new generation high power accelerators is briefly discussed.

A practical guide to the construction of radiometallated bioconjugates for positron emission tomography

Positron emission tomography (PET) has become a vital imaging modality in the diagnosis and treatment of disease, most notably cancer. A wide array of small molecule PET radiotracers have been developed that employ the short half-life radionuclides (11)C, (13)N, (15)O, and (18)F. However, PET radiopharmaceuticals based on biomolecular targeting vectors have been the subject of dramatically increased research in both the laboratory and the clinic. Typically based on antibodies, oligopeptides, or oligonucleotides, these tracers have longer biological half-lives than their small molecule counterparts and thus require labeling with radionuclides with longer, complementary radioactive half-lives, such as the metallic isotopes (64)Cu, (68)Ga, (86)Y, and (89)Zr. Each bioconjugate radiopharmaceutical has four component parts: biomolecular vector, radiometal, chelator, and covalent link between chelator and biomolecule. With the exception of the radiometal, a tremendous variety of choices exists for each of these pieces, and a plethora of different chelation, conjugation, and radiometallation strategies have been utilized to create agents ranging from (68)Ga-labeled pentapeptides to (89)Zr-labeled monoclonal antibodies. Herein, the authors present a practical guide to the construction of radiometal-based PET bioconjugates, in which the design choices and synthetic details of a wide range of biomolecular tracers from the literature are collected in a single reference. In assembling this information, the authors hope both to illuminate the diverse methods employed in the synthesis of these agents and also to create a useful reference for molecular imaging researchers both experienced and new to the field.

Novel polymer vectors of 64Cu

We describe a preparation of novel polymer vectors of 64Cu based on co-polymers of poly- (N-isopropylacrylamide) and poly- (N-hydroxypropylmethacrylamide). DOTA, DTPA, dipicolylamine, thiosemicarbazone and Ag-ionophore-II ligands were tested to bind 64Cu in a polymer chain. Labeling yields with no-carrier-added 64Cu varied from 95 to 99% in 30 min. at laboratory temperature. Vectors were stable in vitro for 24 h in human serum and might be prospective for targeted 64Cu radio or combined radiochemotherapy.

Charged particle induced reaction cross section data for production of the emerging medically important positron emitter64Cu: A comprehensive evaluation

The radionuclide64Cu (T1/2=12.7 h) is an important non-standard positron emitter, suitable for combining PET imaging and targeted therapy. Its production in no-carrier-added form is doneviacharged particle induced reactions, and considerable amount of cross section data are available in the literature. We evaluated seven reactions, namely64Ni(p,n)64Cu,64Ni(d, 2n)64Cu,68Zn(p, αn)64Cu,66Zn(p, 2n)64Cu,64Zn(d, 2p)64Cu,66Zn(p, α)64Cu andnatZn(d,x)64Cu. Data analysis was generally limited up to about 25 MeV and the consistency check of experimental data was carried out using the nuclear model codes STAPRE, EMPIRE and TALYS. In a few cases experimental data were available up to 100 MeV; the consistency check in the high energy region was done only using the code TALYS. A statistical procedure (supported by nuclear model calculations) was then used to fit the data. The derived recommended sets of data, together with 95% confidence limits, are reported. The integral yields calculated from those data are also given. A critical comparison of the various production routes of64Cu is presented. The64Ni(p,n)64Cu reaction, utilizing a highly enriched target, is the method of choice.