DOI 10.1515/ract-2013-2194 | Radiochim. Acta 2014; 102(8): 669–680 Simone Manenti*, Elisa Persico, Kamel Abbas, Mauro L. Bonardi, Luigi Gini, Flavia Groppi, Uwe Holzwarth, and Federica Simonelli Excitation functions and yields for cyclotron production of radiorhenium via deuteron irradiation: nat W(d,xn) 181,182(A+B),183,184(m+g),186g Re nuclear reactions and tests on the production of 186g Re using enriched 186 W Abstract: Excitation functions, thin- and thick-target yields for the 181−186g Re and 187 W radionuclides were mea- sured by the activation stacked-foil thecnique on natu- ral tungsten foils for deuteron energies up to 18.0MeV. These cross sections were validated by comparing the ex- perimental results for thick-target yields with those calcu- lated by integration of the thin-target yields. It was found that the maximum 186g Re content by irradiation of natural tungsten is about 55%, a higher value compared with the one found for proton beam, but not sufcient to use nat- ural tungsten for medical purposes yet. Thus, in order to have a higher specifc activity  S of 186g Re , the use of en- riched 186 W target is necessary. Therefore the irradiation of a thick target of enriched 186 W by accelerated deuterons was studied and the results for the production of 186g Re were compared with those obtained from the irradiation of the same target by accelerated protons. It was found that the deuteron irradiation is preferable for three reasons: larger yield, less contamination by tantalum radioisotopes and smaller required amount of the target, which simplify the separation of the 186g Re from the target itself. Keywords: Rhenium, 186g Re , Excitation function, Yield, Deuteron, Cyclotron, Metabolic radioimmunoterapy. || *Corresponding Author: Simone Manenti, LASA, Università degli Studi di Milano and INFN-Milano, via F.lli Cervi 201, I-20090 Segrate (MI), Italy, e-mail: simone.manenti@mi.infn.it Elisa Persico, Mauro L. Bonardi, Luigi Gini, Flavia Groppi: LASA, Università degli Studi di Milano and INFN-Milano, via F.lli Cervi 201, I-20090 Segrate (MI), Italy Kamel Abbas, Uwe Holzwarth, Federica Simonelli: Institute for Health and Consumer Protection, IHCP, JRC-Ispra, EC via E. Fermi 1, I-21020 Ispra, Varese, Italy 1 Introduction Radionuclides (RNs) play an important role in nuclear medicine both for diagnosis and radiotherapy [1–4]. In or- der to avoid interference with the regular metabolism or during the labelling with some molecules for the produc- tion of radiopharmaceuticals, high specifc activity  S (ac- tivity of the RN of interest/mass of all isotopic carriers, sta- ble and radioactive of the same RN, in GBqg −1 ) RNs are required. In general RNs by neutron irradiation in nuclear reactors are obtained intrinsically with low and in Carrier Added form  S (CA), because they are produced through (,) reactions: the product and the target are isotopes of the same element and cannot be separated by chemical methods. Otherwise it is possible to produce RNs with very high specifc Activity in No Carrier Added form  S (NCA), near to carrier free value, by bombarding the targets with charged particles through (,) or (,) nuclear reac- tions [5, 6]. In particular therapeutic radiopharmaceuticals are ex- pected to deliver large doses of ionizing radiation to spe- cifc region of interest in the body (primary cancers and/or their metastases), while minimizing the exposure of the healthy tissues to the radiation. So the selection of the right candidates for radiotherapy depends on the decay physical characteristics of the RN, the chemical nature of the compound and the biological behaviour of the radio- pharmaceutical [1]. An example of RN with suitable prop- erties for metabolic radiotherapy is rhenium-186g. 186g Re is a - emitter with a half-life of 90.64 h [7]. The  end-point energies of 1 069.5, 932.3keV suggest that this RN is a good candidate for cancers with small dimensions (from few millimetres to few centimetres). Its -emission at 137.155keV [7] is in the energy range suit- able for SPECT. Presently 186g Re is used experimentally in metabolic radiotherapy for palliative purposes and with Brought to you by | Uniwersytet Warszawski Authenticated Download Date | 5/25/15 12:54 PM