Cyclotron Production of High Specific Activity 186gRe for Metabolic Radiotherapy

Patients with primary breast, prostate and lung cancer have a high frequency of bone metastases, ranging from 65% to 85%. Pain palliation in patients suffering from an advanced stage disease is a relevant practice to achieve a better quality of life. For this purpose bone-seeking radiopharmaceuticals are used in the treatment of painful bone metastases for which conventional therapies have failed. Rhenium-186g is used as labelling agent due to its favourable chemical and nuclear properties: T1/2 = 89.4 h, main gamma emission at 137 keV and beta particle of end point energies at 1.07 and 0.93 MeV, suitable for small-medium volume irradiation. It is used as a labelling agent of HEDP for bone pain palliation and is also envisaged for labelling of oligopeptides. Presently 186gRe is produced by neutron capture on enriched 185Re in thermal nuclear reactors (together with its long-lived metastable level 186mRe), with a specific activity (AS) of the order of 1-2 MBq/micro.g, depending on target enrichment and irradiation conditions, thus with an isotope dilution factor IDF of 3,000 to 5,000. The possibility to use this radionuclide for therapeutic purposes is strictly linked to the possibility of increasing further the AS. The goal is to obtain a high AS 186Re in no-carrier-added NCA form by (p,n) or (d,2n) nuclear reactions on a tungsten target of natural or enriched (in 186W) isotopic composition. Irradiations were carried out with the Scanditronix MC40 Cyclotron (K=40) of the Joint Research Centre (Ispra, Italy). 186gRe was produced by proton induced nuclear reactions on commercially available thin natural tungsten foils using the stacked foil technique at different irradiation energies, in which W foils are activated together with Al thin foils as recoil catchers and Ti foils as monitors. The activity of the irradiated target foils was measured using HPGe detectors associated with appropriate gamma spectrometry systems and softwares. The cross-section data obtained for the natW(p,n)186(g+m)Re and 181,182m,g,183,184m,gRe reactions are reported, and compared both with literature values and the model calculation by the code EMPIRE-II of NEA-OECD agency, with which they appear to be in reasonable agreement. The irradiation of natural W target implies the production of a large amount of rhenium radioisotopes, also including stable ones. For radiochemical separation purposes, a radiochromatographic technique based on an acidic alumina mini-column in nitric acid was adopted.

BONARDI M L;  GROPPI F;  MENAPACE E;  PERSICO E;  ABBAS Kamel;  HOLZWARTH Uwe;  SIMONELLI Federica;  GIBSON Peter; 

2008-01-11

SPRINGER

JRC38104

1619-7070,