Excitation Functions and Yields for Re-186g Production by Proton and Deuteron Cyclotron Irradiation

The 186gRe radionuclide is a ß-,¿ emitter that, thanks to its suitable nuclear properties (t1/2 = 90.64 h, Emaxß- 1.07, 0.93 MeV, main E¿ 137 keV), is presently used in palliation metabolic radiotherapy, and also has optimal prospectives for applications in radioimmunotherapy (RIT). The possibility to use this radionuclide for therapeutic purposes is strictly related to the possibility of increasing its specific activity (AS). This improvement may be attained by substituting the common 185Re(n,¿) production route in thermal nuclear reactors with the 186W(p,n) and/or (d,2n) cyclotron production methods, due to the possibility of radiochemical separation of the product from the target in no-carrier-added (NCA) form, reaching a AS(NCA) value close to the theoretical carrier-free (CF) value of AS(CF) = 6.88 GBq.µg-1. We have completed the study of the (p,n) production route, while the (d,2n) method is currently being studied. In both cases, the thin-target excitation functions have been measured by using the stacked-foil technique, while the experimental thick-target yields (TTYs) were measured by using thick natW foils and highly enriched 186W pressed powder. All the irradiations have been carried out with the variable energy cyclotron of JRC-Ispra at different beam energies. The activity of all Re radioisotopes produced in the irradiated targets, has been measured by calibrated HPGe ¿-ray detectors. Regarding Re production via the (p,n) reaction, the excitation functions of all Re radioisotopes were determined and compared with the literature data, with which they are in good agreement. Also the experimental and integrated TTYs have been measured and it was found that the values obtained with the natural W targets are in perfect agreement with those obtained with the irradiation of the enriched 186W target. The latter irradiation was carried out to study only the production of 186gRe and in particular its radionuclidic purity. The experiment confirmed that the radionuclidic purity of the 186gRe is very high and suitable for medical purposes. Radiochemical separation of the product from the target was also carried out, and the results obtained suggest that the ion-exchange chromatography method is very appropriate, with the recovery of the Re indicating a very high radiochemical yield. Finally, all information on the 186gRe production by proton irradiation are compared with the preliminary data obtained by the on going deuteron beam irradiation experiments.

ABBAS Kamel;  HOLZWARTH Uwe;  GIBSON Peter;  SIMONELLI Federica;  BONARDI Mauro;  GROPPI F;  MANENTI S.;  PERSICO E; 

2009-01-20

SPRINGER

JRC47565

1619-7070,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC47565,