Production of high specific activity 177gLu for radioimmunotherapy by deuteron irradiation

Lu-177g is a low energy negatron emitter that, thanks to its favourable decay properties (t1/2 = 6.734 d, negatron emission 100%, Eβ(max) = 489.3 keV, <Eβ> = 163 keV, Eγ = 208.4 keV), is one of the most promising radionuclide to be used in radioimmunotherapy [1]. This RN is mainly produced in thermal nuclear reactor in two different ways [2]: the first in carrier added (CA) form by (n,γ) reaction on enriched target of 176Lu leading to a lower specific activity AS), compared with the theoretical carrier free value AS(CF) = 4.05 GBq·μg-1, the second in no carrier added (NCA) form by (n,γ) reaction on enriched target of 176Yb followed by negatron decay leading, after selective separation of Lu from Yb, to a higher AS. This latter case shows no evidence of production of the longlived impurity 177mLu. An alternative method is to produce 177Lu by the deuteron activation of natural or enriched in 176Yb targets. In this case, the routes of interest are the indirect reaction 176Yb(d,p)177Yb that decays by negatron emission to 177gLu and the direct reaction 176Yb(d,n)177(g+m)Lu.