Investigation of Cr-50(d,n)Mn-51 and Cr-nat(p,x)Mn-51 processes with respect to the production of the positron emitter Mn-51

The positron emitter Mn-51 (t(1/2) = 46.2 min, Ibeta+ = 97%) is of potentia l interest in positron emission tomography (PET). With a view to optimizing its production route, excitation functions for deuteron induced nuclear re actions on isotopically enriched (similar to 95%) Cr-50 were determined rad iochemically over the energy range of 3 to 13 MeV and for proton induced nu clear reactions on Cr-nat in the range of 18 to 38 MeV. Cross sections are presented for the reactions: Cr-50(d, 2n)Mn-50m, Cr-50(d, n)Mn-51, Cr-50(d, t)Cr-49, Cr-50(d, p)Cr-51, Cr-50(d, alpha)V-48, Cr-52(d, 2p)V-52, Cr-nat(p , x)Mn-51, Cr-nat(p, x)Mn-52, Cr-nat(p, x)Mn-52m, Cr-nat(p, x)Mn-54, Cr-nat (p, x)Cr-48, Cr-nat(p, x)Cr-49, Cr-nat(p, x)Cr-51, Cr-nat(p, x)V-48 and Cr- nat(p, x)Ti-45. In the case of proton induced reactions on Cr-nat, the isom eric cross section ratio for the isomeric pair Mn-52m,Mn-g was also determi ned. The results are interpreted in terms of the spins of the two isomers c oncerned. Theoretical thick target yields were derived from the correspondi ng excitation functions. The maximum achievable thick target yield of Mn-51 is 1.1 GBq/mu Ah in the case of the Cr-50(d, n)Mn-51 reaction at E-d = 14 --> 3 MeV, and 3.2 GBq/mu Ah in the case of the Cr-nat(p, x)Mn-51 process f or E-p = 40 --> 20 MeV. The Cr-50(d, n)Mn-51 process is the favourable prod uction route for Mn-51, since the radioisotopic purity is high and a small- sized medical cyclotron is adequate to produce this positron emitter in suf ficient quantities.