Comparison of gallium-68 production yields from (p,2n), (α,2n) and (p,n) nuclear reactions applicable for cancer diagnosis

Gallium-68 (68Ga) is a positron emitter potentially applied for Positron Emission Tomography (PET) modality. In this research, different methods based on (p,2n), (α,2n) and (p,n) nuclear reactions are highlighted by theoretically calculating their potential radioactivity yields. Nuclear excitation functions calculated using the TALYS-2017 codes were employed to compute the End-of-Bombardment (EOB) yields. Among the three evaluated nuclear reactions – 69Ga(p,2n)68Ge → 68Ga, 66Zn(α,2n)68Ge → 68Ga and 68Zn(p,n)68Ga – the calculated EOB yields showed that 68Zn(p,n)68Ga nuclear reaction resulted in the highest radioactivity of up to 1445 MBq/μAh. In addition, several radioactive and non radioactive impurities such as 69Ge, 66Zn, 69Ga, 67Ge, 65Cu could be generated during 68Ga production, either by direct or indirect method. While the indirect method of 68Ga production could result in lower yield than that of the direct method, the indirect method could be more economical especially when the hospitals are too far away from the available cyclotrons. Thus, in this case, development of 68Ge/68Ga generator through indirect method of 69Ga(p,2n)68Ge → 68Ga nuclear reaction could be the best option, though very high proton dose and energy would be required to gain high radioactivity level applicable for clinical use.