Nuclear reactors, cyclotrons and generators are being used to produce nuclear medicine radionuclides. Radiopharmaceuticals based on Gallium-68 (Ga-68) are widely used both experimentally and clinically in Positron Emission Tomography (PET). It has attracted increasing interest in recent years due to the expanding clinical applications. Currently Ga-68 is mainly produced via 68Ge/68Ga generators, which are expensive. Such generators deliver limited activity per elution with restrictive waiting time between elutions. An alternative method is by cyclotron using high enriched Zinc-68 (Zn-68) via the 68Zn(p,n)68Ga reaction. Highly enriched Zn-68 can be used for both liquid and solid targets. The main disadvantage of using liquid targetry is the relatively low production yields of Ga-68, while using solid target enables higher production yield. Investigations have been conducted for producing Ga-68 using a solid target impacted with a proton beam in energies between (13-14) MeV or higher. According to the International Atomic Energy Agency, over half of cyclotrons used for isotope production around the globe use energies between (7.5-11) MeV. The main interest of this work is to produce Ga-68 using energies within this lower range, therefore Ga-68 can be accessed to locations with cyclotrons of lower energy. In this work, an approach to a novel target design to get Ga-68 with low energy protons is conducted. The target design use Havar foil as target window and the proper size for a post handling irradiation. As cyclotrons are most probably to be in a place with workers around, like hospitals, adequate shielding to avoid extra doses is considered. Monte Carlo code FLUKA is used to simulate the processes of interaction of radiation with matter and the radioactive isotope production. For the design in this work, for an incoming beam energy of 7.5 MeV and current of 5 µA, it is found that the produced activity at end of bombardment (EOB) is around 1810 MBq. For a beam energy of 11 MeV and current of 40 µA the activity is about 26.1 GBq. Considering the decay of Ga-68, the final 68Ga-labeled radiopharmaceutical activities are 1331 MBq and 19.19 GBq, respectively. Taking into account a 68Ga-PET radioligand exam, for the lower energy case the possibility of patients to be administrated are three to four. For 11 MeV the quantity of people will be over 20. The results show the feasibility of producing Ga-68 with low energy protons and self-shielding system guarantees the regulation-based dose exposition outer the cyclotron.

Production of Cyclotron-Based Gallium-68 With Low Energy Protons: Preliminary Target Design and Shielding Considerations Cyclotron

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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