Improving the radionuclidic purity of 94mTc for PET imaging

The production of 94mTc as pertechnetate, a t1/2 = 53 min positron emitter, was studied with small and medium energy cyclotrons. At a proton energy of 11 MeV, the irradiation of natural molybdenum provides adequate saturated yields (3 mCi/μA) with tolerable radionuclidic purity for radiopharmaceutical investigations in man. The longer lived 95Tc, 95mTc and 96Tc isotopes can be virtually eliminated by irradiating an isotopically-enriched 94MoO3 target. In a study of alternative entrance channels leading to 94mTc, natural niobium and molybdenum targets were irradiated with 3He and 4He beams. The goal was to reach pure 94mTc through the 94Ru/94mTc generator system, bypassing contamination by the 94gTc ground state.