Production of high purity (94m)Tc for positron emission tomography studies.

The radioisotope (94m)Tc (T(1/2) = 52.5 min; I(beta)+ = 72%; E(beta)+ = 2.47 MeV) is of considerable interest for quantitative biodistribution studies of Tc radiopharmaceuticals using positron emission tomography. The nuclear processes (94)Mo(p,n), (93)Nb((3)He, 2n), (92)Mo(alpha,pn), and (92)Mo(alpha,2n)(94)Ru --> (94m)Tc are of potential interest for the production of (94m)Tc. Detailed cross section and yield measurements showed that the (94)Mo(p,n)-reaction over the energy range E(p) = 13 --> 7 MeV is most suitable: The yield of (94m)Tc is high (2 GBq/muAh), the impurity level is low (provided highly-enriched (94)Mo is used as target material), and a small-sized cyclotron is adequate. Using conventional targetry, sufficient quantities of the radioisotope can be produced. The chemical processing methods employed include both solvent extraction and thermochromatography. The quality of the final product is discussed.

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