Methods for producing Tc-99m radioisotope by proton irradiation of a fluid target matrix. A method of producing Tc-99m includes irradiating a fluid target matrix comprising Mo-100 with a proton beam to transform at least a portion of Mo-100 to Tc-99m. Optionally, the fluid target matrix further includes at least one of O-18, O-16, or N-14, which upon exposure to the proton beam concurrently transform at least a portion of O-18 to F-18, at least a portion of O-16 to N-13, at least a portion of the O-16 to O-15, or at least a portion of N-14 to C-11. The method further includes isolating Tc-99m and optionally at least one of F-18, N-13, O-15, or C-11 from the irradiated fluid target matrix. An additional source of Tc-99m is available from the decay of Mo-99 that is co-produced from the Mo-100 during irradiation with the proton beam.