An injectable radiopharmaceutical formulation containing human serum albumin (HSA) microspheres labeled with technetium-99m (Tc-99m) with diagnostic imaging activity. Technetium Tc 99m-labeled albumin microspheres contain the gamma-emitting Tc99m, a metastable nuclide of molybdenum-99. Upon injection into the hepatic artery, the radionuclide portion allows for SPECT (single photon emission computed tomography) imaging of distribution patterns of the albumin microspheres. This may possibly predict the distribution of other agents with similar particle sizes within the liver and may give a prediction of the tumor response upon administration of such agents.