Abstract: A method for treating a human patient is provided, including administering a radiolabeled form of a therapeutic agent to the patient at a first substantially non-therapeutically-effective dose, wherein pharmacological activity of the therapeutic agent is not due to radioactivity of the therapeutic agent. The method also includes determining information related to a biodistribution of the radiolabeled form of the therapeutic agent in the patient by performing a radioimaging procedure on the patient. Responsively to the information, a decision is made whether or not to treat the patient by administering the therapeutic agent to the patient. If the decision is made to treat the patient, the patient is treated by administering the therapeutic agent to the patient at a second therapeutically-effective dose. If the decision is made not to treat the patient, treatment of the patient with the therapeutic agent is withheld. Other embodiments are also described.