radioactive tracer A radioactive isotope, whose movement can be monitored, that is used to trace the pathways by which individual substances move through an organism, a living system, the abiotic environment, etc. Non-radioactive chemical analogues of certain substances may be used for the same purpose if their movement can be monitored (e.g. caesium, which can be substituted for potassium).

radioactive tracer A radioactive isotope whose movement can be monitored, which is used to trace the pathways by which individual substances move through an organism, a living system, the abiotic environment, etc. Non-radioactive chemical analogues of certain substances may be used for the same purpose if their movement can be monitored (e.g. caesium, which can be substituted for potassium).

tracer, radioactive Radioactive substance that is introduced into the body so that its progress can be tracked by special diagnostic equipment. This technique may help in the diagnosis of conditions such as thyroid disease.