1. 19.5 Radiotracers  Radiotracers=radioactive nuclides that can be introduced into organisms in food or drugs and subsequently traced by monitoring their radioactivity.  Radiotracer nuclides have short half- lives so that they disappear rapidly from the body.

2. Diagnostic Tracers  Medical use = Used to detect the presence of the isotope in the body for diagnosing a problem.  Industrial use = follow gas through pipelines to know when gas arrives; study fertilizer effects on streams; sterilizing medical equipment.

3. Diagnostic tracers  1. Short half-life but long enough to prepare and administer conveniently  2. New element should be non-toxic and non-radioactive.  3. Gamma radiation so it can be detected readily by detectors located outside the body.  4. Chemical properties so it will wither be concentrated in diseased areas (hot spot) or rejected from diseased areas (cold spot).

4. Irradiation therapy  Exposing sample to radiation (nuclear, microwave, infared, ect.)  Gamma radiation used to preserve food. Kills germs, does not make food radioactive.  Humans use internal and external irradiation therapy.

5. Internal irradiation therapy  1. Less penetrating alpha or beta to restrict damage to area.  2. Long enough for therapy to be accomplished.  3. Nontoxic and non radioactive daughter products.  4. Concentrate in target only, to restrict damage.

6. External irradiation therapy  1. Must be gamma so it can penetrate the skin and reach cancer site.  2. Long enough for therapy to be completed.