Radioactive tracers – gamma emitters - can be used to image parts of the body. When introduced into the body, their progress can be monitored from outside, and give information about how an organ is functioning or to analyse blood circulation for example.
There are many factors affecting the choice of which tracer to use for any situation.
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The radioisotope used should be able to be taken up b the organ in question in a natural way, so must have specific chemical properties.
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The lifetime of the tracer needs to be matched to the length of time of the process under study. Choosing this correctly will minimise the amount of tracer used, and the danger to the patient.
Some tracers and their uses are given in the table.
Organ/tissue
Tracer
Uses
General body use
Used to measure volumes of body fluids and salt concentration (sodium, potassium, chlorine)
Blood
Used to measure blood volume and different components (plasma, red blood cells...) and the volume of blood indifferent organs, and to detect internal bleeding
Bone
Used to analyse absorption of calcium, location of bone disease and mineral metabolisation.
Cancerous tumours
Used to detect locate and diagnose tumours
Heart and lungs
Used to measure the heart blood flow, volume and circulation. Also used to investigate respiration.
Liver
Used to diagnose liver conditions
Muscle
Used in muscles, especially heart muscles