Isotopes are atoms of the same element but different masses.
Isotopes of an element have the same number of protons and electrons but have different number of neutrons.
Radioactive decay of an isotope will occur if the isotope is unstable. An example is the three isotopes carbon-11, carbon-12 and carbon-14.Of these only carbon-14 is stable. The emissions from these nuclei are collectively called radiation.
When a nucleus decays by alpha or beta emission the number of protons and neutrons changes. Gamma radiation does not change the make up of the nucleus.
Alpha decay:
88Ra226 → 86Rn222 + 2e4
Beta decay:
6C14 → 7N14 + -1e0
| Radioatcive Isotope | Medical Application | Method |
|---|---|---|
| Iodine-131 | Visualising the size, shape and idoine-concentrating ability of thyriod tissue. | Patients are given a small amount of radioactive sodium-iodide solution to drink.Several hours later the gamma radiation from thryriod-contained radioiodine is measured. |
| Iodine-131 | Liver function tests | The iodine-131 has been incorporated into a dye (rose bengal).The dye is injected into a vein and is removed from the blood by the liver.The rate of disappearance of the dye from the blood is determined by the decrease count rate and used as a measure of liver activity. |
| Arsenic-74/Phosphurus-32 | Detection of Brain Tumors | Arsenic/Phosphurus will concentrate in certain brain tumors and can be used in scanning the head for the presence of brain tumors. |
| Chromium-51 | Measurement of Red Blood Cells | Attaches to red blood cells and is used to measure total red blood cell volume,red cell life and cardiac output. |
| Cobalt-60 | The study of Pernicious Anemia | Vitamin B12 conatins colbalt, so cobalt-60 can be incorporated into vitamin B12. |