What is radioactivity? Clinical use of radioactive isotope.

Radioactivity:

It is the spontaneous emission of accelerated particles(radiation) from an unstable isotope by radioactive decay.

Clinical use of radio active isotope:

A. Diagnostic use

1. Iodine uptake test for diagnosis of thyroid disorders.
2. Radio immune assay of hormones for diagnosis of hormone disorders.
3. Organ scanning e.g. bone scan, brain scan, thyroid scan.
4. Absorption test e.g. for iron. vitamin B12
5. Isotope renogram for mesurement of GFR and renal clearance.
6. RBC life span measurement.

B. Therapeutic use, e.g. radiotherapy in treatment of malignancy.

C. Use in tracer technique: isotopes are used as tracer in metabolic studies to outline the metabolic pathways.

D. Measurement of volumes and spaces. e.g. ECF volume, Blood volume, plasma volume, RBC volume.

E. Measurement of regional blood flow. e.g. Cerebral blood flow, coronary blood flow, renal blood flow.

F. Sterilization of medical instruments.

Isotope: Definition, Types.

Definition:

• Atoms with same atomic number (number of proton), but different atomic weight (number of protons and neutrons).
• Atoms of same element with different atomic weight.

Types of isotope:

1. Stable isotope
• Stability of an isotope depends on the definite neutron to ration which is specific for a specific atom.
• In atoms of low atomic weight stability is usually achieved with neutron to proton ration around one.
• In atoms of high atomic stability is usually achieved with more neutron than proton
• Neutrally occurring isotopes of most of the predominant elements are stable isotopes.
2. Unstable isotope
• These are the isotopes having neutron to proton ration far away from its stability ratio.
• Neutrally occurring isotopes of heavy elements are usually unstable
• Rarely some naturally occurring isotopes of lighter elements can also be unstable
• Unstable isotopes tend to become stable by radio active decay