Isotope

Definition: Atoms with same atomic number but different atomic weight.

Types of isotope:

1.      Stable isotope

2.      Unstable isotope

Radioactivity:

It is the spontaneous emission of accelerated particles from an unstable isotope by radioactive delay.

Clinical use of radioactive 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 eg. Bone scan, brain scan, thyroid scan.

4.      Absorption test, eg from iron, vitamin B12

5.      Isotope renogram for measurement of GFR and renal clearance.

6.      RBC life span measurement.

B. Therapeutic use. Eg. Radiotherapy in treatment of malignancy.

C. Use in tracer technique

D. Measurement of volume and spaces. Eg. ECF volume, Blood volume, Plasma volume, RBC volume.

E. Measurement of regional blood flow. eg. Cerebral blood flow, coronary blood flow, renal blood flow.

F. Sterilization of medical instruments.

Radiation Hazards:

1. Immediate hazards

·        Bone marrow depression

·        Immune suppression

·        Damage to intestinal mucosa causing diarrhea and malabsorption.

·        Baldness

·        Rough and scaly skin

·        In pregnancy: fetal growth retardation, congenital malformation of fetus, fetal death, neonatal death.

2. Delayed hazards

·        Carcinogenesis

·        Sterility

·        Cataract

3. Genetic defect

·        DNA damage

·        Mutation