radiation biology

1. WELCOME

2. MEASUREMENT OF RADIATION
The amount of radiation is measured by rad which
means radiation absorbed dose. It is the amount of
radioactive energy absorbed per gram of the living
tissue.
1 m rad is=0.001 rad
Another unit of measurement is rem. It is called
roentgen equivalent to man. It is derived from the x-
ray dosage or roentgen(r)

3. Radioactive isotopes releases three type of
radiations.
1. Alpha particles: These are large particles
emitted by radioactive isotopes. They travel
only short distances. They cannot penetrate
the organisms. They cause local ionization
2. Beta particles: These are small particles
emitted by radioactive isotopes. They can
travel long distances. They can easily
penetrate the body tissues and cause
ionization
3. Gamma rays: These are short wave length
rays emitted by radioactive isotopes. They
can travel long distances. They can easily
penetrate the body tissues and cause
ionization

4. On the basis of the biological effect produced, the radioactive radiation
can be grouped into two types, namely internal emitters and external
emitters.
A. Internal emitters : The alpha and beta particles have low penetrating
power. Hence they produce their effect in organism only when they
are ingested into the body. Hence they are called internal emitters .
B. External emitters: The radiations with short wavelength like gamma
rays have high penetrating power. They can affect the internal tissues
even when they remain outside by virtue of their penetrating power.
Hence they are called External emitters.

5. Certain elements emit ionizing radiations. These elements are
called radioactive isotopes or radionuclides. ionizing radiations
are high energy radiations. But the neutrons may vary in
number in the same elements such atoms are called isotopes.
Isotopes have same atomic number but different mass
number.

6. They are of 2 types stable isotopes and radioactive isotopes or radio
isotopes or radio active nuclide.
Stable isotopes remain stable and do not emit radiation. Eg. N14, C13,
S33 etc.
radio isotopes are less stable. They undergo spontaneous
decomposition to achieve stability. During this process the nucleus
disintegrates by throwing off a stearm of protons.

7. These are released as radiations. The loss of protons by an
atomic nucleus is called radioactive decay and such
elements are called radioactive isotopes. The important
isotopes are K12, Na24, I31, Fe59, P32, CO60, Ca45. As the result
of radioactive decay, the mass number changes and finally it
becomes stable and different element.

8. The stability of the radioactive isotope can be measured by
its half life. It is the time taken for an initial quantity of
radioactive material to decay to one half of that amount. It
differ from minute to year. Eg. Na 24-15hrs, I 131-8days, CO
60-5.3 YRS.

10. Non-ionizing (or non-ionizing) radiation refers to any type
of electromagnetic radiation that does not carry
enough energy per quantum (photon energy)
to ionize atoms or molecules—that is, to completely remove
an electron from an atom or molecule. Instead of producing
charged ions when passing through matter, the
electromagnetic radiation has sufficient energy only for
excitation, the movement of an electron to a higher energy
state.

11. Thank you