Physics of radiation therapy

The probability  of  your  having cancer during your lifetime is about 1 out of 4 .Currently three major methods are used alone or in combination to treat cancer:

Surgery, radiation therapy  and drugs (chemotherapy).

The success of radiation therapy depends on :
1-    The type and extent of cancer.
2-    The skill of radiotherapist.
3-    The physician who specialized in the treatment.
4-    The kind of radiation used in the treatment.
5-    The accuracy with which the radiation is administered to the tumor.
But because of the possibility of radiation –induced cancer ,it is generally safer to use other types of treatment when possible.

The dose units used in radiotherapy:

  Erythema dose: The quantity of  x-ray that caused a reddening of the skin.
  Rontgen: A unit based on ionization in air (only for x-ray and gamma ray).
  Rad: is defined as 100 ergs/g ,that is a radiation beam that gives 100 ergs of energy to 1 gm of tissue gives  the tissue an absorbed dose of 1 rad.
  Gray(Gy): it is the international (SI) unit of dose
    1Gy=1J/kg       since J=107 erg
     Gy =100 rad