Physics of Radiation Therapy

Physics of Radiation Therapy

Objective
?To get information about ionizing
radiations and medical applications.
?Important factors of treatment.
?Dose units used in radiotherapy.
?Treatment of tumors with
radiotherapy:

Ionizing radiations that are used in medicine can
be divided into two major types:
?Partial radiation; such as ?, ? and neutrons
?Electromagnetic radiation; such as ? and X- Rays
Three main uses of these radiations in medical
applications;
Treatment of cancer (therapy), diagnosis,
sterilization


The choice of treatment depends
on a number of factors including:
?The size of the tumor.
?The position of the tumor.
The aim of the radiation therapy is to cause
damage to the cancerous cells whilst
minimizing the risk to surrounding healthy
tissue.

Dose units used in radiotherapy
For exposure: Roentgens (R) is measuring
the amount of electric charge produced
by ionization in air (exposure) using ?,
X-Rays, since.
1R = 2.58 x 10
-4
C/Kg of air




Treatment of tumors
with radiotherapy
There are two techniques of treatment:
?External beam radiotherapy by passing high
energy photons through the body from an
external source.
?Beach therapy, placing a radioactive source
inside the body adjacent to or within the
tumor.

The dose to the particular organ of the body
depends on the physical characteristic of the
radionuclide
?What particles it emits
?Their energies
?The length of the time the radionuclide is in the
organ.
Two factors determine the length of the time the
radionuclide in the organ, or the effective half-life
T
1/2 eff,
the physical half-life T
and the biological half-life T
1/2 phy
bio
.