Download Physics 5 - NYCC SP-01

Chapter 5
The Types of
Radiation
Types of Radiation
 There
are two main types of
radiation involved in the production
of radiographs and in radiology.
They are primary radiation
(produced in the tube) and
secondary radiation (a result of
primary radiation striking another
object).
Types of Radiation
Types of Radiation
Primary Radiation
Bremsstrahlung
Characteristic
Secondary Radiation
Photoelectric Effect
Comptons Effect
Primary Radiation
There
are two types of
primary radiation:
 Bremsstrahlung (AKA
Braking or White radiation)
Characteristic Radiation.
Bremstrahlung Radiation
 is
a variable process that can give
up a lot or little energy. They are
produced by a slowing of electrons
by the pull of the nucleus of an
atom on the target. This results in
the variable x-ray wavelengths
produced (due to the conservation
of energy).
Characteristic Radiation

is characteristic of the material of the
target. The x-ray produced is a result of
excess energy from one shell to another.
A fast traveling electron going toward a
target will eject an electron in an atom of
the target material. The resultant x-ray
produced is due to the atom which has
lost an electron wanting to return to
stability.
Characteristic Radiation
 To
do this an electron from an
outer shell will drop into the
vacancy. The excess energy
which is due to the two different
energy levels in dropping from
one shell to another is liberated
in the form of characteristic
radiation.
Secondary Radiation
is
produced by primary
radiation striking any
object. There are two
types of secondary
radiation - scattered rays
and characteristic rays.
Secondary Radiation
 Scattered
rays are caused by x-rays
striking organic substances (of less
atomic weight than aluminum); they
are heterogeneous and scattered in
all directions.
 There are two types of scattered
rays that occur at the energy levels
we deal with:
Secondary Radiation
Photoelectric effect - the incoming
photon gives up all energy and emits an
electron. A Characteristic event could
occur.
 This often takes place in the patients
skin at a lower energy levels. Lower
energy levels have a higher probability
of having interaction in the patients
tissues. This is not good for patients
skin dose.

Secondary Radiation
Comptons effect - this takes place at higher
energy levels. An incoming photon strikes an
electron, usually in the outer shell . The
photon is deviated from its original path.
Energy is decreased. At high energy levels
the photons are deflected but still make their
way on to the film and produces fog.
 Increased kV = more compton scattering and
the film becomes more gray.

Secondary Radiation
 Characteristic
rays are caused by xrays striking metallic substances (of
greater atomic weight than
aluminum); these are homogeneous
(all of the same wavelength) and
the wavelength is characteristic for
the metal that is struck.
Secondary Radiation
 Scattered
radiation from the soft
tissues of the body is
responsible for film haziness
and low film contrast. The
methods used for eliminating
some of the scattered radiation
is detailed in the next section.
Secondary Radiation

Characteristic radiation is unimportant in
radiography but very important in
therapy. The filter interposed between
the tube and the patient may itself give
off a characteristic radiation softer than
the rays which it filters out.
Radiation Summary
For
Best Film Image:
»Low kV & High MAS
Best
for Patient:
»High kV & Low MAS