Ch3 Flashcards
- Incoming x-ray
photon interacts with
a loosely bound outer
(or middle) electron of
an atom
• The incoming x-ray
photon surrenders a
portion of its energy,
ionizing the atom.
Comptom scatter
Incoming x-ray photon interacts with the electric field surrounding the
nucleus of an atom of irradiation tissue and disappears.
• The energy of the photon is absorbed and transformed into a
negatron and a positron
Pair Production
An interaction that
occurs at more than 10 MeV in
high-energy radiation therapy
treatment machines
Photodisintegration
Occurs at an energy level of at least 1.022 million electron volts (MeV).
• Beyond diagnostic energy range.
Pair Production
Incoming x-ray photons the interacts a loosely bound outer electron of an atom
- Incoming x-ray photon surrenders a portion of his energy ionizing the atom
Compton scatter
Structures are similar in Atomicnumber z number ) and mass Must be distinguished by the use of
Contrast media
Barium iodine Bright/white
Positive contrast medium
Air dark/black
Negative contrast medium
The greater the difference in the amount of Photoelectric absorption the greater the
Contrast
As the absorption increases so does the potential…
Biologic damages
Less attenuation equals
Darker image
Image must have a significant amount of_____ In density to be clearly visualize
Variations
Atomic number for compact bone
13.8
Atomic number for soft tissue
7.4
Less density tissue less attenuation
Dense tissue more attenuation
These factors are known as
Influence attenuation
Occurrence of photoelectric absorption depends on
Energy E
Atomic number Z 
Absorption increase ….. what happens to E and Z
Energy Incident photons decreases
Z of irritated out of increases
Discovered by Pierre Victor Auger in 1925
> Produces an Auger electron
> Is a radiationless effect
Augar effect
By-products of Photoelectric Absorption
Photoelectron and characteristic x-ray photons
Interaction between x-ray photons and inner shell electrons
Photo electric absorption
Diagnostic energy ranges  23 to 150 kvp
most important mode of interaction
between x-ray photons and the atoms
Photoelectron Absorption
(aka fluorescent radiation)
(the remainder of the released energy which is so low it will be absorbed by the body)
Characteristic photon
Interaction of photons in biologic matter is
Random
Photons that undergo either absorption or scatter does not strike the image reception
Attenuation
Photons that strike the image receptor are transmitted
Transmission
Some primary photons will transverse the patient without interacting and reaching the image receptor
Direct transmission
Other primary photons can’t undergo Compton or coherent interactions as a result may be scattered or deflected with a potential loss of energy
Indirect transmission
x-ray photons that interact with the
atoms of a patient such that they give up all of
their energy and cease to exist
Absorption
x-ray photons that interact with the
atoms of the patient, but only surrender part of their energy.
Scatter
A diagnostic x-ray beam is produced when a stream of very energetic electrons bombards a positively
charged target in a highly evacuated glass tube.
Primary radiation
Target (anode) composition used
Tungsten (a metal)
> Tungsten rhenium (a metal alloy)
• The amount of energy per unit mass is).
absorbed dose
energy level of photons in the x-ray beam, equal to the highest voltage established across the x-ray tube.
Kvp
electron tube current and the amount of time in seconds that the x-ray
tube is activated.
Mas
