reference reading: chapter 2, pp 18- end of chapter
TRANSCRIPT
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Types of Radiation Produced and Interactions
of RadiationReference Reading:
Chapter 2, pp 18- end of chapter
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General (“Braking”) (Bremsstrahlung) Radiation◦ Refers the sudden “braking” of the electrons as
they hit the tungsten target.◦ Most x-rays are produced in this manner. (70%)
Characteristic Radiation◦ Produced when a high-speed electron dislodges
an inner shell electron from a tungsten atom and causes ionization of the atom.
◦ Very little radiation produced in this manner.
Types of X-rays produced at the Tungsten Target
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Occurs when an electron hits, or comes close to hitting the nucleus of a tungsten atom.
If the electron gets a “direct” hit on the nucleus, then ALL of the energy of that atom is given up. This produces a high energy photon of radiation.
General (“Braking”) (Bremsstrahlung) Radiation
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Usually, there is a “near miss”. This slows down the electron and a photon of lower energy is produced.
General, Braking, Bremsstrahlung
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General (“Braking”) Radiation
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Inner shell electron is ejected from the atom, and all the other electrons will “rearrange themselves” to fill the vacancy.
The rearrangement produces a loss of energy that creates an x-ray photon.
Not much radiation is generated in this manner.
Characteristic Radiation
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Characteristic Radiation
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Types of Radiation
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Primary◦ The x-ray beam that exits the tubehead◦ Also referred to as the Primary Beam or the Useful
Beam Secondary
◦ Less penetrating radiation◦ Secondary radiation is produced when the
primary beam interacts with matter. (soft tissues of the head, teeth, bones of the skull, etc.)
Types of Radiation
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Scatter◦ Scatter is harmful to both the patient and the
operator.◦ It is formed when an x-ray has been deflected
from its path.
Types of Radiation
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When the radiation reaches the patient….
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1. The x-rays can pass through the patient without any interaction
2. The x-rays can be completely absorbed by the patient. (Photoelectric Effect)
3. The x-rays can be deflected and become scatter radiation. (Compton Scatter & Coherent Scatter)
What are the possibilities?
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#1 – No Interaction with the Patient
No Interaction
Some of these rays will strike the film, and make radiography possible by producing “densities” on the film.
Will learn more about this later.
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At the atomic level, absorption occurs as a result of the photoelectric effect.
Ionization has taken place within the patient’s tissues.
This accounts for about 30% of the interactions of the x-ray beam with the patient’s body.
#2. Absorbed by the PatientThe Photoelectric Effect
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The Photoelectric Effect
Photoelectric Effect
The x-ray interacts with an inner shell electron of the patient’s body.
The x–ray is absorbed and ceases to exist.
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Compton Scatter
Compton Scatter
Loose, outer shell electron is dislodged from its orbit.
Ionization has taken place.
Accounts for 62% of the scatter that takes place in radiography.
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Coherent Scatter
Coherent Scatter
There is interaction of the x-ray with an outer shell electron, but it is NOT dislodged, so ionization does NOT take place.
Sometimes called “unmodified scatter”.
Accounts for 8% of the interactions of matter with the x-ray beam.
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X-ray Interactions
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