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Understanding Bremsstrahlung Radiation Process
Aug 10, 2024
Overview of Bremsstrahlung Radiation
Introduction
Bremsstrahlung radiation is a process that creates X-ray photons in the X-ray tube.
Requires three essential components:
Source of free electrons
Means of accelerating those electrons
Process for deceleration of electrons
Creation of Free Electrons
Free electrons generated at the
cathode filament
via
thermionic emission
.
Acceleration and Deceleration of Electrons
Electrons are accelerated through the X-ray tube by voltage (kVp).
Deceleration occurs when electrons interact with
tungsten atoms
in the
anode target
.
Bremsstrahlung Radiation Explained
Bremsstrahlung
is the German term for "braking radiation."
Process:
Tungsten atom has a positively charged nucleus surrounded by negatively charged electrons.
Electrons from the cathode are attracted to the positive nucleus, causing them to slow down (brake) and change direction (deflect).
This lost energy is emitted as an X-ray photon.
Analogy for Understanding
Example of throwing a ball at a glass window:
The ball slows down and changes direction, with energy leaving the ball creating cracks in the glass.
Similarly, electrons lose energy when they pass near a nucleus and produce X-ray photons.
Energy of Bremsstrahlung Photons
Depends on the
incoming electron's energy
:
Example: 100 keV incoming electron can produce a maximum 100 keV photon.
If incoming energy is 75 keV, maximum photon energy is also 75 keV.
Controlled by
kVp
settings:
kVp set to 100 creates maximum Bremsstrahlung photons of 100 keV.
kVp set to 75 creates maximum of 75 keV.
Factors Affecting Photon Energy
Proximity of the electron to the nucleus:
Closer approach = more significant reduction in energy and higher photon energy produced.
Further distance = less energy lost and lower photon energy.
Example: If an electron approaches at 90 keV but slows down to 60 keV, the resulting photon is 30 keV (90 - 60 keV).
Graphical Representation of X-rays
X-axis: Photon energies in the X-ray beam.
Y-axis: Number of photons at each energy level.
Bell curve shows the distribution of Bremsstrahlung X-rays:
Short on the left (low-energy photons filtered out).
Short on the right (very few high-energy X-rays created).
Tallest in the center (most common moderate energy levels).
Summary
Bremsstrahlung radiation
is the primary method of X-ray photon creation during X-ray exposure.
Created when high-energy electrons from the cathode interact with tungsten nuclei in the anode.
X-ray photons have a wide range of energies influenced by the proximity of electrons to the nucleus.
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