Overview of Bremsstrahlung Radiation

Introduction

• Bremsstrahlung radiation is a process that creates X-ray photons in the X-ray tube.
• Requires three essential components:
  1. Source of free electrons
  2. Means of accelerating those electrons
  3. 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.