Attenuation: Compton Scatter

This post is the second method of scatter attenuation.

Compton scatter (or Incoherent scatter)

There are three main steps in compton scatter.

1. An incoming x ray photon interacts with an outer orbital electron.

2. The incoming x ray photon knocks the orbital electron out of it orbit (becoming a recoil electron).   The recoil electron loses energy as heat or creates bremsstrahlung radiation within the object being imaged.

3. The x ray photon is deflected in a different direction with less energy (determined by subtracting the binding energy of the orbital electron).   The higher the energy of the incoming x ray photon, the smaller angle of deflection (meaning the x ray photon will continue closer to it’s original path).

Diagram showing high and low energy incoming x ray photons and angle of deflections. Note the higher energy x ray photon stays closer to its original path.

The quantity of compton scatter occurring within an object is determined by the electron density of the absorber. This method of attenuation accounts for approximately 62% of all attenuation.

Should you have any questions about this, please let me know.  Thanks and enjoy!

Next week: Photoelectric effect