How Compton Scatter Happen ?

• Compton scattering occurs when a photon interacts with an outer orbital electron.

• About 57% of interactions in a dental x-ray beam exposure involve Compton scattering. In this interaction, the incident photon collides with an outer electron, which receives kinetic energy and recoils from the point of impact. 

• The path of the incident photon is deflected by this interaction and is scattered in a new direction from the site of the collision. The energy of the scattered photon equals the energy of the incident photon minus the sum of the kinetic energy gained by the recoil electron and its binding energy.

• The probability of a Compton interaction is directly proportional to the electron density of the absorber. The density of electrons in bone (5.55 × 1023/cm3) is greater than in soft tissue (3.34 × 1023/cm3); therefore the probability of Compton scattering is correspondingly greater in bone than in tissue. As a result, Compton interactions also contribute to the formation of an image.