Which interaction produces scatter radiation that exits the patient and may fog the image?

Which interaction produces scatter radiation that exits the patient and may fog the image?

• A. Photoelectric interaction
• B. Compton interaction
• C. Coherent scatter
• D. Pair production

Answer: (B)

Compton scattering is the main source of scatter that exits the patient and fogs the image. In this interaction, an X-ray photon collides with a loosely bound outer-shell electron, giving some of its energy to the electron and being deflected in a new direction with reduced energy. The deflected photon can escape the patient and reach the image receptor, adding unwanted exposure across the image and reducing contrast. This scattered radiation is a primary reason image quality suffers if scatter isn’t controlled, which is why techniques like collimation and grids are used to minimize it. Photoelectric absorption, on the other hand, absorbs photons within the patient and does not produce exit scatter that fogs the image. Coherent (elastic) scatter can occur but contributes much less to image fog at diagnostic energies. Pair production requires energies well above diagnostic X-ray ranges and isn’t a factor in typical imaging.

Compton scattering is the main source of scatter that exits the patient and fogs the image. In this interaction, an X-ray photon collides with a loosely bound outer-shell electron, giving some of its energy to the electron and being deflected in a new direction with reduced energy. The deflected photon can escape the patient and reach the image receptor, adding unwanted exposure across the image and reducing contrast. This scattered radiation is a primary reason image quality suffers if scatter isn’t controlled, which is why techniques like collimation and grids are used to minimize it.

Photoelectric absorption, on the other hand, absorbs photons within the patient and does not produce exit scatter that fogs the image. Coherent (elastic) scatter can occur but contributes much less to image fog at diagnostic energies. Pair production requires energies well above diagnostic X-ray ranges and isn’t a factor in typical imaging.