What is remnant radiation?

Remnant radiation refers to the radiation that remains after the primary x-ray beam has interacted with the patient or any other material, which leads to the attenuation of the beam. As the x-rays pass through the body, some are absorbed, some are scattered, and the remaining radiation that exits the patient is what is termed remnant radiation. This radiation is essential for creating the diagnostic image on the imaging receptor, as it contains information about the internal structures of the body.

The primary beam is involved before any interaction occurs and does not account for any alteration through attenuation. Radiation exiting the tube refers to the initial x-ray beam that has not undergone any interaction, and scattered radiation typically describes the x-rays that have deviated from their original path due to interaction but do not constitute the remnant that directly contributes to the image formation. Thus, the definition provided ensures a clear understanding that remnant radiation is specifically concerned with what remains after the initial beam has passed through matter.