The part of the X-ray beam that has gone through the patient and reaches the image receptor is called which term?

• A. Primary Radiation
• B. Scatter Radiation
• C. Remnant Radiation
• D. Exit Radiation

Answer: (C)

Remnant radiation is the portion of the X-ray beam that remains after it has interacted with the patient and still reaches the image receptor. It includes photons that pass straight through (transmitted) as well as photons that were deflected (scattered) but emerge toward the detector. This exiting beam carries the attenuation information of the tissues, forming the image. Primary radiation is the original beam leaving the X-ray tube before it hits the patient, and scatter radiation is the deflected portion that can degrade image quality. Exit radiation is sometimes used to describe the same exiting beam, but remnant radiation is the precise term for what ultimately forms the radiographic image.