Which part of the x-ray beam has signal intensities that correspond to the anatomy represented on the image receptor?

• A. Remnant beam
• B. Primary beam
• C. Receptor beam
• D. Corresponding beam

Answer: (A)

The signal on the image receptor comes from the remnant beam—the X-rays that have passed through the patient after interacting with tissues. The primary beam is the unaltered beam that leaves the X-ray tube and does not itself carry the image information to the receptor. The remnant beam carries information about anatomy because different tissues attenuate X-rays to different extents; dense structures like bone absorb more and reduce the remnant beam reaching the receptor, which shows up as lighter, radiopaque areas on the image, while less dense tissues transmit more photons and appear darker. Terms like receptor beam or corresponding beam aren’t relevant in this context, so they don’t describe the signal that forms the image.