In CT imaging, the patient skin dose is typically on the order of which unit?

• A. one to several RADS
• B. one to several mrems
• C. one to several Gy-SV
• D. 10 to 20 rems

Answer: (A)

The key idea is that the entrance skin dose from a typical CT exam is described in absorbed dose units and falls in the range of a few rads. In CT, energy is deposited along the beam path and at the skin surface during the rotation, so the skin receives about 1 to a few rad per exam. Since 1 rad equals 0.01 Gy, that corresponds to roughly 0.01 to 0.05 Gy. Other options reflect either much smaller doses (millirems) or different concepts (dose equivalents like rem or Gy-SV) that aren’t as representative for the actual skin absorption in a standard CT scan. A 10 to 20 rem range would imply a far higher exposure than typical CT skin dose. So the entrance skin dose in CT is best described as about one to several RADS.