What will changing the distance of the Target-to-Skin distance do to the patient if its decreased from 40 inches to 38 inches?

• A. Increase in static marks
• B. Increase in patient dose
• C. Decrease in exposure time
• D. No change

Answer: (B)

Decreasing the distance from the X-ray source to the patient increases the dose due to the inverse-square law: beam intensity at the patient is inversely proportional to the square of the distance. Dropping the Target-to-Skin distance from 40 inches to 38 inches shortens the gap by 5%, so the dose to the patient rises by about (40/38)^2 ≈ 1.11, roughly an 11% increase, assuming exposure factors (mA, time, kVp) remain the same. This distance change does not inherently create more static marks, and exposure time doesn’t automatically decrease unless you adjust exposure factors to compensate for the dose increase.