The most likely effect of radiation from diagnostic imaging is which of the following?

• A. Cancer
• B. Epilation
• C. Erythema
• D. Decreased sperm count

Answer: (A)

When x-ray exposure from diagnostic imaging is kept at clinical, low doses, the main concern is the small increase in lifetime cancer risk. This is a stochastic effect: its probability rises with dose, and there isn’t a sharp threshold. In other words, even small amounts of exposure can contribute to cancer risk sometime later in life, which is why cancer is considered the most likely outcome.

The other possibilities reflect deterministic effects, which only appear at much higher radiation doses than those used in diagnostic imaging. Erythema (skin reddening) and epilation (hair loss) require substantial skin doses, far above typical imaging exposures. Decreased sperm count could occur with gonadal exposure, but with modern practice and shielding the likelihood is much smaller than the incremental cancer risk across many imaging exams. So the best answer is that diagnostic imaging modestly increases cancer risk over a person’s lifetime.