According to NCRP Report 160, the largest contributor to the recent rise in patient radiation exposure is the increased use of which imaging modality?

• A. MRI
• B. Diagnostic medical ultrasound
• C. Fluoroscopy and interventional procedures
• D. CT

Answer: (D)

The key idea is that the overall rise in patient radiation exposure has come mainly from how often CT is being used, not from other imaging types. CT scans deliver more radiation per exam than most other routine radiologic tests, and their use has grown extremely rapidly over the years. Because of this combination—high dose per exam and a huge increase in the number of exams—CT becomes the largest contributor to the population’s collective radiation dose, as shown in NCRP Report 160.

For contrast, MRI and diagnostic ultrasound do not use ionizing radiation at all, so they don’t add to radiation exposure. Fluoroscopy and interventional procedures do involve radiation and can be high-dose per procedure, but their overall growth in use hasn’t matched the rapid, widespread expansion of CT, making CT the primary driver of the recent rise.