Since ultrasound doesn't use ___________ there's no radiation exposure to patient.

• A. Ionizing radiation
• B. Thermal conduction
• C. Acoustic impedance
• D. Echo generation

Answer: (A)

Ultrasound uses high-frequency sound waves, which are mechanical energy rather than ionizing electromagnetic radiation. Because of this, there is no ionizing radiation exposure to the patient during standard diagnostic ultrasound. The other terms describe different aspects of ultrasound: thermal conduction is about heat transfer (not the safety basis for exposure), acoustic impedance relates to how sound waves travel through tissues, and echo generation is how the reflected sound waves are turned into an image. None of those explain why there’s no radiation exposure, whereas ionizing radiation is the type of energy that X-rays or CT scans use, which ultrasound avoids.