Which imaging modality uses sound waves to produce an image?

• A. CT
• B. MRI
• C. Ultrasound imaging
• D. X-ray imaging

Answer: (C)

Ultrasound imaging uses high-frequency sound waves emitted by a transducer. These waves travel through the body and reflect off tissues at interfaces with different acoustic properties. The scanner detects the returning echoes, and from their timing and strength it builds a real-time image of internal structures. This method is nonionizing and safe for frequent use, making it especially versatile for evaluating soft tissues, guiding procedures, and monitoring movements like a beating heart or fetal development.

In contrast, CT relies on X-rays to create cross-sectional images, MRI uses strong magnetic fields and radiofrequency pulses to generate signals from tissues, and conventional X-ray imaging uses ionizing radiation to produce 2D projections. None of those primarily depend on sound waves.