Which imaging technique uses sound waves to generate diagnostic images?

• A. CT scan
• B. Magnetic resonance imaging
• C. Sonography (Ultrasound)
• D. Radiography

Answer: (C)

Sound waves create diagnostic images in ultrasound. A transducer emits high-frequency pulses into the body; when these pulses encounter tissues of different densities, they bounce back as echoes. The machine interprets the travel time and strength of these echoes to construct real-time images of structures. Because it uses non-ionizing energy, ultrasound is safe for repeated use and excels at visualizing soft tissues, organs, and blood flow with Doppler. This differentiates it from CT and radiography, which rely on X-rays, and from MRI, which uses magnetic fields and radiofrequency energy.