How Ultrasound Works and What It Detects

Ultrasound is one of the most widely used and versatile diagnostic imaging tools in modern medicine. Unlike X-rays and CT scans, it uses no ionizing radiation, making it particularly safe for pregnant women, children, and patients who require repeated imaging. It is real-time, portable, relatively inexpensive, and capable of visualizing a remarkable range of anatomical structures and physiological processes.

How Ultrasound Works

Ultrasound imaging works by emitting high-frequency sound waves — typically in the range of 2 to 18 megahertz (MHz), far above the range of human hearing (20–20,000 Hz) — and analyzing the echoes that return when those waves encounter different tissues.

A device called a transducer (probe) both emits and receives sound waves. When sound waves travel through the body and encounter a boundary between two tissues with different acoustic properties (called acoustic impedance), some of the sound is reflected back toward the transducer as an echo. The transducer detects these echoes and a computer converts them into a real-time image based on the timing and intensity of the returning signals.