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How does ultrasound use sound waves to examine a fetus or internal organs?

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magnetic resonance imaging — diagnosis Magnetic resonance imaging (MRI) is a powerful diagnostic technique that is used to visualize organs and structures inside the body without the need for X-rays or other radiation.

Ultrasound, or ultrasonography, functions by utilizing high-frequency sound waves—typically above one megahertz—to create images of internal structures. These waves are generated by a piezoelectric transducer, which converts electrical energy into mechanical vibrations directed into the body.123

As these waves travel through the body, they encounter varying acoustic impedance at the borders between different tissues or organs, causing the sound to reflect back as echoes. The transducer acts as a receiver, picking up these echoes and converting them back into electrical signals. An electronic apparatus then analyzes the intensity and time delay of these reflections to determine the position and nature of the underlying tissue.123

This data is displayed as a two-dimensional plot or a moving image. Because ultrasound is a nonionizing form of energy, it is considered safer than X-rays and is a staple in obstetric diagnosis for monitoring fetuses, as well as for examining internal organs like the heart, liver, and kidneys.12