Ultrasound History and Discovery

Medical ultrasound technology has seen continuous advancements and is currently playing a vital role in diagnosing and treating patients. The development of ultrasound technology is rooted in a fascinating history that spans over 225 years. This journey involves contributions from numerous individuals around the world, including both humans and animals.

Let’s explore the history of ultrasound and understand how sound waves have become an essential diagnostic tool in clinics and hospitals globally.

The Early Beginnings of Echolocation and Ultrasound

A common question is, who first invented ultrasound? The Italian biologist Lazzaro Spallanzani is often credited as the pioneer of ultrasound examination.

Lazzaro Spallanzani (1729-1799) was a physiologist, professor, and priest whose numerous experiments significantly impacted the study of biology in both humans and animals.

In 1794, Spallanzani studied bats and discovered that they navigated using sound rather than sight, a process now known as echolocation. Echolocation involves locating objects by reflecting sound waves off them, a principle that underpins modern medical ultrasound technology.

Early Ultrasound Experiments

In Gerald Neuweiler's book *Bat Biology,* he recounts Spallanzani's experiments with owls, which couldn’t fly in darkness without a light source. However, when the same experiment was conducted with bats, they confidently flew around the room, avoiding obstacles even in complete darkness.

Spallanzani even conducted experiments where he blinded bats by using “red-hot needles,” yet they continued to avoid the obstacles. He determined this because the wires had bells attached to their ends. He also found that when he blocked the bats' ears with closed brass tubes, they lost their ability to navigate properly, leading him to conclude that bats relied on sound for navigation.

Though Spallanzani did not realize that the sounds bats made were for orientation and were beyond human hearing, he correctly inferred that bats used their ears to perceive their surroundings.