The theory behind ultrasound technology—using sound echoes to determine the distance of an object—has been around for centuries. The further away a canyon wall is, the longer it takes for your voice to echo off it and return to you. It wasn’t until mankind started to apply this concept to probing the depths of the sea, however, that scientists awakened to its potential for medical use.

The discovery of piezoelectricity in 1877 by the French physicist Pierre Curie (1859–1906) is often considered the founding of ultrasonics. Piezoelectricity is the ability certain substances have to give off pulses of energy when force is applied to them. One of the first practical applications of the new discovery came during World War I, when Paul Langevin (1872–1946), a former student of Curie’s, realized that piezoelectric crystals might give off sound waves that could be used to measure distances and detect enemy vessels at sea. He used this knowledge to develop the first sonographic imaging tool and helped scientists in France and Britain develop the first primitive sonar system for use against German U-boats.

In the 1920s, ultrasound technology was popularly embraced as a wonder treatment, wrongly believed to have amazing curative powers. It was used unsuccessfully against a host of illnesses, including cancer. (In reality, ultrasound waves are among the least intrusive waves that can be directed at the body.)

Indeed, ultrasonics’ real contribution to medicine was its diagnostic capabilities, not its treatment potential. In the 1940s, the Austrian neurologist Karl Dussik (1908–1968) first tried to beam ultrasound waves at a patient in an effort to pinpoint the location of a brain tumor. A few years later, the American naval doctor George Ludwig (1922–1973) used ultrasound to diagnose gallstones; ultrasonic detection of breast and colon cancer followed. And the most well known application of ultrasound today, the detection of a fetal heartbeat and monitoring of fetal growth, was first described in 1959 in Glasgow, Scotland, by the physician and professor Ian Donald (1910–1987).

A modern ultrasound machine is a relatively simple device, firing out ultrasonic pulses that progress through the body until they collide with a tissue boundary, at which point the waves bounce back to the machine. A computer calculates the distance , shape, and speed at which the waves traveled forward and back, forming a two-dimensional—or, thanks to advancements in computer processing, a threedimensional— image of the area.

ADDITIONAL FACTS

  1. Before the development of sonar echolocation, people used long ropes, with knots tied at regular intervals and a heavy piece of lead tied to one end, to measure the depth (in “knots”) of water. Although it’s not clear why, this process was called sounding.
  2. Langevin first noted the therapeutic (and dangerous) qualities of high-intensity ultrasound in the 1920s, when he felt pain in his hand while placing it in a water tank being hit with an ultrasound beam.