Ultrasound has been used for medical imaging purposes since the 1950’s, which makes it a relatively new technology. However, research about the use of high frequency sound waves dates back to the 1700’s when Italian biologist Lozzaro Spallanzani learned how bats are able to maneuver without sight. He discovered that they possess an internal radar which allows them to use high frequency sound for navigation.
In 1826, physicist/engineer Jean-Daniel Colladon accurately determined the speed of sound in water. In 1881, Pierre Curie found the connection between electrical voltage and pressure on crystalline material and invented the first ultrasound transducer (The same crystalline material, lead zirconate titanate, is still used in modern transducers). The sinking of the Titanic led to the very first application of the ultrasound transducer. This transducer or “hydrophone” was developed after the epic disaster to help other ships avoid icebergs. The “hydrophone” was later also used in World War I to detect submarines.
Psychiatrist Dr. Karl Dussik first applied ultrasound to medical purposes by attempting to detect brain tumors in the 1930’s. In the late 1940’s, Dr. George Ludwig successfully used ultrasound on animals to test how it traveled through soft tissue, muscles, and organs. In the 1950’s, a female patient came to Professor Ian Donald with inoperable stomach cancer and he employed his old World War II radar and sonar equipment to discover that she had an ovarian cyst. Professor Donald thus became the originator of obstetric ultrasound. In 1953, Swedish cardiologist Inge Edler and a graduate student in Nuclear Physics at Lund University, Carl Hellmuth Hertz, were first able to detect and measure heart activity using ultrasound equipment borrowed from a ship builder. They founded cardiovascular ultrasound.
In the early stages of medical use, a patient had to be submerged in water in order to produce an ultrasound image because the large difference in the speed of sound in air and the speed of sound in soft tissue allowed the ultrasound to penetrate the body. The transducer was never in direct contact with the patient. Douglas Howry and Joseph Holmes improved the technology of the transducer and invented a device which touched the patient to produce ultrasound images in a manner similar to modern scans. However, a water based gel is still applied to the patient’s skin as the coupling medium that enables the ultrasound beam to enter the body.
Ultrasound technology continues to advance. Two dimensional gray scale imaging, Doppler radar, and later, three dimensional imaging and color flow Doppler radar, have resulted in better diagnoses for a wider variety of patients. The addition of contrast agents to further improve the diagnostic quality and accuracy of images have taken the demand for ultrasound scans to greater levels. Ultrasound is currently the second most commonly used medical imaging category, behind only x-ray. Due to the fact that most ultrasound exams are non-invasive, cost less than other medical tests, and are an efficient means of avoiding unnecessary surgeries, research and development of new medical applications is ongoing. Ultrasound technology not only has an impressive history, but an even more significant future.

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