The development of medical imaging technology known as ultrasound represents a significant advancement in non-invasive diagnosis. Ultrasound uses high-frequency sound waves, beyond the range of human hearing, to create real-time images of internal body structures. Its history is not attributed to a single inventor, but emerged from scientific breakthroughs across military acoustics, industrial material testing, and medical research. This technology shifted from detecting underwater objects and metal flaws to visualizing human anatomy, becoming a ubiquitous diagnostic tool used worldwide today.
The Scientific Foundations of Sound Waves
The fundamental principles governing ultrasound imaging trace back to the study of sound and vibrations by 19th-century physicists. The piezoelectric effect, demonstrated by Pierre and Jacques Curie in 1880, forms the basis for modern ultrasound transducers. They found that certain crystals, such as quartz, generate an electrical charge when subjected to mechanical stress, and conversely, vibrate when an electrical voltage is applied. This dual property allows a single crystal to both transmit a high-frequency sound pulse and receive the returning echoes.
The first practical application of this technology was in military defense, following the sinking of the Titanic in 1912. During World War I, French physicist Paul Langevin was commissioned to develop a method for detecting German submarines underwater. He adapted the piezoelectric principle to create the hydrophone, which laid the groundwork for SONAR, or Sound Navigation and Ranging. This pulse-echo technique, which involves sending out a sound wave and measuring the time it takes for the echo to return, established the core technological requirement for all subsequent ultrasonic imaging.
Pioneers of Diagnostic Medical Ultrasound
The transition from military detection to medical diagnosis began in the 1940s with early experiments on human subjects. Austrian neurologist Karl Dussik is credited with the first published attempt to use ultrasound for medical diagnosis in 1942. He employed a technique called “hyperphonography” to transmit an ultrasonic beam through the head to detect brain tumors or changes in the cerebral ventricles. While his initial interpretations were later determined to be artifacts caused by variations in bone structure, Dussik’s work first explored the diagnostic potential of sound waves in a clinical setting.
A more successful approach emerged in the United States, led by surgeon John J. Wild and engineer John Reid. Starting in the late 1940s, they adapted industrial flaw detectors to create a pulse-echo system specifically for examining soft tissue. Wild and Reid developed the first reliable A-mode (amplitude mode) and B-mode (brightness mode) scanners using a handheld probe. The A-mode provided a one-dimensional display of echo amplitude, while the B-mode generated a two-dimensional grayscale image of the tissue structure. By 1953, focusing on breast tissue, they produced a real-time B-mode image of a small breast tumor, demonstrating the technology’s potential for cancer diagnosis.
The Introduction of Clinical Imaging
The final step in establishing ultrasound as a standard medical tool was its application to obstetrics and gynecology by Scottish obstetrician Ian Donald. In the mid-1950s, Donald partnered with engineer Tom Brown to adapt a commercial ultrasonic flaw detector for use on abdominal masses. He reasoned that sound waves could pass through the fluid-filled uterus and reflect off the dense structures of a fetus or a tumor.
This collaboration resulted in the development of a two-dimensional contact compound scanner, a technical improvement that allowed for much clearer images. In 1958, Donald, Brown, and colleague John MacVicar published a landmark paper describing their success in using ultrasound to differentiate between fluid-filled cysts and solid tumors in the abdomen. They also demonstrated the ability to visualize and measure the fetal head, identify twins, and confirm pregnancy. This work provided the first clinically useful and reliable application of B-mode imaging, leading to the rapid worldwide adoption of the technology. The subsequent development of the first commercially viable machine, the Diasonograph, transitioned ultrasound into an indispensable part of modern prenatal care.