Transvaginal ultrasound transducer, by Diasonic, California, United States, 1990, used to examine the uterus and ovaries

The key technology for producing ultrasound images is the transducer. It sends ultrasound waves into the body when held against it. It then detects the waves when they bounce back from soft tissue, which are converted into an image by a computer. This technique has not changed since the invention of medical ultrasound, although transducers now have different shapes depending on the area of the body being examined.

Ultrasound was a transformative way to create cross-sectional images of inside the body, using high-frequency sound waves. This risk-free technique was pioneered in Glasgow by Professor Ian Donald, engineer Tom Brown and doctor John MacVicar in 1957. The first ultrasound images were recorded on black-and-white film and were always blurred. By the 1980s, technology had advanced to produce moving images with shades of grey, soon followed by 3D imaging.