Wave on Soundwave

It was nature that inspired the first utilisation of ultrasound. In 1794 the Italian scientist Lazzaro Spallanzani concluded that bats used ultrasound for orientation during their night flying. Bats send out ultrasounds produced by their vocal system and detect the echoes which bounce off the surrounding surfaces or from their prey, providing them with information about distance and morphology. Although humans are not able to hear ultrasounds, this ability is shared by other animals, such as dolphins and whales, who use them to communicate amongst themselves.

The use of sonar impulses can first be seen at the beginning of the 20th century. Following the tragedy of the Titanic in 1912, the British mathematician and meteorologist Lewis Fry Richardson invented an instrument to install on ships to identify submerged obstacles. This necessity led on to SONAR, SOundNavigation And Ranging, developed between the two world wars and installed on ships to detect submarines. It works on the basis of the emission of ultrasounds and the successive detection of any echoes bouncing off surfaces present in the sea.

The diagnostic use of ultrasound started from the intuition of the creative Scottish physicist Ian Donald. His passion for constructing various instruments earned him the nickname of “Mad Donald”. After specialising in obstetrics and gynocology,Donald conducted numerous experiments in the use of ultrasound in the diagnosisof cysts, fibrosis and other abdominal tumours. In the middle of the 1950s his workwas underrated by the scientific community until the day in which, thanks to hisultrasonic examination, he managed to save the life of a patient by diagnosing an ovariancyst.

Diagnostic imaging with ultrasound has made it possible for the first time to explore inside the human body and to obtain moving images without the use of radiation. These images are produced by means of a “probe”, an instrument which is placed on the body of the patient. The probe is able to emit a sound wave which registers the echo thrown back from the internal tissues and organs, sending the data to a powerful computer which elaborates it in real time to produce the images. Today, ultrasound constitutes around 20% of the examinations carried out in radiology departments and in patient clinics.

Ultrasound was soon shown to be fundamental in the diagnosis of disease or dysfunction of the liver, kidneys and pancreas, all difficult to examine, but also of organs in rapid movement, such as the heart.It is also vital for studying blood flow, or in those cases where diagnosis is based on the study of anatomical details where the position is not clear, for example prenatal diagnosis or in the search for abnormal internal organ tissue.Its widespread use has become popular due to the harmless nature of its emissions, its relative inexpensiveness and flexibility in taking the equipment to the patient’s bedside. This technique also has a special diagnostic sensitivity to the pathologies of the organs made up of soft tissue or of the glands, such as the thyroid.

If you drop a stone into water, the waves generated by the impact will bounce, creating extensive turbulence. Like every other type of wave phenomenon, ultrasound is subject to reflection, refraction,diffraction and impedence, which change the speed of the transmission and the intensity of the signal. Ultrasound technology allows all these signals to be taken into account, producing images which have become increasingly precise and detailed as the technology has advanced.

Contrast enhanced ultrasound allows the dynamic study of blood flow in deep tissue. At the start of this century, Bracco researchers discovered a contrast agent based on microbubbles, which made possible diagnoses otherwise impossible. The machine emits a beam of ultrasound, to which the microbubbles react by vibrating. This vibration is then recorded and transformed into images.