The ultrasound scan can represent more than suckling babies in the womb. It enables the assessment of organs, tissues, joints, soft tissues and blood vessels, is inexpensive, painless and does not burden the human body according to current knowledge.
The development of Ultrasound
Ultrasound exists in nature - animals like the bat generate it themselves and orientate themselves with their help in the room. Humans began using it in the early 20th century, first to track underwater icebergs and submarines, later to test materials for their integrity.
In the 1930s and 1940s, attempts were made to use ultrasound for therapeutic purposes. In 1938, the Dussik doctor came up with the idea to use it for diagnostics as well, but tried this on his brain. Not a good idea, as it is completely surrounded by bones through which the sound does not penetrate except in the baby.
In 1950, the organ was then visualized: the patient to be examined was placed in a water tub, and the transducer was mounted on a motorized wooden rail - a method that proved to be of limited use for patients.
The gynecologist Donald succeeded in 1958 for the first time to obtain images with an ultrasound device in which the transducer was placed directly on the skin of the patient and moved by hand. A principle that has since been constantly evolving and since the 80s (and the availability of powerful computers) allows the broad diagnostic use of ultrasonography.
How does the sonography work?
At 20 kHz-1 GHz, ultrasound has a frequency that humans can not hear. With a sonography device, such sound waves are generated in a probe (transducer, transducer) and emitted directionally. If they encounter structures, they are reflected and scattered.
This so-called echogenicity varies according to the type of tissue - in the case of fluids such as blood and urine it is low, high in bones and air, eg intestinal gases. The extent of the reflection is measured by the probe, converted into electrical impulses and shown on a screen as gray values: Liquids appear black, bones very bright, organ tissue intervene.
So that the first sound waves are not already deflected by the air between the skin and the transducer before they even reach the structures to be displayed, a hydrous gel is applied to the skin. Meanwhile, a very fine representation of the tissue with high resolution and recently even as a 3-D image succeeds.
In addition, one makes use of the Doppler effect: The frequency of the echo is dependent on the distance of the structure to the transducer, whereby, for example, the flow velocity of the blood (whose solid components move either on the transducer to or away from this) can be represented.