A child's drawing of ultrasound examination
Ultrasound (Sonography)
Author: Gesche Tallen, MD, PhD, Editor: Maria Yiallouros, Reviewer: Prof. Dr. med. Dr. h. c. Günter Henze, English Translation: Hannah McRae, Last modification: 2015/04/22
Ultrasound imaging (sonography) is a medical procedure using ultrasound waves in order to obtain a live image of an organ. During an ultrasound examination, the sound waves are produced by a so-called transducer. The sound of the waves is directed either by the shape of the transducer, a lens in front of the transducer, or by the ultrasound scanner machine to which the transducer is connected.
This focusing produces an arc-shaped sound wave from the face of the transducer. The wave travels into the body and comes into focus at a desired depth corresponding to the patient's body region of interest. To obtain optimal transduction of waves, the doctor usually applies a water-based, skin-friendly gel to the transducer or to the body surface area beyond which the region to be examined is located.
The sound waves partially bounce back from the layers between different tissues. This so-called echo returns to the transducer. The returned sound waves vibrate the transducer, which turns the vibrations into electrical pulses. These travel to the ultrasonic scanner, a big machine attached to the transducer, where they are processed and transformed into a digital image.
Ultrasound imaging is mainly used to examine soft tissues such as:
- the brain and intracranial structures of infants before closure of the soft spot (for example for diagnostics of brain tumours)
- lymph nodes
- heart (for example to monitor negative side effects of certain chemotherapeutic agents)
- organs in the tummy (for example to assess the size and spread of a tumour)
- blood vessels (for example to ensure the correct position of a central line)
An ultrasound examination does not hurt, usually does not take a long time and does not involve a patient's exposure to radiation. Therefore, ultrasound is a preferred diagnostic imaging technique for children with cancer.
