Ultrasound, or ultrasound examination or sonography, is a high-frequency sound whose frequencies are above human hearing. The examination by ultrasound is also called sonography in medicine and is one of the so-called imaging procedures.
Definition and mode of operation
Sonography is best known for ultrasound examinations during pregnancy. However, sonography is also used for many other conditions. Click to enlarge. Ultrasound is applied through ultrasound machines that have a sound-emitting transducer. Shapes of attachments to these devices differ according to the area of application: while devices that are applied to the surface of the body usually have flat-shaped attachments, attachments that are applied inside the body (for example, in the rectum) are correspondingly ergonomically shaped. If the sound waves of the ultrasound act on organic tissue or liquids, for example, they are either reflected, absorbed (taken up) or the sound passes through the corresponding organic material, depending on the nature of the tissue. Due to the corresponding resulting sound of different strengths hitting back an ultrasound device, it is possible to reproduce this data in an image. This is usually done by varying shades of gray; tissue that returns the sound more strongly appears lighter in the image, while the rest appears darker.
Application
Sonography is also used to document and provide information about the diagnosis, differential diagnosis, and course of almost any disease. Pictured: sonography of the shoulder region. Click to enlarge. In medicine, ultrasound is used in a variety of ways; for example, it functions as a diagnostic tool, but also as a means for tissue sections such as biopsies. Ultrasound can be used to different degrees of effectiveness: For example, while it allows for very good data in tissue that is well perfused, ultrasound is not very useful for imaging tissue that is surrounded by bone or contains gases; such as the brain, lungs, or bone marrow. In some cases, organs only become recognizable by ultrasound when an enlargement of the organ is present; the existing enlargement can thus be diagnosed. The classic area of application is in the monitoring of pregnancies – so-called prenatal diagnostics. In this way, the developmental status, size and correspondingly healthy organ development of the unborn child can be observed. In addition to two-dimensional imaging, there are ultrasound procedures that produce three-dimensional or even four-dimensional images. Furthermore, ultrasound can be used to detect foci that are suspicious of cancer. Ultrasound is also used in gynecology and urology to view internal organs such as ovaries or prostate. Ultrasound can also be used to determine the width of blood vessels – for example, if vein problems are present. Examinations of organs such as the thyroid gland or heart are also possible. In the context of required biopsies, body tissue can be removed by ultrasound; likewise, a sampling of body fluids can be performed.
Side effects and dangers
Unlike other imaging procedures, such as X-rays, the use of ultrasound is virtually harmless to both patient and practitioner. Side effects that may accompany treatment with ultrasound is the production of heat in the body due to the sound acting on it. Such a possible local body warming, which can reach a value of about 1.5 degrees Celsius, is not dangerous to health, however, and is released again via the bloodstream, among other things. Nevertheless, it is recommended not to extend a treatment with ultrasound for too long and to observe corresponding guideline values as a preventive measure. Another possible, but rarely occurring side effect can be that gas accumulations in the body burst under the effect of the sound, which can affect surrounding organs. Such an effect is sought, for example, with ultrasound, which is used in non-medical settings and with a cleansing effect.
