Ultrasound (sonography)

Overview: What is ultrasound?

Ultrasound is an examination that has become an integral part of today’s medical practice. It is now standard practice to detect a wide range of health problems in various organs. The ultrasound examination is also called sonography (other spelling: sonography).

Sonography is based on the fact that different tissues in the body reflect (reflect back) sound waves emitted by a transducer to different degrees. He catches it again and a computer then calculates a two-dimensional ultrasound image from it. We can see and evaluate this on a monitor. In this way, various changes in organs and tissues can be detected.

Examples include diseases of the kidneys, thyroid, liver, uterus, ovaries, prostate or heart (cardiac ultrasound = echocardiography). During pregnancy ultrasound as part of prenatal care, gynecologists can find out whether the unborn child is developing normally. A 3-D or 4-D ultrasound is also possible for pregnant women. The images allow expectant parents to see their baby in real time and in multiple dimensions. However, the use of this “baby television” without medical necessity is not uncontroversial.

In principle, there are two ways to perform a sonography:

• From the outside, such as an abdominal or breast ultrasound (breast ultrasound)
• From the inside(endosonography), e.g. vaginal ultrasound and transrectal ultrasound (TRUS)

There are also different variants of sonography that provide additional information, such as Doppler and duplex sonography. They not only show the condition of the blood vessels, but also the speed and direction of blood flow.

An ultrasound is inexpensive, provides quick results and is painless. In addition, sound waves are not hazardous to health and there is no radiation exposure. We use ultrasound not only in diagnostics, but also in the treatment of diseases, for example for pain, to stimulate self-healing processes or for prostate cancer(high-intensity focused ultrasound = HIFU).

How does an ultrasound work?

Sonography works with sound waves that a person cannot perceive or hear. The frequency used ranges from 1 to 40 megahertz. It lies above the human hearing threshold (approx. 20 to 20,000 Hertz).

An ultrasonic device consists of several parts:

• Transducer: It emits sound waves and receives them again at the same time. The transducer contains special crystals (so-called piezoelectric crystals). When they are set into vibration by applying a voltage, ultrasonic waves are generated. Either the doctor places the transducer on the skin from the outside (e.g. abdominal ultrasound) or he or she inserts it into a body cavity (e.g. vaginal ultrasound).
• Computer: This calculates a two-dimensional image from the reflected sound waves.
• Screen: We can see the images on the monitor, usually in black and white (also in color for duplex sonography). We can also capture and save images of specific areas. A later comparison then shows whether anything has changed.

Sonography is based on the fact that tissues in the body have different densities. The impacting sound waves propagate at different speeds and are reflected back to different degrees.

Ultrasound: Different variants

There are different variants of the ultrasound examination that provide the doctor with even more information about vessels (e.g. head, neck, pelvis, legs, abdomen). These include, for example:

• Doppler ultrasound (Doppler sonography): A method with which we can determine the flow velocity of the blood in the blood vessels. In this way, constrictions (stenoses), occlusions or blood clots (thrombi) can be diagnosed. The blood flows more slowly at these points.
• Duplex ultrasound (duplex sonography) – a combination of normal ultrasound examination and Doppler sonography, with which the vessels, the surrounding tissue and the flow conditions of the blood can be determined simultaneously. With color Doppler, the doctor can also show the direction of the blood flow in color. It appears red or blue on the monitor. The blood flow can even be made audible as an acoustic signal.
• Intensity-modulated Doppler – this allows even very slow blood flow to be detected, for example in the veins.

There is also 3D and 4D ultrasound for unborn babies. It provides detailed multidimensional images in which even facial features can be recognized. The 4-D ultrasound shows three-dimensional images in real time – a kind of “live baby TV”. Examinations without medical necessity (indication) are controversial because high ultrasound intensities are required, which causes the body temperature to rise slightly. In Germany, the examination will no longer be permitted without an indication from 2021.

Ultrasound examination - the procedure

An external ultrasound is performed in several steps:

• First, the doctor applies a gel to the area of the body that he or she wants to examine. The gel ensures good contact between the transducer and the skin. The sound waves can therefore penetrate well.
• The doctor places the ultrasound probe on the skin.
• He or she then moves the transducer over the region to be examined while applying slight pressure.
• The organs and tissues can be viewed on the monitor from different directions and angles. Internal ultrasound (endosonography) works according to the same principle.

However, the transducer is usually narrower and the doctor inserts it into a body cavity. This can be the vagina in a vaginal ultrasound or the rectum in a transrectal ultrasound. An ultrasound examination usually only takes a few minutes. It is painless and risk-free.

Areas of application: When is ultrasound used?

There are many different applications for sonography. We can diagnose changes in organs, tissues and blood vessels. But they can also check the success of a treatment or use ultrasound itself as a therapy.

Ultrasound in diagnostics

Some examples:

• heart (cardiac ultrasound = echocardiography): The ventricles, atria or heart valves can be assessed.
• Breast (breast sonography) – cysts, benign changes such as fibroadenomas or signs of breast cancer (always in combination with mammography and possibly magnetic resonance imaging = breast MRI)
• Female reproductive organs: changes to the fallopian tubes, ovaries or uterus
• Prostate (transrectal ultrasound = TRUS) – benign prostate enlargement (benign prostatic hyperplasia = BPH), prostate cancer (always together with other examinations)
• Thyroid gland: size of the thyroid gland, benign or malignant nodules
• Abdominal organs: kidneys, liver, gall bladder, spleen, pancreas, urinary bladder – size and pathological changes
• Vessels, e.g. neck, head, abdomen, pelvis, legs – Constrictions or occlusions
• Joints, e.g. for knee or shoulder pain, joint effusion
• Ultrasound during pregnancy: It is a routine part of prenatal care. Gynecologists check whether the unborn child is developing normally.
• Gastrointestinal tract, e.g. for the assessment of inflammation.
• lungs, e.g. in emergencies and in the intensive care unit.
• Ultrasound with contrast medium, e.g. to assess the blood supply to a mass.

Not all organs can be examined well with the help of sonography. Ultrasound is not suitable for hard structures such as bones.

Ultrasound in therapy

Sonography is also suitable as a treatment method for various clinical pictures. Some examples:

• Pain: Therapists use ultrasound as part of electrotherapy. The heat generated can relieve pain, such as joint pain.
• Prostate cancer: High-intensity focused ultrasound (HIFU) is used – doctors “cook” the tumor with the help of high-energy ultrasound waves
• Kidney stones: Doctors break them up from the outside using ultrasound. The method is called extracorporeal shock wave therapy (ESWL)

Ultrasound: advantages and risks

Sonography has many advantages: it is harmless to health, does not involve harmful radiation and is painless. Ultrasound is also a fast and cost-effective method that delivers rapid results. An ultrasound does not involve any risks. If we use sonography for therapy, only minor side effects are to be expected. In the case of HIFU for prostate cancer, these can be problems with urination or urinary tract infections, for example. Bruising is possible when kidney stones are broken up.