Advantages
Ultrasound is one of the most frequently used procedures for the diagnosis and monitoring of diseases in medicine. This is due to the fact that sonography has a number of advantages compared to other methods: it is very fast and can be performed well without much practice, an ultrasound machine can be found in every hospital and also in almost all medical practices. There are even small ultrasound devices that are easy to transport, so that an ultrasound examination can even be performed directly at the patient’s bed, if necessary. The examination itself is painless for the patient and without any risk, in contrast to other imaging procedures (such as X-ray or computed tomography), where the body is sometimes exposed to a not inconsiderable amount of radiation. In addition, sonography is now quite inexpensive.
Risks
According to current knowledge, medical sonography is free of side effects and risks. Even if the interpretation of ultrasound images seems difficult for the layman, many diseases can be detected by ultrasound. Sonography is very well suited for detecting free fluids (e.g. Baker’s cyst), but tissue structures such as muscles and tendons can also be assessed well (rotator cuff, Achilles tendon).
The great advantage of this examination method is the possibility of dynamic examination. In contrast to all other imaging methods (X-ray, MRI, computed tomography), it is possible to examine while moving and to visualize diseases that only occur while moving. There are different methods of presentation for the measurement results of an ultrasound examination.
They are called fashion, which comes from the English word for method or procedure.The first form of application was the so-called A-mode, which is now almost obsolete and is only used in otorhinolaryngology for certain questions (for example, whether there is secretion in the paranasal sinuses). The “A” in the A-Mode stands for amplitude modulation. The reflected echo is received by the probe and plotted in a diagram in which the X-axis represents the penetration depth and the Y-axis represents the echo strength.
This means that the further up the measurement curve the more echogenic the tissue is at the specified depth. The most common mode used today is B-mode (the “B” stands for Brightness Modulation). With this display method, the intensity of the echo is shown using different levels of brightness.
The individual gray value of a pixel thus represents the amplitude of the echo at that particular position. In the B-mode, a further distinction is made between M-mode and 2D-realtime mode. In the 2D real-time mode, a two-dimensional image is generated on the ultrasound monitor, which is composed of individual lines (each line is generated by an emitted and re-received beam).
Everything that appears black in this image is (more or less) liquid, while air, bone and calcium are shown in white. In order to better evaluate some tissues, it is sometimes useful to use special contrast agents (this method is mainly used for ultrasound in the abdomen area). Certain terms are used to describe the sonogram: The shape of the image visible on the screen depends on the probe used.
Depending on which probe is used and the depth of penetration, this method can produce up to more than a hundred two-dimensional images per second. The M-Mode (sometimes also called TM Mode: (time) motion) uses a high pulse repetition frequency (between 1000 and 5000 Hz). In this mode, the X-axis is a time axis and the Y-axis shows the amplitude of the received signals.
This allows the one-dimensional representation of organ movements. To obtain even more meaningful information, this method is often coupled with the 2D real-time mode. The M-mode is used particularly frequently in echocardiography, as it allows individual heart valves and certain areas of the heart muscles to be examined separately.
This method can also be used to detect cardiac arrhythmias in fetuses. Since the beginning of the 21st century, multidimensional echographies have also been available: 3D ultrasound produces a spatial still image. The recorded data is entered into a 3D matrix by a computer and creates an image which the examiner can then view from different angles.
4D ultrasound (also known as live 3D ultrasound) is a three-dimensional representation in real time, which means that the temporal dimension is added to the three spatial dimensions. With the help of this method, it is therefore possible for the physician to visualize movements (for example of an unborn child or of the heart) practically in the form of a video.
- Anechogen means echo-free
- Hypoechogen means low echo,
- Isoechogenic means echo-equivalent and
- Hyperechogen means echoric.
