Contrast Media: Effect, Uses & Risks

In order to be able to implement special medical examination procedures sensibly and as efficiently as possible for the persons concerned, various aids are required. These chemical substances include, in particular, the so-called contrast media.

What are contrast agents?

Contrast agents are used in ultrasound and X-ray diagnostics as well as in magnetic resonance imaging. Contrast agents are substances that are not used directly for the therapy of diseases and to remedy the symptoms that occur. The primary purpose of contrast agents is to aid in the detection of diseases and abnormalities of organs. The use of contrast media in medicine is mainly limited to the medical methods known as imaging techniques. Contrast media are used in ultrasound and X-ray diagnostics as well as magnetic resonance imaging. These techniques are also called contrast media imaging because of the existing need for contrast media. Various contrast agents must have very specific properties and should not have any effect on the organism. They are excreted in a completely natural way body.

Application, effect and use

In addition to X-ray diagnostics and sonography, highly modern procedures such as magnetic resonance imaging are not performed without contrast media. Contrast agents make it possible to better visualize individual morphologic structures. Contrast agents exploit the physical laws of optics. In this context, the aim is to darken certain anatomical structures by means of very special chemical particles in the contrast medium. By creating shadows, it is possible to selectively modify information emitted by the examination device. This is the basis for increasing the image quality of diagnostic contrast agent images. The individual contrast media have different light and radiation absorption. In addition, the contrast media differ in terms of their composition. They differ in molecular weight, osmolarity and viscosity. Medical technology procedures take advantage of this and work with different contrast media to achieve the best possible quality of images. Contrast media, which are ideal for MRI, for example, are based on creating a difference in density in an artificial way. This involves the optical manipulation of metal ions that have a magnetic nature.

Substances used

Not all contrast media used are based on one and the same principle. Contrast agents in radiology have either high or low density and are referred to as x-ray negative or x-ray positive substances. To the patient or patients, contrast media present themselves as liquids that are introduced into the organism either by mouth or by injection. In the medical field, however, numerous contrast media are administered that differ from one another in their chemical and physical structure. In X-ray diagnostics, contrast media are administered in the form of suspensions of barium sulfate. In addition, many contrast media for X-rays contain iodine. In the field of examinations by ultrasound, in turn, completely different contrast media are preferred. In medical circles, these contrast media are known as echo contrast enhancers. The contrast media usually contain bubbles of air or a well-tolerated gas and usually resemble a foam. The internal organs are, so to speak, “inflated”, whereby a better ultrasound examination can be realized with these contrast media. In magnetic resonance imaging, the extracellular and intracellular contrast agents have meanwhile proven their worth. The latter group of contrast agents is quite rarely selected. Particles called superparamagnetic iron particles belong to this class of contrast agents. Substances that form a chemical bond with manganese are also administered. Extracellular contrast agents are typical imaging aids in MRI. These contrast agents move outside the organ cells, unlike intracellular (intra = inside) contrast agents. These contrast agents contain gadolinium ions and accelerate the magnetization of water in the tissues.

Risks and side effects

In general, modern contrast media are harmless and do not accumulate in the organism in any case. Therefore, health sequelae caused by contrast media are excluded. Usually, contrast media are excreted unnoticed in the normal way and do not cause any discomfort. Some people may develop an allergy or intolerance to contrast media. Mild diarrhea or nausea may occur as additional side effects with contrast media that are administered orally. However, this is usually due to the large amount of liquid in which the contrast agent is dissolved.