What is contrast media and what are its benefits?
What is contrast media and what are its benefits?
Contrast Media
Contrast media refers to substances used in radiological examination for a difference in the radiation absorption between the examined organ and other nearby organs and structures. As a result, the organ to be examined can be clearly seen.
Contrast media can be administered into the body via several ways, such as eating, anal enema, intravascular injection, or cavity injection (Chamari, 1995: Charin, 1999: Somkiat, 1995).
Intravascular contrast medium is a substance that is necessary to differentiate the examined organ and neighbors. This causes the clear images. Therefore, contrast media plays an important role in many radiological examinations, including Computed tomography (CT), Intravenous pyelography), Angiography/Venography, Magnetic Resonance Imaging (MRI).
However, because the contrast media may cause allergies or complications to the body, which can lead to death. This is considered a high-risk examination. According to a study by Katayama et al., reported in Radiology 1990, 12.66% of all 169,284 people, who received ionizing contrast media, showed allergic reactions. Among 168,363 people, who received un-ionizing contras media, had an allergic reaction approximately 3.13 %.
For the prevention of the risk of using contrast media, it can be done at all stages, i.e., before, during, and after the contrast media injection. If nurses and related staffs have good knowledge and understanding of contrast media, then patients will receive quality and safe care.
Type of contrast media
They can be divided into several types according to the properties of the media as follow:
- Divided by radiation opacity (Chamari, 1995: Charin, 1999)
- Negative contrast media is a low molecular weight substance. Therefore, it is less opaque than body tissues. These type of contrast media will form a solid shadow in the radiograph, including air, oxygen, carbon dioxide, nitrous oxide. Currently, air, oxygen, and carbon dioxide are still used because it is easy to find and slow absorption if it can be completely purified and less dangerous. However, nitrous oxide is expensive and fast absorption, so it's not usually used.
- Positive contrast media is a high molecular weight substance and has more opaque than tissue. It causes a white shadow on the radiograph. Almost all contrast media we currently use are this type.
- Divided by solubility properties (Somkiat, 1995)
- Water-soluble contrast media: almost all types of recent contrast media.
- Fat-soluble contrast media: Lipiodol®
- Contrast media suspended in water: Barium sulphate.
- Divided by absorption into the body
- Absorbable contrast media: almost all types of recent contrast media.
- Non-absorbable contrast media: Barium sulphate.
- Divided by the type of excretion
- Excreted through the kidneys: almost all types of absorbable contrast agents will be excreted through the kidneys more than 90%.
- Excreted through the liver in the form of feces: not commonly used nowadays.
