Iodinated contrast

Dr Henry Knipe and Mr Andrew Murphy et al.

Iodinated contrast is a contrast agent frequently used via intravenous administration in computed tomography, although it is also used in fluoroscopy/angiography. 

Basic overview 

Iodine has a particular advantage as a contrast agent because the k-shell binding energy of 33.2 KeV is similar to that of the average energy of diagnostic radiography 1. Consequently, it will have an increased attenuation compared to the anatomical structures that surround it.

There are two main types of iodinated contrast mediums, the first, comprised of a single benzene ring where three iodine atoms are attached, these are known as monomeric agents, the second possesses two tri-iodinated benzene rings known as a dimeric agent (see Figure 1) 2.

The contrast agents are then classified, via their water solubility as ionic or non-ionic.

Ionic agents, disperse into negative and positive ions, and hence have a higher toxicity; whilst the non-ionic agents do not. Therefore, non-ionic agents, are used conventionally now, often containing additional polar OH groups that make them water soluble 3.

Non-ionic contrast agents are available in varying concentrations ranging from 240 to 400 mg/iodine/mL, and it goes without saying, the higher the concentration, the greater the peak of enhancement (measured in Hounsfield units) however, it will become more viscous.

The pre-warming of contrast agents, particularly ones of higher concentration (370 mg/ml) will lower the chances of contrast extravasation 5.

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Article information

rID: 48582
Sections: Radiography, Physics
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    Figure 1: iodinated contrast
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