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Iodinated contrast agents are water-soluble radiopaque compounds primarily used in X-ray and CT imaging to enhance the visibility of vascular structures, organs, and pathologies by absorbing X-rays more than surrounding tissues.
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They are among the most widely used contrast media in diagnostic radiology.
The structure of iodinated contrast media. High-osmolality contrast media (HOCM) have an iodine to molecule ratio of 1.5 : 1. Low-osmolality, nonionic contrast media (LOCM) have an iodine to molecule ratio of 3 : 1. Isosmolar (isoosmolality) contrast media (IOCM) have an iodine to molecule ratio of 6 : 1.
Solomon, Richard. BioMed Research International, vol. 2014, 2014, pp. 1–8, doi:10.1155/2014/934947.
Based on Ionization:
| Type | Charge | Examples |
|---|---|---|
| Ionic | Yes | Diatrizoate (e.g., Hypaque) |
| Non-ionic | No | Iohexol, Iopamidol, Ioversol |
Based on Osmolality
| Type | Osmolality (mOsm/kg) | Examples |
|---|---|---|
| High-osmolar (HOCM) | >1400 | Diatrizoate |
| Low-osmolar (LOCM) | 600–850 | Iohexol, Iopamidol |
| Iso-osmolar (IOCM) | ~290 | Iodixanol (Visipaque) |
Classification of iodinated contrast media according to chemical structure and osmolality.
Bianchi L, Hansel K, Biondi F, et al. Delayed hypersensitivity reactions to iodinated contrast media: A diagnostic approach by skin tests. Contact Dermatitis. 2023;89(5):352-358. doi:https://doi.org/10.1111/cod.14372
| Route | Application |
|---|---|
| Intravenous (IV) | CT angiography, CT urogram, contrast-enhanced CT of chest/abdomen/pelvis |
| Oral | GI tract (e.g., CT enterography, perforation suspicion) |
| Rectal | Distal colon and rectum, CT colonography |
| Intra-arterial | Angiography, interventional radiology |
| Intrathecal | Myelography (non-ionic LOCM only) |
Iodine atoms in the contrast medium absorb X-rays due to their high atomic number (Z = 53), creating a radiopaque (white) appearance of vascular and soft tissue structures.