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Types of MRI Contrast

Magnetic Resonance Imaging, commonly referred as MRI, is an imaging test used as a diagnostic tool for identifying different types of diseases. MRI with contrast provides more accurate diagnosis and enhances the specific structures being diagnosed for abnormalities with the aid of contrast dyes. Contrast dyes are solutions that help accentuate and enhance the image, giving more detailed information for evaluation of the MRI result and are of different types.

  1. Intravascular Contrast Agents

    • Intravascular contrast dyes are considered blood pool agents as they remain longer in the blood compared to the conventional contrast dyes. They are most effective in assessing dead tissues from the heart, myocardial viability, and tumors. A common intravascular contrast agent is gadolinium. This contrast agent is used to enhance visibility of veins when conducting Magnetic Resonance Angiography and brain tumor enhancements. It will remain in the circulation for distribution to the interstitial space and are excreted through the kidneys.

      Gadolinium is used as a chelated compound which is safe when administered. The Food and Drug Administration, however, issued a warning that gadolinium may pose risk among individuals with severe kidney insufficiency and chronic liver disease to develop nephrogenic systemic fibrosis. Other intravascular MRI contrast agents are ultrasmall superpermagnetic iron oxide, gadolinium labeled albumin, chromium labeled red blood cells and gadolinium-DTPA labeled dextran.

    Oral Contrast Agents

    • The main use of oral contrast agents is to enhance the gastrointestinal tract imaging. Clinical studies from the Department of Radiology of University of Regensburg in Germany indicated that abdominal MRI with oral contrast showed more accurate pathological findings and provides a reliable diagnostic tool for evaluation of bowel problems. Perflubron is a gastrointestinal MRI oral contrast agent used for pediatric to promote darker image of the body cavity to enhance visual image.

    Paramagnetic Contrast Agent

    • The paramagnetic type of contrast agent is formed in its chelated compound to render it most suitable for intravenous injection. Intravascular contrast agents fall in this category and are useful in detecting tumors, imaging of the heart, fibrosis, intervertebral collapse, and plaques. Common side effects are the feeling of warmth, nausea, vomiting, seizure and headache.

    Superparamagnetic Contrast Agents

    • The superparamagnetic contrast agents are less soluble hence they are suitable only for magnetic resonance imaging taken from the gastrointestinal tract. Common contrast agents of this type are ferrite and barium sulphate. Oral agents fall under this category of contrast agents used for MRI diagnosis.

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