MRI contrast media

Frequent indications for MRI tests with contrast:

• Detect lesions (tumor/metastasis, abscess)
• Characterization of lesions (e.g. hepatic lesions)
• Imaging of vessels/vascular pathology (= MR angiography)

A contrast series is generally combined with a T1 weighted image. As pathology is often associated with fluid, the combination of contrast and a T2 weighted image has little value (Note: both fluid and contrast have high signal intensity).

There are multiple types of contrast agents available. A commonly used contrast agent is gadolinium (Gd). Gadolinium has paramagnetic properties and reduces the T1 relaxation time of the protons that absorb the contrast. Consequently, these protons will have higher signal intensity (= whiter). In addition to gadolinium, other types of contrast media are used (e.g. the liver-specific contrast agent Primovist). They are only used when indicated.

In order to correctly evaluate enhancement, a series should be made before and after contrast. A fat suppression technique may be used to avoid confusing the fat with enhancement (Note: fat has a high signal intensity on T1 weighted images). Below is an example of a brain tumor (fig. 20) and an example of a classic enhancement pattern of an hepatic hemangioma (fig. 21). Additional details about enhancement patterns will not be addressed in this module.