Contrast enhancement

TheContrast enhancement is a ubiquitous term 'contrast enhancement' mayin radiology and can be used in two ways.

Firstly, it may refer to methods of exaggerating the visible difference between adjacent structures on scans by giving exogenous substances called 'administering contrast agents'.This includes differentiating between normal structures.

Common methods of contrast enhancement include administering

• intravenous diluted gadolinium salts in MRI
• intravenous diluted iodinated salts in CT
• intra-arterial diluted iodinated salts in catheter angiography
• Barium in gastrointestinal fluoroscopy
• a combination of barium and air in gastrointestinal studies
• carbon dioxide in lower gastrointestinal studies or arteriography
• superparamagnetic iron oxide in liver MRI.

For further information There are many different types, seewhich vary by modality (see the article on contrast agents for further information).

ContrastSecondly, contrast enhancement can also refersrefer to a characteristiccharacteristics of abnormal lesions in the body.

The The diffusion of the contrast agents from the blood stream to bodily tissues is physiologically limited.  In In pathologies such as cancer, blood vessels grow which are abnormal and leak the(i.e. neoangiogenesis) with increased leaking of contrast agent from the blood vessels, resultingresults in the lesion being much more visible on contrast-enhanced scans. 

In the case of the CNS, the blood-brain-barrier barrier (BBB) normally limits diffusion of contrast agents.  The blood-brain-barrier The BBB is often disrupted in pathologies of the CNS, leading to their enhancement after the administration of contrast agents on CT and MRI scans.