Contrast enhancement issues in the MR evaluation of the central nervous system
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Because of its high intrinsic contrast resolution, magnetic resonance imaging (MRI) has largely replaced computed tomography (CT) in the diagnosis of central nervous system (CNS) diseases, and the use of contrast media in MRI of the CNS has increased progressively, gadolinium chelates being, by far, the most used ones. Our paper will focus on the current indications for contrast-enhanced MR imaging of the CNS and will outline the current role and the future trends in contrast medium (CM) administration in the diagnosis of CNS disease. Gadolinium chelates are now routinely employed in MRI of the brain and spine and have been shown to be relatively safe and well tolerated at standard doses of 0.1 mmol/kg b. w. Although there is general consensus on the usefulness of CM administration in MRI of the CNS, some controversy still persists on the type of CM to be used, on the administration scheme, and on the imaging protocol. The current trend is toward selective employment of CM, the effect of which can be enhanced by Magnetization Transfer (MT) techniques, to increase the sensitivity of the procedure. Double or triple doses of CM can be useful in the detection of small parenchymal lesions with faint enhancement, in functional/dynamic studies of the brain parenchyma and in MR angiography. Gadoteridol (ProHance®) closely resembles the features of an optimal CM, because it is non-ionic, has a low osmolality and a low viscosity, and may be particularly efficacious when high doses are required.