Magnetic resonance contrast agents in neuroimaging. New agents and applications

Of the four gadolinium chelates in clinical use worldwide, only three are available in the United States: gadoteridol, gadodiamide, and gadopentetate dimeglumine. Although gadopentetate dimeglumine is still administered in many clinical practices, a consequence of being the first agent developed (1988) and until recently the only agent available, gadoteridol demonstrates a higher index of safety--at least on theoretical grounds. With linear chelates such as gadopentetate dimeglumine and gadodiamide, greater release of free gadolinium ion occurs in vivo owing to lower thermodynamic and kinetic stability. The concern with respect to demetallation and resultant increased chronic deposition of gadolinium ion in marrow and liver is greater with gadodiamide. Drug safety appears not to be an issue at high dose for gadoteridol, the only agent approved in this regards. The safety of the other chelates at high dose has yet to be established. The nonionic character of the two newer agents (gadoteridol and gadodiamide) is not of great importance in current clinical practice, in which most examinations are still performed with a dose of 0.1 mmol/kg given as a slow infusion. The non-ionic nature of the newer MR contrast agents may become clinically important in the future, with more common application of bolus injection and high dose. High contrast dose (0.3 mmol/kg) is advocated in routine MR clinical practice for the evaluation of intracranial metastatic disease. Only with prior evidence for multiple metastases and in patients for whom the detection of additional lesions would not influence therapy can the use of standard dose (0.1 mmol/kg) be justified.(ABSTRACT TRUNCATED AT 250 WORDS)