**Abstract**

Clinically available gadolinium chelate-based contrast agents (GBCAs) are divided into two groups by chelate types: linear GBCAs and macrocyclic GBCAs. The characteristic features of GBCAs are introduced in this chapter. Currently, there are two clinical issues related to the administration of GBCAs: nephrogenic systemic fibrosis (NSF) and brain deposition of gadolinium. NSF occurs in patients with chronic renal failure who had magnetic resonance imaging (MRI) examinations with GBCA injections. Frequent administrations would induce NSF, and GBCA stability would be discussed in this chapter. Linear GBCAs are more likely to be deposited in brain tissues than macrocyclic GBCAs. We present the trend of GBCA deposition or retention with our published research studies with our previous researches. We have investigated the effect of GBCAs deposited in the brain for infants.

**Keywords:** gadolinium-based contrast agent, nephrogenic systemic fibrosis, linear chelates, macrocyclic chelates, gadolinium brain deposition
