Time course of the liver enhancement by a novel MR contrast agent 'AMI- 25'

Superparamagnetic iron oxide (SPIO; AMI-25 from Eiken Chemical Co.) have been known to offer excellent tumor-liver contrast in liver MR imaging by reducing the signal intensity only of the liver. To investigate the duration of liver signal decrease caused by AMI-25, 15 patients underwent MR imaging three times; before, 1 hour after, and at the different elapsed time after the drug administration (4-9 hours, 22-26 hours, and 47-49 hours). The liver darkness and the contribution of the drug to hepatic tumor detection were subjectively ranked and liver signal-to-noise ratio (SNR) and tumor-liver contrast-to-noise ratio (CNR) were obtained by the region of interest, and compared among groups with different elapsed time. Both liver darkness and SNR were maintained up to 4-9 hours after the drug administration, and both the contribution to the tumor detection and CNR showed the similar results. Our results show that effect of AMI-25 could be maintained at least several hours after the drug administration, lasting longer than previously thought.