In vivo performance of a liposomal vascular contrast agent for CT and MR-based image guidance applications

Purpose. This study evaluated the in vivo performance of a liposome formulation that co-encapsulates iohexol and gadoteridol as a multimodal contrast agent for computed tomography (CT) and magnetic resonance (MR)-based image guidance applications. Materials and Methods. The pharmacokinetics and biodistribution studies were conducted in Balb-C mice using high performance liquid chromatography (HPLC) and inductively coupled plasma atomic emission spectrometry (ICP-AES) to detect iohexol and gadoteridol concentrations. The imaging efficacy of this liposome system was assessed in New Zealand White rabbits using a clinical CT and a clinical 1.5 Tesla MR scanner. Results. The vascular half-lives of the liposome encapsulated iohexol and gadoteridol in mice were found to be 18.4±2.4 and 18.1±5.1 h. When administered at the same dose the distribution (α phase) half-lives for the free contrast agents were 12.3±0.5 min (iohexol) and 7.6±0.9 min (gadoteridol); while, the elimination (β phase) half-lives were 3.0±0.9 h for free iohexol and 3.0±1.3 h for free gadoteridol. The CT and MR signal increases were measured and correlated with the concentrations of iohexol and gadoteridol detected in plasma samples. Conclusion. The long in vivo circulation lifetime and simultaneous CT and MR signal enhancement provided by this liposome system make it a promising agent for image guidance applications.