Comparison of Fenestra LC, ExiTron nano 6000, and ExiTron nano 12000 for micro-CT imaging of liver and spleen in mice.

Rationale and Objectives The purpose of this study was to compare different contrast agents for longitudinal liver and spleen imaging in a mouse model of liver metastasis. Materials and Methods Mice developing liver metastases underwent longitudinal micro-computed tomography imaging after injection of Fenestra LC, ExiTron nano 6000, or ExiTron nano 12000. Elimination times and contrast enhancement of liver and spleen were compared. Results For all contrast agents, liver contrast peaked at approximately 4 hours and spleen contrast at 48 hours postinjection. A single dose of 100 μL of ExiTron nano 6000 or 12000 resulted in longstanding enhancement of liver and spleen tissue for longer than 3 weeks, whereas repeated injections of 400 μL of Fenestra LC were required to retain contrast at acceptable levels and allowed imaging of the liver/spleen for up to 2 and 9 days, respectively. Conclusion Both ExiTron nano agents provide longer and stronger contrast enhancement of liver and spleen compared to Fenestra LC, and they do so at a 75% lower injection volume in mice.