Liposome Encapsulated MnCl2 as a Liver Specific Contrast Agent for Magnetic Resonance Imaging

Abstract

We examined the usefulness of MnCl₂ entrapped in liposomes as a liver specific contrast agent for magnetic resonance imaging. Toxicity experiments showed that the effective dose for imaging experiments was 7 to 11 times lower than the LD₅₀ of free MnCl₂. In rats with implanted liver tumors, liposome encapsulated MnCl₂ caused a two- to three-fold increase in the relaxation rate of the liver while having little effect on the relaxation rate of tumor tissue. T₁ weighted, magnetic resonance images obtained at 0.5 T of an R3230 adenocarcinoma implanted in the liver showed an increase in the signal intensity of both normal liver and tumor tissue after the injection of free MnCl₂ (25 μmole/kg). However, after the injection of liposome encapsulated MnCl₂ (40 μmole/kg) the liver exhibited a marked increase in signal intensity with little change in the signal intensity of the tumor tissue. These results suggest that liposome encapsulated MnCl₂ has excellent potential as a liver specific contrast agent for the improved detection of liver metastases.