Evaluation of Peri-tumoral Vessels Surrounding Colorectal Liver Metastases After Intravenous Injection of Extruded Magnetoliposomes in Rats: Correlation With 3t Mri and Histopathology

Background: Magnetoliposomes have pronounced signal-enhancing effect on T1-weighted (T1w) images of the liver using qualitative analysis which may be benefical for demonstrating peritumoral vasculature. Purpose: To correlate peri-tumoral vasculature (ring-enhancement) surrounding colorectal liver metastases after injection of magnetoliposomes using T1-weighted (T1w) imaging with histopathology in a rat model. Material and Methods: All experiments were approved by the responsible Animal Care Committee. Three rats injected with CC531 coloncarcinoma cells in the portal vein were imaged at 3T using a small diameter four channel coil. The presence of liver metastases, signal intensity changes within intrahepatic vessels, peri-tumoral vasculature (ring-enhancement) surrounding liver metastases on T1w imaging and histopathology, and the histopathological distribution of iron particles were evaluated. SS SE-EPI and T1w GE sequences were used. Images were evaluated qualitatively and MRI findings were correlated with histopathology. Results: Fifteen liver metastases were present which were all detected at MRI (mean diameter 2.4 mm (SD 0.8 mm, range 1.5 -4.7 mm)). Ring-enhancement surrounding liver metastases at contrast-enhanced T1w GE sequences was present in all liver metastases. Correlation with histopathology showed the corresponding presence of dilated sinusoids filled with iron particles surrounding the liver metastases. Conclusion: Blood-pooling of iron oxide particles within magnetoliposomes was demonstrated with increased and hyperintensity of vessels after injection of magnetoliposomes. Qualitatively, ring-enhancement surrounding the liver metastases was seen on T1w imaging and corresponded histopathologically with the presence of iron particles (magnetoliposomes) within the dilated sinusoids surrounding the liver metastases.