1. precontrast abdominopelvic CT

2. precontrast liver MRI

3. liver MRI using contrast other than extracellular agent or gadoxetic acid

4. the interval between CT and liver MRI was longer than 4 weeks

5. patients who had suspected multiple hepatic metastases (\> 10) on CT

6. distant metastasis other than liver and

7. unavailable reference standard of their hepatic lesions with no pathologic confirmation or follow up imaging.

Liver MRI for Colorectal Cancer Liver Metastasis: Comparative Effectiveness Research for the Choice of Contrast Agents