Hepatic metastases: use of diffusion-weighted echo-planar imaging

Diffusion-weighted MR imaging is increasingly applied to detect and characterize focal hepatic lesions. In this update article, technical aspects regarding diffusion-weighted echo-planar imaging (DW-EPI) of the liver will be addressed, and concepts for image interpretation will be provided. The value of DW-EPI for the detection of hepatic metastases is illustrated on the basis of a review of the literature and our personal experience. In this respect, special emphasis is given to the comparison of DW-EPI with well-established MR imaging techniques such as T2-weighted and contrast-enhanced MR imaging, and advantages and limitations of DW-EPI will be described. Based on the review, it is concluded that DW-EPI is more sensitive than T2-weighted MR imaging and at least as accurate as superparamagnetic iron oxide-enhanced or gadolinium-enhanced MR imaging for the detection of hepatic metastases. Although difficulties occasionally arise in further characterizing small lesions detected with DW-EPI, substantial improvements in the preoperative evaluation of liver metastases in candidates for hepatic resection may be expected.