The diagnostic imagings of liver metastases

The liver is an organ susceptible metastases. Malignant neoplasms of many organs frequently metastasize to the liver, particularly colon malignancies. Most metastases enter the liver via the blood circulation, but metastases through lymphatic vessels and the peritoneum are also common. The morphologies of liver metastases and findings on diagnostic images vary considerably. Numerous modalities are available for diagnostic imaging of liver metastases: ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), angiography, nuclear medicine, and others. Ultrasonography is the simplest, most non-invasive, and cheapest, but relies on the skill of the operator. CT and MRI are also non-invasive, and the sensitivities of these techniques have recently been improved with the development of multidetector CT, contrast agents for MRI that specifically accumulate in the liver, and other advances. Moreover, positron emission CT using fluorine-18-deoxyglucose (FDG-PET) displays a high sensitivity. Angiography is an invasive modality, but is adopted with CT during arterial portography (CTAP) and CT during hepatic arteriography (CTHA), or for the purpose of interventional radiology. Rational selection of appropriate modalities for a given purpose requires familiarity with the characteristics of each modality. In the present paper, we describe the morphologic characters of liver metastases and investigate the associated characteristics and usefulness of each modality.