Ultrasonography, Computed Tomography and Magnetic Resonance Imaging of Hepatocellular Carcinoma: Toward Improved Treatment Decisions

Detection, characterization, staging, and treatment monitoring are major roles in imaging diagnosis in liver cancers. Contrast-enhanced ultrasonography (CEUS) using microbubble contrast agents has expanded the role of US in the detection and diagnosis of liver nodules in patients at high risk of hepatocellular carcinoma (HCC). CEUS provides an accurate differentiation between benign and malignant liver nodules, which is critical for adequate management of HCC and is also useful for guidance of percutaneous local therapy of HCC and postprocedure monitoring of the therapeutic response. The technology of multidetector-row computed tomography (MDCT) has increased spatial and temporal resolutions of computed tomography (CT). It has made possible a more precise evaluation of the hemodynamics of liver tumor, and the diagnostic accuracy of dynamic MDCT has improved. Perfusion CT can measure tissue perfusion parameters quantitatively and can assess segmental hepatic function. Dynamic MDCT with high spatial and temporal resolution enables us to reconstruct 3- and 4-dimensional imaging, which is very useful for pretreatment evaluation. Dual-energy CT makes possible the differentiation of materials and tissues in images obtained based on the differences in iodine and water densities. Monochromatic images, which can be reconstructed by dual-energy CT data, provide some improvement in contrast and show a higher contrast-to-noise ratio for hypervascular HCCs. Dynamic magnetic resonance imaging with fast imaging sequence of 3-dimensional Fourier transformation T1-weighted gradient echo and nonspecific contrast medium can show high detection sensitivity of hypervascular HCC. However, the hepatic tissue-specific contrast medium, gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid, has become an essential contrast medium for liver imaging because of its higher diagnostic ability. It may replace CT during hepatic arteriography and during arterioportography.