**5. Acoustic Radiation Force Impulse (ARFI) and Magnetic Resonance Elastography (MRE)**

The technology applied most recent is acoustic radiation force impulse (ARFI) imaging. AR‐ FI imaging permits evaluation of the elastic properties of a region of interest during realtime B-mode conventional hepatic US examination. Results are expressed in meters per second and the region of interest can be chosen using ultrasound guidance, there by avoid‐ ing large blood vessels and the ribs. Previous reports have indicated that the diagnostic power of ARFI imaging for the staging of liver fibrosis is the same as that of Fibroscan [28. 29].

New technological advances have been made in the clinical application of MRI such as dif‐ fusion-weighted MRI and MRI elastography. The former measures the apparent diffusion coefficient of water and the parameter is dependent on the tissue structure [30]. The latter measures the propagation characteristic of the shear waves from an acoustic driver within the liver. Although MRI elastography has been shown to be superior to APRI and Fibroscan for determining the stage of fibrosis in patients with various under lying liver diseases [31], it cannot be performed on aniron-overloaded liver because of noise. In addition, MRI takes longer and costs more than the ultrasound-base delastographic examinations.
