The pioneer technique has been transient elastography, which is performed with the FibroScan device (Echosens, Paris, France). A single-element ultrasound transducer operating at 5 MHz is built on the axis of a pistonlike vibrator.13 By pushing a button, low-frequency (50 Hz) transient vibrations are transmitted, and the elastic shear waves that are generated propagate through underlying tissues. Pulse-echo ultrasound acquisitions are used to follow the propagation of the shear wave and to measure its velocity.13 Transient elastography measures liver stiffness in a volume that approximates a cylinder 1 cm wide and 4 cm long between 25 and 65 mm below the skin surface. This volume is at least 100 times bigger than a biopsy sample and is therefore far more representative of the liver parenchyma.14 Transient elastography is performed on a patient lying supine with the right arm elevated to facilitate access to the right liver. The tip of the probe contacts the intercostal skin with coupling gel. The operator, assisted by a time-motion image, locates a liver portion at least 6 cm deep and free of large vascular structures (Figure 1). The device gives an estimate of the velocity of shear waves, which can be also expressed in kilopascals through the Young modulus: E = 3 (vs · ρ), where E is the Young modulus, vs is the shear wave velocity, and ρ is the density of tissue, assumed to be the same as water.