Imaging methods based on elastography have come to be widely used in recent years for non-invasive evaluation of tissue mechanical characteristics. These methods use those soft tissues' elasticity changes in response to disease to provide both qualitative & quantitative diagnostic data. Tissue stiffness in reaction to a mechanical force [compression or a shear wave] is measured using specialized imaging modes. Methods based on ultrasound are intriguing because of their many built-in benefits, such as low cost & widespread availability [even at the bedside]