Liver cancer. Power Doppler ultrasound scan of increased blood flow (orange) to a cancer in a 29- year-old woman's liver. Part of the liver is seen as the large grey area at left and top. The cancer is about 2 centimetres across (centre), shown by the arrows and its blood supply. The black area is the gall bladder. This liver cancer (hepatoma) resulted from cirrhosis, a condition caused by damage such as that from alcoholism and hepatitis. Doppler ultrasound scanning detects moving fluids, such as blood, by the frequency change they cause when reflecting high-frequency sound waves. Power Doppler scans use colour to show the moving fluid, but do not show the direction of the flow.