Cardiac ultrasound scanner. Two-dimensional echocardiography being carried out in a hospital's intensive care unit (ICU). Echocardiography is used in diagnosing heart disorders and for monitoring heart function. A transducer, held against the chest, emits ultrasonic waves and detects the reflected echoes. The change in frequency is used to build images (on screen) of the heart structures and assess the velocity and direction of blood flow.