Heart ultrasound. Patient having an echocardiogram taken of his heart. Ultrasound-based diagnostic imaging techniques are used to visualize muscles and internal organs. 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 at top rightt) of the heart structures and assess the velocity and direction of blood flow.