special subjects
Ultrasonography
Variations of Ultrasonography
Ultrasound information can be displayed in several ways: A-mode: As spikes on a graph (used to scan the eye) B-mode: As a 2-dimensional anatomic images (used during pregnancy to evaluate the developing fetus or to evaluate internal organs) M-mode: As waves displayed continuously to show moving structures (used to evaluate the fetus's heartbeat or to evaluate heart valve disorders) B-mode ultrasonography is most commonly done. Doppler ultrasonography uses changes that occur in the frequency of sound waves when they are reflected from a moving object (called the Doppler effect). In medical imaging, the moving objects are red blood cells in the blood. Thus, Doppler ultrasonography can be used to evaluate Whether blood is flowing through blood vessels How fast it flows Which direction it flows in Doppler ultrasonography is used To evaluate how well the heart is functioning (as part of echocardiography) To detect blocked blood vessels, especially in leg veins, as in deep vein thrombosis, when veins are blocked by a blood clot To detect narrowed arteries, especially the carotid arteries in the neck, which carry blood to the brain Spectral Doppler ultrasonography shows blood flow information as a graph. It can be used to assess how much of a blood vessel is blocked. Duplex Doppler ultrasonography combines spectral and B-mode ultrasonography. For color Doppler ultrasonography, color is superimposed on the shades-of-gray image of blood flow produced by Doppler ultrasonography. The color indicates direction of blood flow. Red may be used to indicate flow toward the transducer, and blue may be used to indicate flow away from the transducer. The brightness of the color indicates how fast the blood is flowing. Color Doppler ultrasonography can help assess the risk of stroke because it helps doctors identify and evaluate narrowing or blockage of arteries in the neck and head. The procedure is useful for evaluating people who have had a Transient Ischemic Attacks (TIAs) or 