Medical ultrasound
A contrast medium for medical ultrasonography is a formulation of encapsulated gaseous microbubbles to increase echogenicity of blood, discovered by Dr Raymond Gramiak in 1968 and named contrast-enhanced ultrasound. This contrast medical imaging modality is clinically used throughout the world, in particular for echocardiography in the United States and for ultrasound radiology in Europe and Asia.
Ultrasound
The potential for ultrasonic imaging of objects, with a 3 GHZ sound wave producing resolution comparable to an optical image, was recognized by Sokolov in 1939, but techniques of the time produced relatively low-contrast images with poor sensitivity.
Ultrasonic imaging uses frequencies of 2 megahertz and higher; the shorter wavelength allows resolution of small internal details in structures and tissues. The power density is generally less than 1 watt per square centimetre to avoid heating and cavitation effects in the object under examination. High and ultra high ultrasound waves are used in acoustic microscopy, with frequencies up to 4 gigahertz. Ultrasonic imaging applications include industrial nondestructive testing, quality control and medical uses.