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 energy
As stated above, properties of ultrasound energy traveling through biological tissues has been extensively studied in recent years. The attenuation due to scattering of energy in different tissues can be measured by a device called a transducer. Recorded information from transducers such as the relationship to the site of origin and intensity of the signal can then be put together to form images of what lies inside the target tissues. Higher frequency ultrasound waves generally produce higher resolution images, but attenuation also increases as frequency increases which restricts imaging depth. Consequently, the best frequency has been determined for each type of diagnostic test and body tissue. Some of the more common ultrasound tests include A-scans, M-scans, B-scans, and Doppler techniques. These test produce images ranging from one-dimensional images to moving, real-time two –dimensional images that can often be seen immediately on a screen. 
The advent of ultrasound technology has completely changed the medical diagnostic field due to its non-invasive characteristic. Medical professionals can now observe tissues within the body without having to physically enter the body. This reduces the amount of invasive and risky diagnostic procedures and increases the chances of a correct diagnosis. Some common medical imaging procedures include: