Echogenicity is the ability of a medium to create an echo, for example to return a signal when tissue is in the path of the sound beam. The ultrasound echogenicity is dependent on characteristics of tissues or contrast agents and is measured by calculating the backscattering and transmission coefficients as a function of frequency.
The fundamental parameters that determine echogenicity are density and compressibility. Blood is two to three orders of magnitude less echogenic than tissue due to the relatively small impedance differences between red blood cells and plasma. The tissue echogenicity can be increased by ultrasound contrast agents. Encapsulated microbubbles are highly echogenic due to differences in their compressibility and density, compared to tissue or plasma.
Microbubbles are 10,000 times more compressible than red blood cells. The compressibility of air is 7.65 x 10−6 m2/N, in comparison with 4.5 x 10-11 m2/N for water (on the same order of magnitude as tissue and plasma). This impedance mismatch results in a very high echogenicity. An echo from an individual contrast agent can be detected by a clinical ultrasound system sensitive to a volume on the order of 0.004 pl.

See also Isoechogenic, Retrolenticular Afterglow, and Sonographic Features.

An ultrasound element is a single slab of piezoelectric crystal that is cut into a linear collection of separate pieces. The separate pieces are called elements. Each element is wired separately to the transducer and they are fired in groups that are coordinated by a microprocessor. The elements are electrically configured to control the direction and characteristics of the sound beam.

See also Subdicing.

Equipment Preparation is an essential step in ensuring optimal ultrasound imaging quality and maintaining a safe and hygienic scanning environment. The following considerations should be taken into account:

By following these equipment preparation guidelines, healthcare professionals can ensure accurate and safe ultrasound examinations while promoting infection control measures and maintaining a hygienic environment for both patients and staff.
See also Environmental Protection, Portable Ultrasound Machine, Ultrasound Accessories and Supplies, and Ultrasound System Performance.

Different sound velocities in tissues are causing false distance artifacts. Ultrasound beams can suffer multiple reflections or specular reflections away from the sensor, giving false distance readings.

The far field (also called Fraunhofer zone) is the distal part of an ultrasound beam characterized by a diverging shape and continuous loss of ultrasound intensity with distance from the transducer. The angle of divergence increases with lower transducer frequency and with smaller transducer diameter.

See also Sonographic Features.