From ALOKA Co., Ltd.;
'A Platform for Pure Harmonic Detection
Harmonic Echo™ technology constructs images using second harmonic components, which contain far less artifacts and noise than fundamental-frequency components.
Pure Harmonic Detection is a technology to transmit distortion-free, fundamental-frequency ultrasound beams. And when the fundamental-frequency ultrasound beam is a pure sinusoidal wave, both the fundamental-frequency image and the Harmonic Echo™ image are much clearer with less noise. This technology is especially effective for obese patients and in a variety technically difficult scanning conditions.'

Through diffraction and refraction on intersections edge acoustic shadowing can be created. The acoustic shadowing artifact is the loss of information below a dense object because the majority of the sound energy was reflected back by the object.
Shadowing artifacts occur if decreasing of the echo amplitude is not exponential with penetration depth caused by inhomogeneous tissue layers and fluid or air-filled regions. Bone, air, foreign bodies and calcification stop the transmission of sound waves producing a 'sonic shadow' which is a dark region distal to the echogenic obstructing region. This artifact occurs also in objects like e.g. prosthetic valves.

See also Boundary Layer, and Half-Value Layer.

Albunex and Infoson, used mainly in cardiac evaluations, are first generation one-pass-only contrast agents and have been replaced by the new-generation contrast media. Albunex and Infoson are the same sonicated human serum albumin microbubbles. Infoson is licensed and manufactured in Europe, while Albunex was produced in the USA.
Albunex, an air-filled microbubble with a denatured albumin shell (modified from air-filled albumin microspheres prepared from sonicated 5% human serum albumin), was the first FDA-approved contrast agent, but is no longer in production.
Cardiac shunts and valve regurgitations are often evaluated with Color Doppler Imaging (CDI), which also improved with injections of Albunex, but this agent is pressure-sensitive and does not recirculate. It is effectively a one-pass-only agent, limiting its clinical efficacy.

See also First generation USCA, Echocardiography and Contrast Enhanced Ultrasound.

Anisotropic is an area or structure with varying acoustic properties according to the direction in which they are imaged. For example, the characteristic ultrasound appearances of tendons are hyperechoic, but they appear hypoechoic when the sound beam is not at right angles to the tendon fibers.

The dimension of the ultrasound beam and the transducer array are the origin of the beam width artifact or volume averaging artifact. When the ultrasound beam is wider than the diameter of the lesion being scanned, normal tissues which lie immediately adjacent to the lesion arc included within the beam width, and their echotexture is averaged in with that of the lesion.
Thus, what appears to be the echogenicity of the lesion is really that of the lesion plus the averaged normal tissues. Because of volume averaging, cystic lesions may falsely appear to be solid, and some subtle solid lesions may become impossible to distinguish from surrounding normal tissue and, therefore, not identified at all.

See also Ultrasound Picture and Vector Array Transducer.