Phase in ultrasound describes where the sound wave is in its cycle of amplitude change. Different waves oscillate at different frequencies, so time is often not a suitable measure of phase.
The phase shift is a difference in the phase or the temporal offset of the peaks of a waveform along one scan line.

See also Coherence, and Histogram.

EchoGen® is a fluorocarbon-based (dodecafluoropentane) third generation USCA. EchoGen® consists of microbubbles stabilized with surfactants in a phase shift colloid emulsion (perflenapent). EchoGen® requires no preparation, reconstitution, or refrigeration.
Perflenapent emulsion would represent a significant advance in contrast echocardiography caused by effective and long lasting opacification of the left ventricle and enhanced endocardial border delineation.
The persistence of the contrast effect permits interrogation in multiple echocardiographic views, as well as the visualization and localization of myocardial perfusion deficits at rest by producing a negative contrast effect.
October 12, 2000
Sonus Pharmaceuticals, Inc. announced a strategic decision to refocus the Company on the development of its drug delivery and blood substitute products. At the same time, Sonus has withdrawn the NDA (New Drug Application) and discontinued clinical activity for its ultrasound contrast product, EchoGen®.
August 06, 2001
Sonus Pharmaceuticals, Inc. announced that it has entered into an agreement to sell its ultrasound contrast assets for $6.5 million to Amersham plc. As part of the agreement, Sonus has also assigned to Nycomed its interest in the ultrasound contrast patent license agreement entered into with Chugai Pharmaceutical Co. Ltd. and Molecular Biosystems Inc in January 2001.

Quadrature detection is used in Doppler ultrasound as well as in magnetic resonance imaging and is also called quadrature demodulation or phase quadrature technique. Quadrature detection is the acquisition of Mx and My simultaneously as a function of time by using two separate detector channels. This signal processing method is used for directional Doppler in which the signal reference frequency for the two channels has a phase shift of 1/4 period. The output Doppler signal phase for both channels also depends on the Doppler shift whether positive or negative.
The fast Fourier transform analyzer performs spectral Doppler analysis in ultrasound machines and displays different quadrature Doppler frequencies, when a sample volume cursor is used along time.

Transducers used for the real-time mode are different than for the A-mode, B-, or M-modes. A linear array transducer with multiple piezoelectric crystal elements that are different arranged and fired, transmits the needed larger sound beam.
A subgroup of x adjacent elements (8-16; or more in wide-aperture designs) is pulsed simultaneously; the inner elements pulse delayed with respect to the outer elements. The interference of the x small divergent wavelets generates a focused beam. The delay time determining the focus depth of a real-time transducer can be changed during imaging.
Similar delay factors applied during the receiving phase, result in a dynamic focusing effect on the return. This forms a single scan line in the real-time image. To produce the following scan line, another group of x elements is selected by shifting one element position along the transducer array from the previous group. This pattern is then repeated for the groups along the array, in a sequential and repetitive way.