(CCI) A major limitation of the use of ultrasound contrast agents is the problem that signals from the microbubbles are mixed with those from tissue, so that the distribution of the microbubbles is not optimally displayed either in Doppler or gray scale.
Coherent contrast imaging is a high frame rate implementation of inverting the phase of alternate sound pulses and summing the resulting echoes. The symmetrical signals from linear reflectors are cancelled leaving those from non-linear scatterers, with the advantage that the cancellation is performed without the need to transmit two pulses per image line so that bubble destruction is minimized. Coherent contrast imaging yields best results in the vascular phase of phospholipid microbubbles (such as Definity and SonoVue).

See also Coherence.

Coherence is the degree of phase agreement among waves. A coherent sound wave is one in which all of the signals are in phase.

Many different contrast imaging techniques have been developed. Most are either variations, hybrids, or combinations of the following ultrasound techniques:

See also Coherent Contrast Imaging, Ultrasound Picture and Targeted Contrast Imaging.

From Lantheus Medical Imaging.
Activated DEFINITY® Injectable Suspension is indicated for use in patients with suboptimal echocardiograms to opacify the left ventricular chamber and to improve the delineation of the left ventricular endocardial border. The perflutren lipid microspheres exhibit lower acoustic impedance than blood and enhance the intrinsic backscatter of blood.
Echocardiography with Definity produced more detailed images of the heart in difficult-to-image patients versus echocardiography alone, and images obtained with the contrast agent provided a more accurate assessment of segmental wall motion compared with unenhanced images.

See also Coherent Contrast Imaging.

In August 2001 DuPont Pharmaceuticals Company received FDA approval.

From Bracco Diagnostics, Inc.
SonoVue® was first launched in October 2001 and is now available in all European countries.
SonoVue is a second generation USCA, designed and optimized with regard to the resistance to pressure. SonoVue is an example of an important family of microbubbles whose membrane consists of phospholipids. SonoVue microbubbles are filled with sulfur hexafluoride (SF6), a gas which has a low solubility and diffuses slowly in blood for the gaseous phase of the microbubbles.
In particular, the SonoVue microbubbles, thanks to the high flexibility of their shell, are strongly echogenic in a wide range of frequencies and acoustic pressure and therefore can be used with both destructive and conservative contrast bubble specific imaging methods.

See also Coherent Contrast Imaging.