A liver sonography is a diagnostic tool to image the liver and adjoining upper abdominal organs such as the gallbladder, spleen, and pancreas. Deeper structures such as liver and pancreas are imaged at a lower frequency 1-6 MHz with lower axial and lateral resolution but greater penetration. The diagnostic capabilities in this area can be limited by gas in the bowel scattering the sound waves.
The application of microbubbles may be useful for detection of liver lesions and for lesion characterization. Some microbubbles have a liver-specific post vascular phase where they appear to be taken up by the reticuloendothelial system (RES). Dynamic contrast enhanced scans in a similar way as with CT or MRI can be used to studying the arterial, venous and tissue phase.
After a bolus injection, early vascular enhancement is seen at around 30sec in arterialized lesions (e.g., hepatocellular carcinomas (HCC), focal nodular hyperplasia (FNH)). Later enhancement is typical of hemangiomas with gradually filling towards the center. In the late phase at around 90sec, HCCs appear as defects against the liver background. Most metastases are relatively hypovascular and so do not show much enhancement and are seen as signal voids in the different phases.
Either with an intermittent imaging technique or by continuous scanning in a nondestructive, low power mode, characteristic time patterns can be used to differentiate lesions.

See also Medical Imaging, B-Mode, High Intensity Focused Ultrasound, Ultrasound Safety and Contrast Medium.

From GE Healthcare;;
Optison is the first 'second generation USCA' marketed in the US.
Ultrasound contrast agents used during an ultrasound imaging procedure, enable more accurate diagnosis of the patient's heart condition. The application of Optison allows to image the endocardial borders of the heart, to see cardiac wall motion abnormalities and to guide the selection and monitoring of treatment.
Optison represents a class of microbubbles with a shell formed by sonicating a solution of capsules filled with a perfluoropropane gas. The high molecular weight slows microbubble dissolution and prolongs the enhancement for several minutes. The human albumin-stabilized cavitation bubbles have a surface tension of 0.9 N/m and a surface dilatational viscosity 0.08 msP.

'August 06, 2001 Molecular Biosystems Inc., a subsidiary of Alliance Pharmaceutical Corp, announced the amendment of the Optison Product Rights Agreement (OPRA) dated May 9, 2000 with Mallinckrodt Inc, a unit of Tyco Healthcare. Optison, an intravenous ultrasound contrast agent, was developed by MBI and is being marketed by Mallinckrodt in the U.S. and Europe. Under the amended agreement, MBI will receive an immediate cash payment plus additional unspecified royalties for a two-year period. The amendment of OPRA coincides with an announcement by Nycomed Amersham Imaging that Nycomed and Mallinckrodt will terminate their joint commercialization and development agreement for ultrasound contrast agents, including Optison, effective Dec. 31, 2001. Effective Jan. 1, 2002, all selling and marketing activities will be resumed solely by Nycomed Amersham.'

(Perfluorocarbon exposed sonicated dextrose albumin) PESDA are sonicated dextrose albumin microbubbles containing decafluorobutane gas. PESDA is a sonicated self made contrast agent and not a commercial product.
PESDA microbubbles can be used as a blood pool contrast agent in echocardiography to improve the detection of myocardial perfusion abnormalities.

The persistence of microbubbles is depended of the shell stability and the density of the gas.
This is defined by the equation:
(R x d)/(DIFS x const_sat)
where R is the bubble radius, d the gas density, DIFS the gas diffusivity and const_sat the saturation constant.
Microbubbles are stabilized with thin coatings of substances such as palmitic acid or by encapsulation in microspheres made with albumin, lipids, or polymers. Low-solubility low-diffusibility gases dramatically improve the persistence. Most recently developed ultrasound contrast agents combine these two approaches to prolong contrast enhancement.
Persistence is also a type of temporal smoothing used in both gray scale and color Doppler imaging. Successive frames are averaged as they are displayed to reduce the variations in the image between frames, hence lowering the temporal resolution of the image.

Sonazoid™ is an ultrasound contrast agent (UCA) consisting of stabilized gas microbubbles in an aqueous suspension. Sonazoid™ has overcome the stability problems of first generation USCA and can produce myocardial perfusion images. Myocardial imaging using ultrasound contrast agents provides diagnosis of chronic heart disease and assessment of the coronary arteries and of the coronary blood flow reserve.
Sonazoid™ is taken up by healthy Kupffer cells in the liver and spleen, but break down in high amplitude ultrasound imaging modes such as color Doppler imaging. The bubble rupture produces a transient pressure wave, which results in a characteristic mosaic color pattern from tissues containing the microbubbles (induced acoustic emission). Liver tumors without Kupffer cells will not display the mosaic pattern and can therefore be identified easily.