Medical Ultrasound Imaging
Friday, 3 May 2024
 Info Sheets  Out- side     | 'Blood Pool Agents' Searchterm 'Blood Pool Agents' found in 6 articles 2 definitions [ • ] - 4 booleans [• ]Result Pages : •
Targeted ultrasound contrast agents provide advantages compared with usual microbubble blood pool agents. The goal of targeted ultrasound contrast agents is to significantly and selectively enhance the detection of a targeted vascular site. Tissue-specific ultrasound contrast agents improve the image contrast resolution through differential uptake. Targeted drug delivery via contrast microbubbles is another contrast media concept and provides the potential for earlier detection and characterization of disease. Targeted contrast imaging provides a higher sensitivity and specificity than obtained with a nontargeted contrast agent. The detection of disease-indicative molecular signatures may allow early assessment of pathology on a molecular level. Molecular imaging should be an efficient and less invasive technique to obtain three-dimensional localization of pathology. Ultrasound agents typically remain within the vascular space, and therefore possible targets include molecular markers on thrombus, endothelial cells, and leukocytes. Targeted contrast agents permit noninvasive detection of thrombus, cancer, inflammation, or other sites where specific integrins or other adhesion molecules are expressed. Adhesion molecules such as monoclonal antibodies, peptides, asialoglycoproteins, or polysaccharides are incorporated into the shell of the microbubble or liposome. After injection into the bloodstream, the targeted agent accumulates via adhesion receptors at the affected site, enhancing detection with an ultrasound system. See also Acoustically Active Lipospheres, and Tissue-Specific Ultrasound Contrast Agent. • View NEWS results for 'Targeted Contrast Imaging' (1).   Further Reading: News & More:
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(UCA / USCA) Ultrasonography is the most commonly performed diagnostic imaging procedure. The introduction of sonographic contrast media into routine practice modifies the use of ultrasound in a variety of clinical applications. USCAs consist of microbubbles filled with air or gases and can be classified according to their pharmacokinetics. Among the blood pool agents, transpulmonary ultrasound contrast agents offer higher diagnostic potential compared to agents that cannot pass the pulmonary capillary bed after a peripheral intravenous injection. In addition to their vascular phase, some USCAs can exhibit a tissue- or organ-specific phase. The sonogram image quality is improved either by decreasing the reflectivity of the undesired interfaces or by increasing the backscattered echoes from the desired regions. Different types of ultrasound contrast agents: Ultrasound contrast agents act as echo-enhancers, because of the high different acoustic impedance at the interface between gas and blood. The enhanced echo intensity is proportional to the change in acoustical impedance as the sound beam crosses from the blood to the gas in the bubbles. The ideal qualities of an ultrasound contrast agent:
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high echogenicity;
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low attenuation;
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low blood solubility;
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low diffusivity;
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ability to pass through the pulmonary capillary bed;
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lack of biological effects with repeat doses.
A typical ultrasound contrast agent consists of a thin flexible or rigid shell composed of albumin, lipid, or polymer confining a gas such as nitrogen, or a perfluorocarbon. The choice of the microbubble shell and gas has an important influence on the properties of the agent. Current generations of microbubbles have a diameter from 1 μm to 5 μm. The success of these agents is mostly dependent on the small size and on the stability of their shell, which allows passage of the microbubbles through the pulmonary circulation. Microbubbles must be made smaller than the diameter of capillaries or they would embolize and be ineffective and perhaps even dangerous. The reflectivity of these microbubbles is proportional to the fourth power of a particle diameter but also directly proportional to the concentration of the contrast agent particles themselves. Ultrasound contrast agents produce unique acoustic signatures that allow to separate their signal from tissue echoes and to depict whether they are moving or stationary. This enables the detection of capillary flow and of targeted microbubbles that are retained in tissues such as normal liver. The new generation of contrast media is characterized by prolonged persistence in the vascular bed which provides consistent enhancement of the arterial Doppler signal. Contrast agents make it also possible to perform dynamic and perfusion studies. Targeted contrast imaging agents are for example taken up by the phagocytic cell systems and thus have liver/spleen specific effects. See also Ultrasound Contrast Agent Safety, Adverse Reaction, Tissue-Specific Ultrasound Contrast Agent, and Bubble Specific Imaging. Further Reading: Basics:
News & More:
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From Bayer Schering Pharma AG:
Available in Europe since 1996 and in Japan since 1999. Currently, the marketing situation is unclear. Levovist® is a first generation USCA consisting of galactose (milk sugar) ground into tiny crystals whose irregular surfaces act as nidation sites on which air pockets form when it is suspended in water, much as soda water bubbles form at small irregularities on the surface of the glass. A trace of palmitic acid is added as a surfactant to stabilize the resultant microbubbles. When Levovist® dissolves in blood, air trapped inside the galactose is released as free gas bubbles. These bubbles have a weak encapsulating shell and are easily destroyed by ultrasound. Different contrast ultrasonography methods have been developed since the introduction of Levovist®. Initially, Levovist® was an echo contrast medium for improving sensitivity in color Doppler and Power Doppler examinations, but was found to suffer from significant blooming, making it difficult to observe small blood vessels. However, Levovist® improves the accuracy of echocardiographic examinations in such indications as assessment of left ventricular function. In addition to their vascular phase, some ultrasound contrast agents (USCAs) can exhibit a tissue- or organ-specific phase. Levovist® can accumulate within the liver and the spleen for up to 20 min once it has disappeared from the blood pool and improves the detectability of focal liver lesions and allows more reliable control of interventional tumor treatments. Varied types of information can be obtained by applying contrast imaging at different times after the injection using Levovist® in both the arterial phase and the late organ-specific phase. 1 g Levovist® granules contain 999 mg D-galactose and 1 mg palmitic acid. Brand names in other countries: Levovist/Levograf
Drug Information and Specification
RESEARCH NAME
SHU 508A
DEVELOPER
INDICATION
APPLICATION
Intravenous injection
TYPE
Microbubble
Galactose/Palmitic acid
CHARGE
Negative
Air
MICROBUBBLE SIZE
95% < 10μm
PRESENTATION
Vials of 2.5 g and 4.0 g incl. one plastic ampoule containing 20 ml water for injection, one mini-spike and one disposable syringe of 20 ml
STORAGE
Room temp 15−30°C
PREPARATION
Reconstitute with 5 to 17 ml water
DO NOT RELY ON THE INFORMATION PROVIDED HERE, THEY ARE
NOT A SUBSTITUTE FOR THE ACCOMPANYING PACKAGE INSERT! •
From Bayer Schering Pharma AG:
Sonovist® (sometimes found as Sonavist) is an investigational ultrasound contrast agent with a biodegradable synthetic capsule filled with sulphur hexafluoride. The biodegradable shell of Sonovist is so stable that it can be taken up by Kupffer cells of the reticuloendothelial system or accumulate in the sinusoids. Therefore, Sonovist® has an additional hepato-splenic parenchymal phase following the blood pool phase, analog to the superparamagnetic iron oxide agents used in liver MRI. The microbubbles are stationary in this phase and generate no conventional Doppler signals. This tissue-specific phase has a variable duration and can be imaged by bubble specific imaging modes.
Drug Information and Specification
RESEARCH NAME
SHU 563A
DEVELOPER
INDICATION
APPLICATION
Intravenous
TYPE
Microbubble
Cyanoacrylate (polymer sheIl)
CHARGE
-
Sulphur hexafluoride
MICROBUBBLE SIZE
-
PRESENTATION
-
STORAGE
-
PREPARATION
-
DO NOT RELY ON THE INFORMATION PROVIDED HERE, THEY ARE
NOT A SUBSTITUTE FOR THE ACCOMPANYING PACKAGE INSERT! •
MRX 115 is a liposome based microbubble formulation and has been demonstrated as effective for cardiac blood pool imaging, Doppler enhancement and potentially myocardial perfusion imaging. MRX 115 is based upon the demand for a stable, robust blood pool ultrasound contrast agents, also called DMP 115 or Aerosomes™ (ImaRx LLC) and now Definity®. Result Pages : | Share This Page     Look Ups |
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