Chapter 18: Abdominal Applications of Ultrasound Contrast Agents

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acoustic emission

occurs when an appropriate level of acoustic energy is applied to the tissue; the microbubbles first oscillate and then rupture; the rupture of the microbubbles results in random Doppler shifts appearing as a transient mosaic of colors on a color Doppler display


acute tubular necrosis (ATN)

acute damage to the renal tubules; usually the result of ischemia associated with shock


contrast-enhanced sonography (CES)

agent used to reduce or eliminate some of the current limitations of ultrasound imaging and Doppler blood flow detection


first-generation agents

agents containing room air (i.e., Albunex)


focal nodular hyperplasia (FNH)

liver tumors with an abundance of Kupffer cells; sonographically they are isoechoic to the surrounding normal liver tissue


gray-scale harmonic imaging (GSHI)

allows detection of contrast-enhanced blood flow and organs with gray-scale ultrasound; in harmonic-imaging mode, the echoes from the oscillating microbubbles have a higher signal-to-noise ratio than found in conventional ultrasound; regions with microbubbles (e.g., blood vessels and organ parenchyma) are better visualized


harmonic imaging (HI)

in the HI mode, the ultrasound system is configured to receive only echoes at the second harmonic frequency, which is twice the transmit frequency


hepatocellular carcinoma (HCC)

a common liver malignancy related to cirrhosis; the carcinoma may present as a solitary massive tumor, multiple nodules throughout the liver, or diffuse infiltrative masses in the liver; HCC can be very invasive


induced acoustic emission

after the injection of the tissue-specific UCA Sonazoid, the reflectivity of the contrast-containing tissue increases; when the right level of acoustic energy is applied to tissue, the contrast microbubbles eventually rupture, resulting in random Doppler shifts; these shifts appear as a transient mosaic of colors on the color Doppler display; masses that have destroyed or replaced normal Kupffer cells will be displayed as color-free areas


intravenous (IV) injection

a hypodermic injection into a vein for the purpose of injecting contrast medium


mechanical index (MI)

an index that defines the low acoustic output power that can be used to minimize the destruction of microbubbles by energy in the acoustic field; when the microbubbles in microbubble-based ultrasound contrast agents are destroyed, contrast enhancement is lost


molecular imaging agents

agents include Optison, Definity, Imagent, Levovist, and SonoVue


portal hypertension (PHT)

caused by increased resistance to venous flow through the liver; sonographic findings include dilation of the portal, splenic, and mesenteric veins; reversal of portal venous blood flow; and the development of collateral vessels


renal artery stenosis (RAS)

narrowing of the renal artery; historically, this has been difficult to evaluate sonographically


second-generation agents

agents containing heavy gases (i.e., Optison)


tissue-specific ultrasound contrast agent

a type of contrast agent whose microbubbles are removed from the blood and are taken up by specific tissues in the body; one example is the agent Sonozoid


ultrasound contrast agents (UCAs)

agents that can be administered intravenously to evaluate blood vessels, blood flow, and solid organs