Chapter 32: Vascular Applications of Ultrasound Contrast Agents Flashcards
the use of medical ultrasound imaging after administration of an ultrasound contrast agent
contrast-enhanced sonography
encapsulated gas-containing structures that are typically smaller than 8 microns in size
microbubbles
compositions that, after administration, after the acoustic properties of body tissues (including blood), typically resulting in higher ultrasound signal reflectivity; also known as ultrasound contrast medium
ultrasound contrast agen
microbubbles formed by agitation of saline resulted in strong reflections of US beam arising within normally echo-free lumen of aorta and chambers of heart
“bubble study” echocardiography
assessment of patients with suspected pulmonary hypertension or intracardiac shunts
“bubble study” echocardiography
characteristics of microbubbles in saline
nonuniform in size
relatively large
unstable
unsuitable for sonographic evaluations of left heart and systemic circulations
“bubble study”
3 characteristics of UCA in order for it to be useful:
- nontoxic
- have microbubbles or microparticles that are small enough to traverse pulmonary capillary beds but large enough to reflect US signals
- stable enough to provide multiple recirculations
small IV bolus provides ___ minutes of enhancement
2
Slow IV infusion provides ___ minutes or more of enhancement
12
contained exclusively in body’s vascular spaces
blood-pool UCAs
Tissue specific agents have two unique characteristics
affinity for targeted tissue
ability to alter tissues sonographic detectability
Tissue specific agents change ______
signal impedance
considered molecular imaging agents
tissue-specific agents
have a specific ligand or other binding moeity attached to their shell that has an affinity for a particular receptor (target); enhance thrombolysis using acoustic energy with and without nontargeted UCA microbubbles; potential noninvasive therapy for patients who suffer from embolic stroke
therapeutic agents
can be performed with same transducers used for conventional US; configured to receive only echoes at second harmonic frequency which is twice the transmit frequency
harmonic imaging
echoes from the oscillating microbubbles have a higher signal-to-noise ratio than would be provided by using conventional US so that regions with microbubbles are more easily appreciated visually
Harmonic imaging mode
provides a means to visualize contrast-enhanced blood flow and contrast-containing tissue using B-mode imaging
contrast-specific harmonic imaging
Contrast specific imaging modes designed to utilize _____ acoustic power
low
Contrast-specific imaging modes are defined by ______
mechanical index
avoid or minimize microbubble destruction
mechanical index
briefly increases the transmitted acoustic power to intentionally destroy the microbubbles of contrast
“flash-echo”
used to observe reperfusion of blood into the region over time
“flash echo”
The “bubbles” used for ultrasound contrast are typically smaller than what?
8 microns
For what reason are contrast agents approved for use in the United States?
echocardiography and liver applications
Which of the following is NOT a disadvantage of using saline as a contrast agent?
a. persist through pulmonary circulation
b. nonuniform in size
c. relatively large size
d. unstable or fragile
a
What is the microbubble shell in Definity?
lipid
Which of the following is NOT a characteristic of a viable contrast agent?
a. nontoxic to a wide variety of patients
b. microparticles that pass pulmonary capillary bed
c. size greater than 8 microns
d. stable to recirculate through CV system
c
how is the ultrasound contrast agent administered?
intravenous
For approximately how long will contrast administered in a bolus dose provide enhanced visualization>
2 minutes
Which of the following applications would be best suited for slow IV infusion of contrast agent?
a. cardiac chamber opacification
b. identification of a large vessel wall
c. identification of an aneurysm
d. organ perfusion
a
After the microbubbles are ruptured, how are the shell particles removed from the body?
metabolized
Which type of UCA would best serve a patient/sonographer when the diagnosis is DVT and vessels are difficult to visualize?
tissue-specific agent
Which of the following is NOT an ultrasound system setting necessary for successful use of contrast agents?
a. flash echo
b. low mechanical index
c. high acoustic output power
d. harmonic imaging
c
Which of the following situations would most likely be enhanced by the use of contrast ultrasound agent?
a. carotid with diagnostic level images
b. deep vessels with luminal echogenicity
c. vessels with slow flow identified by power Doppler
d. postoperative complicated bypass surgery
d
In PAD, in which situation would using contrast agent improve the diagnostic quality of the examination?
a. atherosclerotic plaque on posterior vessel wall
b. occlusion of the proximal femoral artery
c. perfusion deficit of calf muscle
d. DVT of popliteal vein
c
Which of the following does NOT limit sonographic visualization of intracranial vessels?
a. acoustic windows
b. high-velocity flow
c. signal attenuation
d. vessel branches
b
In which situation is duplex sonography least effective in the evaluation of organ transplant?
a. postsurgical fluid collections
b. urinary or bile obstructions
c. blood flow to and from organ
d. tissue perfusion
d
What is the most significant advantage to CES over repeated CT for evaluation of endovascular leaks?
real-time blood flow assessment
What would the use of contrast-enhanced ultrasound in the abdominal vasculature prove MOST helpful in?
a. renal artery stent demonstrating laminar flow
b. abdominal aortic aneurysm demonstrating true and false lumen
c. turbulent blood flow through a TIPS
d. competent endovascular graft of abdominal aorta
c
In a cardiac application, what would the use of a saline contrast study help diagnose?
patent foramen ovale
When assessing for vessel occlusion with contrast-enhanced sonography, what are the expected findings?
vessel visualization with no enhanced distal flow
What would contrast-enhanced sonographic imaging in the cerebrovascular circulation prove helpful in?
a. delineation of plaque ulceration
b. assessment of functional lumen
c. identification of string flow
d. all of the above
d
Ultrasound contrast agents alter the ______ of body tissues, resulting in higher signal reflectivity.
acoustic properties
The use of contrast agents has been shown to ______ the limitations of ultrasound imaging, which include contrast resolution on grayscale, slow blood flow, and small vessels.
reduce or eliminate
When a vascular agent’s microbubbles are ruptured or otherwise destroyed, the shell products are ______, and the gas is _____.
metabolized or eliminated
exhaled
Tissue-specific agents must possess two unique characteristics: _____ for the targeted tissue and ability to alter that tissue’s ______ appearance.
sonographic
Tissue-specific UCAs target specific types of tissues with a predictable behavior, so they are considered _______
molecular imaging agents
Although blood pool agents help to better delineate the functional _____ of arteries and veins, they do not enhance the appearance of _____.
lumen
thrombi
Thrombus-targeting UCAs have a therapeutic function by enhancing ______ when insonated.
thrombus
_______ imaging is performed with the same transducers as used for conventional ultrasound and enhances the effectiveness of contrast agent visualization.
harmonic
In harmonic imaging, the echoes from _______ microbubbles have a higher signal-to-noise ratio than conventional ultrasound imaging.
oscillating
When contrast microbubbles are destroyed in an organ, the sonographer is able to observe ______ of the tissue.
reperfusion
UCAs allow for improved delineation of endocardial borders, assessment of regional wall motion, and detection of intacavitary thrombus in the field of _________
echocardiography
Some of the main limitations in iliac vessel visualization that can be overcome with UCAs are overlying _____ and ___ vessels.
bowel gas
deep
In peripheral artery disease evaluations of symptomatic patients, the two areas of improved visualization with CES are perfusion deficits and _______.
arterial collateralization
Contrast agents are most frequently administered via _____ extremity intravenous access site.
upper
The contrast-enhanced sonography can be used in the cerebrovascular circulation to differentiate tight stenosis from ______
occlusion
Some investigators have compared _______ to tumors because of the requirement of nutrient-rich blood supply to grow.
atherosclerotic plaque
Abdominal vascular applications of contast-enhanced imaging including arterial and venous systems as well as abdominal _____ perfusion and masses.
organ
A significant number of patients have anatomic variations of renal vasculature, including _____ renal arteries.
duplicate
The enhancement capabilities of UCAs have been shown to have the ability to ______ nondiagnostic US examination
salvage
Contrast agents available for use in the United States are _____, ______, and _____.
Optison
Lumason
Definity
