UltraSound - Technology Information PortalWednesday, 23 May 2018



Ultrasound Contrast Agents

  • Microbubbles CA Imaging
Magnetic Resonance Imaging Contrast Agents Open this link in a new window
Radiology Contrast Agents Open this link in a new window
Contrast Enhanced Ultrasound 

(CEUS) Contrast agents increase the reflection of ultrasonic energy, improve the signal to noise ratio and caused by that the detection of abnormal microvascular and macrovascular disorders. Contrast enhanced ultrasound is used in abdominal ultrasound (liver sonography) as well as in cerebrovascular examinations e.g., for an accurate grading of carotid stenosis. The used contrast agents are safe and well tolerated.

The quality of the enhancement depends on:
point the concentration of the contrast agent;
point the type of injection, flow rate;
point the patient characteristics;
point the microbubble quality and properties of the filling gas and the shell.
The additional use of ultrasound contrast agents (USCAs) may overcome typical limitations like poor contrast of B-mode imaging or limited sensitivity of Doppler techniques. The development of new ultrasound applications (e.g., blood flow imaging, perfusion quantification) depends also from the development of pulse sequences for bubble specific imaging. In addition, contrast enhanced ultrasound improves the monitoring of ultrasound guided interventions like RF thermal ablation.
See also Contrast Enhanced Doppler Imaging, Contrast Harmonic Imaging, Contrast Imaging Techniques and Contrast Pulse Sequencing.

• View the NEWS results for 'Contrast Enhanced Ultrasound' (1).Open this link in a new window.

• View the DATABASE results for 'Contrast Enhanced Ultrasound' (13).Open this link in a new window.

 Further Reading:
Guidelines and Good Clinical Practice Recommendations for Contrast Enhanced Ultrasound (CEUS)Open this link in a new window
2008   by www.efsumb.org    
  News & More:
Role of ultrasound and contrast-enhanced ultrasound in patients with cerebrovascular disease(.pdf)Open this link in a new window
Friday, 1 March 2002   by eurheartjsupp.oupjournals.org    
The clinical applications of contrast echocardiography(.pdf)Open this link in a new window
2000   by cme.medscape.com     
Bubble Specific Imaging 

Bubble specific imaging methods rely usually on non-linear imaging modes. These contrast imaging techniques are designed to suppress the echo from tissue in relation to that from a microbubble contrast agent.
Stimulated acoustic emission (SAE) and phase / pulse inversion imaging mode (PIM) are bubble specific modes, which can image the tissue specific phase.
In SAE mode bubble rupture is seen as a transient bright signal in B-mode and as a characteristic mosaic-like effect in velocity 2D color Doppler.
PIM are Doppler modes and detect non-linear echoes from microbubbles. In pulse inversion imaging modes the transducer bandwidth extends, resulting in improved spatial resolution and more contrast.
See also Contrast Pulse Sequencing, Microbubble Scanner Modification, Narrow Bandwidth, Contrast Medium, Dead Zone.

• View the DATABASE results for 'Bubble Specific Imaging' (7).Open this link in a new window.

 Further Reading:
Combination of contrast with stress echocardiography: A practical guide to methods and interpretationOpen this link in a new window
2004   by www.cardiovascularultrasound.com    
Contrast Pulse Sequencing 

(CPS) Contrast pulse sequencing is a technique to exploit contrast agent properties with series of three pulses that differ in phase and amplitude. CPS allows bubble specific imaging with non-linear fundamental and higher order harmonics, low MI, and extremely high microbubble-to-tissue background ratio.
See also Ultrasound Contrast Agent Safety.

• View the DATABASE results for 'Contrast Pulse Sequencing' (5).Open this link in a new window.

Microbubble Scanner Modification 

Standard scanners allow visualizing microbubbles on conventional gray scale imaging in large vascular spaces. In the periphery, more sensitive techniques such as Doppler or non-linear gray scale modes must be used because of the dilution of the microbubbles in the blood pool. Harmonic power Doppler (HPD) is one of the most sensitive techniques for detecting ultrasound contrast agents.
Commonly microbubbles are encapsulated or otherwise stabilized to prolong their lifetime after injection. These bubbles can be altered by exposure to ultrasound pulses. Depending on the contrast agent and the insonating pulse, the changes include deformation or breakage of the encapsulating or stabilizing material, generation of free gas bubbles, reshaping or resizing of gas volumes.
High acoustic pressure amplitudes and long pulses increase the changes. However, safety considerations limit the pressure amplitude and long pulses decrease spatial resolution. In addition, lowering the pulse frequency increases destruction of contrast bubbles. However, at low insonation power levels, contrast agent particles resist insonation without detectable changes. Newer agents are more reflective and will usually allow gray scale imaging to be used with the advantages of better spatial resolution, fewer artifacts and faster frame rates.

Feasible imaging methods with advantages in specific acoustic microbubble properties:
point harmonic imaging;
point contrast harmonic imaging;
point harmonic power Doppler;
point subharmonic imaging;
point superharmonic imaging;
point pulse inversion imaging;
point release burst imaging.
Resonating microbubbles emit harmonic signals at double their resonance frequency. If a scanner is modified to select only these harmonic signals, this non-linear mode produces a clear image or trace. The effect depends on the fact that it is easier to expand a bubble than to compress it so that it responds asymmetrically to a symmetrical ultrasound wave. A special array design allows to perform third or fourth harmonic imaging. This probe type is called a dual frequency phased array transducer.
See also Bubble Specific Imaging.

• View the DATABASE results for 'Microbubble Scanner Modification' (4).Open this link in a new window.

 Further Reading:
  News & More:
  Overview top
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