On the acoustic properties of polymer-shell ultrasonic contrast agents.

• Polymer-shelled microbubbles have become the focus of intense research for their enhanced shelf life and demonstrated chemical versatility.  These are properties highly sought after in the ultrasonic contrast agents (UCAs) of the next generation, which will be engineered not only to enhance the contrast of ultrasound-based images, but also to function as carriers of drugs to be delivered locally.  Here, the results of an experimental investigation of three potentially new UCAs are presented.  These microbubbles are stabilized by thick poly (vinyl alcohol) shells.  These UCAs differ from each other in their dimensions and shell thickness (order of 0.5 microns).  Fundamental to their use as drug carrier is the knowledge of the pressure threshold at which the shell of these UCAs fractures.  Therefore, the dependence of this quantity on temperature, number of cycles of the incident pulse, nominal central frequency and pulse repetition frequency of the emitting transducer is examined.  The effect of using blood instead of deionized water is also considered.  The main conclusion to be drawn from these results is that their thick shell notwithstanding, these microbubbles begin to fracture at values of MI which can be acceptable in clinical applications.  This claim is supported also by images acquired by means of commercially available imaging systems.  Finally, these values of the pressure threshold are correlated with estimates of the shells’ visco-elastic constants obtained by fitting Church’s model to the frequency-dependent attenuation coefficient and phase velocity.  Open questions arising from this comparison are briefly discussed.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Strömningsmekanik och akustik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Fluid Mechanics and Acoustics (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Medicinteknik -- Medicinsk laboratorie- och mätteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Medical Engineering -- Medical Laboratory and Measurements Technologies (hsv//eng)

Nyckelord

Microbubble

ultrasound

contrast agent

attenuation

phase velocity

Acoustics

Akustik

Medical engineering

Medicinsk teknik

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vet (ämneskategori)

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