SMS scnews item created by Duncan Sutherland at Fri 9 Oct 2009 1417
Type: Seminar
Distribution: World
Expiry: 14 Oct 2009
Calendar1: 14 Oct 2009 1300-1400
CalLoc1: Carslaw 350
Auth: duncans@bari.maths.usyd.edu.au

# SUMS talk (+concert): Sutherland

Hello everyone,

We had a huge turnout at the SUMS Relay on Wednesday.  Thanks to all 9 teams who turned
up, in particular teams Tachyon and Scroteam who notified us beforehand that they were
coming, cheers.  Congratulations once again goes to Team Vasak and Geoff Bailey (i.e.
Team Geoff), for coming equal first answering all of the questions.  Top effort.

Next week (i.e.  Wednesday October 14), Duncan Sutherland will be giving his 2008
honours talk about microbubble contrast agents.  Don’t worry, it’s an applied talk so
kindergarten students can understand it.  Duncan was kind enough to provide an abstract:

Traditional medical ultrasonography has used the backscattering of acoustic signals from
tissue to investigate an object of interest.  Microbubble contrast agents, which are
typically administered intravenously into a patient’s circulatory system, were first
approved for clinical studies in 1991.  Modern contrast agents are typically a gas
filled microbubble, which may be preformed with a shell of, for example, lipid, polymer
or albumin.  Contrast agents enhance backscatter, due to the high compressibility of the
gas, relative to body tissue.

The oscillatory response of the microbubble to an applied ultrasound field is
complicated and frequency dependent.  The bubble has a size dependent linear resonance
frequency.  Typically the contrast agent size is 1-7 um with resonant frequencies in the
2-15 MHz range, which is used for clinical applications.  As the amplitude of the
driving field is increased, the bubble response is nonlinear, which leads to sub and
higher harmonic generation.  New techniques have been developed for use in specialised
applications to utilise this phenomenon.

I will be discussing the some of the models that have been developed to describe the
response of a single bubble to a driving pressure.  This requires consideration of the
surrounding fluid, internal gas and the shell layer of the microbubble.  The discussion
will focus on a second order ODE, called the Rayleigh-Plesset (RP) equation.  The RP
equation may be extended to include effects due to fluid viscosity and surface tension.
Similarly, it is possible to include damping of the bubble oscillation due to radiation
at the bubble wall.  For contrast agents with encapsulating shells the equation of
motion, due to Church, of the bubble wall is, again, an extension of the RP equation.
Some simulation results will be presented, and limitations of the models will be
discussed.

Talk: Models of Ultrasound Contrast Agents Speaker: Duncan Sutherland Location: Carslaw
350 Date/Time: October 14th, 1-2pm

Hope to see you there for the last SUMS talk of the year.  Meanwhile SUMS is also
planning concerts for week 13 (Wednesday evening and Friday lunchtime), if you would
like to perform in either or both SUMS concerts, please email usydmaths@gmail.com


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