Hi, I'm Dr Eleanor Stride. I'm in the Department of 
Mechanical Engineering at UCL, and my research is all about bubbles.
These bubbles are used in medicine,
both for
imaging and for therapeutic applications as well.
Normally, if you think about putting bubbles 
into the human body, this is not a very good idea. 
They are associated with causing the bends, 
for example, in scuba divers.
But the bubbles that we deal with are much too small for that.
They're almost a hundredth of a human hair in diameter, 
so they're very, very small.
They can pass safely through human blood vessels
without causing a blockage.
And the reason they're used is that,
if you go for an ultrasound scan,
the image that you see on the screen
is all about the density of the tissue in your body.
If you can change the density, then you can make 
one area much clearer, compared with another.
So by putting gas into your bloodstream,
even very tiny amounts, you produce a big density change
and that gives you a very strong ultrasound echo.
That means that clinicians can trace where blood is flowing
much more easily and enhance detection 
if there are any problems.
The other thing that we're looking at with bubbles is using
them for drug delivery, actually using the bubbles as vehicles
into which we can incorporate small amounts of drug. For 
this, the bubbles are coated with a little shell of a polymer 
or something like  that the drug is dissolved in.
The bubbles are traced through the body
under ultrasound imaging so we can see where they're going.
Once they get to the site we're trying to target,
for example, the tumour,
the ultrasound power is turned up, 
we break the bubbles open and release the drug.
By doing that, we localise the release of that drug 
and that minimises the risk of any harmful side effects, 
for example for cancer chemotherapy.
There's a lot to do to make this clinically useful and to get it
into hospitals. The 3 main challenges we're working on are 
making the bubbles better so we develop technology
for making bubbles better so they're identical. This means
we can predict and control how they're going to behave
once they've been injected.
Another problem is making sure once the bubbles are 
in the body that they end up in the right place
and to do that,
we've loaded the bubbles with magnetic nano-particles. 
This means that we can drag them into the right place 
and hold them there,
using an externally-applied magnetic field.
Our last problem is making the bubbles 
as detectable as possible.
To do that, I just need to explain what happens.
When the ultrasound comes in,
the bubbles expand and contract.
And that's what produces the large echoes.
If we can change the process of how 
they expand and contract,
we can change the note at which the bubbles sing
and that means they're much more detectable in ultrasound 
imaging. By engineering the coating around the bubble, 
we can change the way they sound when they're in the body,
and that means they become much more detectable.
