- Hi guys, I'm Olivia.
I am with Sanjiv now at the laser lab of Willis Annexe.
Sanjiv, do you want to tell us about yourself
and what are you doing now?
- Hey, I'm Sanjiv.
I'm one of Tracie Barber's PhD students
and I look into the fluid dynamic aspect
of blood flow in an arteriovenous fistula
and specifically ones that have been stented.
- Yeah, so you mentioned stent.
How does stent and arteriovenous fistula link together?
- So, arteriovenous fistula, it's not a natural phenomenon
that occurs in the body and because of that,
it comes across lots of diseases.
And the main disease that it comes across is known
as stenosis.
Stenosis is basically a vessel being narrowed
because of smooth muscle growth on the walls.
When it gets narrowed, it causes a lot of problems.
The blood vessel becomes restricted and all of that.
So how do surgeons treat that?
They put something called a stent.
So I've got a small stent here.
It's basically a metallic scaffold
and you put it into the vessel and expand it,
thereby holding the vessel open much better.
So that's the subset of fistulas that I look into
and I want to see what does the stent do to the fistula
in terms of fluid dynamics.
- Okay, so how are you looking
into stent and fluid dynamics?
What approach are you adopting?
- So I have computer simulation as well,
I use computational fluid dynamics,
but I've been putting a lot of time
into the experimental aspect of it.
So we get our data from Dopplers, ultrasound Dopplers,
but that's not showing the whole story.
How I get the whole story is use
this technique called particle image velocimetry.
Essentially, we've got a model over there
and we've got a lot of cameras and a laser above it.
So that model of the fistula will be run with fluid.
I'll use a pump to run fluid through it.
That fluid will have fluorescent particles in it.
These fluorescent particles will be illuminated
by this laser that's above.
So when the flow is going through the fistula,
the laser will illuminate the particles.
The illuminated particles will be captured
by this set of cameras that are around.
These cameras are high-speed cameras.
It's able to capture frame by frame
and able to check these movements of these particles.
When it captures two images, let's say,
it's able to see how far the particles have moved,
and since we know how fast the camera is working,
we are able to know what the time difference it has taken
for those particles to move
and thereby creating velocity for that particle.
So that whole domain is filled with velocity data.
I can show you what it looks like on a screen if--
- Yep, sure.
Yeah.
- So when I mentioned particles,
this is what it would look like.
These are the illuminated particles in this model.
This is one image of it and then immediately after,
it'll capture another image
with these particles slightly offset
from its original location.
That offset can be calculated
and a vector field can be plotted.
And you can do all sorts of post-processing to it.
You can see where the high velocity is,
where the low velocity is, where the negative flow is,
where the positive flow is,
and ultimately create pretty videos like this.
Yeah, so that's all of my experimental work in a nutshell.
- Okay.
So the experimental work sounds very engineering.
Was this a clinical problem
or how did you come up with this problem?
- So the vascular surgeon that is co-supervising me came up
with this problem.
He's using the stent in a different way.
Usually, stents have been implanted in one vessel only,
but this surgeon is implanting it across two vessels.
When a stent has been implanted in one vessel,
it only treats the disease temporarily,
but the method that the surgeon has been using
has been more of a long-term treatment.
And he came up to us and asked us to look at it
on a fluid dynamics aspect and see what's the difference.
And that's essentially what I'm doing,
trying to see why this is helpful.
- Yeah, okay.
So, were there any challenges along the way
as you do your experiment?
- Like any research, you've got challenges in every aspect.
Since we're using lasers, we need to be careful.
There's a lot of safety aspects in this research.
There's a lot of data that I need learn how to manipulate
because we've got four cameras here
and particle image velocimetry is a complex methodology.
And yeah, those are normal challenges
that we come across in research anyway.
But for any research I have to make assumptions.
So the fluid that I'm running in, it's similar to blood,
but it isn't mimicking everything that blood does.
So it doesn't have the small particles,
small red blood cells and the effects of red blood cells.
The vessel is rigid so it doesn't have the compliant effect.
So incorporating everything will be too much
and the gain wouldn't match the effort.
So those are the challenges, I guess,
and assumptions that incorporated into my research.
- Yeah, so it sounds like a cool project,
like you incorporate both engineering experiment PIV
with clinical problem.
How do you see your research going further from here?
- Well, hopefully, it seems on the clinical side,
the vascular surgeon is finding a lot of positive outcomes
with his stenting technique.
However, it's just this surgeon's clinic
and a few other clinics in Sydney that we know of
that are using this method.
If I can show that there is a fluid dynamic backing
towards this method then it will help give
this method a better backing, a better groundwork,
and I guess spread it to other fistula clinics,
spread this methodology to other fistula clinics,
thereby preventing so much of disease
in this unnatural structure in the human body.
- Okay.
- So hopefully it affects the clinical community.
- Yeah. - Patients, essentially.
- Okay, cool.
Thanks for all your thoughts on your research.
Yeah, thank you. - Cool, thanks.