- Hi, I'm Sanjiv and we're in the Willis Annex Laser Labs
and this is Azy.
Hi Azy, do you want to give us a quick intro about yourself
and what your research is about?
- Hi Sanjiv, yeah I'm Azy,
I submitted my PhD thesis last March
and now waiting for the examiner's comments.
- What was your PhD on?
- My PhD thesis was on haemodynamical [inaudible]
within the stented peripheral artery
with regards to different stenting techniques.
- Okay, you mentioned stent a couple times,
what is a stent?
- Oh, a stent, have a look at this.
A stent is a metallic medical device
which would be used by a vascular surgeon
to open up the artery
and restore the normal flow of the blood.
So you can see this artery is kinda narrowed
by these two plaques here.
You'll see the clot here so with the stent surgery,
the normal flow of the blood is fully restored.
- And you also mentioned different types of the stenting?
- Oh yeah,
so different techniques of the stentings
are being used by endovascular surgeons
to fully open up the artery.
For example if the bifurcated artery walls,
like if the bifurcated artery has plaques everywhere
like in the main branch here, at the carina here,
like opposite of the carina,
it needs more than one a stent to be treated,
which makes the whole surgery more complicated.
So you'll see these kinds of techniques here.
The simplest one was the PSB
or the Provisional Side Branch technique,
which involves only one stent through the main branch.
The other ones, the most commonly used
was the T-stenting technique, the Culotte and the Crush one
which involves two stents.
- Okay, it's interesting to know
that there's so many different types of methods of stenting.
But expanding on that, what caused the motivation
behind looking into these different stenting methods?
- Yeah, so by investigating the hemodynamics
within the stented peripheral artery,
we would be able to predict the location and severity
of some post-system complications,
so in our case it's inner steri stenosis.
I'll show you what it exactly is.
Here you'll see the incidence of inner steri stenosis.
Here you'll see the stent here,
so after a few days or it can be,
the range is between a few days to few months,
the inner steri stenosis
or the occurrence of this neointimal hyperplasia
may be happening, which causes the artery
to be re-narrowed again.
So what we're doing actually is
we are hemodynamically trying to predict
the likely incidence of these neointimal hyperplasia.
Yeah, Sanjiv don't you think it's amazing,
That we can predict the location and severity
of inner steri stenosis before it actually happens
in a renal surgery?
- It's very clinically useful, yeah,
but building up on that how are you predicting,
what methods are you using to predict when and where?
- Actually we are using two different platforms,
the computational model, which involves lots CAD modelling,
machines and analysis, so I've done all of this
by using different software for CAD modelling.
I used Solidworks and CATIA for machines.
I used ISM, and for analysis
I used ANSYS Fluent.
And for laboratory experiments,
I had to do lots of design and prototyping,
3D printing and fabrication to be able to create the model.
And then out of that, by doing the four measurements
by using the laser-based measurements techniques,
the hi-tech PIV systems.
- You mentioned the, so take the computational method first,
you said you used CAD,
so you basically created a virtual model
of the artery and the stent?
- Correct.
Yeah, I created the geometry of the stent individually
and the geometry of the vascular system
and the peripheral arteries individually
and then virtually implanted the stent into the artery.
- And then mesh, CFD ... ?
- Yes, exactly.
- But what were you looking in your CFD?
What results were you looking for?
What parameters?
- I used a couple of parameters,
actually it's about five parameters I think in my case.
Yeah but I tried to use a time average form
of the paramaters, like time averaged wall sheer stress,
wall sheer stress gradient, oscillatory sheer index,
OSI and ORT and I also introduced,
I also used a new one, which is GOON,
integrated oscillatory number,
which requires lots of coding,
we wrote that
and then attached that to the Fluent as a UDF.
- Okay, so I guess that just gives you wall sheer stress
you're using wall sheer stress
to make these other 5 calculations that you said.
- Correct. Yeah, all calculated are based
on wall sheer stress.
- You're using a UDF.
- Yeah. - Yeah.
And you plotted it across the model is it?
- Exactly.
- And see which points? - Yes.
- Do you have a plot of? - Oh yeah, yeah,
I can show you.
We also use some clinical cases for our modelling as well.
Yeah, here you see one of the clinical cases.
This is taken like after,
this is taken about six months after the surgery.
You'll see the incidence of inner steri stenosis
at two ends of the artery, here and here.
You know for stenting a peripheral artery,
surgeons need to oversize the artery,
and this model is oversized as well,
up to 100% of the normal size, the native size of the model.
- Oversized meaning like bigger than the artery or?
- Yeah, yeah, they're actually opening the stent
up to like bigger than it's native size to be able to kinda,
what's that, optimally oppose the stent
against the artery wall.
- Okay, cool.
- So yeah, then we created the model
before developing the steri stenosis
and then from here we can predict these two sides.
- Yeah, okay, and then from the
- And here you can see one example of my modelling
by using time-averaged wall sheer stress
and time-averaged wall sheer stress gradient,
so the regions in dark blue and dark red here
are the regions prone to the likely inner steri stenosis.
- Okay, yeah, that's very useful for the clinicians as well.
- Exactly. - To know exactly that.
Where are you at risk of steri stenosis.
- Exactly.
- You also mentioned lab models,
what was the process for that?
- For lab models we actually needed
to have a fully transparent model
so we 3D printed the stented artery,
and then created a negative mould of that out of PDMS
'cause the model needed to be fully transparent
for the laser measurements.
Yeah, from that after the prototyping,
we created a whole loop of the system
and then used that for the floor measurements.
But we had some challenges with the experimental models
'cause the struts of the stents
are kinda blocking the fuller view of the measurements.
This problem actually required more time to be resolved.
- Because you need to laser to illuminate what's inside.
- Exactly, yeah. - That's interesting
I guess yeah, challenging as well.
But you mentioned a couple of times that, yeah okay,
you're trying to figure out where are stenosis occurs.
So the strong connection to the clinic.
Was this a problem by a clinician,
given to you by clinicians?
Or did engineers go forth and find this
and say we can do it better.
- Now and then, kinda well,
you know of this stenting the peripheral bifurcated artery
has long been a challenging and unsolved problem.
We actually collaborated with two endovascular surgeons
from Prince of Wales Hospital to provide us feedback
on the clinical side of our study
and then translating the outcome of our study
to the clinical practise.
- Okay, yeah, all right so
- Especially when it comes to you know,
oversizing and different kinds of techniques
and the size of stent in treating
the peripheral bifurcated artery
where the flow of the blood
is higher than the coronary arteries.
- Okay, so getting real time, real useful data
from the clinic, the clinicians using the stents here.
It seems like you've got multiple components
in your research, so do you want
to brush on a couple of challenging areas,
challenging aspects of your research?
- Well, I would say every single part of the research
is challenging, like the challenges associated
with creating this complex geometry
of the stented artery with like two or three stents
into the model, and then meshing that complex geometry
and to modelling, like creating, writing the code
to floor measurements by creating the geometry,
the fully transparent geometry.
You know how hard it is, you're doing,
I know you're doing some research into
- Laser stuff. - Yeah, yeah, with lasers.
So you know how hard is that, yeah.
But this is what's making the entire research interesting.
- Finding new things. - Exactly.
- Trying to push a limit.
That's pretty cool.
Where do you think your research will go from here,
or who do you think will use it, or how will it be applied?
- I think my research was kinda multidisciplinary,
it was kinda a combination of engineering and medicine.
I think yeah it can be used in medical device development
in the FDA, in working with surgeons
to provide the medical outline
with effective use of the endovascular stents
or the vascular medical devices, the vascular devices,
and they can even, this data probably can help them
to find a strategy and technique
to kinda prevent the initiation of the disease
before it actually happens.
- Okay, so like it's a tackling a disease,
it's also seeing what your research is looking into
all the details surrounding a medical device?
And it's using a lot of engineering skills.
Thanks a lot for covering all that,
covering so many components of your research
and I think we've learnt a lot about medical devices.
- Thank you.