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Music
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Herald Angel: And now we come to the talk
entitled low-cost non-invasive biomedical
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imaging. Current medical imaging has
problems: it is expensive, it is large,
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rarely preventively used and maybe you've
heard of the story of a fMRI - this is the
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magnet resonance tomography - they put in
a dead Salmon and they can get a signal
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from brain activity from it. There's also
lots of problems in the software as well.
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A little story, maybe you look it up. And
how this whole mess can be solved with the
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technique called Open Electrical Impedance
Tomography - this will tell us Jean
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Rintoul. Give a big round of applause for
Jean.
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applause
Jean Rintoul: Thank you.
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Hello everyone. Today I
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will be talking about an open source route
for biomedical imaging using a technique
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that's in R&D called Electrical Impedance
Tomography. Not many people have heard of
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it, which is why it seems like it's
important to mention. First of all, I'll
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just give you the vision of what it would
be like if everybody had access to cheap
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biomedical imaging. Right now you only get
imaged when something's gone wrong. And,
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moreover, you only actually get to use
these tools when something has gone wrong
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in a first world country when you're lucky
enough to be close to a hospital and have
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access to these technologies. That's a
very limited number of people. What's even
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worse about it: is it's hard to hack! So,
if you wanted to improve this technology
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yourself - medical physics is an amazing
field - but it would be very hard to do so
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because you don't have a three million
dollar MRI scanner sitting in your garage.
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Maybe you do, that's good for you, just
not many of us do. If we did have cheap
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biomedical imaging we could do things like
do preventive scans so you would wake up
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in the morning you'd like, take a shower,
the device would be quietly imaging your
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body, would warn you if the slightest
little thing when went wrong. You'd do
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machine learning over it, it'd be
wonderful wonderful for health care. So,
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that's the vision of what biomedical
imaging could be. And the other point is
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sometimes we move forward faster when we
share the information. I worked in defense
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for a brief period and people didn't
really share information between each
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other, and I think that inhibited science
from moving forward. So, sharing is
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caring.
So today I'm going to go through a few
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different things. I'm going to go through
the current biomedical imaging
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technologies. I'll give you an
introduction to Electrical Impedance
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Tomography. I'll go through the open
source Electrical Impedance Tomography
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Project. Then I'll go through some
applications that we could apply it to.
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And then I'll suggest a few different next
steps that we can go into because by no
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means is it finished. Right now we have
four different main existing imaging
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modalities. Your MRI scanner, which is a
wonderful tool, it's huge, very expensive.
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The most commonly used imaging is actually
CAT scanner which sends our x-rays through
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your body which is ionizing radiation,
which is bad for you because it causes
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cancer in the long run if you get too many
of those scans and it's actually the first
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first scan that you'll get when you go
into the emergency room. It's the most
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commonly used. And as we all know we've
got those grainy images that come from the
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ultrasound of fetuses, wonderful tool
except for the scattering due to the sound
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gets scattered when you have different
density materials next to each other. And
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not exactly an imaging modality but a very
important diagnostic technique is EEG.
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So you might ask, how do we classify these
right now? we have 3 main types of
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resolution. Spatial, contrast, and time.
Spatial resolution is, basically, what
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space you can determine 2 different
objects from each other. Contrast
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resolution is soft tissue or subtle
differences in tissues. And time
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resolution, as it sounds, is how things
change over time and how quickly you can
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do these images together. Your CAT scan,
your basic machine in a hospital,
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costs 1 to 2.5 million dollars.
You probably didn't get one for Christmas
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to play around with. Oh well. It's also
got this ionizing radiation, you've got
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a lot of maintenance, and
dedicated technicians.
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An MRI, say, your average 3 Tesla magnet
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with its own helium quenching chamber
no less, as well as dedicated technicians
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and experts who can actually read
the images. Again $3,000,000. An amazing
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and beautiful technology, but really
expensive. Amazing spatial resolution, the
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best. When it does something at this very
high spatial resolution, it actually takes
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4 minutes and 16 seconds. Which is a
really long time to take to do this
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wonderful spatial resolution image.
Ultrasound, it's a bit grainy due to
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scattering. On average it costs about
1$115k, not too bad. It's a pretty minimal
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health risk. EEG. EEG doesn't do any image
reconstruction. In fact it does very
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little in many ways. But it is still very
useful. Your average medical grade by EEG
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system is $40k. You might also know of
some open source EEG projects which are
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pretty cool. So just a note on the
radiation of CAT-scans. It's actually the
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biggest contributing cause of radiation in
the United States. So here I just put
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those biomedical imaging modalities onto a
graph so that you can kind of think of
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them in terms of spatial resolution and
time resolution, and where they fall in
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the picture of common things that go wrong
with people. Like, X-rays or CAT scans are
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great for for looking at bone and bone
breaks; pulmonary edema, that's water on
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the lung ,tuberculosis, huge in third-
world countries, massive problem. You
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don't actually need super high spatial
resolution to be able to detect it. And
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it's important to sort of understand what
you can do at different spatial and time
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resolutions. Under like, the optimal goal
of all of this, I put non-invasive
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electrophysiology. What that is, is high
spatial resolution and high time
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resolution. That's where you can measure
ion activation, or basically what cells
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are doing when they communicate with each
other, which is right now only done in an
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invasive manner.
Today I'm gonna talk about this new
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technique called Electrical Impedance
Tomography and describe where it will fit
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in amongst what already exists. So what is
it. Okay yeah basically you send AC
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currents through the body, say a 50
kilohertz current. And that will take
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different routes based on what tissue
there is. So it might go around some cells
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and straight through others. And that's
really important because differentiating,
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say, fat from muscle is one thing that you
could do. But you can go further and
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differentiate, say, tumors from healthy
tissue. Because tumors have different
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impedance spectra to the healthy tissue.
So as you can see, that would be very
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useful to do. This set up here is a called
a phantom. What it is, it's like a
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simulated human body. You get some
saltwater - the body is 80% water as you
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might know -you get some meat or
vegetables. You put it inside and then you
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use that to image. So we have current
flowing through all these different
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directions and we recreate an image. Right
now it's used for lung volume
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measurements. This is a baby with an EIT
setup. Muscle and fat mass, there's a
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paper on gestural recognition that just
came out this year, you can look at
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bladder and stomach fullness. There's some
research papers on breast and kidney
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cancer detection. There's another research
paper on hemorrhage detection for stroke.
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You can also look at the ... there's more
R&D on the depth of anesthesia in in
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surgery as well, which would be another
interesting use for it. So all of these
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are sort of in the works and you might
ask, "Great, that sounds amazing, why
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isn't everybody using it already?" Well
yeah it's really an R&D technique right
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now and it has a big problem: its spatial
resolution seems pretty limited. So it's
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limited by the number of electrodes. But I
will discuss some potential ways to get
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around that. As we go, it might not ever
get to the spatial resolution of MRI.
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But maybe we don't need it to to be
useful. Because it's so compact. It's so
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cheap, nothing about it is expensive. It's
got better source localization than EEG.
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It does not ionize,
it's not harmful to human tissue. It's
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also got great time resolution, so it has
advantages and disadvantages. I'll just
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remind you of what the first MRI scan
looked like at this point in time. As you
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can see it looks pretty crappy in 1977.
And now it looks pretty awesome. That's a
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slice of my head by the way in a 3 Tesla
MRI scanner. This is what early EIT looks
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like. That's with 16 electrodes only. What
will it look like in a few years time I
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don't know. I hope that MRI gives you a
pathway that it will take take too.
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Now I'll introduce you to the OpenEIT
project. The OpenEIT project is obviously
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open source. It has a PCB design done in
Eagle CAD. It has firmware written in C.
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It has a Python dashboard that lets you
see the reconstruction in real time. It
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also has a reconstruction algorithm which
I'll go into. And you can get it from
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github right there. So how does it
reconstruct an image? OpenEIT right now
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has 8 electrodes and what you do is, you
send this 50 kHz current through every
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combination of those 8 electrodes and you
get a different impedance value for each
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of those measurements. On the left you can
see basically what you're doing. You know where the
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electrodes are positioned and you get one
value going horizontally. You add it to
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another value coming from another
direction. And again, you can sort of see
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it's getting a low resolution image as it
goes around adding those values together.
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If you use many, many views you bring the
image back. This is the radon transform,
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that's what it's called, and you
basically just send lots of current
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through these different slightly different
angles and you build up something called a
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sinogram which is over there. And then you
invert it to get the image back. I used
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OpenCV which is a really common image
processing library to do this. You can
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just do it with a regular image yourself
and try it out. But what I did is exactly
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the same as what you do with a regular
image, except I use current to be the
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input data. So this is the PCB design
in Eagle. Basically it has a
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few different features. A connector for
your 8 electrodes. It's running an ARM
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Cortex M3, which is quite nice. It has a
dedicated DFT engine for doing your direct
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Fourier transform in real, time which is
also quite nice. A JTAG debugger to easily
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reprogram it. It's got coin cell or
external battery options. It has UART to
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get the serial data off. And you can also
flip it to Bluetooth mode and get the data
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off by Bluetooth if you felt like going
Wireless.
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At this point you might be asking "Is this
safe for me to play around with?", which
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is a really great question because the
answer is actually "Yeah! it is". There's
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some guidelines called the IEC60601-1
guidelines for safer use in humans. And
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basically which says it should be, and
openEIT is less than 10 micro amps which
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is great because that's well within their
guidelines. If you want to compare it to
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other things that are completely legal,
say I don't know if you've seen there's
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like late-night TV ads for those abs
stimulators that stimulate your muscles,
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there are about 15 to 20 milliamps just
for reference and as a scale to look at
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the 10 micro amps. So some of you might
have used them already and that's hugely
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more current than what we're putting
through to image the body here. This is
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what the dashboard looks like. It does the
reconstruction. You can connect to serial
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at baseline. You can obviously adjust
sliders to look at the area that you want
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to look at. You can read from a file and
fiddle around however you would like to.
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This is what it looks like when you
reconstruct something. I have a phantom up
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there which is a part of water with a cup
in it. I moved the cup around anti-
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clockwise so you can see in each of the
pictures I move it around a little bit
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more. And you can see the reconstruction
there with me moving the cup around again.
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This might not be wow-ing you with the
resolution, with only 8 electrodes. It's a
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proof of concept but that's okay. Let's
see if we can make this I make this go.
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Here's a real-time video demonstration of
it. Here's me with a shot glass. I'm
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moving around anti-clockwise. Hopefully
you can see on the left the image being
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reconstructed in real time. And there we
go, move to the bottom. You can see it
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over there and again up to the top. you
can see it over there. So that's a basic
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proof of principle version of it running.
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So the first MRI scan of human
lungs wasn't that amazing.
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Early EIT scan wasn't either.
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applause
Something else that you can use it
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that for is differentiating objects.
Multi-frequency. This is what they're
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doing the breast cancer and kidney cancer
scans on. Basically you send different
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frequencies through these times, called
multi-frequency Electrical Impedance
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Tomography and you build up a spectrum.
Here I've got an apple, a pear oh no a
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sweet potato and and some water. And I've
sent through these different frequencies
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and I get these different spectrums.
They're different, you can see that
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they're different. They're quite obviously
different but yeah you can also just
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simply classify. And on the left you can
see where the water is, the apple is, the
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sweet potato is. Or, the sweet potato and
the apple a little bit harder that one.
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But that's basically what you do when you
detect cancer. So that's what I did. But
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maybe we should look at the other papers
and see what they did because they did
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better than me. So there's this guy called
Aristovich, 2014 he published spatial and
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temporal resolution, and using this
technique 200 micro meters less than 2
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milliseconds which covers most of the
applications that I listed on that graph
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at the start of the talk. The downside
here is that it was an intracranial array,
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so it was under the skull. So very dense
electrodes, a lot more electrodes. I only
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used 8 he used like 256 so you can see
that it can be, like, the potential is
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there.
So how should we use it first? what's a
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nice low hanging through fruit? What about
medical imaging in the developing world
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where I believe 4 billion people don't
have access to medical imaging. No MRI, no
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CAT scans. Why is the EIT good for that?
It's cheap to mass-produce, super
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portable, super low power. So that would
be a great place to start. What could we
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do first? I'm going to go back to this
image again and have a look. Tuberculosis
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affects a lot of people in the developing
world and you don't need amazing spatial
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resolution to detect it. That would be a
good one. Or what about a pulmonary edema?
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Pulmonary edema is water on the lung. It's
actually already used for that. You can
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quite easily see the different volume
present, or the different conductivity
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maps it's called, of a working lung and a
not so working lung right there.
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Next steps. So what should we do to make
this technique better? What should we do
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for OpenEIT to make it better? If you want
to innovate again, that's the github
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project. Just go ahead. Oh that's an
avocado, it has a seat in the middle. Who
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knew? I do. So I see the two main routes forward
as: One would be this low-cost biomedical
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imaging for the developing world. You
could just stick with the static imaging
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reconstruction because why not. you'd need
a few more electrodes than it currently
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has. One of the main problems with the
technique is how you stick it to the skin.
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So my suggestion for that is why don't you
just use a water bath and stick the body
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part of interest in a body of water,
because water gets rid of a lot of the,
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it's called the contact impedance problem.
Or, on the kind of exciting science front,
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you've got the advancing neuroscience
option. Which would be measuring both high
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spatial resolution and high time
resolution. So that's the non-invasive
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electrophysiology solution. Or, and that
would be super awesome, there's a couple
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of ways forward to do that and I'm going
to sort of discuss each of those.
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So roughly there's physical configuration
improvements that could be done. There's
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things that you can do to improve the
spatial resolution. There's things you can
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do to improve the time resolution. And
this is interesting tack on at the end
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that I thought I'd mentioned, which is
'write' functionality. So we're using very
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small currents to read an image. What if
we pumped the current up a little before
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you know it you're writing. I think not
invasive deep brain stimulation in a
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focused way, that would be very very cool.
So, contact impedance. Major problem right
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now, there is a well-known solution I
haven't done it yet you do this thing
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called differential referencing, common
mode rejection should be done I haven't
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done it that's the next step. That means
that it will work when you just attach it
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with electrodes on the body. What happens
is, electrodes have a like some
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capacitance and different amounts which
kind of interfere with the the measurement
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that you want to make which you want to be
very accurate and just of your body. You
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don't want to include the electrode
information in there that's changing.
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There's a way to remove that that's well
known already. Another physical
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configuration improvements: just increase
the number of electrodes. Wonderful, now
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you've just improved the resolution. Or
the placing the part in water. Another set
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of next steps would be on the mathematical
side. I mentioned that I use linear back
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projection which is a wonderful technique,
that's how they do CAT scans. With X-rays
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that's exactly what they do.
However, it makes some appalling
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assumptions, like parent moves and
straight lines. That is not true. What you
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should do is get a finite element model
and solve Maxwell's equations because
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current bends around objects. Actually it
works in three dimensions too which might
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not be all that surprising but it needs to
be solved for those three dimensions which
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is why you just need to solve
Maxwell's equations and
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create a finite element model.
And there's a quite a bit of work on
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mathematical solutions that get higher
resolution.
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That's another improvement area. And now
as I mentioned this awesome new technique.
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Which, actualy there's a paper on
this year called
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magneto-acoustic electical tomography.
You might remember
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the FBI rule from high school.
When you have a current flowing,
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perpendicular to that there will be a
force. Now that force, say it's vibrating
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with 50 kilohertz. that's the AC signal
that you're sending through. Now you have
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a vibrating compression wave. That's
sound. You can pick that up with a little
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piezoelectric element. And that's actually
a focus of work. From that you can get
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really good edge information, because as I
mentioned earlier, sound scatters at
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edges. So you would also get the
electrical impedance tomography
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information for the tissue sensitivity.
Why not combine those results together and
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you would have a better tool. It currently
gets lesser resolution in the middle
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simply from how you every combination of
electrodes just ends up having a less
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dense number in the middle. You can also
do something as simple as increasing the
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power that you send through if you're game
to do that. This is a kind of gory
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picture. Right now epileptics, if they're
really troubled by their problem, which
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they are often, they go into a hospital
have their brains opened up and they
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stick this array on their head through
their skull. And they leave it open
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for a week. And they try to induce
seizures through sleep deprivation.
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And then they measure the activation
potentials that way to locate the foci or
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where they going to do surgery to stop you
from having seizures. But it would be much
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better and nicer if you could do it not
invasively and you probably can if you
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improve the time resolution of EIT.
there's nothing stopping you from doing
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that by the way. You just have to, like,
it's just a next step really.
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And then I'll also mention write-
functionality. So there was a paper that
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came out halfway through this year by a
guy called Neil Grossman (?) and what he
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did is, he showed that you can stimulate
neurons by sending current through the
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skull and in a focused way. Now why that's
interesting is, you can non-invasively
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stimulate neurons. So that's the write-
functionality. It's unknown what
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resolution is or how well you could
control the the focal point here. But it
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works in the principle of beat frequencies
so he sent through two kilohertz and 2.05
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kilohertz and basically had a beat
frequency of 10 Hertz arise from that and
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basically stimulated neurons in this area
that he can control via an x- and y-axis
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which is very impressive. Leaves a lot of
questions open. Those are some possible
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next steps that it could go in. Obviously
I think this is interesting. I hope that
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you do too. I'd love it if you would want
to sign up to a mailing list I'll give a
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link on the next page. If you want to
collaborate email me. If you know any
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funding bodies that might be interested in
the developing medical imaging for
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the third world I'd love to be put in
contact. If you wanted a kit and, if there
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were enough people that wanted a kit,
probably of the next version which would
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have 32 electrodes sign up to the mailing
list, talk to me. Thanks.
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applause
Rintoul: Thank you
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applause Herald Angel: Thank you
very much. We have a little bit
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time for Q&A. And please if you have to
leave the room make it in a very quiet
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way. So is there ... there are some
questions I've seen microphone 4 first.
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Please go ahead.
Audience member: So, a great thing
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thinking about developing countries and
getting them medical tech. But at the very
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first beginning you said imagine a world
where this imaging would be all available
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like every day and it creeped me out a
little bit. Do you really think that it's
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a good idea to go in the shower in the
morning and have your I don't know your
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bathtub telling you that there is a small
mass inside your lungs.
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Rintoul: That's a good question. Basically
the question was: There's a privacy
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concern with looking inside your body. It
doesn't sound that great to some people.
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To those people I would say you should
turn off I know that sounds a little
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harsh. But please just turn it off, don't
use it. And with all scientific movements
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forward comes great risk, I also say. And
it can be used for good or evil and it's
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up to us as a society how we want to
choose to use it. And how we structure
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ourselves and potentially motivate and
incentivize corporations to use it in a
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responsible way. Part of making this open
is I hope that, basically if people have
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access to it you can choose for yourself
how you'd want to use it.
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Herald Angel: And next question would be
from the Signal Angel please.
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Signal Angel: Yes I have a couple of
questions from the internet. First of all,
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what type of AC frequencies in use? the
asker assumes sinusoidal but he wonders if
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you also tried square wave, triangular and
other shapes.
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Rintoul: That's also a really interesting
question. It's about what kinds of waves
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are used, what kinds of AC signals.
Typically it's done with AC sine waves
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ranging all over the place, depending on
what application you want to use up for. I
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mentioned multi frequency EIT for cancer
detection. That uses a lot of different
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frequencies so if you wanted to use other
waveforms I think that would be really
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interesting. Nobody's tried, you can, that
should be done.
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Herald: So since there's a big queue on
microphone 3 I would go there please.
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Audience member: Yes I have a technical
question. Assuming that you won't use this
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techniques on humans or organic matter at
all and what are the limitations for the
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resolution. The spatial resolution. And is
there a possibility to reduce the spatial
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resolution.
Rintoul: You mean increase the spatial
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resolution or reduce it?
Audience member: Reduce the voxel size
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Rintoul: So increase the spatial
resolution. Yes absolutely. So I was
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trying to go through a few of the next
steps that could get to that. One of them
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is magneto-acousto electrical tomography
because you get two different types of
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information which you could put together
to form a higher resolution image. So
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that's one way and if you didn't need to
worry about human safety I recommend you
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just turn the power up, that will also
work.
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Herald: Okay I think we go back to the
signal angel for one short one please.
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Signal Angel: Yes I have another question
from the internet. from a doctor this
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time. He wonders if there are any clinical
studies that compare pulmonary edema
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diagnostics with EIT to ultrasound and why
don't we just work on cheap ultrasound
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instead.
Rintoul: That's a good question. People
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are working on cheap ultrasounds.
Ultrasound gives different information to
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EIT. It has a problem of the sound
scattering. So it's a different type of
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information which has different pros and
cons. And and I think people should make
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cheap ultrasound. And I would like to see
the hybrid modality come together. You can
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get really good tissue distinction with
EIT so there's pros and cons.
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Herald: Okay then, microphone 2 please.
Audience member: You had a really good
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talk my question so far you always need
direct contact to the electrode, right? So
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it has to be direct contact or in water.
Is there way to detect or measure the
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signal without direct contact? So maybe in
if the if the object is in air or any
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other gas?
Rintoul: Right. I wish there was. No is
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the short answer. Unless ...
Audience member: Any research on making it
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happen?
Rintoul: Well yeah you can you can use
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X-rays. They work wonderfully to to go
through the air. But if you use them I
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mean you do increase your chance of cancer
so don't use them all the time on
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yourself. Again CAT scanners are a little
bit expensive.
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Herald: Thank you and I think we have time
for one more from microphone 3
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Audience member: My question would be
what, so maybe I've missed it, but what's
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the order of magnitude for cost so would
this be feasible at like a hackerspace for
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this to implement. And does the industry
see the possibility to make money.
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Rintoul: Yes a lot of those sort of these
early like R&D papers yeah they should be
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applied and you could make money with it
absolutely. And there's no component in
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there that costs more than a couple of
cents. I suppose a cortex m3 like costs a
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couple of dollars. And I mean I don't know
what your budget is but yes you I think
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you could do this in a hackerspace without
any problems. There's nothing stopping
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anyone from doing this and as we know
microcontrollers are becoming cheaper and
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cheaper. So why not.
Herald: I don't get Hasty's signs from the
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sideline so I think I can take another
question from 2 please.
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Audience member: So far you have showed us
images of 2d planes. What about volumes
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Rintoul: Yes so there's work on solving
for volumes using finite element models
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and solving Maxwell's equations. Basically
I just did the shortest route to reach
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image reconstruction that was available
which was linear back projection which is
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typically done in a 2d plane. So
absolutely, you can do it in three
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dimensions.
Herald: So I'm very sorry we are out of
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time the queue back there you can have the
chance to chat with our speaker just right
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now. The next talk coming up is in about
15 minutes and it's I think also in
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English. See you then and a big round of
applause for our speaker, excuse me.
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applause
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music
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