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