34C3 - Low Cost Non-Invasive Biomedical Imaging

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

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