[Brad Sutton] So the purpose of this video is to show you how a functional MRI scan is done uh at the Biomedical
Imaging Center at the Beckman Institute. We like to use functional MRI to see how different parts
of the brain are involved in different tasks that we might have people do. So by giving people a
task while they're in the scanner, watching the images of their brain, we can tell where what
parts of the brain are active during that task and how the brain is acting differently. And we can
look to see how does that change as you get older, how does that change with various interventions,
how does that change with the types of things that you eat and the types of exercise that you do.
So what we're seeing here is we're seeing the subject, myself, get into the scanner to get
ready for the experiment. They have headphones on and earplugs because it's a really loud
scan. We need to be able to talk to them to tell them the instructions.
That coil being placed over the head is a set of antennas that are going to listen to the
signals coming from the brain. It has lots of elements arranged around the head. That's to
help us so we can image very quickly. Each one of those elements can run a very small imaging
experiment really sensitive to the tissue that's closest to it and so we want to put lots of coils
around the head so that we can get lots of imaging done at the same time. So Aaron is giving me a
squeeze ball because it's a really loud scan. If I have any problems during the scan,
I'm going to squeeze that squeeze ball and it's going to alert him to stop the scan and come in
and ask me questions. In the back of the room, there's a video screen. You can kind of see the
glow off the ground and that's how I'm going to see the task that they're going to present
to me. So Aaron is going to the console uh here to run the scanner. And the first scan is just a
localizer, it allows us to see where the brain is at in the scanner so that we can then prescribe
uh slices in order to image the right parts of the brain for the rest of it. So this first scan
will run very quickly and it will just pop up a set of images that show us the three different
views of the brain. So one from looking at the top down on the head, one from looking at the side of
the head, and then one looking from the front of the head and you can see that here. So it goes
side view and then front view and then top down view as you go across. All those gray boxes at
the edge are the coils that we've placed around the head that are sensitive to the different parts
of the brain. And all we're doing now is just setting up where the next scan should be acquired
in order to give us some better localization. This next scan just does a really quick 3D scan
of the whole head to help us align things automatically for the follow-up scans.
All right the third scan, which is now highlighted in blue, is a structural scan. So what that means
is, it's going to provide a really high resolution scan of the structure of the brain so we're going
to be able to see in fine detail and with really good contrast. So contrast means that we'll have
lights and darks that will show us what the structure of the brain is.
And so this scan will give us approximately one millimeter spatial resolution throughout the
brain, uh maybe a little bit less. I think this one says point eight by point eight by point eight
millimeters uh and it will go through and it'll scan the whole head. And it takes a while to get a
really good structural scan like this so it takes about six minutes for this scan to run. So we will
let this run a little bit. We wanted to give you a little audio to go with it so what you might
hear when you're in the scanner. When you're in the scanner, the scanner makes lots of sounds
and it will make those sounds because uh there are a lot of torque going on
the wires in the scanner and so those can make a great deal of sound while you're in there. And it
can go up to 130 decibels. That's why we have you wear earplugs and headphones as you're in there
so that it'll dampen out that sound. The next two scans after this one's done uh we will be
running some visual uh functional tasks. We're going to look and see what parts of your brain
are responding to a visual flashing checkerboard. So we're going to have you look in the center of
the screen as we display this checkerboard and we're going to scan pictures of your brain. We're
going to take a picture every two seconds of all the slices of your brain and we're going to show
you this flashing checkerboard. And we're going to look for which parts of the brain increase
their signal when the flashing checkerboard is going versus when it's not. So when it's not,
we're going to show you a little plus sign in the background, which is called a fixation cross. So
uh so you'll see here, we have to start the scan and the stimulus, the flashing checkerboard,
at the same time so we know everything's lined up so we know which images go with the flashing
checkerboard scan. So we get this running and you're going to hear that scan sounds quite
different than the structural scan. It's much more choppy but it's acquiring images really quickly.
They're low resolution images and they don't have a whole lot of contrast but the point of this scan
is to get a time series of images of the brain so that we can watch and see where the brain signal
goes up when the flashing checkerboard is on. And so you can see the flashing checkerboard on here
and we would have people on the scanner going to see just one of these screens. I'm showing you two
here but that TV monitor in the back of the room, the subject's able to see it through a mirror
mounted in the coil. And they're going to keep their eyes right in the center on the plus sign,
on the white plus sign. And their visual cortex, the part of the brain processing
the visual information, is going to react to the flashing checkerboard that you see there. And so,
in order to get a signal, we have to do this on and off several times um because the signal and
an MRI scanner may go up and down just based on uh other things that are happening in the
scanner. And so in order to truly believe that the signal we're getting is related to
um it's low when the thing is off and it's high when whatever task we're having you do is on.
Uh we have to do that several times. We have to turn it back off and turn it back on and turn it
back off and turn it back on. And so typically we go through, this is a blocked task, it's
blocked because we have about 20 seconds on and 20 seconds off and we might do four or five repeats.
The visual flashing checkerboard is very robust so we don't need very many repeats to get a good
image of the activation of the brain. And we'll show you how that's processed at the end of the
video here in order to get that activation out. Um Aaron is showing you that we can actually watch
some of these things in real time as they as they come out on the scanner so we can see the activity
show up as we're scanning. Now we're going to do a second task and that is finger tapping.
Uh and so we're going to have people, when they see the flashing checker board, just to tap their
fingers uh. And so we want them to tap all their fingers on both hands and just when the flashing
checkerboard is on and to rest in between. And we have to be very careful. Any motion in the image
will show up as activation so we have to have people sit very still and support their hands in a
way that they don't have to move their hands into position in order to tap because even a slight
motion will move the brain a little bit. In the scanner, you're just laying on a on a pillow in
there and if you shift your hands around your head can move and so we want to make sure people stay
very still. So while the flashing checkerboard is going, they'll be tapping their fingers on
both hands and as fast as they can. And I like to do you know thumb against the first, the second,
third and fourth fingers and then back again and tap through. And we'll have them do that with
both hands and that way both sides of the brain in the motor cortex. The part of the brain involved
in muscle movement is called the motor cortex and we'll see both sides of the motor cortex light up.
Normally you would see crossing over that if I tap my left hand, I would get the right side of
my brain to light up and if I type my right hand, I get the left side of my brain to light up. And
so by tapping on both, we'll see later when we process this data, that we will get both sides
of the brain. All right, so the experiment is over and we're going to let the subject get out here.
And so the room is completely encased in copper and so you can see we have this door that has to
be shut tight. It keeps all the signals outside of the room from getting in. In MRI, you're the
protons in the water in your body are transmitting radio signals so we need to keep all the radio
signals outside the scanner from getting in there. Uh so that we can so that we can pick up on the
radio signals from your protons. So this is the result of the structural scan, you can see there's
good contrast lights and darks. We can see all sorts of structures in the brain. It was a full 3D
scan at 0.8 millimeter isotropic resolution so we can re-slice it and view it in lots of different
orientations. You can see the eyes in that image too so we get lots of information about
what's in the head. So now for the visual task, uh if we think about the visual task, your eyes take
in light and they project it to the visual cortex which is in the base in the back of your brain.
And so we can see what we measured in our scan and sure enough the flashing checkerboard
caused activation in those in those red and yellow pixels. Those are statistical maps,
it's showing us what the z score is, whether pixels increase their signal intensity uh when the
when the flashing checkerboard was on versus when it was off. And so you can see uh that, for the
most part, there's a couple pixels lining up at other places but for the most part this is highly
localized to what is the visual cortex there in the in the back and the base of the brain.
Yep so all the information you're looking at with your eyes goes all the way to the back your head
in order to be processed initially. And then we go to the finger tapping task
with the flashing checkerboard and so what do we expect first? Well uh it turns out your
motor cortex is about halfway back on top of your brain and primary motor cortex and your body is
laid out on that motor cortex. So your fingers for tapping are about a 45 degree angle out
from the edge and so if we look at this I'll point out a couple of things you can see. That
about 45 degrees out from the edge there's a large amount of activation. You can also see there's a
lot of activation here at the base of the brain so the visual cortex is being activated again
because we're giving people instructions uh based on uh the visual signal. They're tapping
their fingers when the flashing checkerboard is on. Okay but you can see that out at the
edge at the top of the head, out at the edge at about 45 degrees, the fingers are showing
up really well here in this task. Okay so please let us know if you have any questions.