This is your brain in a magnet
This morning I went back to the Mass General Hospital's imaging
facility in Charlestown, to participate in an experiment for David
Gow. The previous
experiment used magnetoencephalography (MEG) and
electroencephalography (EEG) for brain imaging. Today was an
experiment using functional Magnetic Resonance Imaging (fMRI), which
provides more detailed images of the brain, but is more cumbersome.
I've done fMRI once before, so I had some idea what to expect.
Click on the thumbnails for the full size picture.
First things first: I have to get rid of all metal, so that means no
jewelry, no wireframe glasses, no clothes. Here I am wearing the
silly hospital johnny and special plastic eyeglasses which have no
metal in them. I could have worn my contact lenses, but I will need
to keep my eyes open to see the computer screen, and my last
experience showed me that my contact lenses dry out and get
uncomfortable under such conditions. So I wear these things and look
like Elvis Costello's dweeby brother.
Through the window behind me, you can just see the massive toroidal
magnet with the light shining through the hole in the middle -- that's
where I'm about to go. You can also see David Gow in reflection,
taking the picture.
Then we go into the magnet room and I get "tucked in" to go into the
magnet. In order to keep my head still, they fit my head into a
cradle, pack it all around with foam rubber and headphones and all,
and then fit the "Hannibal Lecter" cage over my face. The cage
includes a little mirror, which reflects the computer screen at the
other end of the hole through the magnet. In turn, the screen is
projected through a window from a computer in another room. During
the experiment, I will hear stimuli over the pneumatic headphones, and
watch the screen for reference responses.
Here, Christina has got me set up with a button box in one hand (for
responses) and a squeeze bulb in the other (for emergency signal, if
it's needed), although she also put a sheet over me so you can't
really see them. Remember, no metal allowed anywhere near the magnet,
so all these pieces of equipment are plastic. They can talk to me
over the headphones, but unlike the SQUID, they can't have a
microphone near me once I'm inside, so I communicate using the squeeze
bulb.
The Squeeze -- claustrophobia
Inside all this stuff, I had expected to deal with mild
claustrophobia, but the first time in the magnet was really bad -- I
was panicky enough that I made them take me out. They turned on a
ventilator, giving a little breeze of fresh air flowing through the
magnet, and that made the difference -- I was okay, and I went back in
with no major problems.
Christina takes me back out again, to talk with me. It's hard to
communicate during this experiment. Unlike the SQUID, the
magnetometer is very noisy: it beeps and burps and squeals and blats
while operating, and there's also the constant thumpa-thumpa of some
kind of pump at about 120 beats per minute. I told them how much it
sounded like the background music at Burning Man, and they all got a
kick out of it.
But there was a problem with their equipment. The experiment sequence
would start and then hang right away -- getting stuck somehow. They
called in specialists from other parts of the lab, and rolled me in
and out a couple of times while messing around, but couldn't get it
straightened out. So, after all that effort, we didn't collect any
data -- bummer! They'll take some time to fix the problem and I'll
come back, probably in a couple of weeks, to run the experiment again.
Film at 11.
This page maintained by
Wil Howitt
or wil a t otolith d o t com
Last updated 4 August 2005
