Magnetic Attraction

Today I had an interesting and unique experience – I had my brain scanned by functional magnetic resonance imaging (fMRI). The point of this was to take part in one of my friend’s psychology research experiments, earn �27 and also (arguably most importantly) get a picture of my brain.

Doing an fMRI is an unusual thing. Magnetic resonance imaging basically involves using big electromagnets positioned around your body to line up all of your atoms in one direction. Once they’re lined up, the electromagnets are then used to give them a nudge, which makes them vibrate and throw out electromagnetic radiation that can be detected by yet more magnetic fields. The salient points here are that MRI involves lots of big and powerful magnetic fields.

By big, I mean a very big and loud machine that (in this case) wrapped around my entire body with little room to spare. By powerful, I mean a 3 tesla magnetic field, which is roughly 50,000 times greater than the Earth’s magnetic field. This of course means that you have to be really careful not to take any metal into the MRI scanner room, or even worse, the MRI scanner itself, lest it fling itself out of your grip and slam against the magnet casing, cutting through anything that happens to be in its path along the way (e.g. clothes, flesh, etc).

I’ve encountered MRI scanners before. When I was in San Diego, the lab I worked with did some research with MRI so I had a chance to check that out. These things are very automated these days – you can run them with just one person, providing they know what they’re doing. The safety aspect was quite relaxed in San Diego; I had a chance just to stroll into the scanner room while the machine was on after a quick and cursory check for offending metal objects.

In contrast, at Cambridge I had to sign all sorts of forms (because I was a test subject this time) and undergo a thorough metal check; my sweater was not acceptable because it had a couple of metal clips. Glasses, watch and belt also had to go – but not trousers, because apparently if the metal is ‘attached’ to clothes then it’s OK.

Next, I lay down on the scanning bed and put on some ear plugs and ear protectors. I was instructed not to move my head at all during the scanning, which was expected to take about an hour, and they helpfully gave me a leg rest so I could lie down more comfortably. I also got a blanket.

Thus equipped, the scanning bed carried me into the depths of the scanner. This MRI scanner was a full body one, capable of imaging all parts of the body. However, for this experiment, they just wanted to look at my brain*. Anyway, in order to reduce the power needed for the magnets, the scanner is as compact as possible, which means there’s only a few inches of clearance between your body and the walls of the scanner. A bit like a coffin, I imagine. Apparently a lot of people have real claustrophobia problems when they start to slide into the scanner, but I felt fine (clearly I have an underdeveloped survival reflex). Likewise, it wasn’t too bad when I was fully inside the scanner.

(*Apparently the Cambridge University MRI group is trying to buy their own head-only scanner).

They had a little mirror set up just above my nose so that I could see a computer screen being projected onto the wall behind the scanner (no screens, because they contain metal). In my right hand was a little switch I used to send my responses for the experiment, and in my left was a panic button in case I had to get out quickly.

The whole thing took maybe 80 minutes; the experiment only lasted about 40, but they had to calibrate the scanner beforehand so that they could image the right slices of my brain, and afterwards they had to do a full structural imaging of my brain. During all of this time the scanner made lots of strange humming noises (not as loud or unpleasant as I expected). In fact, I didn’t even mind having to lie in the same position or keep my head still.

Granted, I did doze off a couple of times during the experiment (I’m told everyone does) and I really did need to go to the toilet towards the end, but it was all good. I can now rest easy in the knowledge that images of my brain will help the grand progress of science in some small way, and also that I’ll be getting a picture of my brain in a few weeks.

(Some notes. I gave a very simplified explanation of how MRI works – here’s a more detailed explanation. Also, when I say ‘functional MRI’, I simply mean that the scanning is producing a video of my brain’s activity (i.e. how it is functioning) rather than just a single static picture of its structure).

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