The main magnetic field (B[sub]0[/sub]) of MRI machines doesn’t really have an idle per se. The field is always on at the rated field strength of the scanner (0.1-3 Teslas clinically) and the scan area is subjected to radio waves when the machine is “on” and actively scanning.
Also, as you stated, metal-object safety is important in MRI scanners. Listen to the techs and don’t try to sneak something metal in.
Expanding a bit on this, once you bring a superconducting magnet to field, you don’t need to pump more current in to maintain the field; as long as the superconductors remain below their critical temperature, the field will remain up.
Keeping them below said critical temperature involves refilling the liquid nitrogen and liquid helium reservoirs periodically. If they warm above the critical temperature, they abruptly cease being superconductive and become resistive, which heats them up further, which makes them more resistive, so on and so forth, until the liquid helium suddenly turns to gas and is released in a very loud and very expensive white plume. This is called a “quench”.
I’ve seen exactly one quench; the tech from Varian was bringing our new 300 online when it quenched. I’m told one of the old 200s we have did a cold quench (the magnet slowly demagnetized while being kept cryo), which is much rarer.
I’ve always found MRIs (I’ve had them on my head) to be a wonderful place to take a nap, especially after school.
When I got mine I had no idea what to expect. I glanced at it and I couldn’t tell the opening was a hole, I thought it was just a concave area I would sit near. Then they rolled the table out from inside it. That was a shock.
It took a few minutes to relax inside but eventually I almost fell asleep.
Well, I’ll have my mp3 player with me; who knows if they’ll let me use it? Since my actual head won’t be in the contraption, they might; then again, it’s close enough to the magnet, they might not be able to. At any rate, I’ll be sedated (I’ve confirmed my ride for tomorrow), and they may be able to plug it into the sound system. I have all my “old people” music on it! 
'Twas my very first experience with public hysteria. Sobbing, gasping, choking, charming. Fortunately there was an unoccupied anesthesiologist available so I could get it done. Sedation rocks!
I get regular (every 6-12 months) MRIs of my head to check my multiple sclerosis.
They probably won’t let you take the iPod in the room - they pretty much strip everything made of metal off of you at the start. My feet hang out of the machine and I’m still not allowed to wear shoes, even shoes that I’m sure have no metal in them. But I’d be surprised if they don’t have a sound system they can hook you up to. At my facility, they come in and hand you a list of the CDs they own, and you choose one to listen to during the scan. There was plenty of “old people” music on the list. Have them turn the volume up louder than you think you want it - it is very loud listening to the buzzing and clanking of the machine.
I am a fidgeter and I have never needed sedation. The contrast agent did make me throw up the first time I had one, but not since. Will you have contrast injected?
Good luck! I was pretty scared for my first one (but that was partly because they were screening me to see if I’d had a stroke - I arrived at the ER with my main complaint being that I could only taste on one side of my mouth). Since then, it’s easier than going to the dentist, really, and no one asks me questions while they have their hands in my mouth.
I had an MRI to check my brain was there and in working order some years ago. 
I stripped myself of all my jewelry. The strange thing is I was offering to take off my harness boots which have giant metal rings on the ankles and I remember the tech going all indecisive since – possibly – I was only going to be in it up to my knees or so. :dubious:
Since I’m deaf, the noise didn’t bother me. However, the dimness and the vibrating of the machine humming to itself combined to drag me inevitably toward dreamland. I kept waking myself up because I was worried that the techs might not want to see what scans of a sleeping brain looked like. In retrospect that was probably somewhat illogical, but that was my thought process at the time.
(You should see me when I’m the passenger in a car – I can konk right out!)
Don’t bring the mp3 player into the room with the MRI. They may be able to plug it into the sound system in the control room, but if they can’t, make sure you leave it outside the MRI room.
1.) WOOOOOOT! for Godspell.
2.) May I borrow the soundtrack?
3.) I’ve had a handful or so done on my knee/two on my stomach and I would get super fidgety. As a way to help myself get around this during the MRI, I would do an activity that required a lot of concentrated movement before I had to go to the appointment. Then, while in the waiting room, I would do something-or-another-akin-to meditating exercises to help calm down.
Oh, and fair warning, if you go to the one at Memorial, it talks to you. Voice = SUPER ANNOYING! Rather grating as well, too. Also, hope that all turns out for the better with the results!!!
ENugent, I don’t know if I’ll have contrast dye or not. I’ve had it before, though, for CTScans, and the only problem I have with it that my veins are a bitch to find! 
engineer_comp_geek, thanks for the warning about the mp3 player; a friend is driving me. If they won’t hook my player up to the sound system, I’ll leave it with the friend who is driving me. I guess I’ll take off all my jewelry before I go (I have a necklace and three rings I wear pretty much all the time. . .)
Her Royal IMFness, let’s address your questions one at a time. One, yes, w00t for Godspell. Two, yes you may borrow it. Three, meditation sounds like a good idea; of course, if they give me enough Xanax, my entire thought process will consist of “oooooh, pretty”. Four, no, it’s not at Memorial. It’s at The Imaging Center. Don’t know if that one has an annoying voice or not.
I’m leaving here about 11:15 to go get the test, so I’ll let you all know later when I’m capable of posting again.
I do not suffer from claustrophobia so I have no problems with CAT scans or MRIs. Except for the noise (MRIs are very loud) I would easily just go to sleep.
If you are not going in head first, I don’t think you will have any problems at all.
That describes it perfectly. I had one years ago for migraines, so I only went into it up to my shoulders. A lot of people hate being in the enclosed space, but I didn’t mind it.
If there’s been a spider in there with me, however; I would have freaked.
I had mine today, for my breast cancer, and it didn’t bother me.
I picked country music, and hearing Tim McGraw’s *Live Like You were Dying * was a bit :eek: :dubious:
I had one in 1989, and another in 1990 for knee injuries.
The first one was just boring as hell, and there was a little air vent blowing on my feet, so they got really cold.
The second one was much like the first, although without the vent, and my mom went with me and we chatted during it, which made it much less boring.
Basically, MRI = boring and loud.
I’ve never considered myself to be claustrophobic, but after thinking about lying down for an hour in one of those things… darn.
Maybe I’m lacking in culture, but I don’t get this at all. Who is John Cage, and why is his music bad (or good) for being trapped in a small metal tube?
John Cage’s most famous piece was 4’33". Four minutes and thirty-three seconds of the performer doing nothing at all - in other words, you get to listen to ambient sound for 4’33".
In this case, ambient sound consists of the MRI machine doing its best impression of an unbalanced washing machine grinding gears.
Tell me about your experience with MRI:
About like lying in a garbage can while a truck runs it over. Very very loud, very confined, very tedious. Not horribly unpleasant, but I asked for and got a sedative, or I would have felt extremely uncomfortable and claustrophobic.
I had one a year ago.
Head first pretty much the whole body went in. It was to check my ears.
I picked a Beetles CD. They asked.
It was boring.
My recommendation, make sure you blow your nose and pee first. Do it twice.
Otherwise, no big deal. It will bang and buzz a bit. But it’s just doing it’s job.
I got a DVD of my head afterwords. Pretty cool.