MRI Machines

Tumor in a salivary gland, benign, no big deal. Whipped it out.

John

No, it's full of all sorts of gooey and gooshy stuff.

John

Messy wet stuff. I prefer electronics.

John

Google "They're made out of meat" :-)

You miss my point. It's a cute and classic piece of writing:

Clifford Heath.

There are a number interesting modes of dying involving cryostats.

Best regards, Spehro Pefhany

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The short version is

"If God didn't want us to eat animals, why did he make them out of meat?"

John

Yeah. And I froze my knee once, kneeling on the floor, when I spilled some LN2.

The MRI magnets are usually vented outside, so a quench is no big deal. The ballpark-8-feet-high NMR magnets I work around are no big deal either; in a reasonably-sized room, they don't displace enough oxygen to be a hazard.

Here's a 600 MHz (14T) unvented Varian/Oxford magnet:

At Jlabs, the underground electron accelerator in Virginia, the magnets are big, in a small tunnel, and there are alarms and blowers and stuff. If one quenches, staff are instructed to clear out pronto.

John

Look at the bright side: Until you lose consciousness you can speak at a high pitch like Mickey Mouse because of the helium. Should be fun ;-)

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And made into video too:

I had a full head MRI about a year ago. I don't suffer claustrophobia and can tune out pretty much any noise. They actually had to nudge me awake to put the gadolinium contrast IV in.

hmm, can one make a homebrew version, with a little less power output, something sized to scan a cricket leg?

That entirely depends on the size of your bank account. And probably on whether you are married or not. Because you won't have much time for your family for the next 10 years or so and the garage will be a royal mess.

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me

ss.

if all you want to do is determine composition, you can do that on a table top at home with some work and a good frequency synthesizer.. Getting a image, however would probably involve as stated above" 10 years, a divorce, a messy garage" and the addition of a array of 10 PCs running linux in parallel. Seriously, if you want to play with NMR/MRI at home, search "proton procession magnetometer"

I work 10 floors above a bunch of nmr magnets, I believe they are a

3, a 5, and a 9 tesla. We have to map the fields in the building for professors with pacemakers, but they usually only show up on the gaussmeter to maybe 10-20 feet above the magnets and almost nothing to the sides. A quench usually is just a loud BANG, followed by much louder cursing as they calculate the bill for new coolent and the cost of flying in the technician and gear to reactivate the field. I think in 8 years of working here I've only seen 2 quench events. If they do quench, the coolent is already mostly gone before the actual event. Since the NMR coils are ring superconductors, you only supply energy to create the field , then disconnect the charger system until you need to do any repair work, which may be years down the road, the I^2R losses are that low.

Steve Roberts

Steve Roberts

I think the first ever MRI could just about manage a finger.

Still needs a fairly juicy magnet though.

I think a single PC would be enough for the sort of resolution a home-brew kit would be likely to acheive. And getting the linear field gradient right always seemed to be something of a black art.

What impresses me most are the mobile MRI vans. I presume with the magnet cold all the while and self calibrated realligment. Ordinary fixed installation ones take a lot of moving.

Regards, Martin Brown

** Posted from **

Are you sure? I thought that the coils attached to the patient (mask etc?) were for creating the RF field to excite the resonance and for picking up the return signal, and the gradient coils were within the magnet casing. The forces on the gradient coils must be quite large, and that may explain the noise.

AFAIK the EU has decided to make more advanced MRI pretty much illegal (or more precisely, approaching the MRI machine much faster than a snail could travel subjects you to an "electromagnetic" field that some guy with a nice tin hat told a credulous eurocrat might sprain your Chi or something like that). So a bunch of people who know not much about physics made up some laws and then when someone competent finally read the directive it was too late so they just asked the member states to not enforce it for a while or something. Anyway when these eurocrats end up getting sick, they'll find out that they need to go to the US for the most advanced diagnistic scans since they banned it in the EU. The pity is that they will have been well enough paid to afford it whereas others won't and will have to use nice safe x-rays instead of those nasty magnetic fields.

Chris

Could be. The gradient coils may be a bit farther out. On the NMR systems, which I actually get to see the insides of, the RF coils are inside, closest to the sample, and the gradient coils are outside them, at room temp, and the main superconductive magnet is outside all that.

Yup, I think these are MRI gradient coils...

Yeah, that's crazy. If you look at the allowed levels of AC mag fields, it becomes illegal to walk, talk, or chew inside the Earth's static field.

John

Wait until their CO2 taxes fester some more. Then Europeans may have to get their lung volumes measured and a poll tax is assessed based on the results ;-)

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Aha! Then BLOWHARD will be taxed heavily ?:-)

...Jim Thompson

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