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Comment by itslennysfault | Hacker News Reader

That's crazy... Did they bill you for the cost of shutting down the MRI and refilling the helium?

Depending on the mass they may have been able to remove it manually. A colleague used to use paperclips to study the field lines, and those had very little force.

It was easy to remove. No shutdown required.

They probably left it until the next maintenance cycle. Nobody wants the downtime.

Or sent the tech in with a plastic putty knife to scrap it to somewhere he could get a hand on it and rip it out of there.

Even after adding MRI levels of force a 1oz pen is still gonna be something that you can pick up.

Wouldn't that cause heavy distortion in the image though?

I know very little about MRIs, but it seems likely that they could recalibrate the machine and effectively adjust for something small.

Not removing it sounds dangerous though.

The problem is that normal MRI math tries its damnedest to avoid actually solving the right equations. Instead, with a flat enough field, you can assume linearity and just FFT the thing. They'll physically place bits of metal and magnets at various places on the big magnet to calibrate and better adjust the field to being approximately linear. A hunk of metal bigger than a shim sounds like it would mess with that.

Shim it with some more pens?

It would come off ok, this happens from time to time, but that facility needs to lift its game.

Peripheral staff (nurses, anaesthetic techs etc) visiting are the usual source of these accidents.

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