Re: MRI Machines

On Tue, 24 Jun 2008 19:30:42 -0400, RFI-EMI-GUY
<Rhyolite@xxxxxxxxxxxx> wrote:

Jim Thompson wrote:
On Tue, 24 Jun 2008 11:34:07 -0700, John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Tue, 24 Jun 2008 13:28:46 -0400, RFI-EMI-GUY
<Rhyolite@xxxxxxxxxxxx> wrote:

Well I spent a half hour of my life under the magnet of an "open" MRI
machine yesterday. Still a bit claustrophobic. While I sort of
understand the theory of the MRI, what I don't understand is what
creates all the noise and racket. Any experts out there that can tell me
whats going on?
Pulsed gradient coils. These are "small" 3-axis coils that sweep a
gradient field across your innards, modulating the nuclear resonant
frequencies of your molecules to produce the spatial resolution. These
are generally water-cooled, with ballpark 20 KW constant-current
drivers per axis, playing all sorts of weird waveforms.

They scanned my head last year, with the gradient coils around my head
like some horror mask: noisy and boring.

John

A few years ago they scanned my sinuses.

I must admit a claustrophobic feeling also :-(

...Jim Thompson

I told the tech to give me a time check every so often so I wouldn't
lose my mind, then I worked out a design problem in my head for 30
minutes as a distraction. I can put up with a lot of stuff but being
inside or under that thing creeps me out. I keep having visions of
oxygen cylinders getting sucked through the drywall and crushing me or
the magnet quenching and getting burned in a puff of steam.

What an absurd fear. It quenches, a lot of cold helium blows out, the
O2 in the room is displaced, and you die painlessly of asphixiation.

John


.

Relevant Pages

  • Re: MRI Machines
    ... While I sort of understand the theory of the MRI, what I don't understand is what creates all the noise and racket. ... gradient field across your innards, ... They scanned my head last year, with the gradient coils around my head ...
    (sci.electronics.design)
  • Re: MRI Machines
    ... While I sort of ... They scanned my head last year, with the gradient coils around my head ... then I worked out a design problem in my head for 30 ... the magnet quenching and getting burned in a puff of steam. ...
    (sci.electronics.design)
  • Re: MRI Machines
    ... While I sort of understand the theory of the MRI, what I don't understand is what creates all the noise and racket. ... gradient field across your innards, ... They scanned my head last year, with the gradient coils around my head ...
    (sci.electronics.design)
  • Re: MRI Machines
    ... While I sort of understand the theory of the MRI, what I don't understand is what creates all the noise and racket. ... gradient field across your innards, ... They scanned my head last year, with the gradient coils around my head ...
    (sci.electronics.design)
  • Re: MRI Machines
    ... While I sort of ... gradient field across your innards, ... They scanned my head last year, with the gradient coils around my head ...
    (sci.electronics.design)