MRI Disarms Police Officer


(Rochester-WABC, September 15,
2000) _ An off-duty cop lost his
side-arm this week after a magnetic
resonance imaging machine ripped it
from his hand, shooting off a round
at a clinic in Rochester.


The Sergent, who was visiting the
suburban clinic to undergo an MRI,
mentioned to the staff that he had his
handgun with him. Sgt. William Benwitz
was told it was all right to keep it during
the scan, but as soon as he entered the
room, the MRI's heavy duty magnet
yanked the .45 caliber gun out of his hand,
causing it to fire once. No one was hurt,
and the bullet lodged into a wall of the
clinic.


It took three hours to power down the
magnet and free the weapon. An MRI is
four times as powerful as magnets used to
lift cars in junkyards.


Sgt. William Benwitz, who runs a
firearms training unit, said it would be too
risky to try firing the weapon because its
molecular structure might have been
altered. ``Until we send this gun back to
the factory, we're not even going to
test-fire it,'' he said in Friday's Rochester
Democrat and Chronicle. ``The metal is
more brittle than it should be.''


(Copyright 2000 by The Associated
Press. All Rights Reserved. AP
Contributed to this report.)

"Considering the events of recent years,
the world has a long way to go to regain
its credibility and reputation with the US."
unknown

Gunner wrote:

MRI Disarms Police Officer


(Rochester-WABC, September 15,
2000) _ An off-duty cop lost his
side-arm this week after a magnetic
resonance imaging machine ripped it
from his hand, shooting off a round
at a clinic in Rochester.


The Sergent, who was visiting the
suburban clinic to undergo an MRI,
mentioned to the staff that he had his
handgun with him. Sgt. William Benwitz
was told it was all right to keep it during
the scan, but as soon as he entered the
room, the MRI's heavy duty magnet
yanked the .45 caliber gun out of his hand,
causing it to fire once. No one was hurt,
and the bullet lodged into a wall of the
clinic.


It took three hours to power down the
magnet and free the weapon. An MRI is
four times as powerful as magnets used to
lift cars in junkyards.

Quite amazing, as almost any hospital that has an MRI machine has had an
accident of some sort with it. It might only have been a pocket
screwdriver, keyring or ballpoint pen, but it usually gets the message
across. Also, the machines will not give good images if any metal of
any type is inside the magnet, as it distorts either the static or
dynamic magnetic fields (or both) inside.

I would suspect the gun is scrap, as it would have hit the magnet
with enormous force. I know of several MRI accidents which caused
serios injury or death. At Johnson&Johnson's Technicare unit, a
forklift strayed too close to an operating magnet and was yanked across
the room. A technician was killed, and the lift truck operator was
injured. At a hospital in St. Louis, a compressed gas bottle that
was SUPPOSED to be aluminum was thrown across the MRI room and nearly
killed several people. At another hospital, a floor buffer was picked
up and slammed against the machine.

Jon

Hey,

I am waiting for an MRI on my knee and while filling out the form it
asked about all things metal. Infact it's the first form (even at the
hostpital) where I have been asked if I have a Penis Implant (are they
metal?!) I find it strange that the staff at this hostpital thought
nothing of a gun?? I actually had a metalworking magazine with me in
the waiting area and they almost didn't give me the form as for my
injury they wouldn't usually 'risk' a metal worker with the MRI. I
guess enough people who work with metal every day (machinist and welders
they mentioned) have so many metal slivers the MRI tries to remove them
all at once.

TTYL, Jeff


Gunner wrote:

MRI Disarms Police Officer


(Rochester-WABC, September 15,
2000) _ An off-duty cop lost his
side-arm this week after a magnetic
resonance imaging machine ripped it
from his hand, shooting off a round
at a clinic in Rochester.


The Sergent, who was visiting the
suburban clinic to undergo an MRI,
mentioned to the staff that he had his
handgun with him. Sgt. William Benwitz
was told it was all right to keep it during
the scan, but as soon as he entered the
room, the MRI's heavy duty magnet
yanked the .45 caliber gun out of his hand,
causing it to fire once. No one was hurt,
and the bullet lodged into a wall of the
clinic.


It took three hours to power down the
magnet and free the weapon. An MRI is
four times as powerful as magnets used to
lift cars in junkyards.


Sgt. William Benwitz, who runs a
firearms training unit, said it would be too
risky to try firing the weapon because its
molecular structure might have been
altered. ``Until we send this gun back to
the factory, we're not even going to
test-fire it,'' he said in Friday's Rochester
Democrat and Chronicle. ``The metal is
more brittle than it should be.''


(Copyright 2000 by The Associated
Press. All Rights Reserved. AP
Contributed to this report.)


"Considering the events of recent years,
the world has a long way to go to regain
its credibility and reputation with the US."
unknown

In article , Gunner says...

The Sergent, who was visiting the
suburban clinic to undergo an MRI,
mentioned to the staff that he had his
handgun with him. Sgt. William Benwitz
was told it was all right to keep it during
the scan,

Something's funny here - was he holding the weapon in has *hands*?

Even the rivets in a holster or belt would have been too much
for an MRI magnet. I think somebody's either really really
stupid (and has already been fired) or this is one of those
stories that won't stand up under a snopes microscope.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

In article rs.com, Jon Elson
says...

injured. At a hospital in St. Louis, a compressed gas bottle that
was SUPPOSED to be aluminum was thrown across the MRI room and nearly
killed several people.

In NY a child was killed by a "non-ferrous" O2 bottle recently
as well.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

jim rozen wrote:
In article , Gunner says...


The Sergent, who was visiting the
suburban clinic to undergo an MRI,
mentioned to the staff that he had his
handgun with him. Sgt. William Benwitz
was told it was all right to keep it during
the scan,


Something's funny here - was he holding the weapon in has *hands*?

Even the rivets in a holster or belt would have been too much
for an MRI magnet. I think somebody's either really really
stupid (and has already been fired) or this is one of those
stories that won't stand up under a snopes microscope.

Jim



I expect the officer felt a tugging at his holster, instinctively
grabbed the gun as it was exiting the holster.

--
- -
Rex Burkheimer
WM Automotive
Fort Worth TX

In article , Rex B says...

I expect the officer felt a tugging at his holster, instinctively
grabbed the gun as it was exiting the holster.

No MRI tech would ever let a fully clothed, armed individual
*near* the machine.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

In article ,
jim rozen wrote:
In article , Gunner says...

The Sergent, who was visiting the
suburban clinic to undergo an MRI,
mentioned to the staff that he had his
handgun with him. Sgt. William Benwitz
was told it was all right to keep it during
the scan,

Something's funny here - was he holding the weapon in has *hands*?

Even the rivets in a holster or belt would have been too much
for an MRI magnet. I think somebody's either really really
stupid (and has already been fired) or this is one of those
stories that won't stand up under a snopes microscope.

Jim


Hey, I just had an MRI done yesterday. I spent some time talking with the
people there and learned several neat things. First of all, if you have ever
made metal chips or gotten a face full of rust from under a car, you need to
tell them. They will take x-rays of your head to see if you have any loose
fragments in there. Um... yeah... Ok, the only place a metal sliver is a
problem is in the eyes. If you have one elsewhere in the body, the scar
tissue that forms around it will hold it in place. The same holds true for
surgical staples, etc. They still want to know about them, but they can work
around them. Metal slivers in the eye will be encapsulated (so they don't
irritate things) but no scar tissue ever forms on it, so it is mobile. The
magnet can move this around and the concern is that it will damage the
retina or optic nerve. Implants and such are usually secured well enough
that they aren't worried about them tearing loose, only distorting the
images. Small ferrous objects that make it into the room aren't usually a
problem if they are not loose (they didn't have a problem with the rivets in
my jeans or the metal lugs on my shoes. Presumably, they are well secured
enough and small enough to not shoot across the room). For the most part,
non-ferrous is fine so long as it isn't in the magnet with you (distorts the
image) but ferrous is a no-no. The bigger it is or the less it is secured to
something, the worse the situation. A steel rivet on a belt, not a problem,
an unsecured side arm in a persons hand, big problem. An artificial hip that
is well healed, probably not a problem as it is well secured to you and you
are fairly massive (and well secured to the table).

Some tattoos (specifically "permanent make up") may become irritated, but
that has less to do with the big super-conductive magnet and more to do with
the big pulsing magnet they use to generate the signals they are looking
for. Conductive particles and changing fields and you get heat. On your arm,
probably not so noticeable, but in your eyelids, you may notice it.

All in all, a wondrous, magical machine. Even after learning how they get
an image out of all that stuff, it is still just this side of magic.

In article , ( says...

Hey, I just had an MRI done yesterday. I spent some time talking with the
people there and learned several neat things. First of all, if you have ever
made metal chips or gotten a face full of rust from under a car, you need to
tell them. They will take x-rays of your head to see if you have any loose
fragments in there. Um... yeah... Ok, the only place a metal sliver is a
problem is in the eyes. If you have one elsewhere in the body, the scar
tissue that forms around it will hold it in place. The same holds true for
surgical staples, etc. They still want to know about them, but they can work
around them. Metal slivers in the eye will be encapsulated (so they don't
irritate things) but no scar tissue ever forms on it, so it is mobile. The
magnet can move this around and the concern is that it will damage the
retina or optic nerve. Implants and such are usually secured well enough
that they aren't worried about them tearing loose, only distorting the
images. Small ferrous objects that make it into the room aren't usually a
problem if they are not loose (they didn't have a problem with the rivets in
my jeans or the metal lugs on my shoes. Presumably, they are well secured
enough and small enough to not shoot across the room). For the most part,
non-ferrous is fine so long as it isn't in the magnet with you (distorts the
image) but ferrous is a no-no. The bigger it is or the less it is secured to
something, the worse the situation. A steel rivet on a belt, not a problem,
an unsecured side arm in a persons hand, big problem. An artificial hip that
is well healed, probably not a problem as it is well secured to you and you
are fairly massive (and well secured to the table).

My niece was in a bad car crash last year and fractured a number of
vertebrae. Before they could do the MRIs needed to image the area
before surgery, they had to do an endoscopy on her first. She
had swallowed her tongue stud. That would have been a problem in
the magnetic field, apparently.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

On Mon, 14 Mar 2005 03:01:03 GMT, Gunner wrote:

Sgt. William Benwitz, who runs a
firearms training unit, said it would be too
risky to try firing the weapon because its
molecular structure might have been
altered. ``Until we send this gun back to
the factory, we're not even going to
test-fire it,''

A reasonable precaution, but...

he said in Friday's Rochester
Democrat and Chronicle. ``The metal is
more brittle than it should be.''

....but not for that reason. A DC magnetic field (the only
thing present when a scan isn't happening) isn't going to make
anything brittle. Magnetized, sure, but not brittle. I base
this on 12 years in the field (heh...) worth of experience.

Dave Hinz

On 14 Mar 2005 05:03:59 -0800, jim rozen wrote:
In article rs.com, Jon Elson
says...

injured. At a hospital in St. Louis, a compressed gas bottle that
was SUPPOSED to be aluminum was thrown across the MRI room and nearly
killed several people.

In NY a child was killed by a "non-ferrous" O2 bottle recently
as well.

Key point being, it wasn't non-ferrous, and they failed to check.

On Mon, 14 Mar 2005 07:30:54 -0500, Jeff Williams wrote:
Hey,

I am waiting for an MRI on my knee and while filling out the form it
asked about all things metal. Infact it's the first form (even at the
hostpital) where I have been asked if I have a Penis Implant (are they
metal?!) I find it strange that the staff at this hostpital thought
nothing of a gun?? I actually had a metalworking magazine with me in
the waiting area and they almost didn't give me the form as for my
injury they wouldn't usually 'risk' a metal worker with the MRI. I
guess enough people who work with metal every day (machinist and welders
they mentioned) have so many metal slivers the MRI tries to remove them
all at once.

Nah, it won't take out a metal sliver, they're too small to have
much pull on them even with that large of a magnet. You have _stronger_
magnets in your computer's hard drive, by the way.

What it'll do, is _maybe_ wiggle it around a bit in uncomfortable
ways; the long axis of the sliver wants to align with the
magnetic field at that location. Won't move it, though. From an
imaging perspective, it'd give a distored (spacial and contrast)
image in that location out to maybe an inch or two, depending on
how big it is and it's shape. RF Heating might also be a concern,
but less so than the discomfort and image problems.

Dave Hinz

On 14 Mar 2005 04:54:28 -0800, jim rozen wrote:
In article , Gunner says...

The Sergent, who was visiting the
suburban clinic to undergo an MRI,
mentioned to the staff that he had his
handgun with him. Sgt. William Benwitz
was told it was all right to keep it during
the scan,

Something's funny here - was he holding the weapon in has *hands*?

Even the rivets in a holster or belt would have been too much
for an MRI magnet. I think somebody's either really really
stupid (and has already been fired) or this is one of those
stories that won't stand up under a snopes microscope.

It'd be easy to research this one. If someone was injured, the FDA
will have records online.

"Dave Hinz" wrote in message
...
You have _stronger_
magnets in your computer's hard drive, by the way.

I didn't know they could produce permanent magnets anywhere near 2T, let
alone 20.

Boy, those are some impressive magnets then... hey, they'd make great
replacements for those tricky superconducitng rigs in MRI's!
BG

RF Heating might also be a concern, but less so than the discomfort
and image problems.

That's an UL with tatoos, but as I recall it only causes a little
distortion, not really any heating or "pull".

Tim

--
"California is the breakfast state: fruits, nuts and flakes."
Website: http://webpages.charter.net/dawill/tmoranwms

On Mon, 14 Mar 2005 14:53:35 -0600, Tim Williams wrote:
"Dave Hinz" wrote in message
...
You have _stronger_
magnets in your computer's hard drive, by the way.

I didn't know they could produce permanent magnets anywhere near 2T, let
alone 20.

Most MRI systems are 1.5T. Some of the newest ones are 4T, but those
are few and far between.

When I worked in MR Engineering, we, well, were playing around with
magnets, oddly enough. The permanent magnets in a Hawk hard drive
(1 gigabyte full height - these were old) came in above the measurement
capability of our gauss meter, which went up to above 4T. So, at
the surface, it's more than a 4T permanent magnet, in those drives.

Boy, those are some impressive magnets then... hey, they'd make great
replacements for those tricky superconducitng rigs in MRI's!
BG

It's strong, but the field isn't anywhere near even (parts per billion
is needed), or large enough.

RF Heating might also be a concern, but less so than the discomfort
and image problems.

That's an UL with tatoos, but as I recall it only causes a little
distortion, not really any heating or "pull".

Um, no. RF Heating is a real and measurable phenomenon in MRI imaging.
The "SAR" (specific absorption ratio) calculates just how much RF
you can pump into the patient, based on their mass. Also, RF
coupling to the body coil can increase this; some brands of MRI
scanners have "decoupling plates" where the patients' arms go,
so that they don't get the warming (and detune the system...) by
getting to close to the RF coil. Different manufacturers probably
handle decoupling in different ways, but a simple spacer does wonders.

On 14 Mar 2005 10:40:05 -0800, the inscrutable jim rozen
spake:

In article , Rex B says...

I expect the officer felt a tugging at his holster, instinctively
grabbed the gun as it was exiting the holster.

No MRI tech would ever let a fully clothed, armed individual
*near* the machine.

True, but then there was last week's movie about the undercover
cop teaching the community about safe handgun handling when he
shot himself in the foot. That was right after he told them he
was the only one in the room professional enough to handle a
weapon. I pity that community and their police force if he's
an example of screened personnel, don't you?

http://www.ogrish.com/archives/cop_a...r_09_2005.html

--
EAT SOYLENT McD!
----------------------
http://diversify.com People-free Websites

In article , Larry Jaques says...

No MRI tech would ever let a fully clothed, armed individual
*near* the machine.

True, but then there was last week's movie about the undercover
cop teaching the community about safe handgun handling when he
shot himself in the foot. That was right after he told them he
was the only one in the room professional enough to handle a
weapon. I pity that community and their police force if he's
an example of screened personnel, don't you?

I'm not going to tell you what *one* officer left behind at the
range one day.

But it was blue and it went bang.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

Um, no. RF Heating is a real and measurable phenomenon in MRI imaging.
The "SAR" (specific absorption ratio) calculates just how much

early 80's, former coworker working with mri r+d. screwing things into
the power cabinet. Engineer fires it up. some seconds later, poop hit s
the fan. open cabinet, loose stuff in thar, much chastisement follows.

reinstalls items, same outcome. they notice small ball bearings rollin
round the bottom of the cabinet. Weren't ball bearings, they used to be
the stainless screws....had to switch to brass IIRC.


mid eighties, same place, working on a mri scanning system[which
scientist had faked test results, making project useless] but had
basically an mri for test tubes. wrenches and gas bottles chained to the
wall, leave your wallet at the door. someone decided to measure the bore
diameter without turning off the magnet. one set of 6" 'non magnetic'
calipers extruded through a ~1 inch hole. oops.

proton accelerator I worked at had a whole set of beryillium copper
wrenches, screwedrivers etc that stayed in the magnet chamber...... Get
anywhere near where they was blasting protons and my atm card wouldn't
work for a week....

On Mon, 14 Mar 2005 19:26:00 +0000 (UTC), ()
wrote:

In article ,
jim rozen wrote:
In article , Gunner says...

The Sergent, who was visiting the
suburban clinic to undergo an MRI,
mentioned to the staff that he had his
handgun with him. Sgt. William Benwitz
was told it was all right to keep it during
the scan,

Something's funny here - was he holding the weapon in has *hands*?

Even the rivets in a holster or belt would have been too much
for an MRI magnet. I think somebody's either really really
stupid (and has already been fired) or this is one of those
stories that won't stand up under a snopes microscope.

Jim


Hey, I just had an MRI done yesterday. I spent some time talking with the
people there and learned several neat things. First of all, if you have ever
made metal chips or gotten a face full of rust from under a car, you need to
tell them. They will take x-rays of your head to see if you have any loose
fragments in there. Um... yeah... Ok, the only place a metal sliver is a
problem is in the eyes. If you have one elsewhere in the body, the scar
tissue that forms around it will hold it in place. The same holds true for
surgical staples, etc. They still want to know about them, but they can work
around them. Metal slivers in the eye will be encapsulated (so they don't
irritate things) but no scar tissue ever forms on it, so it is mobile. The
magnet can move this around and the concern is that it will damage the
retina or optic nerve. Implants and such are usually secured well enough
that they aren't worried about them tearing loose, only distorting the
images. Small ferrous objects that make it into the room aren't usually a
problem if they are not loose (they didn't have a problem with the rivets in
my jeans or the metal lugs on my shoes. Presumably, they are well secured
enough and small enough to not shoot across the room). For the most part,
non-ferrous is fine so long as it isn't in the magnet with you (distorts the
image) but ferrous is a no-no. The bigger it is or the less it is secured to
something, the worse the situation. A steel rivet on a belt, not a problem,
an unsecured side arm in a persons hand, big problem. An artificial hip that
is well healed, probably not a problem as it is well secured to you and you
are fairly massive (and well secured to the table).

Some tattoos (specifically "permanent make up") may become irritated, but
that has less to do with the big super-conductive magnet and more to do with
the big pulsing magnet they use to generate the signals they are looking
for. Conductive particles and changing fields and you get heat. On your arm,
probably not so noticeable, but in your eyelids, you may notice it.

All in all, a wondrous, magical machine. Even after learning how they get
an image out of all that stuff, it is still just this side of magic.
What I find magical is the guy who invented it for physics science
eventually had it used to save his life. It's really crazy how things
we do can have totally unintended results.
ERS

On 14 Mar 2005 15:58:15 -0800, jim rozen
wrote:

In article , Larry Jaques says...

No MRI tech would ever let a fully clothed, armed individual
*near* the machine.

True, but then there was last week's movie about the undercover
cop teaching the community about safe handgun handling when he
shot himself in the foot. That was right after he told them he
was the only one in the room professional enough to handle a
weapon. I pity that community and their police force if he's
an example of screened personnel, don't you?

I'm not going to tell you what *one* officer left behind at the
range one day.

But it was blue and it went bang.

Jim

Local cop did that a couple years ago. One of the smart asses at the
range fired off all of this cops magazines as fast as he could into
the backstop. When the office came trotting back to retreive his
suddenly remembered handgun, everyone swore all those rounds were
fired upwards towards town...and they all hoped nobody was hit...as
the rounds would match HIS weapon..

No one really liked the prick.

Gunner

"[L]iberals are afraid to state what they truly believe in, for to do so would result in even less votes than they currently receive. Their methodology is to lie about their real agenda in the hopes of regaining power, at which point they will do whatever they damn well please. The problem is they have concealed and obfuscated for so long that, as a group, they themselves are no longer sure of their goals. They are a collection of wild-eyed splinter groups, all holding a grab-bag of dreams and wishes. Some want a Socialist, secular-humanist state, others the repeal of the Second Amendment. Some want same sex/different species marriage, others want voting rights for trees, fish, coal and bugs. Some want cradle to grave care and complete subservience to the government nanny state, others want a culture that walks in lockstep and speaks only with intonations of political correctness. I view the American liberals in much the same way I view the competing factions of Islamic
fundamentalists. The latter hate each other to the core, and only join forces to attack the US or Israel. The former hate themselves to the core, and only join forces to attack George Bush and conservatives." --Ron Marr

On Tue, 15 Mar 2005 00:08:40 GMT, yourname wrote:

Um, no. RF Heating is a real and measurable phenomenon in MRI imaging.
The "SAR" (specific absorption ratio) calculates just how much

early 80's, former coworker working with mri r+d.
reinstalls items, same outcome. they notice small ball bearings rollin
round the bottom of the cabinet. Weren't ball bearings, they used to be
the stainless screws....had to switch to brass IIRC.

Yup, GE found out brass was a good thing as well.

mid eighties, same place, working on a mri scanning system[which
scientist had faked test results, making project useless] but had
basically an mri for test tubes. wrenches and gas bottles chained to the
wall, leave your wallet at the door. someone decided to measure the bore
diameter without turning off the magnet. one set of 6" 'non magnetic'
calipers extruded through a ~1 inch hole. oops.

Nice I did have to take a flashlight into the bore from time to
time. Batteries are surprisingly magnetic. Er, so I heard, thatis.

proton accelerator I worked at had a whole set of beryillium copper
wrenches, screwedrivers etc that stayed in the magnet chamber...... Get
anywhere near where they was blasting protons and my atm card wouldn't
work for a week....

Nasty stuff, beryllium. We switched to titanium as soon as we could
find a source for titanium crecent wrenches and so on. Pricy stuff...

"Dave Hinz" wrote in message
...
Most MRI systems are 1.5T. Some of the newest ones are 4T, but those
are few and far between.

Really? Then were do I keep reading 10-20T from?

When I worked in MR Engineering, we, well, were playing around with
magnets, oddly enough. The permanent magnets in a Hawk hard drive
(1 gigabyte full height - these were old) came in above the measurement
capability of our gauss meter, which went up to above 4T. So, at
the surface, it's more than a 4T permanent magnet, in those drives.

Huh. Anyone know offhand what the top field strength of the toughest
magnetic materials is these days? I always thought magnets topped out
around iron's saturation levels (1-2T)...

It's strong, but the field isn't anywhere near even (parts per billion
is needed), or large enough.

As I recall, MRI's use a Helmholtz coil (I think), basically two short
solenoids seperated by a distance. The space between them has a relatively
constant field. Not perfectly constant, so they must have to use extra
coils and tweaks either way, no?

Um, no. RF Heating is a real and measurable phenomenon in MRI imaging.
The "SAR" (specific absorption ratio) calculates just how much RF
you can pump into the patient, based on their mass.

I'll admit you've got me on the RF part... All I know is the field aligns
hydrogen atoms (and maybe others), then RF is applied and re-radiated...how
the hell they decipher the 10^20llions of hydrogen atoms spatially is beyond
me.

Also, RF coupling to the body coil can increase this;

Basically induction heating a person? Or more likely capacitively (B and E
are related anyway, so who cares) given the lossy nature of flesh.

Tim

--
"California is the breakfast state: fruits, nuts and flakes."
Website: http://webpages.charter.net/dawill/tmoranwms

On Mon, 14 Mar 2005 16:22:28 -0800, Eric R Snow wrote:

What I find magical is the guy who invented it for physics science
eventually had it used to save his life. It's really crazy how things
we do can have totally unintended results.

Ironically enough, one of the R&D techs at G.E. died of a tumor that
would have been trivially detected on the systems he worked on every
day. Went in for a "hey you - we need a warm body to scan" scan, ...
not good.

On Mon, 14 Mar 2005 20:19:05 +0000, Dave Hinz wrote:

Nah, it won't take out a metal sliver, they're too small to have
much pull on them even with that large of a magnet. You have _stronger_
magnets in your computer's hard drive, by the way.


Hard drive magnets are plenty strong, but I've never had one try to rip my
Swiss army knife through the fabric of my Levis at a distance of 20ft. My
wife was having an MRI, and I forgot to empty my pockets before entering
the room. My knife started pulling toward the machine as soon as I walked
in the door - I left quickly, and made sure I had nothing metallic when I
returned.

-Ron

Nasty stuff, beryllium. We switched to titanium as soon as we could
find a source for titanium crecent wrenches and so on. Pricy stuff...


Said wrenches probably dated from the 40's. Beryllium Copper is fairly
stable, IIRC, not like 'beryllium' still used for springy copper type stuff

Ron DeBlock wrote:
On Mon, 14 Mar 2005 20:19:05 +0000, Dave Hinz wrote:


Nah, it won't take out a metal sliver, they're too small to have
much pull on them even with that large of a magnet. You have _stronger_
magnets in your computer's hard drive, by the way.


this is bull****

go down to the hospital and try.

In article ,
Tim Williams wrote:
"Dave Hinz" wrote in message
...
You have _stronger_
magnets in your computer's hard drive, by the way.

I didn't know they could produce permanent magnets anywhere near 2T, let
alone 20.

Boy, those are some impressive magnets then... hey, they'd make great
replacements for those tricky superconducitng rigs in MRI's!
BG

RF Heating might also be a concern, but less so than the discomfort
and image problems.

That's an UL with tatoos, but as I recall it only causes a little
distortion, not really any heating or "pull".


Could be a legend, but it was on the info/warning/tell-us-about-it sheet I
got. Even without any ink I noticed some heating while scanning. They were
shooting my shoulder and I could feel it on the back of my neck kind of
across the shoulders. Subtle, but there. I suppose it could have been from
the equipment, but it dissipated very fast when they stopped scanning and I
would think that a large warm piece of equipment would not cool down that
fast...

Now that I think of it, if you are refering to the Myth Busters shot at the
legend, they couldn't detect anything with an IR thermometer. I suspect that
there is a world of difference when it is in your skin. Did they test that?
I don't remember...

-- Joe

--
Joseph M. Krzeszewski Mechanical Engineering and stuff
Jack of All Trades, Master of None... Yet

In article ,
Tim Williams wrote:
"Dave Hinz" wrote in message
...
Most MRI systems are 1.5T. Some of the newest ones are 4T, but those
are few and far between.

Really? Then were do I keep reading 10-20T from?

When I worked in MR Engineering, we, well, were playing around with
magnets, oddly enough. The permanent magnets in a Hawk hard drive
(1 gigabyte full height - these were old) came in above the measurement
capability of our gauss meter, which went up to above 4T. So, at
the surface, it's more than a 4T permanent magnet, in those drives.

Huh. Anyone know offhand what the top field strength of the toughest
magnetic materials is these days? I always thought magnets topped out
around iron's saturation levels (1-2T)...

It's strong, but the field isn't anywhere near even (parts per billion
is needed), or large enough.

As I recall, MRI's use a Helmholtz coil (I think), basically two short
solenoids seperated by a distance. The space between them has a relatively
constant field. Not perfectly constant, so they must have to use extra
coils and tweaks either way, no?

Um, no. RF Heating is a real and measurable phenomenon in MRI imaging.
The "SAR" (specific absorption ratio) calculates just how much RF
you can pump into the patient, based on their mass.

I'll admit you've got me on the RF part... All I know is the field aligns
hydrogen atoms (and maybe others), then RF is applied and re-radiated...how
the hell they decipher the 10^20llions of hydrogen atoms spatially is beyond
me.


Here ya go Tim. This is what took MRI from just that side of black magic to
just this side of it. Time to exercise your math skills (or just look at the
pretty pictures and you will get a good deal of the info).

http://www.cis.rit.edu/htbooks/mri/inside.htm

I believe that somewhere in Chapter 5 there is a spiffy picture that more or
less sums up how they got from RF signals to images.

Really interesting was that mid way through Chapter 9 we find:

Another frightening story was of a law enforcement officer being allowed
to go near a magnet with a loaded firearm. The handgun was pulled out of
its holster, and into the magnet. The force of the impact with the magnet
caused the gun to discharge. Luckily, no one was injured in this incident.
In addition to the damage to the MRI and the bullet lodged in the scan
room wall, the gun was magnetized.

Just how old was that original story?

-- Joe

--
Joseph M. Krzeszewski Mechanical Engineering and stuff
Jack of All Trades, Master of None... Yet

On 14 Mar 2005 15:58:15 -0800, jim rozen
wrote:


I'm not going to tell you what *one* officer left behind at the
range one day.

But it was blue and it went bang.

Jim

I'll see your "one left behind" and raise you many levels of more
dangerous place.

Loaded S&W 357 found on the toilet paper holder in a McDonalds
restroom. Turned it over to the local PD after assurances that I would
get it back if unclaimed and not suspicious. I called two weeks later
to see if it had been claimed. No record of it in the property room.

That got my mind in overdrive. I could picture a cop taking it home.
So, I went into my concerned citizen routine. Everyday, I would go
another notch up the ladder. Finally the assistant chief called to say
the mystery was solved. A federal marshall had left it and had called
the PD the same day. They handed it over without recording it.

In article , Andy Asberry says...

I'll see your "one left behind" and raise you many levels of more
dangerous place.

Loaded S&W 357 found on the toilet paper holder in a McDonalds
restroom.

Ahh, not good. This is one reason I decided to teach my
daughter to shoot - so that she can learn the right thing
to do if she ever comes across something like this.

Imagine if some kid had fired off a round in there....

"Hey, look what I found....!"

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

One incident I discovered when preparing for a lecture I gave to
anesthesiologists was a large oxygen cylinder (300 size IIRC) that was
wheeled into the room while a patient was in the machine. The cylinder flew
ten feet and landed across the opening, pinning the patient inside. After
quenching the field they were able to get her out, badly bruised but
otherwise unhurt. Fortunately the thing didn't arrive end on, it could have
gone inside with her and crushed her completely. Yuck!

--
Bob (Chief Pilot, White Knuckle Airways)


"Dave Hinz" wrote in message
...
On 14 Mar 2005 05:03:59 -0800, jim rozen wrote:
In article rs.com,
Jon Elson
says...

injured. At a hospital in St. Louis, a compressed gas bottle that
was SUPPOSED to be aluminum was thrown across the MRI room and nearly
killed several people.

In NY a child was killed by a "non-ferrous" O2 bottle recently
as well.

Key point being, it wasn't non-ferrous, and they failed to check.

In article , Bob Chilcoat says...

One incident I discovered when preparing for a lecture I gave to
anesthesiologists was a large oxygen cylinder (300 size IIRC) that was
wheeled into the room while a patient was in the machine. The cylinder flew
ten feet and landed across the opening, pinning the patient inside. After
quenching the field they were able to get her out, badly bruised but
otherwise unhurt. Fortunately the thing didn't arrive end on, it could have
gone inside with her and crushed her completely. Yuck!

This is pretty much what happened to the child who was getting an
mri around here.

They thought the kid was in some kind of respiratory distress (not
true, there was a problem with a sensor) and decided to bring a
small portable 02 bottle over to begin giving oxygen.

The bottle was in an anteroom and was was hand-carried into the
room, was ripped out of the person's hands and entered the
scanner, and crushed the child's head.

I always thought one could make a nice magnetic scanner to pre-screen
all items entering into an mri suite.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

On Tue, 15 Mar 2005 03:52:25 GMT, yourname wrote:


Nasty stuff, beryllium. We switched to titanium as soon as we could
find a source for titanium crecent wrenches and so on. Pricy stuff...


Said wrenches probably dated from the 40's. Beryllium Copper is fairly
stable, IIRC, not like 'beryllium' still used for springy copper type stuff

That's good to know. Still wore gloves with the stuff, though.

On 15 Mar 2005 05:31:57 -0800, jim rozen wrote:
In article , Dave Hinz says...

Nice I did have to take a flashlight into the bore from time to
time. Batteries are surprisingly magnetic. Er, so I heard, thatis.

Not all of them. The alkaline ones are - we have a total
field magnetometer for field work. It has to be powered
with plain carbon-zinc cells. Those are much much less
magnetic than the alkaline cells, which have steel jackets.

Hm, never tried that. If I ever go back to GE (heh) maybe I'll
mention it...

On Mon, 14 Mar 2005 21:16:54 -0600, Tim Williams wrote:
"Dave Hinz" wrote in message
...
Most MRI systems are 1.5T. Some of the newest ones are 4T, but those
are few and far between.

Really? Then were do I keep reading 10-20T from?

Dunno. Maybe for in-vitro use, for NMR spectroscopy use, but not for human
scanning - I think 4T or 5T is about the upper limit, even for research
sites. Something about signals being induced into nerves at some
point, from what I recall, or at least a concern of that. It's also
a bitch to site even a 4T magnet, the fringe fields get pretty expensive
to manage.

When I worked in MR Engineering, we, well, were playing around with
magnets, oddly enough. The permanent magnets in a Hawk hard drive
(1 gigabyte full height - these were old) came in above the measurement
capability of our gauss meter, which went up to above 4T. So, at
the surface, it's more than a 4T permanent magnet, in those drives.

Huh. Anyone know offhand what the top field strength of the toughest
magnetic materials is these days? I always thought magnets topped out
around iron's saturation levels (1-2T)...

These weren't iron, they were chrome-plated rare earth magnets of some
sort. Strong enough that they held strong through my hand. Hint:
don't let 'em go around and hit each other, because blood blisters will
result (based on a sample of one).

It's strong, but the field isn't anywhere near even (parts per billion
is needed), or large enough.

As I recall, MRI's use a Helmholtz coil (I think), basically two short
solenoids seperated by a distance.

Yes, there's an inner coil and a counter-wound outer coil.

The space between them has a relatively
constant field. Not perfectly constant, so they must have to use extra
coils and tweaks either way, no?

Yes, the GE magnets have 18 "shim coils", first, second, and third-order
corrections. The simplest is just X/Y/Z; get the overall gradient
from say front to back the same. Second-order does opposing corners,
third order starts getting strange. Some delightful math to calculate
how to get the shims in order, as they all interact heavily.

Um, no. RF Heating is a real and measurable phenomenon in MRI imaging.
The "SAR" (specific absorption ratio) calculates just how much RF
you can pump into the patient, based on their mass.

I'll admit you've got me on the RF part... All I know is the field aligns
hydrogen atoms

Well, the protons in them, but yes,

(and maybe others),

There are a few others but the frequencies get strange. I think all the
diagnostic work is using hydrogen.

then RF is applied and re-radiated...how
the hell they decipher the 10^20llions of hydrogen atoms spatially is beyond
me.

Well, there are gradient aplifiers which make the RF pulse only resonate
one location cleanly (this is wrong but close enough to make the point).
The RF hits the protons there, they flip (usually to 90 degrees to
get the most signal). As they re-align to the magnetic field, they disturb
their electrons, which give off an echo of the RF pulse.

The echo is detected with the same RF coil (goes from transmit to receive
very quickly), which gets fed into a 2-dimensional Fast Fourier Transform,
breaks it into frequencies which tells you a number of things, and then
does it again with more lines of data (each of which also came from a FFT),
and FFT's _that_ into the image. Sort of.

Also, RF coupling to the body coil can increase this;

Basically induction heating a person? Or more likely capacitively (B and E
are related anyway, so who cares) given the lossy nature of flesh.

Right. It's usually localized to, say, the arms where they're
closest to the coil. A person inside an antenna acts as an RF "slug"
(heh) and both lowers the frequency of, and widens the peak of, how the
antenna is tuned.

It's neat seeing how these scanners are made. There are guys on
the manufacturing floor using technology that hasn't changed in
generations, or even centuries. Mix that with superconductors chilled
with liquid helium, and there's a ton of interesting stuff going on.

On Tue, 15 Mar 2005 03:29:43 GMT, Ron DeBlock wrote:
On Mon, 14 Mar 2005 20:19:05 +0000, Dave Hinz wrote:

Nah, it won't take out a metal sliver, they're too small to have
much pull on them even with that large of a magnet. You have _stronger_
magnets in your computer's hard drive, by the way.


Hard drive magnets are plenty strong, but I've never had one try to rip my
Swiss army knife through the fabric of my Levis at a distance of 20ft.

Right, it's got a _big_ field, but it's not as _strong_ of a field.
A static charge from walking across carpet on a dry day can be thousands
of volts, but there's no current behind it.

My
wife was having an MRI, and I forgot to empty my pockets before entering
the room. My knife started pulling toward the machine as soon as I walked
in the door - I left quickly, and made sure I had nothing metallic when I
returned.

Steel-toed boots are...interesting...around an MR magnet.

On Tue, 15 Mar 2005 03:53:53 GMT, yourname wrote:


On Mon, 14 Mar 2005 20:19:05 +0000, Dave Hinz wrote:

Nah, it won't take out a metal sliver, they're too small to have
much pull on them even with that large of a magnet. You have _stronger_
magnets in your computer's hard drive, by the way.

this is bull****
go down to the hospital and try.

I worked on MRI scanners for a dozen years. I have direct personal
experience and a verifyable resume. You, are ".
Thank you for sharing your thoughts, I will give them all the consideration
they are due.

On 15 Mar 2005 07:36:38 -0800, jim rozen wrote:

The bottle was in an anteroom and was was hand-carried into the
room, was ripped out of the person's hands and entered the
scanner, and crushed the child's head.

I always thought one could make a nice magnetic scanner to pre-screen
all items entering into an mri suite.

Every MRI scanner that GE ships comes with a kit that includes
small magnets that the scan techs are supposed to use for that.
If the incident you mention is the one I think it was (1994-ish?),
then that was a GE scanner. The hospital got in quite a bit
of trouble for the incident, due to procedures not being followed.

Dave Hinz wrote:
On Tue, 15 Mar 2005 03:53:53 GMT, yourname wrote:


On Mon, 14 Mar 2005 20:19:05 +0000, Dave Hinz wrote:

Nah, it won't take out a metal sliver, they're too small to have
much pull on them even with that large of a magnet. You have _stronger_
magnets in your computer's hard drive, by the way.

this is bull****
go down to the hospital and try.


I worked on MRI scanners for a dozen years. I have direct personal
experience and a verifyable resume. You, are ".
Thank you for sharing your thoughts, I will give them all the consideration
they are due.

And when the guy with the MD after his name tells be i gotta get an

xray before they let me in the MRI machine
I think I will listen to him before you, giving your thoughts all the
consideration they are due.

On Tue, 15 Mar 2005 23:03:38 GMT, yourname wrote:
Dave Hinz wrote:
On Tue, 15 Mar 2005 03:53:53 GMT, yourname wrote:
On Mon, 14 Mar 2005 20:19:05 +0000, Dave Hinz wrote:
Nah, it won't take out a metal sliver, they're too small to have
much pull on them even with that large of a magnet. You have _stronger_
magnets in your computer's hard drive, by the way.

this is bull**** go down to the hospital and try.

I worked on MRI scanners for a dozen years. I have direct personal
experience and a verifyable resume. You, are ".
Thank you for sharing your thoughts, I will give them all the consideration
they are due.

And when the guy with the MD after his name tells be i gotta get an
xray before they let me in the MRI machine
I think I will listen to him before you, giving your thoughts all the
consideration they are due.

You seem to have confused "won't take out a metal sliver" with "safe to
have metal in your eyes during an MRI scan". Thanks for playing,
though.