A question about MRI machines.

[Gawdzilla]

Why do they have to be designed so that the patient goes in head first?

[RecoveringYuppy]

They don't and aren't.

ETA: Type "MRI macine" in to Google and look at the images. Some of the most common machine types are shown being used feet first. Go to the Wikipedia article and they' discuss "open" and "upright" designs.

[Professor Yaffle]

Why do they have to be designed so that the patient goes in head first?

Do they have to go in head first? Not according the the experiences of the people posting here:

http://boards.straightdope.com/sdmb/archive/index.php/t-324393.html

I suppose it depends on what part of the body they want to look at. If it is the chest, for example, it makes sense to go head first. If its the knee, feet first.

[Pulvinar]

"We're just doing a head scan, but what the hell, we'll slide your whole body through first."

[steve s]

My mother once had an MRI for her hip and she went feet first.

Steve S

[phunk]

Orientation doesn't matter, whichever end they need to scan goes in first. Unless you're dramatizing it for TV and the patient is claustrophobic. Then, they have to go in head first always.

[Gawdzilla]

Every one I've ever been in, VA and civilian, they put me in head first. (Eleven times now.)

[Professor Yaffle]

Every one I've ever been in, VA and civilian, they put me in head first. (Eleven times now.)

What were you having scanned?

[Loss Leader]

Never had an MRI. My body is riddled with metal.

[Gawdzilla]

What were you having scanned?

Abdomen, mostly. Once the head, and twice the lungs, but mostly heart to nuts.

[NoahFence]

Orientation doesn't matter, whichever end they need to scan goes in first. Unless you're dramatizing it for TV and the patient is claustrophobic. Then, they have to go in head first always.

^^

This.

I myself have been in MRIs both directions.

[Tiktaalik]

Feet first here, for a knee. And, I only went in up to about my chest; head stayed out the whole time.

[Trent Wray]

Yes as others have said, it's both ways, dependent usually on what you need to have scanned.

[I Ratant]

Once for knee & back, feet first.
Each scan took 45 minutes!

[Brian-M]

Never had an MRI. My body is riddled with metal.

Should that matter? As I understand it, surgical steel has nickel mixed in with it to make it non-magnetic.

[epepke]

I had an abdominal MRI, and they put me in feet first.

Maybe when they put you in head first, they want you to shut up.

[Gawdzilla]

Should that matter? As I understand it, surgical steel has nickel mixed in with it to make it non-magnetic.

Shrapnel isn't surgical steel, IIRC.

[Loss Leader]

Should that matter? As I understand it, surgical steel has nickel mixed in with it to make it non-magnetic.


I have no idea. I have a defibrilator. It looks like it has a lot of metallic parts. It sets off metal detectors. Medical people have told me I can't have an MRI.

[casebro]

The MRI would scramble the electronics of your defibrilator.

[casebro]

One guy I knew sad he didn't want all the atoms in his body spinning in the same plane, so he wouldn't do the MRI.

[genesplicer]

The MRI would scramble the electronics of your defibrilator.

And the magnetic field might rip the unit from his/her chest or the wire from the heart... Or at least that's how it worked for a welder friend of mine. All the small particles of metal in his skin were rather unceremoniously and semi-painfully ripped from him and deposited on the inside of the MRI tube. Dozens of tiny, painful wounds.

[Trent Wray]

MRI fun:

BQ8lu59CeFc&feature=related

[Andrew Wiggin]

And the magnetic field might rip the unit from his/her chest or the wire from the heart... Or at least that's how it worked for a welder friend of mine. All the small particles of metal in his skin were rather unceremoniously and semi-painfully ripped from him and deposited on the inside of the MRI tube. Dozens of tiny, painful wounds.

This is why I had to have a series of X-rays before getting a MRI. Luckily they didn't find any metal bits in critical areas. I checked the 'have you ever operated a machine tool or grinder without safety glasses' box, causing the radiology department to have a minor meltdown. Apparently folks who do metalworking usually just lie about that part.

[Andrew Wiggin]

One guy I knew sad he didn't want all the atoms in his body spinning in the same plane, so he wouldn't do the MRI.

Tell him it'll give him a case of meatspin, and he might like it. Tell him to google that. Don't google that yourself, at least not from work.

[catsmate1]

And the magnetic field might rip the unit from his/her chest or the wire from the heart... Or at least that's how it worked for a welder friend of mine. All the small particles of metal in his skin were rather unceremoniously and semi-painfully ripped from him and deposited on the inside of the MRI tube. Dozens of tiny, painful wounds.
But what about the MRI machine? Was it damaged?:)

[casebro]

And what about the pacemaker? Was it re-implatable?

[Camillus]

I have no idea. I have a defibrilator. It looks like it has a lot of metallic parts. It sets off metal detectors. Medical people have told me I can't have an MRI.

That may not be true any more. There have been trials of MRI scans on patients with implanted medical devices (http://firstwatch.jwatch.org/cgi/content/full/2011/1004/1) and they don't seem to be adversely affected by the scan. I know that where I work we MRI scan children who have ICDs.

[ria_rokz]

I've had three MRIs on my head*/neck and went in head first (of course). Friday I had one of my knee and I went in feet first up to my waist. It was awesome. way less freaky.

*the good news, to those who may have wondered, is that there appears to be a brain in there.

[Delvo]

There's no single simple rule to cover all implants. Almost all of them were magnetic originally, but MRI has caused implant manufacturers to start seeking alternative materials to make them from. With simple structural parts like a replacement for the top or bottom end of the femur (the most common metal parts I've X-rayed), it's not necessarily hard to switch from one type of metal to another. For electronics, it's harder to do because each component of an electronic system really needs to have specific electrical properties, so you have to either find another material that's good enough to replace each magnetic component, or redesign the system to somehow not need specific parts or materials that electronic systems usually do need. As a result, new MRI-safe versions of electronic implants have been getting made, but the process has been gradual, and even with the simplest purely physical implants like I mentioned first, there are still patients alive now with the older kind in them, even though new kinds are available now. Part of the job of an MRI department is to find out the exact model of implant you've got and check it on their list of which ones are MRI-safe and which ones aren't.

[Soapy Sam]

Every one I've ever been in, VA and civilian, they put me in head first. (Eleven times now.)

Is it possible your head is on the wrong end?:D

[Mister Earl]

Just be glad you're not getting an MRI scan done in Japan. :D

MRI? (http://www.youtube.com/watch?v=el-qPduShuU)

[bruto]

I've had three MRIs on my head*/neck and went in head first (of course). Friday I had one of my knee and I went in feet first up to my waist. It was awesome. way less freaky.

*the good news, to those who may have wondered, is that there appears to be a brain in there. In your knee? I've heard it alleged that some people have their brains mounted below the waist, but it's usually above the knee!

[Loss Leader]

That may not be true any more. There have been trials of MRI scans on patients with implanted medical devices (http://firstwatch.jwatch.org/cgi/content/full/2011/1004/1) and they don't seem to be adversely affected by the scan. I know that where I work we MRI scan children who have ICDs.


That would be great. I'd love to have those kind of diagnostic tests opened up to me.


Part of the job of an MRI department is to find out the exact model of implant you've got and check it on their list of which ones are MRI-safe and which ones aren't.


And the wires and the connectors. If a set of wires and patches get too old, new ones are put in but generally the old ones are just left there in your body forever. So, a newer model AICD doesn't remove the entire risk.

[Gawdzilla]

Had another one yesterday, post auto accident. They insisted that I had to go in head first. "That's the way it's set up."

[Patrick1000]

Why do they have to be designed so that the patient goes in head first?

The body part being scanned needs to be in the center of the magnetic field....

With most scanners, this means if your head, cervical spine, thoracic spine, chest are being scanned, you'll go in head first to acheive this position(scanned body part in the center of the magnetic field).

For lumbar spine scans, hip, knee, foot they may well put you in feet first, depending on the scanner lay out.

"Open scanners" have a different lay out altogether, but the principles are the same, and scanned body part needs to be positioned in the magnetic field's center.

If you want more details I can provide them.

[Gawdzilla]

With most scanners, this means if your head, cervical spine, thoracic spine, chest are being scanned, you'll go in head first to acheive this position(scanned body part in the center of the magnetic field).

So they are designed that way.

[Patrick1000]

So they are designed that way.

For the most part yes.....

[jadebox]

That may not be true any more. There have been trials of MRI scans on patients with implanted medical devices (http://firstwatch.jwatch.org/cgi/content/full/2011/1004/1) and they don't seem to be adversely affected by the scan. I know that where I work we MRI scan children who have ICDs.

My wife has a medical implant, an infusion pump. For years they wouldn't do MRIs on her. But, now they do. She has to, though, immediately go to the doctor than maintains the pump to make sure it wasn't damaged or accidentally reprogrammed by the MRI.

I found a document online that discusses this:

http://www.mrisafety.com/safety_article.asp?subject=54

The site includes similar articles on many other implants. See: http://www.mrisafety.com/list_search.asp

-- Roger