Of the two, though, I would think the MRI.
[This message has been edited by InarticulateBabbler (edited October 11, 2007).]
PET scans work with a radioactive glucose isotope, which is attracted toward high-metabolic cells, such as cancer. Cancer is hungry for sugar, the doctors have told me. The test results show the temperature differences in the body, cancer being a high-metabolic area shows in "hot" colors like orange red and yellow; low metabolic cells showing in blues and greens. My doctor didn't need film, the imaging company sent him my test results on the internet and he could log in and see them without waiting. They do a CAT scan at the same time, and overlay the test results, but I didn't ask questions about the details of what the CAT scan did that the PET scan didn't.
My understanding is that MRIs are less about what is going on inside the organs, as a look at the organ itself. I'm guessing an MRI would pick up a foreign object. I'm not sure exactly how the CAT scan falls into that scenario.
MRIs are loud, and sound like the Emergency Broadcast signal we still hear on American radio stations from time to time. You have to wear a couple of layers of hearing protection (earplugs and earmuffs) to protect your hearing. The tube they put you in is tight, so tight you may only have a fist-width between you and the top of the tube. PET scans, on the other hand, are in a (slightly) larger tube, and while you can hear them, they aren't nearly as abraisively loud as the MRI. By the way, when they did the MRI on me, I could literally feel my intestines jump around when it passed over my stomach area. It was unnerving. If you are claustrophobic, this won't be a fun test. For both tests, you have to lay PERFECTLY still for 45 minutes. No wriggling, moving, or doing anything other than breathing slowly.
If the item is something intentionally implanted it would more than likely be made of a non-magnetic material. This would definately show up in an MRI. But if there is any suspicion that the item might be magnetic no doctor or hospital would allow the test.
Also, on an episode of HOUSE, House shot a bullet into this corpse that had died of cancer, then put the body through an MRI. The bullet fragments came through the skull and wrecked the MRI machine. How true is this? I don't know, but I would think they'd have run the idea by someone who did know.
An MRI and CT (Probably shouldn't call it a catscan. If you must refer to it colloquially, CAT scan would be better.) are both used in different situations to image different things.
Without knowing what your patient presented with, I would bet a head CT would be ordered in which pretty much any foreign object could be detected, unless that object had a similar electron density to water.
Edit: If you want more information on any of the medical imaging modalities, just let me know and I'll try to help you out.
[This message has been edited by Rahl22 (edited October 11, 2007).]
The scan took place as I lay on a special table, and, if I remember correctly, they ran the light scanner over me in short bits so that I could hold my breath each time--hold-light on, then breathe, then hold-light on, then breathe. Had plenty of space around me, wasn't claustrophic at all.
I'm not sure how they'd do a head CT scan.
But an MRI does use a powerful magnetic field, so they wouldn't use it if they thought you had anything in you that would react to the field, and be pulled right out of your body.
MRI's are only used if pathology is organic in nature (tumor, cyst, etc)
Are you sure contrast would be used when evaluating a foreign object in the head? I'm not a physician, but I've never seen that.
Imagine we are going to run a CT scan, I guess, on this patient, and we are trying to detect a foreign object in his head. It is also important that our patient is not conscious for the procedure, is the CT scan still recommended?
[This message has been edited by Zero (edited October 12, 2007).]
quote:
hteadx,Are you sure contrast would be used when evaluating a foreign object in the head? I'm not a physician, but I've never seen that.
The reason why you never see this is because most physicians always assume there is bleeding involved with a foreign body. Hence why I said if no bleeding is suspected.
But I'm assuming he wanted reality for his story and if there are no contraindications (allergies, active bleeding, or increased intracranial pressure) for contrast most doctors would prefer contrast.
BTW, here's an article on which implants/foreign objects are contraindications to using an MRI:
http://orthopedics.about.com/od/hipkneereplacement/f/mri.htm
Also, why not do an x-ray first? Lots of foreign objects show up on those, and it's usually done as a preliminary, let's-see-what-we-have-here sort of test.
The contrast, by the way, within about hmm... 30 to 45 seconds after being injected, has a strange sensation of a rush of sudden heat in the back of your throat, and then in your urinary tract so it feels like you just wet your pants. The nurse warned me not to panic when I felt it happen. It wasn't uncomfortably hot, but it was still a pretty strong feeling. The heat flush lasts for about a minute or so, then subsides.
Having spent a brief month filling in on housekeeping duty at the local hospital, and having had to mop the MRI/CT room, I can tell you the technicians sometimes spill drops of the contrast on the floor and it's a bear to mop up because it dries like sugar water on the floor... leaving hard to clean spots that are also hard to see if the light isn't right. It's a bit sticky. There's another fact you won't find in a medical text book.
[This message has been edited by Elan (edited October 15, 2007).]
They did brain sugury on a friend of mine. They accidently removed his brain and he became more intellegent.
they did investigative surgury on a politician's head. they never did find anything.........
Rommel Fenrir Wolf II