Technology Magnetic Resonance Imaging (MRI)

Discussion in 'Technology' started by Mirthful Me, Aug 31, 2004.

  1. Mirthful Me

    Mirthful Me New Member

    Ever had an MRI? A fairly common procedure in most industrial nations, it is an incredible leap in diagnostic imaging, and provides extremely detailed multi-planar pictures of anatomical structures. New advances are allowing interventional and functional MRI procedures to be performed.

    I'm available to field questions regarding the clinical applications, design concepts, and future capabilities of MRI as well as any myths/fears/anecdotal occurrences.
  2. DreamLandMafia

    DreamLandMafia Premium Member

    Is it like an XRay?? or does it measure something else in your body??
  3. Mirthful Me

    Mirthful Me New Member

    Non Invasive Radiology

    MRI is a class of diagnostic imaging equipment that provides "slices" of an anatomical region (your head, knee shoulder, etc.). This is accomplished without ionizing radiation (X-Rays); instead it uses an intense magnetic field (static), RF radiation, and a controlled varying magnetic fields (gradients). MRI works by “measuring” hydrogen densities (we are mostly water therefore we are mostly hydrogen). These measurements create density plots that are converted digitally into images (this is an oversimplification but it’s a start). Since the measurements are hydrogen based, soft tissue imaging is possible (as opposed to X-Rays which only provide bone detail). The impact of MRIs cannot be overstated: some conditions are no longer a mystery (whiplash being one, a boon to insurance companies and a bane to ambulance chasing lawyers). Conditions that were once only determined by autopsy (aneurysm for example) are now easily discovered.

    An example of MRI "legal eagle anger"
  4. Cinderloft

    Cinderloft Premium Member

    What I want to know is why are they so expensive, because I assume they must be. Not many around, and there is a huge waiting list in both the US and Canada to have one done. A friend of mine is going for one in the middle of Oct. and has been waiting a little over 9 months already. This is in Atlantic Canada. From what I hear, it is way worse out west.

  5. Mirthful Me

    Mirthful Me New Member

    Money matters

    An MRI is expensive because the equipment, build out, ancillary equipment, and service contracts (tremendous overhead) is expensive (I'm not cheap either, just easy). A typical MRI scanner (Superconducting High Field is anywhere from 1.3 to 2.1 million dollars U.S.) add everything else and your in the hole for 2.2 to 3 million and now operating expenses become a factor.

    As to the presence (or lack thereof) of MRI scanners, in the U.S. MRI scanners are common and backlog for MRIs are low (the exception being HMOs that will not utilize "outside" services, and of course VA/military hospitals), my clinics generally offer same day, or next day appointments. Canada is a different story (although things have improved), because of their socialized medicine structure, there is no incentive to provide timely service, especially on big-ticket items like MRI. There are plenty of Canadians that choose to go south of the border, and pay cash for high-end diagnostics, rather than wait for indigenous services.
  6. oddtodd

    oddtodd Premium Member

    I believe I had one , I was in a magnetic ring for sure . They injected me with a clear liquid ( about 3/4 cup i think) . What could this be if not an MRI , and what would the liquid be ? ( I had a head injury , don't remember what they told me , just knew they were trying to help)
  7. Cinderloft

    Cinderloft Premium Member

    Perhaps they scanned your CAT?

    /Varsity Blues rocks...
  8. oddtodd

    oddtodd Premium Member

    this is my cat , he is not amused....
  9. oddtodd

    oddtodd Premium Member

    sorry , will post a link the server some un needed work

  10. Cinderloft

    Cinderloft Premium Member

    Aaaahhhh!!! The beast! Cat-zilla is attacking the city! Aaaahhh! Super large image file!!! Its attacking my browser! The end is nigh!

    Seriously, perhaps it was a CAT scan, as there was head trauma involved. Hope that you had a full recovery. What happened anyways?

    On a side note, does the Atkins diet work with pets? ;)
  11. oddtodd

    oddtodd Premium Member

    HAHAHAHA , no Atkins doesn't work , old age and fewer and fewer teeth has him svelt at the moment .

    Fell off the 2nd level of some scaffolding and had to have my squash stapled shut . Left a nice blood stain on the patio of a client who took the time to hide his "medicinal" plants before calling the ambulance . Full recovery cept for the divot my barber is amazed at .
  12. oddtodd

    oddtodd Premium Member

    Back on topic . The liquid left a metalic taste in my mouth . Docs said it was common . Just wondering what this was , and what kind of radiating(or not) gizmo I was in .
  13. Cinderloft

    Cinderloft Premium Member

    Good to hear. Cant believe he actually took the time to hide his stash while you were laying there bleeding. What is the laws on posession where you live? Some states have life in prision, not that I condone what he did, but it is a prime example of the unseen dangers of the drug war, but that is another topic for another forum for another time. Thankfully everything worked out ok, and you are all right.
  14. Mirthful Me

    Mirthful Me New Member

    Definitely not an MRI

    OT, you had a CT Scan (Computerized Tomography, previously called a CAT Scan, Computed Axial Tomography), which is just an X ray tube that spins around, and axial images are created. Please note that this is infinitely more sophisticated than an X ray. The metallic taste you noticed is a side affect of Iodine contrast (please resist the urge to call it "dye", radiological contrasts are clear, dye is an oxymoron). Iodine is radio-opaque (blocks X rays), and is useful in discerning vascular structures when administered intravenously (hence the application in obtaining a diagnosis in regards to your head injury). Radio-opaque contrasts (barium is another) can be administered in a variety of ways to visualize different anatomical structures (gastro-intestinal tract is a common area of interest, use your imagination). CT imaging is preferred for acute phase diagnostics for trauma patients due to the high speed of imaging (current generation CT scanners can fully image the head in under 30 seconds).

    Back to MRI, the typical MRI scanner bears a striking resemblance to a CT scanner even though the imaging physics are completely different (ionizing radiation vs. magnetic field/RF waves). The other advantage of MRI is that most exams do not require a contrast agent, and when indicated the MRI contrast does not cause reactions typical of Iodine (with any pharmaceutical agent, a reaction is possible). MRI has only recently become viable for limited acute phase trauma diagnostics, and only at large hospitals that have a dedicated system for such imaging techniques.

    Please note that my statements concerning imaging capabilities/techniques are made in the broadest and most general terms, specific imaging protocols within a given location may vary from what I have posted (my lawyer made me write this).
  15. oddtodd

    oddtodd Premium Member

    Thanks so much !!

    I was also concerned if a radioactive substance was introduced to my body as well ? .... however slight it may have been . I think iodine fits the bill for this ??. A follow up question if you don't mind .

    Just curious , I grew up in New Hampshire and have been exposed to enough radon that this would be like giving an alchoholic a sample size bottle of mouthwash .

    Thanks !
  16. Mirthful Me

    Mirthful Me New Member

    Penetrating Counts...

    Iodine is not radioactive, it is radio-opaque (blocks X Rays), Nuclear Medicine studies function by the introduction of radio-pharmaceuticals into the body (intravenously, inhaled, or ingested) and how they disperse throughout the body and subsequently deposit (accumulate). The only radiation you received was from the CT scanner (a fair amount, but considered safe, and inconsequential in comparison to the medical need). Radiation exposure is cumulative, and there is no tolerance developed to it’s effects, quite the opposite, as one reaches maximum dose levels (lifetime) the effects of even small exposures can be noticed.
  17. oddtodd

    oddtodd Premium Member

    Thanks again , no more parties in the cellar when I make it home next time . Very informative , I will pass the knowledge along .....
  18. DontTreadOnMe

    DontTreadOnMe Member

    Dear Uncle,
    I'mglad you brought this up as I have a question or two about MRIs.

    Why are they sooooo noisy---enoguh to give you a headach, I'm told?
    Why do they vibrate, or is this a myth?
    What if I'm claustophobic?
    What is an open MRI?

    Finally, I went to a neurologist awhile back, suffering from monthly migraines. He wanted to do a MRI. I told him I was claustophoic. He then said I really didn't need an MRI, maybe a CAT would do just as well. Are they equally good diagnostic tools? Was he just looking for money from Blue Cross?
  19. pineappleupsidedown

    pineappleupsidedown Premium Member

    Are MRI's safe? What are the side effects? If you work with metal (i.e. steel grinding, where you inhale steel all day) does that affect how the MRI goes?

    If a doctor is so willing to do a MRI, he is either looking for money or just really likes the concept of them and wants to send as many clients through them as possible.

    Side note: if you are willing to try it, i have found a cyropractor very helpful for my chronic headaches (she said she can usally help monthly headaches and pains as well) which I've had daily for a good 6 months until i started going.

  20. Mirthful Me

    Mirthful Me New Member

    A proton flipping we go...

    The noise associated with an MRI is the result of the main (static) magnetic field being manipulated by the gradients (current amplifiers). By pulsing current through coils in the bore the magnetic field is manipulated to acquire the respective slice orientations (Axial, Sagittal, Coronal, or a combination of these to match anatomical structures). As with a loudspeaker in a sound system, current through a coil creates a transduced motion (sound from a speaker) or a knock (MRI scanners don’t have a cone to reproduce the sound so the coil (a rather massive phenolic structure with copper windings) itself moves, hence a knock (current generation MRI scanners manipulate the field so fast the “knock” has become a buzz. Ear protection should always be worn during MRI exams (some low field units aren’t loud, but why take a chance), either earplugs, or acoustic damping headphones. With headphones they should be able to play music during your exam.

    With the sound explained it is easy to extrapolate that there is some vibration associated with the exam. Most manufacturers have made adequate progress in isolating the patient from this unwanted result of magnetic field manipulation. Current generation scanners the sensation is barely perceptible.

    Claustrophobia is an issue with MRI, and often prevents the patient from completing an exam. The typical way to deal with claustrophobic patients is a mild sedative (oral Valium or Xanax) to minimize the perceived anxiety. Sometimes this is not enough, and a patient must undergo conscious sedation techniques (should only be performed in a hospital setting), where a patient is sedated with intravenous drugs (Versed, Diprovan, or cocktail of choice) and is barely aware of their surroundings. I always recommend that people who know they are claustrophobic make arrangements with their physician in advance to address this issue in order to avoid an unpleasant experience (and thereby making future MRIs more of an ordeal).

    Open MRI scanners have been developed by several manufactures to accommodate patients that are claustrophobic or of large body size. While a good concept and quite popular, they are a poor second to high field superconducting MRI scanners in resolution, image quality, and speed. These machines are heavily marketed and appeal to some patients, but quite often a patient needs to be rescanned (on a high field) in order to obtain a satisfactory exam. Worse still is the occasion when pathologies are missed due to poor image quality… not all MRI scanners are created equal! As an additional note, a person may come across an “extremity MRI” where the part to be imaged is inserted into the machine (knee, wrist, etc), run the other way, quickly… the image quality from these units is substandard.

    MRI and CT (or CAT) scanners are two distinct diagnostic tools, each with strengths and weaknesses. For the symptoms you describe an MRI scan is indicated, a CT scan would leave many possible pathologies an unanswered question. MRI is the pinnacle of soft tissue imaging today, and even subtle pathologies can be detected; CT is limited in this regard. CT can only image in the Axial plane, while MRI can image in any orthogonal plane (or combination of planes). MRI scan can be tuned to different tissue types (even flowing blood, MRA) and provide exception small structure detail. Bottom line, get an MRI (in your case DTOM) especially for joint imaging, soft tissue, and neurological exams, get a CT scan for chest, abdomen, and pelvis exams. Obviously this is a general recommendation, and your physician is the final arbiter of what exams will be ordered (sometimes both, or other exams in conjunction with).