MRI vs CT?

[pberggren1]

I was wondering if a CT scan is more valuable than a MRI?

My Rheumy and I were concerned about my CT scan exposure and the radiation. She said that maybe I could get at least an MRI of my nasopharynx to reduce my exposure to radiation and maybe go with a CT of my chest. She said she would look into it. That was about a week and a half before the CT that was already booked for May 19. May 19 came and my Rheumy called me and said that the CT scan was better to have. I had the scan and broke out in hives for a while because of the contrast media.

I always thought that an MRI gave better resolution of the images compared to CT?

Is a CT better for us Weggies because it shows Wegs activity better than a MRI?

Please help me with this one. My Rheumy didn't give me an explanation. I see her on June 2 and will definitely talk to her about this then.

I wish I lived near JHU and would go and see Phil Seo.

I am also going to press my doc more to consult with Gary Hoffman or another Wegs specialist.

I am just a little pissed off right now at my Rheumy about this CT thing and about not getting a hold of Gary Hoffman yet either.

[JanW]

I will leave it to Sangye to discuss the MRI vs CT thing, but I will say that according to Merkel at Boston University, Weggies should avoid contrast at all cost. In general, you don't need it for chest CTs except in specific cases -- I'm thinking maybe if they are looking for clots -- Sangye can advise.

I just remember that really stuck with me when I watched his webcast on the VF website.

[elephant]

Phil, the MRI shows more than a CT scan. But CT scans are cheaper than MRI, so if you ever go to ER ( emergency room) they do X_Rays first ( cheaper) then CT, then MRI's.

[Sangye]

The difference between ordering a CT vs MRI is about what tissue and type of problem you're looking for. A general rule of thumb is that MRI is used to visualize soft tissue and CT is used to visualize bone. Or MRI is neuro/ortho and CT is "everything else." For example, if you have a question about the spinal cord, vertebral discs, tendons or ligaments, a CT will not show them well-- you need an MRI.

This (http://www.ct-scan-info.com/mrivsctscan.html) is a good short article that discusses when to use each and why.

This (http://www.thumbmri.com/mrivscat.asp) is a list of which one to use for particular conditions.

Contrast is used to show greater detail and is sometimes necessary. If you're looking for blood clots in the lungs, they must do a pulmonary angiography (CT with contrast injected at high speed) to visualize the blood vessels. A regular CT or a CT with contrast injected at normal speed is useless when looking for clots.

Phil, you need better communication with your rheumy. (And you definitely should push for a Wegs specialist to be involved) You are right to grill your doctor about which test and why, etc.... The danger of excessive radiation exposure in Weggies is quite high. I've had so many I'm surprised parts of me haven't fallen off. I'm joking about it, but it's a major issue that will likely be a problem for me someday.

[jola57]

Phil, think of CT as for bones and MRI for soft tissue. The only exception is the contrast CT when they inject the dye/radio isotope. That is a necessity to see the blood vessels when looking for a clot when they do a seties of scans after injection. MRI is better for showing wegs because it gives greater detail of soft tissues where wegs can show up.

[Sangye]

MRI is not good for checking the lungs. The article above says "CT is far superior at visualizing the lungs and organs in the chest cavity between the lungs. MRI is not a good tool for visualizing the chest or lungs at all." Even in my case, where the concern for any additional radiation is sky-high, my Wegs doc has said MRI is not an option for looking at my lungs.

[jola57]

Hm I wonder about that Sangye, MRI gives better slices of the soft tissue so why would it not be good for lungs. I will ask around my collegues about the reasons.

[Sangye]

I'd love to know why! Even my original docs said I had to have CTs to check my lungs and not MRI.

[pberggren1]

Thanks for those articles Sangye! This helps me put everything into better perspective now.

Thanks to Jola, Jan, and Elephant too.