There have been a lot of posts about different strength MRI's. I recently had an MRI of my spine done after 3 months on a higher powered machine and thought that I would share with anyone curious the difference in images.
In the T1 MRI, the radiologist noted inhomogeneity in the spinal cord and was unable to draw any conclusions as to whether or not there were any spinal lesions. The T2 is very clear with the spinal cord and better shows pressure on the cord.
From the Health Centers, "How Does an MRI Work?"
"How does an MRI work? What's all that noise? What does it all mean?
Next time you're scheduled for an MRI, read this first!
An MRI works by finding the hydrogen protons in water. It moves the protons around with a powerful superconducting magnet, housed in the MRI scanning tube. When the magnet is on, it's thousands of times more powerful than the magnetic field of earth. So the magnet is left on, and all the hydrogen protons line up. Then the scanner stirs them up with radiofrequency waves, generated by copper coils in that tube that you're laying in. The machine turns those coils on and off. This happens hundreds of times a minute, so that's what all that noise is about. The hydrogen protons act differently, depending upon what kind of tissue they're in, so this can generate a pretty accurate picture.
This is why a 1.5 Tesla machine is better than a .5 Tesla - bigger magnet means more protons jump up and beg to be noticed. A 3 Tesla is even better, but they're hard to find.
• So what's all the deal with T1 and T2?
In a plain ol' MRI, signal intensity is proportional to the amount of hydrogen protons. More protons, the brighter the image. They can tell the machine to only watch for longitudinal movement (T1, aka spin-lattice relaxation time) or tranverse relaxation movement (T2, aka spin-spin relaxation time) and they can twiddle this even further with variations in the strength, orientation, and timing of RF pulses. T1 weighted is best for looking at brain structures (like black holes,) while T2 is better for looking at non-enhancing brain lesions. T1 is best for looking at the brain and spinal cord after gadolinium is given, as the gadolinium shows up really brightly.
• And what the heck is FLAIR?
Fluid-attentuated recovery, if that helps. To put it simply, it's just a pulse sequence that blacks out the CSF so that the rest of the brain can be seen better. It's easier to see hyperintense lesions with FLAIR.
Evidently, with the right combination of numbers, any particular tissue can be blacked out. Think of T2 and T1 as mathematical vectors that the radiologist plugs into the machine to get different looks at your brain."
Thanks for putting those side by side. There is clearly a huge difference. We need to make every effort we can to get the best possible images for diagnosis and follow-up.
I'm certainly not an MRI expert. Not even an amateur. But I'll be interested to hear what the report and doctor have to say about the cord. I see two places that look like there is some disc protrusion into the thecal sac. While that alone can be quite painful, I don't see any pressure on the cord itself. If your are having a lot of pain from nerve root compression in the thecal sac, epidural injections may help you.
Thanks so much for sharing your inner self. I hope you find some answers soon.
I have to step in here, even though the science behind these images makes my head spin. I really understand very little about how MRIs work, but I do get some basics. It seems that there is a lot of confusion about MRI terminology.
The strength of an MRI magnet is expressed in Teslas (named after a scientist pioneer called Tesla). So a 3T (3 Tesla) scanner is twice as strong as a 1.5T machine, and will produce much clearer images. The software used in conjunction with this hardware makes a big difference too.
When the number is listed before the T, this refers to the strength of the magnet.
When you see terminology such as T1 and T2, this refers to different techniques used during the test. Various types of abnormalities show up differently, depending on the technique used. FLAIR is another technique or sub-technique. These techniques can be used in conjunction with the various strengths of magnets. So, for example, a 3Tesla magnet can do T1 and T2 images, as can a 1.5Tesla magnet.
Please take a look at our Health Pages, where MRI techniques and images are discussed in several places. I hope Quix will step in here and be more definitive. This is a complex subject which seems to be misunderstood often. I'm certainly not the best person to explain it, or even a good candidate, but I know that others are often confused.
I think that the difference here is between the two different techniques, T1 and T2. This is a totally different concept than the stregnth of the MRI, which would be expressed as 1T, 1.5T, 3T etc.
T1 and T2 are positive/negative pictures of the same thing. If you look at the two images above you will see that the fluid, the CSF, is bright white in the T2 images, but it is dark in the T1 images. Look closely at the space on either side of the spinal cord. Each technique has it's purpose.
The left hand picture us done using the T1 technique and the right-hand picture was done using the T2 technique. The T1 technique does not show small detail as well as the T2, but it is where we see the "black holes" of nerve degeneration. The "black holes" correlate better with our growing disability and less well with the relapses.
Now, even though you requested that the second set of images be down on a 2T, both of the images above were run on a 1.5T. You can see this in the very top left hand corner. There is no difference in the magnet strength. It is unfortunate that the two things - technique and strength of magnetic field - use such similar naming systems. We really have to pay attention to whether the "T" precedes or follows the number.
There are three health pages on this topic. These are "How MRIs Show Lesions in MS", "Lesions! Lesions! Lesions!", and "How MRs Work".
Thanks for the blurb from the MRI Center. Every description we get will help someone to understand better.
Talk about showing off one's amateur status. I kept looking at those and wondering why they looked so different, why the one on the right was lite up. Also wondered why I had never heard a 2T machine mentioned before.
Thanks Ess and Quix for the lessons here. They will stick with me now I think and I hope to be more observant of the position of all Ts and 2s.
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