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Why the Strength of the MRI Mac...

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WHAT IS THE DIFFERENCE BETWEEN THE OLD MRI's AND THE NEW 3T MRI

This was written in 2008


I came across a good back-to-back comparision of the 1.5T MRI versus the 3T MRI on MS patients with known multiple brain lesions without enhancement. They did an MRI using the MS protocol of thin, 3mm slices. The neuroradiologists reading the films were not told which machine they were done on. The 3T machine consistently picked up more lesions - on average 25% more.  So, it was only a quarter more lesions for twice the power.

Now if you already have 12 lesions, who cares if there are 12 or 16? In the vast majority of cases the increased number of lesions picked up does not affect the diagnosis, the treatment, or the prognosis. And, as we 've discussed elsewhere, a huge number of the lesions in the brain do not "speak up" with specific symptoms. So there isn't a huge rush to convert to the newer and much more expensive machines.

However, I make a big deal of the issue here for the reason that several of us, including me, have languished without a diagnosis because of having "no" or "not enough" lesions on the MRI. If you are in diagnostic limbo and everyting you are suffering from screams "Multiple Sclerosis", but the MRI is not diagnostic, you need every bit of increased sensitivity you can get. Even several of our neuros have told us regretfully, "You might have lesions that are just too small to be seen." WELL??

I again tell the same, old story about my diagnosis. I had ZERO spinal lesions on a 1.5T machine in March, 2007.  In April I developed a fairly severe L'Hermitte's sign (lighting zaps down my left leg when I flexed my neck) This is common in MS, but it is also occasionally a symptom of cervical spinal cord lesions from other causes like tumors, cysts, or Lyme disease. My neuro ordered a repeat MRI of the spine on the 3T MRI. Suddenly there were SIX old (non-enhancing) lesions.

T-Lynn had no lesions, but classic disease for years. Suddenly she had "brain atrophy". Her first MRI sign was the accumulation of so many old, reabsorbed (and invisible) lesions, called "black holes", that when the brain tissue contracted around them the MRI showed loss of brain volume! After this diagnosis they did an MRI on a 3T machine and she showed lesions thoughout the brain.

Granted it's only two cases, but it is two cases where the diagnosis was delayed and we were dismissed by the neuro's as being crocks. When faced with the "undiagnosed" that small increase in resolution becomes very important. When someone looks at the pictures they may not look that much clearer. What the person does not see is the comparison back to back on old and on new machines, and what the appearance of just a few more lesions can mean clinically. There's no way they could see this.

There are several things to consider here.  One is that many areas of the country simply do not have the 3T amchines available to the public.  They may be only in the large academic medical centers, or have their use restricted to inpatients or just on brain imaging.  They are definitiely more expensive and some insurances will not allow them or will pay less, leaving increased cost to the patient.  I also think some doctors do not want to admit that they have been missing diagnoses, even if the reason is beyond their control. They don't want to admit they don't have access to better equipment, so they deny it is better. Yes, I have sat in the doc's lounge and heard discussions and rationalizations for more than twenty years. Doctors in general, and neurologists in particular, can have huge egos and need to "save face."

Then, again, we must remember that the vast majority of the some 400,000 people in the UK and US with MS were diagnosed using the older equipment. For them the new one wasn't needed. We here, who are just lacking sufficient MRI evidence to convince our neurologists are the one's most likely to benefit from use of the higher resolution machines.

Final word (really??) If the signs and symptoms are suggestive and the MRI bafflingly negative - why not go for an image with a better resolution?

 

However, it is not that easy.  The story is not that simple anymore:

 

 

 

This is an addendum that I posted on October 29, 2009. 

 

 

I have inadvertently mislead the forum into thinking that the strength of the MRI machine is the only thing that determines quality or the ability to discern tiny lesions. For a long time I thought that this was true. But, in the last year I have been learning that the software and the techniques used are also critically important. I have mentioned this here and there in posts, but have not talked about it with the full forum.

The software that analyzes the electromagnetic signals has grown in elegance and sophistication by leaps and lightyears. My neuro discussed this briefly with me last year. He stated that the 3.0T MRI at the nearby university (OHSU) had really mediocre software, so he was continuing to send his patients to the private imaging center that is associated with Providence Health Systems. this center uses the most elegant software.

I am beginning to realize that a good 1.5T MRI with the latest/best software can be superior to a humdrum 3.0T machine.

 

Also, they are developing new techniques for the magnetic pulsing and it's analysis that increase the yield in seeing MS lesions. My newest MRI (last winter) noted that several of my lesions were "more prominent". But, the report went on to say that a couple more sophisticated techniques, like Double Inversion Recovery and 3D Inversion had been used and this "may" have made the same, old lesions stand out more.

So, we cannot talk in absolutes of "3T vs 1.5T" machines any more. I know this takes away a lot of what we thought we knew in terms of assessing how good our MRIs were. This is unfortunate, but it is a reality. Since I have no way to know or understand what these software tecniques are, then I can no longer assume that any old 3T machine is way better than a 1.5T machine. I believe that in general a 3T is superior, but the 1.5T can apparently be enhanced a great deal.

 

The most recent recommendations for the MRI protocol for the diagnosis of MS (put out not long ago by the Consortium for MS Centers) has DROPPED the recommendation that the lowest acceptable MRI strength is 1.0T. They make no lowest requirement. Instead, they discuss that the standard of quality should be the resolution of the images. Shell (sllowe) will be reporting on these new recommendations soon. I assume that this requirement was dropped, because new advances in software and techniques allow even the lower strength MRIs to give much better images than before.

So....this leaves us with no way to know with any assurance how good our films are. This makes the whole "negative MRI" harder to evaluate. Unfortunately, some of our neurologists do not seem to be aware of how good the MRI machines they use really are - or aren't.

I have continued to hear comments by neuros that closed machines are superior to the open ones, but I am also aware that the software is improving for the open ones.

Sorry about all this, but real info that we can't assess is better than believing something false that may lead us to make erroneous conclusions.

Quix



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Start Date
Mar 15, 2008
by Quixotic1
Last Revision
Oct 30, 2009
by Quixotic1