MRI Discrepancy?

[Patti]

Hi all!  I have a question.  In August I had a routine MRI and they found a recurrence of 2.8 cm x 0.6cm.  Two months later they did another MRI at another facility in preparation for stereotactic surgery and that MRI measured the tumor to be 3.1.cm x .86 cm.  Can there be that big of a discrepancy between 2 machines or was there more growth in 2 months? Anyway, I had the radiation on November 6 and have a follow-up MRI scheduled for early February. I am feeling ok, I think. I get headaches sometimes. Any input would be appreciated!

[arizonajack]

Can there be that big of a discrepancy between 2 machines or was there more growth in 2 months?

The answer can be yes to both parts of the question.

MRIs image the tissue in slices and there is space between the slices. With as little as a 1mm slice and a 1mm space, there could easily be a discrepancy between two machines combined with some growth in a two month period.

Your AN grew in length by about 10% in two months. My own grew 20% in 6 months.

Even an average growth rate coupled with the discrepancy between the two machines could easily explain the change in dimensions.

At your next MRI don't be surprised (or upset) if there is some swelling. That's the natural progression as you can see by the following series of images:

http://ars.els-cdn.com/content/image/1-s2.0-S0360301612004336-gr3.jpg

[Patti]

Thanks for the answer and for psychologically preparing me for the swelling! 

[Blw]

The most likely difference was due to type of machine. The first MRI may have been done on a standard machine, but in order to be accurate for the surgery, they use a machine with a bigger magnet. This imager is called 3T (I think that stands for 3 Tesla). Think of a higher power microscope. They need the better image to identify the margins for irradiating.

[Patti]

Good to know!  People ask me why I had to have my follow-up scan in the city (2 hours away and much aggravation) and I didn't know the answer.  I had the scan Wednesday and will get the results when I go down AGAIN on the 29th.  I keep being "cool" about this stuff but it seems that every time I have an MRI I can only think about negative outcomes.  You can't believe the scenarios I invent in my head!

[PaulW]

As this is only 3 months after SRS this is far too early to tell what the outcome will be. Whether its bigger smaller necrosis showing or not will probably matter little to the long term result which typically takes 3 - 5 years to tell with some certainty. This MRI is really to make sure nothing crazy is going on like 10mm growth. And to give them a better understanding should it not respond to radiation in a year or two... radiation is a three plus year journey. Dont panic if the results are not what you expected