We've noticed that when Siemens performs their quarterly preventative maintenance (PM) on our Allegra scanner that the shape/size of our mprages changes after the system is brought to spec. This may pose a problem if we scan a subject before a PM to create a surface reconstruction, and then scan the same subject again after a PM and want to align the data to the surface volume. Has anyone encountered this problem at their site, and if so, how have they dealt with it? One option we considered is just stopping the PMs, but that wasn't advised by Siemens. Another option is to use some non-linear transformation tool on the software end. Any advice, especially from other Siemens Allegra sites, would be greatly appreciated.

Thanks Mark Pinsk

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