Hi Molly,

no one can really tell you that. My feeling is, that it is pretty safe, given that you have already 4 time points in the base. The base will be very stable and the main reason for the base is that it is an independent space different from any single time point. Which remains true.

You can take a couple cases and run them from scratch and using the old base and compare yourself. The base will be at a different location so visual comparison will be tricky. It is (technically) possible to create a new base (including the new time points) at the same location as the old. That could help preserve edits. But I think there are no scripts for that. Also in your case that may not need to be necessary.

Best, Martin

On Tue, 2018-10-16 at 17:47 +0000, Molly Prigge wrote:

Hello Freesurfer experts,

We have a large longitudinal dataset (n=~200) of up to 4 time points per participant.  All images were processed using Freesurfer v6.0 and have already undergone QA, and editing the cross, Base or long where needed.

We are finishing up collection of a 5th time point and will begin collecting a 6th time point next year (average interscan interval 2.5 years).  We are running the new scans through the same Freesurfer v6.0 and same workstation as the previous time points.

Is it appropriate to use the Bases already created with Times 1-4 for the 5th and 6th timepoint long file creation?  We are hoping to avoid losing all the QA editing already done on the Base and long files from Times 1-4 and not have to redo all QA on Times 1-5 long files when time 6 is complete.

We appreciate any guidance.

Thanks! Molly

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Molly DuBray Prigge, PhD Research Associate Department of Pediatrics molly.prigge at hsc.utah.edu MRI Study Phone: 801.585.9061

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