I would like to know how the deformation of the mri is performed when warping an anatomy template
A deformation field is computed between the two head surfaces (from the template head surface to the digitized head points), then applied to the other surfaces and the MRI. This is done by function bst_warp, if you are interested in technical details:
brainstorm3/toolbox/anatomy/bst_warp.m at master · brainstorm-tools/brainstorm3 · GitHub
How much does it affect the results? How likely do you recommend using an age-matched template (BIC - The McConnell Brain Imaging Centre: NIHPD-obj 1) and warp it instead of using individual MRIs when working on subjects aged between 5 and 18 years old.
If you have the individual MRIs, why would you not use them?
I don't have any experience about this, but this has been discussed multiple times already, other users might be able to help you:
@yuhanmc @christianoreilly @mclerc @Alexandre @John_Mosher @fleroy @tmedani @clairekabdebon @padibpour @ClaireK Any suggestion?