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mtc.applyssm [2010/11/24 06:27] (current)
jochen created
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 +====== MTC::​ApplySSM - re-sample an MTC with a sphere-to-sphere-mapping object ======
 +===== Motivation =====
 +BrainVoyager'​s GLM format requires that, across subjects, the regression outputs of multiple sessions must match in the number of vertices. Given that each subject'​s brain reconstruction (white/gray matter boundary segmentation result) yields meshes with different numbers of vertices, and that the spatial location requires matching, the most typical approach is spherical inflation followed by a vertex-wise matching of a regular, icosahedron surface.
 +Each of the regular surface'​s (target) vertices is then mapped to either a source vertex (SSM) or position within a triangle (TSM). At this point, BrainVoyager QX uses vertex-based matching which has two major advantages: computational speed (no interpolation required) and reduced complexity (without the exact shape of the triangle and surrounding vertices, a high-quality interpolation is impossible). Still, it is a trade-off for whether vertex- or triangle-based matching should be used; potentially to be made based on the application (e.g. derivation of smooth, univariate maps as opposed to multi-variate statistics with data "as raw as possible"​).
 +===== Requirements =====
 +To use this method a "​raw"​ MTC (single-subject VTC sampled at the coordinates of the smoothed, reconstructed mesh of the respective subject'​s cortical brain hemisphere) as well as the SSM file created either by BrainVoyager or NeuroElf must be available.
 +===== Reference / mtc.Help('​ApplySSM'​) =====
 +<​file>​ MTC::​ApplySSM ​ - resample MTC with SSM mapping
 + ​FORMAT: ​      ​newmtc = mtc.ApplySSM(ssm)
 + Input fields:
 +       ​ssm ​        ​Sphere-to-Sphere-Mapping (SSM) object
 + ​Output fields:
 +       ​newmtc ​     MTC with resampled timecourses</​file>​
 +===== Usage =====
 +The usage is straight forward. Create and/or load both objects (which must match in the number of source vertices!) and then apply the method and use (and/or save) the outcome as required.
mtc.applyssm.txt ยท Last modified: 2010/11/24 06:27 by jochen