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MNI305 to MNI152 Affine Transform Matrix

Source: R/coordinate_spaces.R
MNI305_to_MNI152.Rd

The canonical 4x4 affine transformation matrix for converting RAS coordinates from MNI305 (fsaverage) space to MNI152 space.

Usage

MNI305_to_MNI152

Format

A 4x4 numeric matrix (affine transform in homogeneous coordinates).

Source

FreeSurfer: $FREESURFER_HOME/average/mni152.register.dat

Details

This matrix is derived from FreeSurfer's mni152.register.dat file, located at $FREESURFER_HOME/average/mni152.register.dat.

The transform accounts for the approximately 4mm difference between MNI305 and MNI152 coordinate systems. It includes small rotation, scaling, and translation components.

To apply: for a point p = c(R, A, S), compute MNI305_to_MNI152 %*% c(p, 1) and take the first 3 elements.

See also

https://surfer.nmr.mgh.harvard.edu/fswiki/CoordinateSystems MNI152_to_MNI305, transform_coords

Examples

# Transform a single point from MNI305 to MNI152
point_305 <- c(10, -20, 35)
point_152 <- (MNI305_to_MNI152 %*% c(point_305, 1))[1:3]
print(point_152)  # approximately c(10.695, -18.409, 36.137)
#> [1]  10.6941 -18.4064  36.1385