fsbrain (version 0.5.5)

vox2ras_tkr: The FreeSurfer default vox2ras_tkr matrix.

Description

Applying this matrix to a FreeSurfer CRS index of a conformed volume will give you the RAS coordinates of the voxel in surface coordinates, i.e., in the coordinates used in surface file like `lh.white`. The central voxel is 127,127,127 when using zero-based indices (or 128,128,128 when using one-based indices), meaning its surface RAS coordinates are 0.0, 0.0, 0.0. The returned matrix is the inverse of the `ras2vox_tkr` matrix.

Usage

vox2ras_tkr()

Value

numeric 4x4 matrix, the FreeSurfer vox2ras_tkr matrix.

See Also

Other surface and volume coordinates: ras2vox_tkr()

Examples

   # Compute surface RAS coordinate of voxel with CRS (0L, 0L, 0L):
   vox2ras_tkr() %*% c(0, 0, 0, 1);
   # Show that voxel with CRS (128,128,128) is at the
   #  origin (0.0, 0.0, 0.0) of the surface RAS coordinate system:
   (vox2ras_tkr() %*% c(128, 128, 128, 1))[1:3];